Functionalized nanomaterials for sample preparation methods

Functionalized nanomaterials for sample preparation methods

15

Erkan Yilmaz1,2 and Mustafa Soylak3 1 Faculty of Pharmacy, Department of Analytical Chemistry, Erciyes University, Kayseri, Turkey, 2Nanotechnology Research Center (ERNAM), Erciyes University, Kayseri, Turkey, 3 Faculty of Sciences, Department of Chemistry, Erciyes University, Kayseri, Turkey

Abbreviations [C8MIM][PF6] Acryloyl-β-CD AFB1 APTES BPEI C16mimBr C60 CNTs DCC DESs d-SPE EDTA EDXRF ETAAS FAAS FIA FT-IR G GC GC
FID GC
MS/MS GO HPLC HR-CS-ETAAS ICP-AES ICP-OES ILs LC
UV LOD LOQ MAA

1-octyl-3-methylimidazolium hexafluorophosphate acryloyl-β-cyclodextrin aflatoxin B1 3-aminopropyltriethoxysilane polyethyleneimine 1-hexadecyl-3-methylimidazolium bromide fullerenes carbon nanotubes N,N-dicyclohexylcarbodiimide deep eutectic solvents dispersive solid-phase extraction N-(trimethoxysilylpropyl) ethylenediamine triacetic acid energy dispersive X-ray fluorescence spectrometry electrothermal atomic absorption spectrometry flame atomic absorption spectrometer flow injection analysis Fourier-transform infrared spectroscopy graphene gas chromatography gas chromatography
flame ionization detection gas chromatography
tandem mass spectrometer graphene oxide high-performance liquid chromatography high-resolution continuum source electrothermal atomic absorption spectrometer inductively coupled plasma atomic emission spectrometry, inductively coupled plasma optical emission spectrometer ionic liquids liquid chromatography
ultraviolet spectrophotometer limit of detection limit of quantification methacrylic acid

Handbook of Nanomaterials in Analytical Chemistry. DOI: https://doi.org/10.1016/B978-0-12-816699-4.00015-3 Copyright © 2020 Elsevier Inc. All rights reserved.

376

Handbook of Nanomaterials in Analytical Chemistry

MALDI
MS MIPs MOFs MNPs MWCNTs MWCNTsCOOH NADESs ND NMs NPs PAHs PAN PANI PDMS PF PT-SPE RSD SEM SPE SPME SWCNTs TAR TEM TMSPDETA TMSPEDA TSP-MS-MS XPS α-ZOL β-ZAL β-ZOL

15.1

matrix-assisted laser desorption/ionization mass spectrometer molecularly imprinted polymers metal
organic frameworks metal nanoparticles multiwalled carbon nanotube carboxylated multiwalled carbon nanotubes natural deep eutectic solvents nanodiamond nanomaterials nanoparticles polycyclic aromatic hydrocarbons 1-(2-pyridylazo)-2-naphtol polyaniline polydimethylsiloxane preconcentration factor pipette-tip solid-phase extraction relative standard deviation scanning electron microscopy solid-phase extraction solid-phase microextraction single-walled carbon nanotubes 4-(2-thiazolylazo)resorcinol transmission electron microscopy N1-(3-trimethoxysilylpropyl) diethylenetriamine N-(3-trimethoxysilylpropyl) ethylenediamine thermospray tandem mass spectrometer X-ray photoelectron spectroscopy α-zearalenol β-zearalanol β-zearalenol

Introduction

An important sentence “There is a lot of space down there,” by R. Feynman in 1959, took its place in the history as the first step of nanotechnology. At that time, it was unpredicted that there would be such advanced technological development in this field [1,2]. In general, materials in particle size ranging from 10 to 100 nm are classified as nanomaterials (NMs). Because of the different physical and chemical properties of NMs, according to the micro-sized and bulk materials, NMs appear in almost every field—from chemistry to biology, medicine to agriculture, electronics to biotechnology, and food industry to pharmacology [3
5]. Surface energy of small particles and higher surface atoms fraction lead to these unexpected features when compared with micro-sized and bulk materials. High surface atoms fractions that lead to high surface-area-to-volume ratio of NMs are one of the most important features. This situation is related to the presence of more

Functionalized nanomaterials for sample preparation methods

377

active atoms in the NMs. These more active atoms in the NMs are the most important driving force causing specific affinity and interaction with different free atoms, molecules, and ions [6
10]. High surface area of NMs and special interactions between NMs and different species (atoms, molecules, and ions) lead to high adsorption capacity for different organic, inorganic, and bioactive species [11
13]. NMs also provide easy functionalization and reusability, improved electronic properties, such as high conductivity, fast response to physical event, and chemical reactions. Due to these unique features, NMs have taken their place among the most preferred materials in various branches of analytical chemistry, such as sample preparation methods, separation techniques, and qualitative and quantitative analyses [11
14]. In the last few decades, undoubtedly, the most important turning point in the change and development of analytical and bioanalytical sciences has been the use of NMs as sorbent in solid-phase extraction (SPE)/microextraction (SPME)-based sample preparation methods, column filler material in chromatographic systems [high-performance liquid chromatography (HPLC), liquid chromatography (LC)
mass spectrometry (MS), gas chromatography (GC)
MS, LC
tandem mass spectrometer (LC
MS/MS), etc.], substrate in detection system, and sensing agent in sensor and biosensor systems [15
21]. NMs can mainly be classified on the basis of dimensionality and chemical form of materials, which is explained in Fig. 15.1, and can also be classified according to different criteria, such as dimensionality, morphology, composition or uniformity, and agglomeration state [22]. An alternative, complementary classification may divide nanoparticles (NPs) into two main groups, namely, organic and inorganic, according to their chemical composition. While carbonaceous and polymeric materials are classified as organic NMs, metallic and metal-oxide NMs are classified as inorganic NMs. The main reason for the frequent use of NMs in sample preparation and analysis procedures that form the basis of analytical chemistry is that they can be modified by using different functionalization agents. Modification of NMs with different groups and species provides advantages, such as high affinity and adsorption capacity, against the analytes’ high enrichment factors (EFs), accelerating the adsorption and desorption steps in the separation- and preconcentration-based methods. In addition, it also offers advantages such as improved separation efficiency, easier dispersibility in the liquid phases, low detection limit, fast response time, and selective response signal for chromatographic, spectroscopic, sensor- and biosensorbased separation, and analysis techniques [23
28]. The most commonly used methods in the production and functionalization of NMs are as follows [29
40]: 1. 2. 3. 4.

coprecipitation, reduction or oxidation, solvothermal or hydrothermal procedure, chemical vapor deposition,

378

Handbook of Nanomaterials in Analytical Chemistry

Figure 15.1 Classification of nanomaterials attending to dimensionality and chemical forms. 5. 6. 7. 8. 9. 10. 11.

physical vapor deposition, electrospinning, thin film formation, surface coating, immobilization, impregnation, sol
gel,

Functionalized nanomaterials for sample preparation methods

12. 13. 14. 15. 16.

379

discharge method, laser vaporization, laser ablation, electrochemical polymerization and in situ polymerization.

15.2

Functionalized nanomaterials for sample preparation methods

15.2.1 Carbon-based nanomaterials Carbon-based NMs have been the most commonly used materials in all disciplines, such as energy, chemistry, medicine, health, biotechnology, and pharmacy, since the discovery of fullerene (C60) in 1985 and carbon nanotubes (CNTs) in 1991 [41
43]. In particular, carbon-based NMs [e.g., fullerenes, CNTs, carbon nanofibers, carbon nanocones graphene, graphene oxide (GO), carbon nanodisks, nanohorns] and their functionalized forms have been preferred as a sorbent in many SPE/SPME methods [44
48]. The SPE/SPME methods based on carbon-based functionalized NMs are frequently used for the separation and preconcentration of trace amounts of organic, inorganic, and bioactive species in environmental, water, biological, food, and pharmaceutical samples. Moreover, these are among the most researched materials of the 21st century. Fullerenes are soccer ball
shaped polyhedral NMs obtained by the coiling of the graphene together. C60, C70, C240, C540, and C720 isomers of fullerenes can be obtained by using more carbon atoms. C60 as the most used isomer has a diameter of approximately 1 nm. A carbon atom in fullerene is bonded to three carbon neighbors by sp2 hybridization in five- to six-membered rings arranged as 20 hexagons and 12 pentagons [49,50]. CNTs are produced by rolling up graphite sheets into nanoscale tubes [i.e., single-walled CNTs (SWCNTs)] or with additional graphite tubes wrapped around the cores of the first layer of roll of graphite sheets. They are classified as SWCNTs, double-walled CNTs (DWCNTs), and multiwalled CNTs (MWCNTs). After the discovery of these special nano-carbons, scientists focused on the different applications because of their excellent surface structure, high surface area, and unique mechanical, chemical, and thermal stability. A carbon atom in CNTs is bonded to three carbon neighbors by sp2 hybridization and has π
π bonds between carbon atoms. Hence, CNTs can establish π
π and van der Waals interactions with atoms, ions, and molecules. These unique properties have made CNTs one of the most widely used adsorbents in SPE/SPME applications. Though SWCNTs, DWCNTs, and MWCNTs are produced from the same carbon source, they show very different adsorption performances because of their different numbers of graphite sheets [51
53]. Nanodiamond (ND) is also a commonly used nano-carbon in laboratory and industry scale due to its unique chemical, mechanical, and physical features, such

380

Handbook of Nanomaterials in Analytical Chemistry

as high surface area, high resistivity to corrosive chemicals, very high hardness, high biocompatibility, high thermal conductivity, and low friction coefficient. Hence, NDs are preferable materials in SPE/SPME applications [54,55]. Graphene (G) and GO are innovative nano-carbons that marked this century and are called the “mother” of all graphitic carbon materials [56,57]. Graphene fabricated in 2004 has been recorded in the literature as a material that has given its inventor a Nobel Prize. When compared with CNTs, fullerenes, NDs, carbon nanofiber, and other carbon-based NMs, graphene and GO provide more effective and attractive performance for sorption-based sample preparation methods due to their unique properties, such as improved nanosheet morphology, very effective π
π interactions toward to analytes especially carbon-based ring structures, and very high specific surface area (i.e., a theoretical value of 2630 m2 g21), which lead to high adsorption capacity for analytes [58
60]. In 2004 carbon dots (carbon quantum dots or C-dots) were recognized by accident while separating SWCNTs from carbon soot using gel electrophoresis. C-dots have been classified as star of nano-carbon allotropes. They gained important interest by scientists due to their effective and preferable properties, such as simple and cheap production with high quantities, great biocompatibility, and excellent optical property. C-dots mainly consist of sp3 and sp2 carbon atoms. Hence, they have a similar structure with graphenic nanosheets, 2D graphene, and 1D CNTs. Although C-dots have been widely used in many areas, such as electronic, bioimaging, and optical application, they are already being used in sample preparation applications [61,62].

15.2.1.1 Functionalization of carbon-based nanomaterials 15.2.1.1.1 Covalent functionalization of carbon-based nanomaterials Although all the nano-carbon allotropes described above contain unique properties, the most important properties of them are that they are functionalized by covalent or noncovalent functionalization methods in order to use the desired properties for many applications. The covalent functionalization can be carried out by direct covalent sidewall functionalization with the molecule of interest or by indirect covalent functionalization with carboxylic groups previously introduced on their surface. In many literature studies, it is observed that the covalent functionalization reactions are majorly used procedures consisting of oxidization, hydrogenation, halogenation, cycloaddition, nucleophilic addition, and radical addition. By using these functionalization reactions, a linkage between the carbon skeleton of NMs and the functional groups is formed. As mentioned above, these modifications can occur by direct sidewall functionalization with aid of silanized groups located on the surface of the carbon NMs or indirect functionalization with carboxylic groups located on the defects of the carbon NMs [63
65]. The main disadvantage of covalent functionalization is that the well-organized carbon structure of NM is disturbed, which cause significant changes in their valuable physical or chemical features.

Functionalized nanomaterials for sample preparation methods

381

In the covalent functionalization, carbon-based NMs are generally oxidized by using strong acids, such as H2SO4 and HNO3, at high temperature. In this way,
COOH,
OH, and
C 5 O
groups are introduced in their structure [63
65]. The NMs have
COOH,
OH, and
C 5 O
groups that can be used directly or modified with desired functional groups by different substitution reactions. After oxidation, these NMs have zero net charge, and “point of zero charge” or “isoelectric point” is formed for these NMs, that is, the surface charges of these oxidized NMs vary with the ambient pH values. When the pH value of sample solutions is reached to values higher than “point of zero charge” or “isoelectric point,” the surface of oxidized NMs has gained negatively charged. In this case, cationic species, such as metal ions, cationic surfactants, and organic compounds, which have positive charge, can be adsorbed on the surface of NMs by electrostatic interactions. Around point-of-zero-charge region, the surface of oxidized NMs has neutral charge. In this case, van der Waals interactions and hydrogen bonding are formed between NM and neutral species, such as metal
ligand complex and organic compounds. On the contrary, at lower pH values than the point of zero charge, there is a competition between protons and cations for the same sites on oxidized NMs, which cause a decrease in the adsorption. For example, metal ions can be adsorbed on the oxidized surface of NMs at high pH value and eluted by using acidic solutions. Hence, the pH value of solution medium is important and needs optimized factor in SPE/SPME studies. Moreover, oxidation process leads to the formation of holes in the NMs. In this manner, inorganic and organic species in solution phase can be entered into these holes and retained. SPE methods are generally used in the separation and enrichment of trace analytes found in aqueous media. Therefore dispersion of sorbents in the aqueous phase is one of the most critical processes. As the hydrophobic properties of the pristine carbon NMs are dominant, it is very difficult to disperse in the aqueous medium. In this way the modification results in a significant increase in extraction efficiency by allowing the NMs to be dispersed easily in the aqueous medium. In general, functionalized CNTs are easier to disperse than the corresponding pristine materials, therefore facilitating their characterization and purification. In many cases the oxidation is just the previous step to the immobilization of different molecules. Covalent modification of NMs with complexing agents, organic compounds, polymers, and extraction solvents has an important place in SPE/SPME applications. Some examples of the applications of oxidized and covalent-modified carbon-based NMs for adsorption-based separation and enrichment studies in the literature are explained later. Sun et al. prepared carboxylated MWCNTs (MWCNTs-COOH) as dispersive SPE (d-SPE) sorbent for the separation and preconcentration of trace amounts of pyrethroid pesticides prior to their GC
electron capture detector (ECD) detections. They optimized the d-SPE method and used seven pyrethroid pesticides at trace level in carrot cucumber, tomato, eggplant, and spinach samples for analysis. The d-SPE/GC
ECD procedure provided high extraction efficiency between 88.5% and

382

Handbook of Nanomaterials in Analytical Chemistry

108.2%, low limit of detection (LOD) (0.5
2.9 μg kg21), and limit of quantification (LOQ) (1.5
9.7 μg kg21) values [66]. Lo´pez-Feria et al. checked the applicability of MWCNTs and carboxylated SWCNTs (SWCNTs-COOH) for SPE of atrazine, chlortoluron, simazine, diuron, terbuthylazin-desethyl, malathion parathion and dimethoate pesticides at trace level in virgin olive oil samples. They filled 30 mg of CNT sorbents in a cartridge to prepare SPE system. Analytes sorbed on the CNTs were eluted with 500 μL of ethyl acetate, and the eluent volume was evaporated until 50 μL by nitrogen stream. Concentrations of analytes were analyzed with the GC
MS method. They used these prepared SPE column system at least 100 times, which performed successfully every time. The developed procedure provides LOD between 1.5 and 3.0 μg L21 [67]. Sun et al. used carboxylated SWCNT fibers as a SPME sorbent for the separation and preconcentration of many chlorophenols (CPs) and organochlorine pesticides (OCPs) in aqueous samples followed by GC
ECD detections. They used sol
gel-coating procedure to fabricate carboxylated SWCNT fibers. In this procedure a sol
gel solution was prepared by mixing 120 mg of TSO-OH, 200 μL of dichloromethane, 150 μL of tetraethyl orthosilicate (TEOS), 15 mg of methylhydrosiloxane (PMHS), 80 μL of trifluoroacetic acid (TFA), and 5% of water. Next, the sol
gel coating was formed on the outer surface of the fused-silica fiber by vertically immersing fiber into the prepared sol
gel solution, and then the fiber was left to interact with the carboxylated SWNTs in dichloromethane solution. The carboxylated SWCNT fibers were dried before SPE application. The carboxylated SWCNT fibers showed more effective sensitivity and selectivity than commercial SPME fibers. The SPME/GC
ECD procedure was applied to analyze CPs and OCPs in lake and wastewater samples, with high recovery results (89.7%
101.2%) [68]. Kueseng and Pawliszyn fabricated a MWCNTs-COOH/polydimethylsiloxane (MWCNTs-COOH/PDMS)
coating thin film as a new 96-blade SPME system for trace amount of phenolic compounds prior to HPLC
ultraviolet (HPLC-UV) determination. In this synthesis procedure, MWCNTs-COOH particles (5%, w/w of PDMS) were dispersed in dichloromethane solution by sonication for 3 min. Then, 3 g of PDMS prepolymer was added into the solution including MWCNTs-COOH and sonicated for 5 min to disperse into the prepolymer. Next, the coating procedure was carried out by immersing of 2 cm portions of each pin into the MWCNTsCOOH/PDMS mixture for 5 s. The coated blade was cured in an oven at 150 C. The extraction and analysis procedure provided acceptable extraction performance between 64% and 90% with relative standard deviation (RSD) # 6% and low LOD between 1 and 2 μg L21. Moreover, when compared with traditional methods, the MWCNTs-COOH/PDMS 96-blade SPME apparatus has better performance, such as simple and easy applicability, cheap and easy coating procedure, and high reusability (minimum 110 extraction application) [69]. Kou and Liang carried out a comparative SPE method for the separation and preconcentration of trace amounts of bisphenol and tetrabromobisphenol A prior to LC
MS
MS determinations. For this purpose, they compared SPE performances

Functionalized nanomaterials for sample preparation methods

383

of MWCNTs, carboxyl-functionalized MWCNTs, and fullerenes and decided to use carboxyl-functionalized MWCNTs as sorbent. They applied the developed SPE method for determining trace amounts of bisphenol and tetrabromobisphenol A in lake water and sea water samples with good recoveries between 82% and 99% with the RSD , 5.0% [70]. Chang et al. introduced a microwave-assisted surface functionalization method to obtain carboxyl and carbonyl-modified diamond NPs. In this synthesis procedure, diamond nanopowders were added into an oxidized acid solution consisting of HNO3 and H2SO4 (1:3, v/v), and the mixture was irritated by microwave radiation at 100 W power. The temperature was set to 100 C and was applied for 3 h. In the polyarginine-coated diamond NP preparation step, an 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)-mediated coupling reaction was used as follows: carboxyl-modified diamond NPs were mixed with a solution containing EDC (22 mg mL21, 63.7 μL), polyarginine (4 mg mL21, 155 μL), and H3BO3/NaOH buffer (5 mM, pH 8.5). The mixture was shaken gently for 2 h at room temperature and the prepared polyarginine-coated diamond NPs were washed and dried. The new sorbent was used for the extraction of phosphorylated peptides from complex samples and selective preconcentration of multiphosphorylated peptides prior to direct matrix-assisted laser desorption/ionization (MALDI)
time-of-flight (TOF) mass-spectrometric detections. The new sorbent has shown an effective affinity for multiphosphorylated peptides because of the multiple arginine
phosphate interactions. The developed method provided the analysis of 50 μL of sample containing nonfat milk, α-casein, and r-casein at a concentration as low as 1 3 1029 M [71]. Similar synthesis method was used for the fabrication of polylysine-coated diamond NMs as sorbent for the separation, preconcentration, and digestion of DNA oligonucleotides in one microcentrifuge tube prior to MALDI-TOF mass-spectrometric analysis (MS) [72]. Kong et al. fabricated carboxylated/oxidized diamond NPs by oxidizing them and using them for the extraction and analysis of proteins followed by MALDI-TOF mass-spectrometric (MS) analysis [72]. Silane groups, such as (3-aminopropyl)triethoxysilane (APTES), (3-chloropropyl)-trimethoxysilane, N-(3-trimethoxysilylpropyl) ethylenediamine (TMSPEDA), N1-(3-trimethoxysilylpropyl) diethylenetriamine (TMSPDETA), and 3methacryloxypropyltrimethoxysilane, are frequently used as coupling agent for covalent modification of NMs. Many desired functional groups are covalently attached to NMs via these silane groups [73
77]. Sua´rez et al. immobilized carboxylated SWCNTs (COOH-SWCNTs) onto porous glass in a different SPE application. In the synthesis procedure, they oxidized SWCNTs with 20 mL of H2SO4:HNO3 (3:1) solution by using ultrasonic irritation (50 W, 60 Hz) for 90 min. Then, the obtained carboxylated SWCNT particles were washed with ultrapure water and dried. In order to obtain silanized glass surface, cleaned glass sample was mixed with a known volume of 3-amino propyl triethoxy silane and 0.05 M mL ammonium acetate (pH 5.0) and heated at 80 C in a water bath for 2 h. After this reaction time, the mixture was filtered on 0.45 μm filters, washed and dried at 95 C. Next, the obtained silanized glass was added into a solution including 0.6 mL of glutaraldehyde and 5 mL of 0.1 M orthophosphate at

384

Handbook of Nanomaterials in Analytical Chemistry

pH 8.5 and was mixed until the completion of reaction. In the last step, the obtained activated glass and COOH-SWCNTs were mixed together in a 3 mL dimethylformamide solution containing 0.7 mg of 1,3-dicyclohexylcarbodiimide for 5 h. The prepared COOH-SWCNT-modified glass was washed, dried, and characterized by atomic and electron microscopy methods [73]. Lv et al. modified GO and silica particles with three different kinds of silane coupling agents, including APTES, 3-methacryloxypropyltrimethoxysilane, and (3-chloropropyl)-trimethoxysilane. The functionalized materials were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and Zetasizer Nano ZSP. The authors used these new materials for ultrasonic-assisted d-SPE of sulfamerazine and sulfameter. The obtained results showed that the (3-chloropropyl)-trimethoxysilane-modified GO had a good and better sorption and extraction performance than other materials for the separation and preconcentration of sulfonamides in milk samples with high extraction efficiencies between 92.16% and 103.81% and RSDs lower than 3.20%. After d-SPE, concentrations of analytes were measured with HPLC [74]. Sitko et al. prepared aminosilanized GO (GO-NH2) by modifying GO with APTES for selective preconcentration of Pb(II) ions. In the synthesis procedure, the authors used Hummers’ method for fabrication of GO. The obtained GO particles were added into anhydrous ethanol and dispersed. Then, 10 mL of APTES was added to the suspension and the mixture was heated at 70 C for 4 h. The obtained aminosilanized GO material was characterized by SEM, Raman, x-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) methods. Pb(II) ions were adsorbed on the surface of GO-NH2-like complex formation. After dispersive micro-SPE step, Pb(II) ions sorbed on the GO-NH2 material were measured directly by injecting the suspended GO-NH2 into graphite tube for electrothermal atomic absorption spectrometry (ETAAS). Modification of GO with APTES provided excellent dispersibility in aqueous samples, which lead to very effective interaction with Pb(II) ions with very fast adsorption. The developed method provided low LOD of 9.4 ng L21 and high preconcentration factor of 100 [75]. Huang et al. used a hydrothermal synthesis procedure to modify graphene with APTES. The fabricated graphene-APTES material was used for SPE of polycyclic aromatic hydrocarbons (PAHs) at trace level in environmental water samples prior to HPLC determinations. The authors used only 10 mg of sorbent for the separation and preconcentration of PAHs traces from 100 mL of sample solution due to high surface area and high adsorption capacity of NMs. The developed method provided high extraction efficiency changing from 84.6% to 109.5% for PAHs [76]. In a different application, GO was modified with APTES, TMSPEDA, and TMSPDETA. These three different obtained materials were used for selective SPE of hexavalent chromium traces at pH 3.5. The amount of amino silanes attached to GO decreases in the order of APTES . TMSPEDA . TMSPDETA. Hence the APTES-modified GO was used for selective and sensitive SPE of Cr(VI) ions prior to low-power energy dispersive X-ray fluorescence spectrometry (EDXRF) analysis. The method was used for the analysis of Cr(VI) in water samples with recoveries of 99.7 6 2.2 [77].

Functionalized nanomaterials for sample preparation methods

385

Xiao et al. prepared a new coating material, polymeric fullerene, for modifying the fibers in SPME apparatus. The obtained SPME apparatus was used in the headspace SPE method for the separation and preconcentration of naphthalene congeners, benzene, toluene, ethylbenzene and xylene (BTEX), and phthalic acid diesters in water samples. Concentrations of analytes in the last phase were measured by GC
flame ionization detection (FID) detection system [78]. In a different application, polysilicone fullerene
coating material was prepared for SPME and determination of trace amounts of semivolatile compounds. fullerene polymers was fabricated by the reaction of excess of fullerene (C60) with ω-azido-undecyl-polymethylsiloxane in reflux system. Then, the prepared PF was coated on the commercial PDMS of 100 μm thickness. When compared with the PDMS, the new fibers showed better sensitivity, selectivity, and extraction performance; thermal stability; and life span [78]. Yu et al. used sol
gel method to fabricate hydroxyfullerenecoated SPME fiber. Fullerol (fullerene polysiloxane) was prepared by the reaction of C60 with aqueous NaOH and H2O2 in the presence of tetrabutylammonium hydroxide. They used IR and SEM methods for the characterization of new material. The prepared headspace SPME apparatus was used for the separation and preconcentration of polar aromatic amines, PAHs, and polychlorinated biphenyls prior to GC
FID and GC
electron capture detection [79]. Vallant et al. prepared aminosilica-modified fullerene for SPE of proteins, peptides, and flavonoids with recoveries of B99%. In the production of sorbent, fullerenoacetic acid and epoxyfullerenes were reacted with (aminopropyl)trimethoxysilane in the reflux system [80]. Vallant et al. synthesized dioctadecyl methano fullerene, fullerenoacetic acid, and iminodiacetic acid fullerene materials from pristine fullerene by using different chemical reactions. The new materials were used for the extraction and preconcentration of serum compounds prior to MALDI
MS/MS analysis [81]. Complexing agents, such as 5-aminosalicylic acid, 4-(2-thiazolylazo)resorcinol (TAR), 8-hydroxyquinoline, eriochrome black T, 1-(2-pyridylazo)-2-naphthol, dithizone, 1,5-diphenylthiocarbazone, ethylenediamine, (5-bromo-2-pyridylazo)-5(diethylamino)phenol, 1-(2-thiazolylazo)-2-naphthol, 1-(2-pyridylazo)-2-naphthol, and ethylenediaminetetraacetic acid, are frequently used for selective retention of trace heavy metal ions on the sorbent surface. It has been reported in many studies that the extraction efficiencies and adsorption capacities of heavy metal ions increased with the nonreversible covalent modification of the surfaces of NMs with these complexing agents [82
90]. Soliman et al. fabricated 5-aminosalicylic acid
modified MWCNTs by covalent immobilization [82]. In the fabrication procedure, pristine MWCNTs were converted to MWCNTs-COOH by a well-known oxidization method. Pristine MWCNTs were reacted with a concentrated mixture of H2SO4/HNO3 in an ultrasonic bath at 55 C for 7 h, and the obtained MWCNTs-COOH particles were washed with ultrapure water and dried in an oven. In the second step, N,N-dicyclohexylcarbodiimide (DCC) was used to link MWCNTs-COOH particles to 5aminosalicylic acid. For this purpose, 2 mmol of 5-ASA (amino salicylic acid), 2.0 g of DCC, and 2.0 g of MWCNTs-COOH were mixed in dimethylformamide (DMF) solution, and the obtained mixture was stirred for 48 h at room temperature.

386

Handbook of Nanomaterials in Analytical Chemistry

The fabricated MWCNTs-5-ASA material was characterized by scanning electron microscope, FT-IR spectroscopy, and surface coverage determination and was used for the separation and preconcentration of Pb(II) traces prior to inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. Trace Pb(II) ions in aqueous sample solution (pH 4.0) were preconcentrated on 50 mg of the new fabricated sorbent and eluted with 4.0 mL of 2 M HNO3. After optimization step, the developed SPE method was applied to water samples [82]. In a different complexing agent immobilization procedure, Madadizadeh et al. produced 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol-modified MWCNTs in two steps [83]. Pristine MWCNTs were first oxidized with concentrated HNO3 and then reacted with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a reflux system. The prepared sorbent was used for SPE of trace amount of Cd(II) ions followed by ETAAS determination. Preconcentration factor, LOD, and RSD values for Cd(II) ions were found as 300, 0.14 ng L21, and 6 3.6%, respectively. The developed SPE-ETAAS procedure was used for the analysis of cadmium in different water samples [83]. Tajik and Taher used similar oxidization and complexing agent modification reactions to link 1-(2-pyridylazo)-2-naphtol (PAN) on the surface of MWCNTs. The prepared PAN-MWCNT sorbent was used for the separation and preconcentration of Zn(II) ions in aqueous sample solutions (pH 5) prior to its flame atomic absorption spectrometer (FAAS) analysis. Preconcentration factor, LOD, and RSD values for Zn(II) ions were found as 250, 0.07 pg mL21, and 6 1.2%, respectively. The suggested method was successfully applied to biological and water samples [84]. A different research group prepared PAN-modified MWCNTs with similar covalent modification method and used it as a sorbent for SPE of Co(II) ions at trace level [85]. Moghimi and Siahkalrodi modified graphene material with N-methyl-glycine and 3,4-dihydroxybenzaldehyde by using a reflux synthesis unit. The prepared material was used as a sorbent for selective SPE of Pb(II) ions. After SPE stage, the concentration of lead in eluent phase was measured with FAAS [86]. Madadrang et al. linked ethylenediamine triacetic acid (EDTA) on the GO surfaces through a silanization reaction between N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (EDTA-silane) and hydroxyl groups on GO surface. The new sorbent has shown selective sorption properties for Pb(II) ions at pH 6.8 [87]. Pytlakowska et al. prepared 2,20 -iminodiacetic acid
modified GO sorbent for the separation and preconcentration of Pb(II), Zn(II), Cu(II), and Cr(III) traces from water samples by applying dispersive micro-SPE procedure. Their modification method is based on the nucleophilic substitution of dimethyl-2,20 -iminodiacetate hydrochloride to the surface of GO. Heavy metal ions preconcentrated on the sorbent at pH 6.5 were analyzed by EDXRF. The adsorption capacities of new sorbent were found as 108.4, 117.1, 80.7, and 119.6 mg g21 for Cu(II), Cr(III), Pb(II), and Zn(II) ions, respectively [88]. Zhao et al. prepared two different complexing agents (single- and double-arm amide
thiourea) and used them for covalent modification of ND particles. These two sorbents were used for selective sorption of uranium ions. In the functionalization method the synthesized single-arm or double-arm amide
thiourea complexing

Functionalized nanomaterials for sample preparation methods

387

agent was reacted with oxidized NDs in a reflux system. The obtained results showed that the prepared two sorbents have very fast adsorption kinetics for uranium (equilibrium time: 2 min), high adsorption capacities (B200 mg g21), and great selectivities for uranium (between 72% and 82%) [89]. In a different application, MWCNT was oxidized and chemically functionalized by 3-hydroxy-4-((3-silylpropylimino) methyl) phenol to produce an effective sorbent for SPE of Fe31, Cu21, Zn21, Ni21, Co21, and Pb21 ions [90]. Polymeric nanocomposites consisting of inorganic NPs and organic polymers are a new strategy to obtain innovative materials that provide desired properties, and these nanocomposites show better performance than their microparticle counterparts and might lead to improved physical and chemical properties. Modification of NMs with polymers might provide selective extraction of analyte(s) and high adsorption capacities for analytes due to their highly branched structure that consists of many reactive organic functional groups, well-ordered three-dimensional (3D) molecular configuration, and large internal and external surfaces. Moreover, they provide high chemical stability toward corrosive solutions, such as H2SO4 and HNO3, and high thermal stability for thermal desorption stages in SPE/SPME applications [91
98]. Modification of carbon NMs with different polymers as covalent is an important task for the fabrication of SPE/SPME sorbents. These reactions are called polymergrafting reactions and can be carried out by two different ways: (1) high reactive polymers can react directly with NMs, which have a bonding agent, such as carboxy, amine, silane, and hydroxy functional groups. (2) NMs, which have bonding agents, such as carboxy, amine, silane, and hydroxy functional groups, act as a polymer initiator with a monomer M1, and, in a second step, copolymerization with a M2 monomer synthesis polymer
modified NMs (NMs-(M1)m-(M2)n) (where m and n are the degrees of polymerization). In the second strategy, monomers are bonded on the surface of NMs as radical covalently. Chemical defect functionalization is the most suitable and more preferred method than sidewall functionalization. The use of NMs, which have oxygen-containing groups on their surface, is the most preferred strategy because of the great variety of reactions of oxygen groups [91
98]. Behbahani et al. fabricated polypropylene amine dendrimers (POPAM)
grafted MWCNT hybrid material as sorbent. The synthesis procedure consists of three stages: (1) oxidized MWCNTs (MWCNTs-COOH) were converted to MWCNTsCOCl in the SOCl2 and DMF medium by heating at 80 C for 50 h, (2) MWCNTsNH2 was produced by the reaction of MWCNTs-COCl with NaN3 at 100 C in DMF medium, and (3) the generation of first, second, and third POPAM on the amino-functionalized MWCNTs. The new material was used for SPE of Au(III) and Pd(II) traces from the aqueous phase prior to their AAS determinations [91]. Zhang et al. modified MWCNTs covalently with molecularly imprinted polymers (MIPs) by using acryloyl-β-cyclodextrin (acryloyl-β-CD) and methacrylic acid (MAA) as the binary functional monomers and erythromycin as the template. This synthesis procedure consisted of five successive steps: (1) formation of carboxyl group on the surface of MWCNTs (MWCNTs-COOH) by oxidizing with acids, (2) synthesis of MWCNTs-COCl in SOCl2 medium by reflux system at 60 C for 24 h,

388

Handbook of Nanomaterials in Analytical Chemistry

(3) synthesis of MWCNTs from MWCNTs-COCl in the presence of APTES and vinyltriethoxysilane, (4) production of acryloyl-β-cyclodextrins, and (5) reaction of MWCNTs particles with acryloyl-β-cyclodextrins in the presence of ethylene glycol dimethacrylate and α,α0 -azoisobutyronitrile [92]. The characterization studies for this new material were carried out by using techniques such as FT-IR spectroscopy, SEM, and transmission electron microscopy (TEM). SEM and TEM results showed that the average thickness of the MIP layer on the surface of MWCNTs was approximately 25 nm. The new sorbent was used for the separation and preconcentration of erythromycin from chicken muscle prior to its HPLC-UV detection. Tan et al. fabricated MIP-modified membrane-protected MWCNTs as a sorbent system for the separation and preconcentration of triazine at trace level in water and milk samples. In the microextraction application, MWCNTs-MIP prepared was set inside a polypropylene membrane envelope and then was clamped onto a paper clip. For extraction, the prepared membrane was first impregnated with toluene and later immersed in sample solutions. Analytes sorbed on the MWCNTs-MIP were desorbed and analyzed by LC analysis. In the fabrication of this new sorbent, MWCNTs-COOH particles were converted to MWCNTs-CH2 5 CH2 and then prometryn MWCNTs-MIPs were fabricated by the copolymerization of MAA and 3(trimethoxysilyl) propyl methacrylate in the presence of prometryn on the surface of MWCNTs-CH2 5 CH2 [93]. In a different application, Chen et al. modified MWCNTs with MIPs by using 4vinylpyridine and MAA as bifunctional monomers. As in previously described methods, pristine MWCNTs were converted to MWCNTs-COOH by oxidizing acids and then MWCNTs-COCl with thionyl chloride by reflux system at 80 C for 24 h. MWCNTs
CONHCH 5 CH2 was obtained by the reaction of MWCNTs-COCl with acrylamide [94]. In the last step, 200 mg of MWCNTs
CONHCH 5 CH2 was mixed in a solution including 0.1421 g of rhein, 0.1722 g of MAA, 0.2028 g of 4-VP, and DMF for 0.5 h, and then 1.982 g of ethylene glycol dimethacrylate, 30 mg of 2,2-azobisisobutyronitrile, and DMF were added into the first mixture, and the obtained second mixture was purged with nitrogen and left for polymerization at 60 C in a water bath. The prepared MWCNTs-MIP was used as a sorbent for SPE of trace amount of rhein (4,5-dihydroxyanthraquinone2-carboxylic acid). The concentration of rhein in eluent was analyzed with HPLC [94]. Kibechu et al. modified reduced GO with pyrene-imprinted polymer to obtain new GO-MIPs as an SPE material for the separation and preconcentration of PAHs in water samples. After extraction, analyses were carried out by GC
TOF/MS. The new GO-MIP sorbent was produced by a free-radical polymerization of 4vinylpyridine and MAA monomers and ethylene glycol dimethacrylate cross-linker. They analyzed PAHs in water samples with recoveries between 73% and 105.4%. The new sorbent was used at least five times, which performed successfully every time [95]. Sedghi et al. prepared GO@MIP composite by using the GO sheets as polymerization surface, acrylamide and β-cyclodextrin as functional monomers,

Functionalized nanomaterials for sample preparation methods

389

diphenylamine (DPA) as target molecule, N,N-methylene bisacrylamide as crosslinker, and azobisisobutyronitrile as initiator. The new composite was characterized by XRD, FT-IR, thermogravimetric analysis (TGA), SEM, and energy-dispersive spectroscopy (EDS) methods. Host
guest interactions between cyclodextrin-based polymer and diphenylamine by the inclusion complex through the interaction of DPA and β-CD lead to high extraction efficiency. The innovative GO@MIP sorbent provided highly improved imprinting effect, high adsorption capacity, and fast adsorption kinetic [96]. Cheng et al. fabricated a novel GO-MIPs for dispersive SPME of trace amount of bis(2-ethylhexyl) phthalate (DEHP) in environmental water samples prior to its HPLC-UV determination. They used precipitation-polymerization method. In this method, GO, MAA, ethylene dimethacrylate, and DEHP were used as supporting materials, functional monomer, cross-linker, and template molecules, respectively. The developed d-SPME method was applied to analyze DEHP in environmental water samples with good recoveries (82%
92%). EFs of over 100-fold with the LOD of 0.92 ng mL21 were obtained [97]. Liang et al. fabricated a monolithic column consisting carbon quantum dots-doped dummy MIP and used this column system for the extraction and preconcentration of aflatoxin B1 (AFB1) in peanut followed by its HPLC
fluorescence determination. The synthesis procedure was based on the in situ polymerization reaction in the presence of 5,7-dimethoxycoumarin as dummy template molecule. The in situ polymerization reaction was carried out in a water bath [98]. Good recovery results ranging from 79.5% to 91.2% with low intra- and interday RSDs (1.2% and 4.9%) were obtained for the extraction and analysis of AFB1 in peanut. LOD, limit of quantitation, and enhancement factor were found as 0.118, 0.393, and 71 ng mL21, respectively [98].

15.2.1.1.2 Noncovalent functionalization of carbon-based nanomaterials Although the functionalized adsorbents obtained by covalent modification of NPs with a complexing agent or organic group offer significant use advantages, the production of these materials is difficult. Hence, noncovalent modification of NPs with different functional groups, such as complexing agent-organic groups [TAR, poly (diallylmethylammoniumchloride) Aliquat 336, tartrazine, di-(2-ethylhexyl) phosphoric acid, tannic acid, tri-octyl phosphine oxide, 5-(4-dimethylamino-benzylidene)-rhodanine, etc.]; biomolecules (carbohydrates, proteins, enzymes, and DNA); polymers [polyaniline (PANI), polypyrrole, poly(3,4-dioxythiophene), polydiphenylamine, polyethyleneimine, polyvinylalcohol, poly(2-aminothiophenol), etc.]; surfactants; ionic liquids (ILs) (butylmethylimidazoliumhexafluorophosphate [BMIm] [PF6], hexylmethylimidazolium hexafluorophosphate [HMIm][PF6], etc.); and biological materials (bacteria, like biochar), is a good choice [99
102]. The executive forces in noncovalent modification are the hydrophobic, van der Waals, and/or electrostatic interactions classified as physical adsorption. These physical modification methods generally are simpler, effective, cheap, and ecofriendly than covalent modification methods to obtain desired extraction sorbents.

390

Handbook of Nanomaterials in Analytical Chemistry

When reviewing literature studies, it is observed that impregnation functionalization of NMs with complexing agent-organic groups is used frequently in the extraction of heavy metals and radioactive species since especially impregnation of complexing agents or organic compounds on the surface of NMs provide high selectivity and high adsorption capacity toward metal and radioactive species due to functional groups having O, S, N, etc. atoms [99
102]. ALOthman et al. impregnated MWCNTs with TAR to obtain selective sorbent toward Ni(II), Pb(II), Cd(II), and Zn(II) ions. In this modification procedure, 0.2 g of MWCNTs was added in 0.5% of TAR solution (25 mL), and the obtained mixture was stirred for 12 h. TAR-impregnated MWCNTs were filtered, washed, and dried prior to use. They filled the new sorbent in the glass column system for SPE of metal ions at trace level. The metal ions, which retained on the TARimpregnated MWCNTs at pH 7.0, were eluted with 3 mol L21 acetic acid and analyzed FAAS detection system. The developed SPE method was applied to analyze trace amounts of heavy metal ions in food samples [99]. Habila et al. fabricated 1-nitroso-2-naphthol-impregnated MWCNTs as SPE sorbent for the separation and preconcentration of lead(II) and copper(II) ions prior to their FAAS determinations. The developed SPE method was applied to different food and water samples [100]. Gouda et al. used MWCNT impregnated with 2-(2-benzothiazolylazo)orcinol (BTAO) as SPE sorbent for the extraction and preconcentration of trace levels of Zn(II) Cu(II), Pb(II), Ni(II), and Cd(II) ions. In general impregnation procedure, 200 mg of MWCNTs was mixed with 1.0 3 1023 mol L21 of BTAO solution for 12 h. The obtained sorbent was filled into 150 mm 3 10 mm glass column for the extraction of heavy metal ions. The metal ions at trace levels were sorbed on the MWCNTs-BTAO material at pH 7.0 and eluted with 5.0 mL of 2.0 mol L21 HNO3. The preconcentration factor was found as 100. The LODs were found in range of 0.7
2.2 μg L21 [101]. Soylak and Topal used MWCNTs impregnated with tartrazine for SPE of trace amounts of Cd(II) and Pb(II) ions, followed by their FAAS determination. The suggested SPE-FAAS procedure provided LODs of 6.6 and 0.8 mg L21, respectively, for Pb(II) and Cd(II) and preconcentration factor of 40 [102]. Noncovalent modification of NMs with polymers consists of two steps: (1) physical mixing of NMs in solution and (2) in situ polymerization of monomers in the presence of NMs or surfactant-assisted formation of polymers on the surface of NMs [103
110]. Sahmetlioglu et al. modified MWCNTs with polypyrrole and used the obtained composite material for SPE of Pb(II) ions in water samples. In the synthesis procedure an acidic mixture consists of 0.25 g of MWCNTs and 250 μL of pyrrole monomer was stirred for 30 min at 0 C in ice bath. Then, stoichiometric amount of acidic ammonium persulfate solution was added into the mixture drop by drop and stirred for 5 h. At this stage, black polypyrrole particles were formed on the surface of MWCNTs. The obtained polypyrrole
MWCNT composite was washed, dried, and filled into a glass column [103].

Functionalized nanomaterials for sample preparation methods

391

Chen et al. modified MWCNTs with branched cationic polyethyleneimine (BPEI) to obtain an inorganic
organic hybrid material. They converted MWCNTs into MWCNTs-COOH by oxidizing them in a sulfuric acid/nitric acid mixture (3:1, v/v). Modification of MWCNTs-COOH with BPEI was based on the electrostatic attraction between the carboxyl groups on the oxidized MWCNT surface and the positively charged protonated amines in the polymer. The prepared material was filled in a minicolumn for online SPE of As(V) at trace level at pH 5.8. The column system was combined to hydride generation atomic fluorescence spectrometry. The developed method was applied to water samples [104]. Nabid et al. used MWCNTs-poly(2-amino thiophenol) nanocomposites as sorbent for SPE of trace levels of Cd(II) and Pb(II) ions in some environmental samples. The N and S atoms in conducting polymer share electron pairs with metal ions, which lead to the adsorption of metal ions on the macromolecular chains. In the fabrication of poly(2-amino thiophenol) on the surface of MWCNTs, 0.5 g of MWCNTs and 1.15 mmol of 2-aminothiophenol were stirred at 5 C in ice bath. Then, stoichiometric amount of acidic ammonium persulfate solution was added into the mixture drop by drop and stirred for 5 h. At this stage, poly(2-amino thiophenol) was formed on the surface of MWCNTs. The obtained nanocomposites were washed and dried in a vacuum oven at 60 C for 24 h [105]. Zhang et al. used in situ electrochemical polymerization method to fabricate a novel sulfonated graphene/polypyrrole (SG/PPy) SPME coating on a stainless steel wire. The optimum parameters for sorbent fabrication process were SG doping amount of 1.5 mg mL21 and polymerization time of 15 min. The SG/PPy coating used at least 200 replicate extractions with excellent mechanical durability and thermal stability. Moreover, the new material showed higher extraction capacity and selectivity to volatile terpenes than commonly used commercial materials. SG/PPy coating was practically used to analyze the volatile compounds from fennel and star anise samples [106]. Han et al. prepared an SPME-coating material by using polysilicon fullerene. The new material was used for the extraction and preconcentration of aromatic compounds at trace level. The obtained results showed that the new polysilicon fullerene was more selective, sensitive, and efficient than nonpolar PDMS commercial availably. Further, the lifetime, reproducibility, and thermal stability of polysilicon fullerene coat are better than the PDMS commercial availably [107]. Zhang et al. prepared poly(3-methylthiophene carbazole)/GO composite on a stainless steel wire by using electrochemical synthesis procedure. The new device was utilized as headspace SPME device for the separation and preconcentration of dodecanol, nonanal, undecanol, decanal, and octanal. After extraction stage, the concentration of analytes was measured by GC. The SPME fiber was denoted as P (3MeT-Cz)/GO fiber and it has a coating thickness of about 55 μm [108]. Another possible application of electrochemical deposition method was searched by Behzadi et al. They prepared poly(o-anisidine)/GO nanosheets on a steel wire as headspace SPME device. The new device was used for the separation and preconcentration of trace levels of xylenes, toluene, benzene, and ethylbenzene prior to their GC detections [109].

392

Handbook of Nanomaterials in Analytical Chemistry

Kojidi et al. prepared poly(2,6-diaminopyridine)-modified GO composite materials by a simple in situ polymerization of 2,6-diaminopyridine monomer in a mixture of GO particles. In that synthesis method, 120 mg of GO was dispersed in a solution, including water and ethanol solution. Then, 1036 mg of 2,6-diaminopyridine was added into the mixture of GO and the polymerization started with the rapid addition of ammonium persulfate. The mixture was obtained at 0 C for 24 h. The obtained black precipitate was washed with different solutions, dried, and filled in a glass column for SPE of cadmium(II) traces. The new material was characterized by FT-IR, XRD, and SEM methods. The concentration of cadmium in last phases was measured by FAAS [110]. The introduction of new green extraction solvents, such as surfactants, ILs, deep eutectic solvents (DESs), switchable solvents, and bioderived solvents in the liquid phase
based analytical sample preparation methods was remarkable. These solvents were used as effective and selective extraction ones in thousands of liquid phase
based separation and preconcentration methods, such as liquid
liquid extraction, single drop microextraction, dispersive liquid
liquid microextraction, and solidified organic drop microextraction. Once the scientists realized that these solvents showed a high selectivity to different analytes, the idea of using these solvents in combination with solid-phase sorbents leads to new ideas and practices in the SPE/SPME fields [111
114]. For instance, the covalent or noncovalent modification of NMs with surfactants, ILs, DESs, and bioderived solvents leads to the enhancement of the extraction procedure and fulfills the principles of green analytical chemistry [112
115]. Perhaps the most important and desired benefits of their use as functionalizing agents in the modification of different nano-sized sorbents are low toxicity and biodegradability. Furthermore, they can be used as green extraction mediums for the separation and preconcentration of trace organic, inorganic, and bioactive species [111
119]. ILs are synthesized by combining asymmetric organic cations with different types of organic or inorganic anions. The common organic cations used are ammonium, pyridinium, pyrrolidinium, and imidazolium, whereas organic or inorganic anions are chloride, bromide, hexafluorophosphate, and tetrafluoroborate. As ILs provided low vapor pressure, wide viscosity range, and high thermal stability to users, those are preferred in sample preparation, chromatography, and electrochemistry applications instead of using toxic organic solvents. ILs show high affinity to some inorganic, organic, and bioactive species due to the presence of dipole
dipole, electrostatic interactions, and hydrogen bonding along with the alkyl groups of cations in them. Hence, the modification of NMs with ILs provided high adsorption capacity, improved selectivity, and high interactive characteristics toward analytes. NMs modified with ILs can be used in different sorptive-based extraction procedures (e.g., SPE, μSPE, SPME, d-SPE, and DμSPE) [111
119]. Combination uses of ILs with solid-phase sorbents were reported for the first time in 2005. In this study, SPME fiber was coated with disposable ILs before taking the extraction step. 1-Octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) IL was used for the modification of PDMS. The prepared fiber

Functionalized nanomaterials for sample preparation methods

393

was used for an SPME of headspace of benzene, ethylbenzene, xylenes, and toluene in paint samples [112]. Li et al. prepared a headspace SPME device that consists of MWCNTs-COOH, IL (i.e., 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate), reduced graphene oxide (rGO), PANI, and stainless steel wires. The synthesis procedure includes two steps: (1) formation of 3D porous materials (MWCNTs-rGO-IL) by one-step selfassembly process and (2) coelectrodeposition of MWCNTs-rGO-IL with PANI on stainless steel wires by cyclic voltammetry. The new material was characterized and used for the headspace SPME of octanol, nonanol, geraniol, decanol, undecanol, and dodecanol prior to performing GC analysis [113]. Zhang et al. prepared a 3D IL-ferrite functionalized GO nanocomposite (3D-ILFe3O4-GO) as a sorbent in pipette-tip SPE (PT-SPE) of 16 PAHs in human blood samples. Analyses were carried out by GC
MS detections. When compared with conventional SPE applications, the PT-SPE method provided important applicable advantages, such as use of low volume of solvent (1.0 mL) and blood sample (0.2 mL) and usability for many times (at least 10 times). Analytes in the blood samples can be analyzed with the developed method between good recoveries (85.0%
115%). The LOQs were found in the range of 0.007
0.013 μg L21 [114]. In a different application, IL-functionalized graphene was fabricated for PT-SPE of auxins in soybean sprouts. In this procedure, thiolene click chemistry was used for the functional modification of pentafluorobenzyl imidazolium bromide IL with graphene. The modification of graphene with ILs leads to an aggregation prevention of graphene as well as improvements in the interaction between graphene and analytes by hydrogen bonding, π
π interactions, electrostatic interactions, and ionic exchange [115]. Hamidi et al. synthesized an IL-functionalized magnetic GO/polypyrrole composite for mixed hemimicelles dispersive micro-SPE of methotrexate from urine samples prior to its spectrophotometric determination [116]. 1-Hexadecyl-3methylimidazolium bromide (C16mimBr) was used as IL. The authors modeled interactions between methotrexate and sorbent by molecular docking, and the interaction energy was found as 28.35 kcal mol21 [116]. Zhang et al. fabricated a new 3D IL-functionalized magnetic GO nanocomposite (3D-IL@mGO), characterized by SEM, vibrating sample magnetometer, and XPS methods and applied for the magnetic d-SPE (MSPE) of 16 PAHs in vegetable oil followed by the GC
MS analysis [117]. The new material was synthesized in two steps: Step 1: the synthesis of IL@mGO was carried out by solvothermal reaction under N2 gas, 1.0 g NaOH, 2.5 g FeCl3  6H2O, and 7.5 g NaAc were mixed in 100 mL EG at 50 C until the transparent solution was obtained. Then 50 mg 1-(3aminopropyl)-3-methylimidazolium bromide and 50 mg of GO were combined and stirred vigorously at 80 C for 1 h prior to solvothermal reaction. The resulting IL@mGO was washed for several times and dried. Step 2: the synthesis of 3DIL@mGO was carried out by free-radical copolymerization; 100 mg of IL@mGO, 0.0143 mol of divinylbenzene, and 0.020 mol of maleic anhydride were dissolved in tetrahydrofuran under the inert gas. Then, 1.0 g of benzoyl peroxide was mixed with the obtained solution at 80 C and refluxed under inert atmosphere for 2 h.

394

Handbook of Nanomaterials in Analytical Chemistry

The obtained 3D-IL@mGO material was washed, dried, and used in the MSPE application. Wu et al. used IL-coated magnetic GO NPs as a mixed hemimicelles SPE material for cephalosporins in biological samples followed by HPLC analysis [118]. The synthesis procedure consisted of two main steps: the synthesis of GO from graphite by the modified Hummers method and the synthesis of magnetic GO NPs (Fe3O4/ GO NPs) by solvothermal reaction. In general, DESs are prepared by mixing two or more components to obtain a new liquid, which has a lower melting point than each individual component. The main driving force in the formation of these solvents is the hydrogen bond between the constituent components. DESs were discovered by Abbot et al. in 2003 when they searched the solvent features of the eutectic mixtures of different types of ammonium salts and urea [119,120]. Although many DES can be produced by self-association of hydrogen bond donors (HBDs) and acceptors, the most preferred DESs are prepared by the combination of choline chloride (ChCl) with carboxylic acids (e.g., citric, succinic, and oxalic acids), urea, and glycerol as HBDs. Furthermore, DESs can be prepared by natural, available, and cheap components, such as alcohols, sugars, amino acids, and organic acids. These DESs are called natural deep eutectic solvents (NADESs). In general, DESs and NADESs have been used as extraction solvents in the liquid phase
based extraction methods due to their green properties, adjustable viscosity, and high selectivity characteristics toward analytes. At the same time, the preparation and use of SPE systems in desired properties as a result of modification of different sorbents with DESs and NADESs have attracted considerable attention of scientists [119
122]. Liu et al. modified graphene with a DES, which was prepared from choline chloride and ethylene glycol. In the modification procedure, 200 mg of GO was added in the solution, including 200 mL of water, 140 mg of ChCl, and 120 mg of EG, and the obtained mixture was stirred and refluxed at 80 C for 12 h. In the last step, 2 g of hydrazine hydrate was added, and this mixture was stirred at 80 for 24 h. The new sorbent was used for the PT-SPE of sulfamerazine traces prior to performing HPLC analysis. Sulfamerazine in water samples was extracted and analyzed with low LOD (10 mg L21) and high extraction efficiencies (91.01%
96.82%) [120]. Different applications of DES with sorbents were reported by Wang et al. in 2016. They fabricated GO-DES@silica by using DESs and GO-IL@silica by using ILs. In the synthesis procedure, GO was modified by DESs or ILs to obtain GODES and GO-IL, and then the prepared materials were connected to surface of silica by a covalent bonding between COOH groups of GO and amino group of silica. Subsequent reactions of these materials with hydrazine solution lead to the formation of G-DES@silica and G-IL@silica materials. The obtained final products (GDES@silica and G-IL@silica) were used for the separation and preconcentration of CPs in water samples prior to HPLC-UV determinations. The results showed that GDES1@silica (ChCl:formic acid, 1:2), GO-DES4@silica (ChCl:urea, 1:2),

Functionalized nanomaterials for sample preparation methods

395

G-IL3@silica ([HMIM][Tf2N]), and GO-IL4@silica ([EMIM][Br]) have a better extraction performance than that of other sorbents for the extraction of CPs [121]. Yousefi et al. produced DES magnetic bucky gels by modifying magnetic MWCNTs with DES (choline chloride/urea). Modification of magnetic MWCNTs with DES was based on the noncovalent interactions. The new DES magnetic bucky gels were used as sorbents in d-SPE of OCPs in water samples with EFs between 270 and 340 [122]. Functionalization of NMs with living or died bacteria, such as Escherichia coli, Pseudomonas aeruginosa, Geobacillus toebii, Geobacillus thermoleovorans, Bacillus sp., Pleurotus eryngii, and Bacillus altitudinis, plays an important role in the sample preparation methods. These sorption-based methods are called “biosorption” in the literature [123
125]. Aydemir et al. modified MWCNTs with died E. coli bacteria to prepare a biosorbent for the SPE cobalt, copper, nickel, and cadmium at trace level followed by FAAS analysis. In order to immobilize nonliving E. coli on the MWCNTs, the same amount of nonliving E. coli and MWCNTs was mixed together in water at 200 rpm for 2 h. After immobilization, E. coli
MWCNTs was separated from aqueous phase, dried, stabilized in a vacuum oven at about 80 C
105 C for 24 h and ground. The new sorbent has high adsorption affinity metal ions at a pH value of 7. The retained ions on the E. coli
MWCNTs were eluted by using 0.5 M nitric acid [123]. Tuzen et al. prepared P. aeruginosa immobilized MWCNTs as biosorbent for the separation and preconcentration of nickel(II), cadmium(II), lead(II), chromium (III), manganese(II), and cobalt(II) ions at trace levels. They used mixing technique, on the basis of the physical immobilization, to obtain biosorbent [124]. Ozdemir et al. prepared B. altitudinis
immobilized ND as SPE sorbent for the separation and preconcentration of Pb21, Co21, Cr61, and Hg21 ions. In the preparation method of B. altitudinis
immobilized ND, 3 mL distilled water and 300 mg of dried and autoclaved B. altitudinis were shaken in a 250 mL glass bottle for 8 h, then, 300 mg of ND was added into the bacteria mixture and thoroughly mixed. The obtained biosorbent was filled into a column for SPE applications. After extraction, concentrations of analytes in eluent were measured by ICP-OES [125].

15.2.2 Metallic and metal-oxide nanomaterials Metallic and metal-oxide NPs belong to inorganic-based NM class formed by combining one, two, or three metals and/or their oxides. Metal and metal-oxide NPs are frequently used in sample preparation methods, chromatographic separation methods, spectroscopic analysis techniques, and sensor technologies due to their availability by simple and cheap preparations, their easy modification abilities with organic and inorganic-based materials, their effective mechanical, chemical, electrical, and catalytic properties, having a large surface area and high adsorption capacities. As the most used metallic NPs in analytical applications are Ag, Au, Pd, Pt, Cu, Ni, Fe, Co, and Mn, the usually preferred metallic NPs are Fe3O4, Al2O3, TiO2, MnO, ZrO2, CeO2, and ZnO [126
130].

396

Handbook of Nanomaterials in Analytical Chemistry

The first stage of immobilization of preproduced metal NPs (MNPs) and metaloxide NPs is the chemical modification of the substrate surfaces. The second stage is the immobilization of preproduced MNPs and metal-oxide NPs by electrostatic interactions or weaker physical interactions with unmodified surfaces. Many methods have been introduced to directly fabricate MNPs and metal-oxide NPs on surfaces in one step [e.g., hydrothermal growth, potentiostatic anodization, electroless and electrochemical deposition, liquid-phase deposition (LPD), and in situ chemical oxidation] [131
134].

15.2.2.1 Functionalization of the metallic and metal-oxide nanomaterials 15.2.2.1.1 Chemical functionalization of the surface of the metallic and metaloxide nanomaterials Immobilization of MNPs and metal-oxide NPs on a substrate is started with the chemical modification of the substrate by three different processes: (1) silanization, (2) sol
gel, and (3) usage of bifunctional compounds. 15.2.2.1.1.1 Silanization The modification of surfaces of materials with thiolterminated and amine-terminated silane groups is one of the most used procedures for immobilizing MNPs and metal-oxide NPs. In the silanization reactions, a surface is covered by silanol groups and then hydrolysis of alkoxy groups with the liberation of silanol groups and the release of alcohols, and producing siloxane linkages on the surface by the release of water molecules, which leads to the formation of covalent bonds between the surface and silanol groups [126]. Silane groups, such as 3-methacryloxypropyltrimethoxysilane APTES, (3-chloropropyl)-trimethoxysilane, TMSPDETA, and TMSPEDA, are frequently used as coupling agents for covalent modification of NMs. Required MNPs and metaloxide NPs are covalently attached to NMs via these silane groups. 15.2.2.1.1.2 Sol
gel method The sol
gel method is considered effective to modify the surface of substrates. Obtaining of a high surface area and stable surfaces is the most important advantage of the sol
gel method. The chemical and physical properties of the materials obtained by the sol
gel method are related to the experimental conditions applied. The sol
gel method involves two main reactions: (1) hydrolysis of the precursor in the acidic or basic mediums and (2) polycondensation of the hydrolyzed products. In this way a polymeric network is formed in which MNPs can be retained [126]. 15.2.2.1.1.3 Bifunctional compounds Bifunctional compounds are molecular linker agents and frequently used for the immobilization of MNPs on a surface. The natures of both the MNP and the solid substrate are important to accomplish effective chemical modification by using bifunctional compounds. For example, MNPs can be immobilized on a surface, and thiol functionalization with alkanedithiols is applied to immobilize MNPs on inorganic and organic substrates [135].

Functionalized nanomaterials for sample preparation methods

397

15.2.2.1.2 Functionalization of the surface of the metallic and metal-oxide nanomaterials via interactions Immobilization of MNPs with electrostatic interactions is based on the attractive electrostatic interactions of charged surfaces with opposite-charged MNPs, and these methods play an important role in the analytical applications [127
130]. As an example application, polymeric monoliths functionalized with quaternary ammonium groups are the good substrates for the attachment of the citrate-capped iron-oxide NPs [127]. In these methods, high molecular weight polycations and polyanions are used as electrostatic interaction agents between surface and MNPs. This immobilization method is generally called “layer-by-layer deposition,” while poly(allylamine hydrochloride), as polycation, is commonly used for the immobilization of negative-charged MNPs, such as citrate-capped gold nanospheres [128], citrate-stabilized AgNPs [129], and poly(styrene sulfonate) as polyanion is usually used for immobilization of positive-charged MNPs, such as cetyl trimethylammonium bromide-capped gold nanorods [130]. Weaker physical interactions, such as van der Waals forces, can become executive force to immobilize MNPs and metal-oxide NPs on different substrates utilized for analytical applications. For example, metal-oxide NPs can be immobilized on the carbon-based electrodes by immersing the substrate in the colloidal solution of MNPs for a certain time [131]. Although physical interaction-based immobilization methods are frequently used, the stability and the durability of the obtained materials are important because of the weak interactions between MNPs and metal-oxide NPs and the solid substrate.

15.2.2.1.3 Functionalization of the surface of the metallic and metal-oxide nanomaterials via in situ chemical oxidation In situ chemical oxidation of metallic substrates is used to obtain nanostructured surfaces for different analytical applications. When compared with other immobilization procedures, this method provides high stability and durability. In an example application, TiO2 NPs can be obtained on the surface of metals by the oxidization of Ti wires at ,100 C with hydrogen peroxide [132].

15.2.2.1.4 Functionalization of the surface of the metallic and metal-oxide nanomaterials via solvothermal synthesis The solvothermal synthesis method can be explained as follows: reaction of components in water or a in different solution medium at high temperature and high pressure. When reactions are carried out in water, the method is called “hydrothermal.” Most of the MNPs and metal-oxide NPs, such as Ag, Au, Pd, Pt, ZnO, Fe3O4, MnO, CuO, Mn3O4, and NiCo2O4, can be produced simply by the solvothermal synthesis method [126,133,134].

15.2.2.1.5 Functionalization of the surface of the metallic and metal-oxide nanomaterials via liquid-phase deposition LPD can be used for the fabrication of a thin layer of metal-oxide NP films, such as TiO2, ZnO, ZrO2, Cr2O3, CoO, In2O3, MnO, NiO, and CuO. Mainly the LPD

398

Handbook of Nanomaterials in Analytical Chemistry

method is based on the hydrolysis reaction of metal-fluoro complex ions and then the precipitation of metal-oxide NPs by an addition of H3BO3 or metallic Al [136
138].

15.2.2.1.6 Functionalization of the surface of the metallic and metal-oxide nanomaterials via electroless and electrochemical deposition Reductions of metal ions to MNPs by using a reducing agent (electroless) or by applying an external current (electrochemical deposition) are another simple way to form MNPs at the surface of a substrate. In the electrochemical deposition method, substrates behave as cathodes, and the reduction of metal ions is carried out on the surface of the substrate. Both electrochemical deposition and electroless methods are binder-free immobilization techniques, because any linker agent is not used. The desired chemical composition, the size, and the composition of MNPs can be provided by changing experimental conditions [139
141].

15.2.2.1.7 Functionalization of the surface of the metallic and metal-oxide nanomaterials via potentiostatic anodization Potentiostatic anodization is another method to fabricate metal-oxide NPs on solid substrates. In this system, metallic substrates behave as electrode for the growth of metal-oxide NPs on them. In this system an anodic voltage was applied to the metals in the fluoride-containing nonaqueous electrolyte medium to obtain metaloxide NPs or surface-oxide films. An example of synthesis is explained on the formation of TiO2 nanotubes on a Ti substrate [126]. The obtaining of pores on the metallic surface is the first stage of synthesis, which is performed for the formation of a water-soluble hexafluorotitanate(IV) complex [TiF6]22. In the second stage, [TiF6]22 is converted to Ti(OH)4 by instantaneous hydrolysis reaction in the pores of metals. In the final step, electrochemical anodization is applied for the formation of metal-oxide NPs at the surface of the metallic substrate. These methods can also be applicable for the fabrication of different valve metals, such as zirconium, tantalum, hafnium, niobium, and tungsten [126]. For analytical applications, including detection and sample preparation, MNPs and metal-oxide NPs can be modified with different materials, such as carbonbased NMs (SWCNTs, DWCNTs, MWCNTs, fullerenes, nanodimonds, graphene, GO, and C-nanofiber), polymers, silicon-based substrates, and metallic surfaces. A considerable number of metal, metal-oxide NPs, and their functionalized forms are frequently preferred for sample preparation methods, such as SPE, SPME, and liquid-phase microextraction due to their simple functionalization capabilities with different materials (polymers, carbon-based NMs, nanofibers, and so on), high surface areas, high adsorption capacities, and high chemical and mechanical stability [142
146]. Jiang et al. synthesized gold NP-modified reduced GO as a sorbent for SPE of ochratoxin A, AFB1, aflatoxin M1, zearalanone, zearalenone, α-zearalanol, β-zearalanol, α-zearalenol, and β-zearalenol in a milk sample prior to their ultrahigh performance liquid chromatography (UHPLC)
MS/MS analysis. Au NPs were obtained by a chemical reduction of Au31 ions in the presence of ascorbic

Functionalized nanomaterials for sample preparation methods

399

acid and sodium citrate. The developed SPE-UHPLC
MS/MS procedure allows the LOQ between 0.02 and 0.18 ng mL21, acceptable recoveries between 70.2 and 111.2 with RSD, in the range of 2.0%
14.9% [142]. Trujillo-Rodrı´guez and Anderson modified SPME fibers with silver-based polymeric IL sorbents to obtain a new SPME device. In the first step of synthesis procedure, IL monomers were formed by cations, including the Ag1 coordinated with two 1-vinylimidazole ligands. In the second step, polymeric IL sorbents were obtained on the commercial fibers by free-radical polymerization in the presence of either silver bis[(trifluoromethyl)sulfonyl]imide and/or a dicationic IL cross-linker. They prepared seven different types of SPME devices by using different combinations of ILs, cross-linkers, and their different mole ratios. The new SPME devices were used to separate and preconcentrate unsaturated compounds prior to performing the GC
FID analysis [143]. Yazdi et al. fabricated polypyrrole-silver nanocomposite for the separation and preconcentration of trace amounts of parabens in water and beverage samples by hollow fiber SPME. After performing the extraction step, analyses were carried out by HPLC-UV. First, polypropylene hollow fibers were modified with polypyrrole by a polymerization reaction in the presence of FeCl3. The prepared polypyrrolemodified hollow fibers were immersed in a solution of AgNPs, which was prepared by the modified Tollens procedure. LOD, LOQ, and linear range values for analytes were 0.01, 0.05, and 0.05
200 μg L21, respectively [144]. Yang et al. coated SPME fibers with nanoscale graphitic carbon nitride/copper oxide hybrid material (nano-g-C3N4/CuO) for the separation and preconcentration of pyrene, naphthalene, acenaphthene, anthracene, phenanthrene, and fluorene PAHs, followed by their GC analysis. The prepared new SPME device provided a better adsorption performance than each of the pristine nanoscale graphitic carbon nitride (nano-g-C3N4) or copper oxide (CuO). LODs lying in the range of 0.025
0.40 ng mL21, RSDs from 2.5% to 7.3%, lying in the linear range from 0.1 to 1000 ng mL21, were obtained with this new extraction system [145]. Ghani et al. constructed highly porous copper foam fibers on the surface of an unbreakable copper wire to obtain a new sorbent for the extraction and preconcentration of trace levels of xylene, toluene, benzene, and ethylbenzene in waters prior to their GC
FID analysis. A simple and rapid electrochemical method was used to fabricate the highly porous copper foam on the surface of copper wire. Under optimum conditions, LODs in the range of 0.12
0.41 μg L21, RSDs from 6.9% to 9.6%, in the linear range from 1 to 500 μg L21, and recoveries more than 88% were obtained by using this new extraction and analysis combination [146]. Yazdi et al. used MWCNT-zirconium oxide nanocomposite materials (MWCNTs-ZrO2) as coating materials for hollow fiber SPME of polyaromatic hydrocarbons before HPLC-UV determinations. Modification of polypropylene hollow fibers included the following steps: (1) conversion of Zr(OH)4 to ZrO2 NPs on the MWCNTs via a heating process to obtain MWCNTs-ZrO2 nanocomposite and (2) modification of polypropylene hollow fibers with the as-prepared MWCNTsZrO2 nanocomposite by sonication method [147].

400

Handbook of Nanomaterials in Analytical Chemistry

15.2.3 Magnetic nanomaterials In the last two decades, magnetic SPE methods using magnetic adsorbents have become one of the most commonly used methods for the separation and enrichment of organic, inorganic, and bioactive species at the matrix level. In 1973 Robinson ˇ r´ıkova´ and Safaˇ ˇ r´ık used et al. suggested the first magnetic separation [148]. But Safaˇ magnetic SPE term as an analytical application in 1999 [149]. They prepared a magnetic charcoal sorbent for magnetic SPE of safranin O and crystal violet in water samples [149]. About 460-fold preconcentration factor was obtained for analytes. The MSPE method is based on the adsorption and desorption of analytes on magnetic adsorbents that are added to the sample solution containing the analytes. In this method, different types of polymers, NMs, metals, and metal oxides that can be used as adsorbents are modified by magnetic particles, such as nano-sized Fe3O4, γ-Fe2O3, ZnFe2O4, and ZnFe2O4. In this way, adsorbents that do not show magnetic properties are given magnetic properties [150,151]. Magnetic NPs, such as Fe3O4 and γ-Fe2O3, have low stability in a solution medium, especially under acidic conditions, which cause the decomposition of materials in a short time and loss of their magnetic properties. To prevent this drawback, the materials obtained are modified by silica, alumina oxides, or different groups that are resistant to harsh working conditions [29,152]. The selection of the suitable sorbent-used MSPE is the most important step to be taken in this method, which affects the extraction efficiency as in other methods. Some of the most used new-generation SPME sorbents in MSPE applications are as follows [153
159]: 1. carbon NPs (CNTs, fullerenes, ND, graphene, GO, carbon dots, and modified carbon NPs); 2. metal oxides (SiO2, Al2O3, TiO2, etc.); 3. polymers (cyclodextrine, polypyrrole, polyaniline, gelatin, chitosan, polydivinylbenzeneco-methacrylic acid, etc.); 4. metal
organic frameworks; 5. MIPs; 6. mesoporous and nanoporous silicates; and 7. graphene-like materials (MoS2, MoSe2, WS2, C3N4, etc.).

The SPME is used to separate and preconcentrate a wide range of trace analytes in different matrix mediums, including the following [159
163]: 1. food, drug, and biological sample analysis; extraction and preconcentration of metals, dyes, pesticides, pharmaceutical active ingredients, etc.; 2. biomedicine; isolation, extraction, and preconcentration of different bioactive species, such as DNA, RNA, enzymes, proteins, peptides, and cells; 3. environmental analysis; extraction and preconcentration of metals, dyes, pesticides, pharmaceutical active ingredients, surfactants, PAHs, mutagenic, and carcinogenic analytes in water and sewage samples; and 4. earth and mineral science; extraction and preconcentration of valuable metals and radioactive species.

Functionalized nanomaterials for sample preparation methods

401

Some MSPE applications in the literature for the separation and preconcentration of trace organic and inorganic analytes are summarized in the following. ˇ r´ıkova´ and Safaˇ ˇ r´ık tested the applicability of magnetic SPE proceIn 2002 Safaˇ dure for high volumes of urine samples. For this purpose, they fabricated a reactive copper phthalocyanine dye immobilized magnetite particles for the separation and preconcentration of crystal violet dye as a model analyte in high volumes of urine samples as crystal violet leads to an increased risk of cancer for living cells [164]. In 2005 the same research group used the MSPE method to separate and preconcentrate nonionic surfactants based on aliphatic alcohols, hydrogenated fatty acid methyl esters, and oxyethylated nonylphenol in water samples [165]. Huang and Hu fabricated, characterized, and used γ-mercaptopropyltrimethoxysilane-modified silica-coated magnetic NPs (SCMNPs) as an innovative SPME sorbent for the separation and preconcentration of Pb, Hg, Cu, and Cd at trace levels in environmental and biological samples. In this method, 50 mg of magnetic sorbent was added in the sample solution, including metal ions (pH 6.0), and the obtained mixture was ultrasonicated for 10 min to ensure the adsorption of analytes on the magnetic sorbent. Then the sorbent was isolated from the sample solution phase by applying external magnetic field, and analytes on the sorbent were eluted with 1.0 mol L21 HCl and 2% (m/v) thiourea elution solution by using ultrasonication power. Analyte concentrations in the eluent phase were measured by ICP-MS. The LODs for analytes were between 24 and 56 pg L21 [166]. Suleiman et al. used bismuthiol-II-immobilized SCMNPs for the separation and preconcentration of trace amounts of Pb, Cu, and Cr in lake and river water samples. Analytes in the aqueous phase were extracted to 100 mg of magnetic nanosorbent phase at pH 7.0 by using an ultrasonic irritation source. A 1.0 mol L21 HNO3 solution was used to desorb analytes from the sorbent. Concentrations of analytes were measured by ICP-OES [167]. An important application of the magnetic sorbents (as on-chip online SPE) was reported by Li et al. in 2009. The authors fabricated a PDMS/glass hybrid microchip for online SPE and electrophoresis separation of the trace amount of fluorescence isothiocyanate-labeled phenylalanine. The extraction phase was prepared by the modification of the magnetic microspheres with hydroxyl-terminated PDMS (PDMS-OH). The extraction phase conveniently immobilized into the SPE channel by magnetic field. In this system, injection of the sample solution into the SPE channel (PDMS-OH microspheres bed) and desorption of analyte from the sorbent phase into the electrophoresis channel were electrically driven [168]. Cheng et al. used 1-hexadecyl-3methylimidazolium bromide (C16mimBr)-coated Fe3O4 magnetic NPs as an magnetic adsorbent for the mixed hemimicelles SPE of trace amounts of 2,4-dichlorophenol and 2,4,6-trichlorophenol compounds in environmental waters followed by HPLC-UV analysis. The new nano-sized sorbent provided a high surface area that leads to high adsorption capacity and high extraction efficiencies (74%
90%) at a minimum level of sorbent (40 mg) [169]. Jiang et al. used zincon-immobilized silica-coated magnetic Fe3O4 NPs for the magnetic SPE of trace amounts of lead in water samples prior to the determination by using a graphite furnace atomic absorption spectrometer. The detection limit

402

Handbook of Nanomaterials in Analytical Chemistry

(LOD), EF, and recovery results of the proposed method were found as 10 ng L21, 200, and 84%
104%, respectively [170]. Cui et al. prepared chitosan-modified magnetic NPs by an emulsion method for the magnetic separation and preconcentration of Cr(III) and Cr(VI) in lake and tap water samples prior to ICP-OES detection. The LOD, PF, and RSD% for Cr(III) and Cr(total) were found as 100, 0.02, and 0.03 ng mL21 and 4.8% and 5.6%, respectively [171]. Wang et al. used a hydrothermal reaction procedure to synthesize a Fe3O4-functionalized metal
organic framework (m-MOF) composite as an MSPE sorbent. They synthesized the metal
organic framework from Zn(II) and 2aminoterephthalic acid. X-ray diffraction, FT-IR, TGA, SEM, and magnetization methods were used for the characterization of m-MOF composites. The new magnetic sorbent was used for the separation and preconcentration of trace amounts of copper followed by ETAAS detection [172]. Azodi-Deilami used magnetic MIP (m-MIP) NPs as a magnetic SPE sorbent for tracing the amount of paracetamol in human blood plasma samples. In the synthesis of the m-MIPs, magnetite (Fe3O4) as the magnetic component, 2-(methacrylamido) ethyl methacrylate as a cross-linker, and MAA as a functional monomer were used. The m-MIPs synthesized were characterized by TEM, FT-IR, XRD, and vibrating sample magnetometry methods. Analysis of paracetamol in the last phase was measured by HPLC. The LOD, LOQ, PF, and RSD% recoveries for paracetamol were 0.17 μg L21, 0.4 μg L21, 40, and 4.5%, respectively [173].

15.3

Conclusion

From the detailed studies mentioned earlier, it is obvious that nanotechnology is a field that has been constantly renewed and developed rapidly. One of the most important scientific disciplines that have benefited from the unique opportunities and advantages offered by nanotechnology is undoubtedly the analytical chemistry, and it is obvious that this trend will rapidly increase day by day. The combination of dimensions, unique structures, and surface morphologies make NPs effective and interesting materials for sample preparation methods. Moreover, the functionalization capability of NMs by different agents and methods is one of the most important properties, which are used as per their desired capabilities, such as selectivity toward analyte or analytes, high adsorption capacity, solubility, physical, and chemical resistivity. Hence, the simple functionalization capability of NMs expands their applications in the field of sample preparation methods.

References [1] K.E. Geckeler, H. Nishide (Eds.), Advanced Nanomaterials, John Wiley & Sons, 2009. [2] C. Lutz, J.A. Steevens (Eds.), Nanomaterials: Risks and Benefits, Springer Science & Business Media, 2008.

Functionalized nanomaterials for sample preparation methods

403

[3] C.N.R. Rao, A. Mu¨ller, A.K. Cheetham (Eds.), The Chemistry of Nanomaterials: Synthesis, Properties and Applications, John Wiley & Sons, 2006. [4] K.T. Ramesh, Nanomaterials, Nanomaterials, Springer, Boston, MA, 2009, pp. 1
20. [5] H. Hosono, Y. Mishima, H. Takezoe, K.J. MacKenzie (Eds.), Nanomaterials: Research Towards Applications, vol. 161, Elsevier, 2006. [6] C.N.R. Rao, A. Mu¨ller, A.K. Cheetham (Eds.), Nanomaterials Chemistry: Recent Developments and New Directions, John Wiley & Sons, 2007. [7] A. Tiwari, A. Tiwari (Eds.), Bioengineered Nanomaterials, CRC Press, 2013. [8] M.S. Johal, Understanding Nanomaterials., CRC Press, 2012. [9] M.R. Mozafari (Ed.), Nanomaterials and Nanosystems for Biomedical Applications, Springer Science & Business Media, 2007. [10] G.A. Ozin, A. Arsenault, Nanochemistry: A Chemical Approach to Nanomaterials, Royal Society of Chemistry, 2015. [11] G.E. Fryxell, G. Cao (Eds.), Environmental Applications of Nanomaterials: Synthesis, Sorbents and Sensors, World Scientific, 2012. [12] X. Wang, Y. Guo, L. Yang, M. Han, J. Zhao, X. Cheng, Nanomaterials as sorbents to remove heavy metal ions in wastewater treatment, J. Environ. Anal. Toxicol. 2 (7) (2012) 154. [13] M. Ahmadi, H. Elmongy, T. Madrakian, M. Abdel-Rehim, Nanomaterials as sorbents for sample preparation in bioanalysis: a review, Anal. Chim. Acta 958 (2017) 1
21. [14] G. Yuan, Natural and modified nanomaterials as sorbents of environmental contaminants, J. Environ. Sci. Health, A 39 (10) (2004) 2661
2670. [15] A. Mehdinia, M.O. Aziz-Zanjani, Recent advances in nanomaterials utilized in fiber coatings for solid-phase microextraction, TrAC, Trends Anal. Chem. 42 (2013) 205
215. [16] K. Pyrzynska, Use of nanomaterials in sample preparation, TrAC, Trends Anal. Chem. 43 (2013) 100
108. [17] J.C. Vinci, L.A. Colon, Fractionation of carbon-based nanomaterials by anion-exchange HPLC, Anal. Chem. 84 (2) (2011) 1178
1183. [18] G. Aragay, F. Pino, A. Merkoci, Nanomaterials for sensing and destroying pesticides, Chem. Rev. 112 (10) (2012) 5317
5338. [19] M. Zhang, H. Qiu, Progress in stationary phases modified with carbonaceous nanomaterials for high-performance liquid chromatography, TrAC, Trends Anal. Chem. 65 (2015) 107
121. [20] G.B. Braun, S.J. Lee, T. Laurence, N. Fera, L. Fabris, G.C. Bazan, et al., Generalized approach to SERS-active nanomaterials via controlled nanoparticle linking, polymer encapsulation, and small-molecule infusion, J. Phys. Chem. C 113 (31) (2009) 13622
13629. [21] M.F. Cardinal, E. Vander Ende, R.A. Hackler, M.O. McAnally, P.C. Stair, G.C. Schatz, et al., Expanding applications of SERS through versatile nanomaterials engineering, Chem. Soc. Rev. 46 (13) (2017) 3886
3903. [22] C. Buzea, I.I. Pacheco, K. Robbie, Nanomaterials and nanoparticles: sources and toxicity, Biointerphases 2 (4) (2007) MR17
MR71. [23] A. Speltini, D. Merli, A. Profumo, Analytical application of carbon nanotubes, fullerenes and nanodiamonds in nanomaterials-based chromatographic stationary phases: a review, Anal. Chim. Acta 783 (2013) 1
16. [24] F. Valentini, G. Palleschi, Nanomaterials and analytical chemistry, Anal. Lett. 41 (4) (2008) 479
520.

404

Handbook of Nanomaterials in Analytical Chemistry

[25] Y. Su, Y. Xie, X. Hou, Y. Lv, Recent advances in analytical applications of nanomaterials in liquid-phase chemiluminescence, Appl. Spectrosc. Rev. 49 (3) (2014) 201
232. [26] S. Tong, S. Liu, H. Wang, Q. Jia, Recent advances of polymer monolithic columns functionalized with micro/nanomaterials: synthesis and application, Chromatographia 77 (1
2) (2014) 5
14. [27] J. Wang, S. Zheng, Y. Shao, J. Liu, Z. Xu, D. Zhu, Amino-functionalized Fe3O4@SiO2 core
shell magnetic nanomaterial as a novel adsorbent for aqueous heavy metals removal, J. Colloid Interface Sci. 349 (1) (2010) 293
299. [28] D. Huang, C. Deng, X. Zhang, Functionalized magnetic nanomaterials as solid-phase extraction adsorbents for organic pollutants in environmental analysis, Anal. Methods 6 (18) (2014) 7130
7141. [29] A.H. Lu, E.E. Salabas, F. Schu¨th, Magnetic nanoparticles: synthesis, protection, functionalization, and application, Angew. Chem. Int. Ed. 46 (8) (2007) 1222
1244. [30] C. Pereira, A.M. Pereira, C. Fernandes, M. Rocha, R. Mendes, M.P. Ferna´ndez-Garcı´a, et al., Superparamagnetic MFe2O4 (M 5 Fe, Co, Mn) nanoparticles: tuning the particle size and magnetic properties through a novel one-step coprecipitation route, Chem. Mater. 24 (8) (2012) 1496
1504. [31] V. Kruefu, A. Wisitsoraat, A. Tuantranont, S. Phanichphant, Ultra-sensitive H2S sensors based on hydrothermal/impregnation-made Ru-functionalized WO3 nanorods, Sens. Actuators, B: Chem. 215 (2015) 630
636. [32] D. Jagadeesan, M. Eswaramoorthy, Functionalized carbon nanomaterials derived from carbohydrates, Chem. Asian J. 5 (2) (2010) 232
243. [33] D. Li, J.T. McCann, Y. Xia, Use of electrospinning to directly fabricate hollow nanofibers with functionalized inner and outer surfaces, Small 1 (1) (2005) 83
86. [34] C.R. Crick, J.C. Bear, A. Kafizas, I.P. Parkin, Superhydrophobic photocatalytic surfaces through direct incorporation of titania nanoparticles into a polymer matrix by aerosol assisted chemical vapor deposition, Adv. Mater. 24 (26) (2012) 3505
3508. [35] B.G. Trewyn, I.I. Slowing, S. Giri, H.T. Chen, V.S.Y. Lin, Synthesis and functionalization of a mesoporous silica nanoparticle based on the sol
gel process and applications in controlled release, Acc. Chem. Res. 40 (9) (2007) 846
853. [36] S. Mohanty, S.K. Nayak, B.S. Kaith, S. Kalia (Eds.), Polymer Nanocomposites Based on Inorganic and Organic Nanomaterials, John Wiley & Sons, 2015. [37] V. Amendola, P. Riello, M. Meneghetti, Magnetic nanoparticles of iron carbide, iron oxide, iron@iron oxide, and metal iron synthesized by laser ablation in organic solvents, J. Phys. Chem. C 115 (12) (2010) 5140
5146. [38] X. Wang, L.H. Liu, O. Ramstroem, M. Yan, Engineering nanomaterial surfaces for biomedical applications, Exp. Biol. Med. 234 (10) (2009) 1128
1139. [39] M.R. Awual, M.M. Hasan, G.E. Eldesoky, M.A. Khaleque, M.M. Rahman, M. Naushad, Facile mercury detection and removal from aqueous media involving ligand impregnated conjugate nanomaterials, Chem. Eng. J. 290 (2016) 243
251. [40] W. Cai, L. Tan, J. Yu, M. Jaroniec, X. Liu, B. Cheng, et al., Synthesis of aminofunctionalized mesoporous alumina with enhanced affinity towards Cr(VI) and CO2, Chem. Eng. J. 239 (2014) 207
215. [41] L.I. Lulu, Y.A.O. Lu, D.U.A.N. Li, Application of Lithium-Selenium Batteries Using Covalent Organic Framework Composite Cathodes, Acta Physico-Chimica Sinica 35 (7) (2018) 734
739. [42] F.L. De La Puente, J.F. Nierengarten (Eds.), Fullerenes: Principles and Applications, Royal Society of Chemistry, 2011.

Functionalized nanomaterials for sample preparation methods

405

[43] J. Munoz, M. Gallego, M. Valca´rcel, Solid-phase extraction
gas chromatography
mass spectrometry using a fullerene sorbent for the determination of inorganic mercury(II), methylmercury(I) and ethylmercury(I) in surface waters at sub-ng/ml levels, J. Chromatogr. A 1055 (1
2) (2004) 185
190. [44] Y. Cai, G. Jiang, J. Liu, Q. Zhou, Multiwalled carbon nanotubes as a solid-phase extraction adsorbent for the determination of bisphenol A, 4-n-nonylphenol, and 4-tertoctylphenol, Anal. Chem. 75 (10) (2003) 2517
2521. [45] V.A. Lemos, L.S.G. Teixeira, M.D.A. Bezerra, A.C.S. Costa, J.T. Castro, L.A.M. Cardoso, et al., New materials for solid-phase extraction of trace elements, Appl. Spectrosc. Rev. 43 (4) (2008) 303
334. [46] P. Liang, Y. Liu, L. Guo, J. Zeng, H. Lu, Multiwalled carbon nanotubes as solid-phase extraction adsorbent for the preconcentration of trace metal ions and their determination by inductively coupled plasma atomic emission spectrometry, J. Anal. At. Spectrom. 19 (11) (2004) 1489
1492. [47] Q. Liu, J. Shi, J. Sun, T. Wang, L. Zeng, G. Jiang, Graphene and graphene oxide sheets supported on silica as versatile and high-performance adsorbents for solid-phase extraction, Angew. Chem. Int. Ed. 50 (26) (2011) 5913
5917. [48] S. Chigome, G. Darko, N. Torto, Electrospun nanofibers as sorbent material for solid phase extraction, Analyst 136 (14) (2011) 2879
2889. [49] J. Liu, A.G. Rinzler, H. Dai, J.H. Hafner, R.K. Bradley, P.J. Boul, et al., Fullerene pipes, Science 280 (5367) (1998) 1253
1256. [50] B.I. Yakobson, R.E. Smalley, Fullerene nanotubes, Am. Sci. 85 (4) (1997) 324
337. [51] R.H. Baughman, A.A. Zakhidov, W.A. De Heer, Carbon nanotubes—the route toward applications, Science 297 (5582) (2002) 787
792. [52] S. Iijima, T. Ichihashi, Single-shell carbon nanotubes of 1-nm diameter, Nature 363 (6430) (1993) 603. [53] M.S. Dresselhaus, G. Dresselhaus, R. Saito, A. Jorio, Raman spectroscopy of carbon nanotubes, Phys. Rep. 409 (2) (2005) 47
99. [54] V.N. Mochalin, O. Shenderova, D. Ho, Y. Gogotsi, The properties and applications of nanodiamonds, Nat. Nanotechnol. 7 (1) (2012) 11. [55] A.M. Schrand, S.A.C. Hens, O.A. Shenderova, Nanodiamond particles: properties and perspectives for bioapplications, Crit. Rev. Solid State Mater. Sci. 34 (1
2) (2009) 18
74. [56] A.K. Geim, Graphene: status and prospects, Science 324 (5934) (2009) 1530
1534. [57] D.R. Dreyer, S. Park, C.W. Bielawski, R.S. Ruoff, The chemistry of graphene oxide, Chem. Soc. Rev. 39 (1) (2010) 228
240. [58] Y. Zhu, S. Murali, W. Cai, X. Li, J.W. Suk, J.R. Potts, et al., Graphene and graphene oxide: synthesis, properties, and applications, Adv. Mater. 22 (35) (2010) 3906
3924. [59] A. Khan, J. Wang, J. Li, X. Wang, Z. Chen, A. Alsaedi, et al., The role of graphene oxide and graphene oxide-based nanomaterials in the removal of pharmaceuticals from aqueous media: a review, Environ. Sci. Pollut. Res. 24 (9) (2017) 7938
7958. [60] X. Chen, X. Hai, J. Wang, Graphene/graphene oxide and their derivatives in the separation/isolation and preconcentration of protein species: a review, Anal. Chim. Acta 922 (2016) 1
10. [61] X. Li, M. Rui, J. Song, Z. Shen, H. Zeng, Carbon and graphene quantum dots for optoelectronic and energy devices: a review, Adv. Funct. Mater. 25 (31) (2015) 4929
4947. [62] Y. Wang, S. Kalytchuk, Y. Zhang, H. Shi, S.V. Kershaw, A.L. Rogach, Thicknessdependent full-color emission tunability in a flexible carbon dot ionogel, J. Phys. Chem. Lett. 5 (8) (2014) 1412
1420.

406

Handbook of Nanomaterials in Analytical Chemistry

[63] G.W. Lee, J. Kim, J. Yoon, J.S. Bae, B.C. Shin, I.S. Kim, et al., Structural characterization of carboxylated multi-walled carbon nanotubes, Thin Solid Films 516 (17) (2008) 5781
5784. [64] K.K. Liu, C.L. Cheng, C.C. Chang, J.I. Chao, Biocompatible and detectable carboxylated nanodiamond on human cell, Nanotechnology 18 (32) (2007) 325102. [65] M. He, L. Huang, B. Zhao, B. Chen, B. Hu, Advanced functional materials in solid phase extraction for ICP-MS determination of trace elements and their species—a review, Anal. Chim. Acta 973 (2017) 1
24. [66] P. Sun, Y. Gao, C. Xu, Y. Lian, Determination of seven pyrethroid pesticide residues in vegetables by gas chromatography using carboxylated multi-walled carbon nanotubes as dispersion solid phase extraction sorbent, Food Addit. Contam., A 34 (12) (2017) 2164
2172. [67] S. Lo´pez-Feria, S. Ca´rdenas, M. Valca´rcel, One step carbon nanotubes-based solidphase extraction for the gas chromatographic
mass spectrometric multiclass pesticide control in virgin olive oils, J. Chromatogr. A 1216 (43) (2009) 7346
7350. [68] Y. Sun, W.Y. Zhang, J. Xing, C.M. Wang, Solid-phase microfibers based on modified single-walled carbon nanotubes for extraction of chlorophenols and organochlorine pesticides, Microchim. Acta 173 (1
2) (2011) 223
229. [69] P. Kueseng, J. Pawliszyn, Carboxylated multiwalled carbon nanotubes/polydimethylsiloxane, a new coating for 96-blade solid-phase microextraction for determination of phenolic compounds in water, J. Chromatogr. A 1317 (2013) 199
202. [70] L. Kou, R. Liang, Determination of tetrabromobisphenol A and bisphenol A in environmental water using carboxylated multiwalled carbon nanotubes as sorbent for solidphase extraction combined with liquid chromatography-tandem mass spectrometry, Se Pu 32 (8) (2014) 817
821. [71] C.K. Chang, C.C. Wu, Y.S. Wang, H.C. Chang, Selective extraction and enrichment of multiphosphorylated peptides using polyarginine-coated diamond nanoparticles, Anal. Chem. 80 (10) (2008) 3791
3797. [72] X. Kong, L.L. Huang, S.C.V. Liau, C.C. Han, H.C. Chang, Polylysine-coated diamond nanocrystals for MALDI-TOF mass analysis of DNA oligonucleotides, Anal. Chem. 77 (13) (2005) 4273
4277. [73] B. Sua´rez, B.M. Simonet, S. Ca´rdenas, M. Valca´rcel, Determination of non-steroidal anti-inflammatory drugs in urine by combining an immobilized carboxylated carbon nanotubes minicolumn for solid-phase extraction with capillary electrophoresis-mass spectrometry, J. Chromatogr. A 1159 (1
2) (2007) 203
207. [74] Y. Lv, Q. Deng, K.H. Row, T. Zhu, Silane coupling agents modified silica and graphene oxide materials for determination of sulfamerazine and sulfameter in milk by HPLC, Food Anal. Methods 12 (2018) 687
696. [75] R. Sitko, P. Janik, B. Feist, E. Talik, A. Gagor, Suspended aminosilanized graphene oxide nanosheets for selective preconcentration of lead ions and ultrasensitive determination by electrothermal atomic absorption spectrometry, ACS Appl. Mater. Interfaces 6 (22) (2014) 20144
20153. [76] K.J. Huang, J. Li, Y.M. Liu, L. Wang, Sensitive determination of polycyclic aromatic hydrocarbons in water samples by HPLC coupled with SPE based on graphene functionalized with triethoxysilane, J. Sep. Sci. 36 (4) (2013) 789
795. [77] P. Janik, B. Zawisza, E. Talik, R. Sitko, Selective adsorption and determination of hexavalent chromium ions using graphene oxide modified with amino silanes, Microchim. Acta 185 (2) (2018) 117.

Functionalized nanomaterials for sample preparation methods

407

[78] C. Xiao, S. Han, Z. Wang, J. Xing, C. Wu, Application of the polysilicone fullerene coating for solid-phase microextraction in the determination of semi-volatile compounds, J. Chromatogr. A 927 (1
2) (2001) 121
130. [79] J. Yu, L. Dong, C. Wu, L. Wu, J. Xing, Hydroxyfullerene as a novel coating for solidphase microextraction fiber with sol
gel technology, J. Chromatogr. A 978 (1
2) (2002) 37
48. [80] R.M. Vallant, Z. Szabo, S. Bachmann, R. Bakry, M. Najam-ul-Haq, M. Rainer, et al., Development and application of C60-fullerene bound silica for solid-phase extraction of biomolecules, Anal. Chem. 79 (21) (2007) 8144
8153. [81] R.M. Vallant, Z. Szabo, L. Trojer, M. Najam-ul-Haq, M. Rainer, C.W. Huck, et al., A new analytical material-enhanced laser desorption ionization (MELDI) based approach for the determination of low-mass serum constituents using fullerene derivatives for selective enrichment, J. Proteome Res. 6 (1) (2007) 44
53. [82] E.M. Soliman, H.M. Marwani, H.M. Albishri, Novel solid-phase extractor based on functionalization of multi-walled carbon nano tubes with 5-aminosalicylic acid for preconcentration of Pb(II) in water samples prior to determination by ICP-OES, Environ. Monit. Assess. 185 (12) (2013) 10269
10280. [83] M. Madadizadeh, M.A. Taher, H. Ashkenani, Determination of ultra-trace amounts of cadmium by ET-AAS after column preconcentration with a new sorbent of modified MWCNTs, Environ. Monit. Assess. 185 (5) (2013) 4097
4105. [84] S. Tajik, M.A. Taher, A new sorbent of modified MWCNTs for column preconcentration of ultra trace amounts of zinc in biological and water samples, Desalination 278 (1
3) (2011) 57
64. [85] D. Afzali, A. Mostafavi, Potential of modified multiwalled carbon nanotubes with 1-(2pyridylazo)-2-naphtol as a new solid sorbent for the preconcentration of trace amounts of cobalt (II) ion, Anal. Sci. 24 (9) (2008) 1135
1139. [86] A. Moghimi, S. Yousefi Siahkalrodi, Extraction and determination of Pb(II) by organic functionalisation of graphenes adsorbed on surfactant coated C18 in environmental sample, J. Chem. Health Risks 3 (3) (2018) 1
12. [87] C.J. Madadrang, H.Y. Kim, G. Gao, N. Wang, J. Zhu, H. Feng, et al., Adsorption behavior of EDTA-graphene oxide for Pb (II) removal, ACS Appl. Mater. Interfaces 4 (3) (2012) 1186
1193. [88] K. Pytlakowska, M. Matussek, B. Hachuła, M. Pilch, K. Kornaus, M. Zubko, et al., Graphene oxide covalently modified with 2,20 -iminodiacetic acid for preconcentration of Cr(III), Cu(II), Zn(II) and Pb(II) from water samples prior to their determination by energy dispersive X-ray fluorescence spectrometry, Spectrochim. Acta, B: At. Spectrosc. 147 (2018) 79
86. [89] X. Zhao, S. Zhang, C. Bai, B. Li, Y. Li, L. Wang, et al., Nano-diamond particles functionalized with single/double-arm amide
thiourea ligands for adsorption of metal ions, J. Colloid Interface Sci. 469 (2016) 109
119. [90] M. Ghaedi, M. Montazerozohori, N. Rahimi, M.N. Biysreh, Chemically modified carbon nanotubes as efficient and selective sorbent for enrichment of trace amount of some metal ions, J. Ind. Eng. Chem. 19 (5) (2013) 1477
1482. [91] M. Behbahani, T. Gorji, M. Mahyari, M. Salarian, A. Bagheri, A. Shaabani, Application of polypropylene amine dendrimers (POPAM)-grafted MWCNTs hybrid materials as a new sorbent for solid-phase extraction and trace determination of gold (III) and palladium (II) in food and environmental samples, Food Anal. Methods 7 (5) (2014) 957
966.

408

Handbook of Nanomaterials in Analytical Chemistry

[92] Z. Zhang, X. Yang, H. Zhang, M. Zhang, L. Luo, Y. Hu, et al., Novel molecularly imprinted polymers based on multi-walled carbon nanotubes with binary functional monomer for the solid-phase extraction of erythromycin from chicken muscle, J. Chromatogr. B 879 (19) (2011) 1617
1624. [93] F. Tan, M. Deng, X. Liu, H. Zhao, X. Li, X. Quan, et al., Evaluation of a novel microextraction technique for aqueous samples: porous membrane envelope filled with multiwalled carbon nanotubes coated with molecularly imprinted polymer, J. Sep. Sci. 34 (6) (2011) 707
715. [94] X. Chen, Z. Zhang, X. Yang, Y. Liu, J. Li, M. Peng, et al., Novel molecularly imprinted polymers based on multiwalled carbon nanotubes with bifunctional monomers for solid-phase extraction of rhein from the root of kiwi fruit, J. Sep. Sci. 35 (18) (2012) 2414
2421. [95] R.W. Kibechu, S. Sampath, B.B. Mamba, T.A.M. Msagati, Graphene-based molecularly imprinted polymer for separation and pre-concentration of trace polycyclic aromatic hydrocarbons in environmental water samples, J. Appl. Polym. Sci. 134 (37) (2017). Available from: https://doi.org/10.1002/APP.45300. [96] R. Sedghi, B. Heidari, M. Yassari, Novel molecularly imprinted polymer based on β-cyclodextrin@ graphene oxide: synthesis and application for selective diphenylamine determination, J. Colloid Interface Sci. 503 (2017) 47
56. [97] L. Cheng, S. Pan, C. Ding, J. He, C. Wang, Dispersive solid-phase microextraction with graphene oxide based molecularly imprinted polymers for determining bis(2ethylhexyl) phthalate in environmental water, J. Chromatogr. A 1511 (2017) 85
91. [98] G. Liang, H. Zhai, L. Huang, X. Tan, Q. Zhou, X. Yu, et al., Synthesis of carbon quantum dots-doped dummy molecularly imprinted polymer monolithic column for selective enrichment and analysis of aflatoxin B1 in peanut, J. Pharm. Biomed. Anal. 149 (2018) 258
264. [99] Z.A. ALOthman, M. Habila, E. Yilmaz, M. Soylak, Solid phase extraction of Cd(II), Pb(II), Zn(II) and Ni(II) from food samples using multiwalled carbon nanotubes impregnated with 4-(2-thiazolylazo) resorcinol, Microchim. Acta 177 (3
4) (2012) 397
403. [100] M.A. Habila, E. Yilmaz, Z.A. AlOthman, M. Soylak, 1-Nitroso-2-naphthol impregnated multiwalled carbon nanotubes (NNMWCNTs) for the separation-enrichment and flame atomic absorption spectrometric detection of copper and lead in hair, water, and food samples, Desalin. Water Treat. 87 (2017) 285
291. [101] A.A. Gouda, S.M. Al Ghannam, Impregnated multiwalled carbon nanotubes as efficient sorbent for the solid phase extraction of trace amounts of heavy metal ions in food and water samples, Food Chem. 202 (2016) 409
416. [102] M. Soylak, Z. Topalak, Multiwalled carbon nanotube impregnated with tartrazine: solid phase extractant for Cd(II) and Pb(II), J. Ind. Eng. Chem. 20 (2) (2014) 581
585. [103] E. Sahmetlioglu, E. Yilmaz, E. Aktas, M. Soylak, Polypyrrole/Multi-walled carbon nanotube composite for the solid phase extraction of lead(II) in water samples, Talanta 119 (2014) 447
451. [104] M. Chen, Y. Lin, C. Gu, J. Wang, Arsenic sorption and speciation with branchpolyethyleneimine modified carbon nanotubes with detection by atomic fluorescence spectrometry, Talanta 104 (2013) 53
57. [105] M.R. Nabid, R. Sedghi, A. Bagheri, M. Behbahani, M. Taghizadeh, H.A. Oskooie, et al., Preparation and application of poly(2-amino thiophenol)/MWCNTs nanocomposite for adsorption and separation of cadmium and lead ions via solid phase extraction, J. Hazard. Mater. 203 (2012) 93
100.

Functionalized nanomaterials for sample preparation methods

409

[106] C. Zhang, Z. Zhang, G. Li, Preparation of sulfonated graphene/polypyrrole solidphase microextraction coating by in situ electrochemical polymerization for analysis of trace terpenes, J. Chromatogr. A 1346 (2014) 8
15. [107] S.Q. Han, C.H. Xiao, C.Y. Wu, Properties of polysilicone fullerene as the coating for solid-phase microextraction, Chin. J. Anal. Chem. 29 (12) (2001) 1374
1378. [108] J. Zhang, L. Yang, M. Wu, X. Guo, B. Zeng, F. Zhao, Electrochemical preparation of poly(3-methylthiophene-carbazole)/graphene oxide composite coating for the highly effective solid-phase microextraction of some fragrance, Talanta 171 (2017) 61
67. [109] M. Behzadi, M. Mirzaei, Poly(o-anisidine)/Graphene oxide nanosheets composite as a coating for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene and xylenes, J. Chromatogr. A 1443 (2016) 35
42. [110] M.H. Kojidi, A. Aliakbar, A graphene oxide based poly(2,6-diaminopyridine) composite for solid-phase extraction of Cd(II) prior to its determination by FAAS, Microchim. Acta 184 (8) (2017) 2855
2860. [111] B. Hashemi, P. Zohrabi, S. Dehdashtian, Application of green solvents as sorbent modifiers in sorptive-based extraction techniques for extraction of environmental pollutants, TrAC Trends Anal. Chem. 109 (2018) 50
61. ˚ . Jo¨nsson, M.J. Wen, Disposable ionic liquid [112] J.F. Liu, N. Li, G.B. Jiang, J.M. Liu, J.A coating for headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in paints followed by gas chromatography
flame ionization detection, J. Chromatogr. A 1066 (1
2) (2005) 27
32. [113] L. Li, M. Wu, Y. Feng, F. Zhao, B. Zeng, Doping of three-dimensional porous carbon nanotube-graphene-ionic liquid composite into polyaniline for the headspace solidphase microextraction and gas chromatography determination of alcohols, Anal. Chim. Acta 948 (2016) 48
54. [114] Y. Zhang, Y.G. Zhao, W.S. Chen, H.L. Cheng, X.Q. Zeng, Y. Zhu, Threedimensional ionic liquid-ferrite functionalized graphene oxide nanocomposite for pipette-tip solid phase extraction of 16 polycyclic aromatic hydrocarbons in human blood sample, J. Chromatogr. A 1552 (2018) 1
9. [115] H. Zhang, X. Wu, Y. Yuan, D. Han, F. Qiao, H. Yan, An ionic liquid functionalized graphene adsorbent with multiple adsorption mechanisms for pipette-tip solid-phase extraction of auxins in soybean sprouts, Food Chem. 265 (2018) 290
297. [116] S. Hamidi, A. Azami, E.M. Aghdam, A novel mixed hemimicelles dispersive microsolid phase extraction using ionic liquid functionalized magnetic graphene oxide/polypyrrole for extraction and pre-concentration of methotrexate from urine samples followed by the spectrophotometric method, Clin. Chim. Acta 488 (2019) 179
188. [117] Y. Zhang, H. Zhou, Z.H. Zhang, X.L. Wu, W.G. Chen, Y. Zhu, et al., Threedimensional ionic liquid functionalized magnetic graphene oxide nanocomposite for the magnetic dispersive solid phase extraction of 16 polycyclic aromatic hydrocarbons in vegetable oils, J. Chromatogr. A 1489 (2017) 29
38. [118] J. Wu, H. Zhao, D. Xiao, P.H. Chuong, J. He, H. He, Mixed hemimicelles solid-phase extraction of cephalosporins in biological samples with ionic liquid-coated magnetic graphene oxide nanoparticles coupled with high-performance liquid chromatographic analysis, J. Chromatogr. A 1454 (2016) 1
8. [119] A.P. Abbott, G. Capper, D.L. Davies, R.K. Rasheed, V. Tambyrajah, Novel solvent properties of choline chloride/urea mixtures, Chem. Commun. 1 (2003) 70
71. [120] L. Liu, W. Tang, B. Tang, D. Han, K.H. Row, T. Zhu, Pipette-tip solid-phase extraction based on deep eutectic solvent modified graphene for the determination of sulfamerazine in river water, J. Sep. Sci. 40 (9) (2017) 1887
1895.

410

Handbook of Nanomaterials in Analytical Chemistry

[121] X. Wang, G. Li, K.H. Row, Graphene and graphene oxide modified by deep eutectic solvents and ionic liquids supported on silica as adsorbents for solid-phase extraction, Bull. Korean Chem. Soc. 38 (2) (2017) 251
257. [122] S.M. Yousefi, F. Shemirani, S.A. Ghorbanian, Deep eutectic solvent magnetic bucky gels in developing dispersive solid phase extraction: application for ultra trace analysis of organochlorine pesticides by GC-micro ECD using a large-volume injection technique, Talanta 168 (2017) 73
81. [123] M. Tuzen, K.O. Saygi, C. Usta, M. Soylak, Pseudomonas aeruginosa immobilized multiwalled carbon nanotubes as biosorbent for heavy metal ions, Bioresour. Technol. 99 (6) (2008) 1563
1570. [124] N. Aydemir, N. Tokman, A.T. Akarsubasi, A. Baysal, S. Akman, Determination of some trace elements by flame atomic absorption spectrometry after preconcentration and separation by Escherichia coli immobilized on multiwalled carbon nanotubes, Microchim. Acta 175 (1
2) (2011) 185. [125] S. Ozdemir, E. Kilinc, K.S. Celik, V. Okumus, M. Soylak, Simultaneous preconcentrations of Co21, Cr61, Hg21 and Pb21 ions by Bacillus altitudinis immobilized nanodiamond prior to their determinations in food samples by ICP-OES, Food Chem. 215 (2017) 447
453. [126] F. Pena-Pereira, R.M. Duarte, A.C. Duarte, Immobilization strategies and analytical applications for metallic and metal-oxide nanomaterials on surfaces, TrAC, Trends Anal. Chem. 40 (2012) 90
105. [127] J. Krenkova, F. Foret, Iron oxide nanoparticle coating of organic polymer-based monolithic columns for phosphopeptide enrichment, J. Sep. Sci. 34 (16
17) (2011) 2106
2112. [128] M. Inuta, R. Arakawa, H. Kawasaki, Analyst (Cambridge, UK) 136 (2011) 1167. [129] W. Lu, Y. Luo, G. Chang, F. Liao, X. Sun, Layer-by-layer self-assembly of multilayer films of polyelectrolyte/Ag nanoparticles for enzymeless hydrogen peroxide detection, Thin Solid Films 520 (1) (2011) 554
557. [130] X. Hu, W. Cheng, T. Wang, Y. Wang, E. Wang, S. Dong, Fabrication, characterization, and application in SERS of self-assembled polyelectrolyte
gold nanorod multilayered films, J. Phys. Chem. B 109 (41) (2005) 19385
19389. [131] Y. Wei, M. Li, S. Jiao, Q. Huang, G. Wang, B. Fang, Fabrication of CeO2 nanoparticles modified glassy carbon electrode and its application for electrochemical determination of UA and AA simultaneously, Electrochim. Acta 52 (3) (2006) 766
772. [132] D.D. Cao, J.X. Lu¨, J.F. Liu, G.B. Jiang, In situ fabrication of nanostructured titania coating on the surface of titanium wire: a new approach for preparation of solid-phase microextraction fiber, Anal. Chim. Acta 611 (1) (2008) 56
61. [133] S. Baruah, J. Dutta, Hydrothermal growth of ZnO nanostructures, Sci. Technol. Adv. Mater. 10 (1) (2009) 013001. [134] C. Cheng, B. Yan, S.M. Wong, X. Li, W. Zhou, T. Yu, et al., Fabrication and SERS performance of silver-nanoparticle-decorated Si/ZnO nanotrees in ordered arrays, ACS Appl. Mater. Interfaces 2 (7) (2010) 1824
1828. [135] N. Kohler, G.E. Fryxell, M. Zhang, A bifunctional poly(ethylene glycol) silane immobilized on metallic oxide-based nanoparticles for conjugation with cell targeting agents, J. Am. Chem. Soc. 126 (23) (2004) 7206
7211. [136] S. Deki, Y. Aoi, J. Okibe, H. Yanagimoto, A. Kajinami, M. Mizuhata, J. Mater. Chem. 7 (1997) 1769. [137] B. Lin, T. Li, Y. Zhao, F.K. Huang, L. Guo, Y.Q. Feng, J. Chromatogr., A 1192 (2008) 95.

Functionalized nanomaterials for sample preparation methods

411

[138] T. Li, Y. Xu, Y.Q. Feng, J. Liq. Chromatogr. Relat. Technol. 32 (2009) 2484. [139] Z. Zhang, S. Dai, D.A. Blom, J. Shen, Synthesis of ordered metallic nanowires inside ordered mesoporous materials through electroless deposition, Chem. Mater. 14 (3) (2002) 965
968. [140] W. Wang, N. Li, X. Li, W. Geng, S. Qiu, Synthesis of metallic nanotube arrays in porous anodic aluminum oxide template through electroless deposition, Mater. Res. Bull. 41 (8) (2006) 1417
1423. [141] K. Nielsch, F. Mu¨ller, A.P. Li, U. Go¨sele, Uniform nickel deposition into ordered alumina pores by pulsed electrodeposition, Adv. Mater. 12 (8) (2000) 582
586. [142] K. Jiang, Q. Huang, K. Fan, L. Wu, D. Nie, W. Guo, et al., Reduced graphene oxide and gold nanoparticle composite-based solid-phase extraction coupled with ultra-highperformance liquid chromatography-tandem mass spectrometry for the determination of 9 mycotoxins in milk, Food Chem. 264 (2018) 218
225. [143] M.J. Trujillo-Rodrı´guez, J.L. Anderson, Silver-based polymeric ionic liquid sorbent coatings for solid-phase microextraction: materials for the selective extraction of unsaturated compounds, Anal. Chim. Acta 1047 (2019) 52
61. [144] M.N. Yazdi, Y. Yamini, H. Asiabi, Fabrication of polypyrrole-silver nanocomposite for hollow fiber solid phase microextraction followed by HPLC/UV analysis for determination of parabens in water and beverages samples, J. Food Compos. Anal. 74 (2018) 18
26. [145] Y. Yang, P. Qin, J. Zhang, W. Li, J. Zhu, M. Lu, et al., Fabrication of nanoscale graphitic carbon nitride/copper oxide hybrid composites coated solid-phase microextraction fibers coupled with gas chromatography for determination of polycyclic aromatic hydrocarbons, J. Chromatogr. A 1570 (2018) 47
55. [146] M. Ghani, S.M. Ghoreishi, S. Masoum, Highly porous nanostructured copper oxide foam fiber as a sorbent for head space solid-phase microextraction of BTEX from aqueous solutions, Microchem. J. 145 (2019) 210
217. [147] M.N. Yazdi, Y. Yamini, H. Asiabi, Multiwall carbon nanotube-zirconium oxide nanocomposite hollow fiber solid phase microextraction for determination of polyaromatic hydrocarbons in water, coffee and tea samples, J. Chromatogr. A 1554 (2018) 8
15. [148] P.J. Robinson, P. Dunnill, M.D. Lilly, The properties of magnetic supports in relation to immobilized enzyme reactors, Biotechnol. Bioeng. 15 (3) (1973) 603
606. ˇ r´ıkova´, I. Safaˇ ˇ r´ık, Magnetic solid-phase extraction, J. Magn. Magn. Mater. 194 [149] M. Safaˇ (1
3) (1999) 108
112. [150] Q.A. Pankhurst, J. Connolly, S.K. Jones, J. Dobson, Applications of magnetic nanoparticles in biomedicine, J. Phys. D: Appl. Phys. 36 (13) (2003) R167. [151] S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L. Vander Elst, et al., Magnetic iron oxide nanoparticles: synthesis, stabilization, vectorization, physicochemical characterizations, and biological applications, Chem. Rev. 108 (6) (2008) 2064
2110. [152] R.H. Kodama, Magnetic nanoparticles, J. Magn. Magn. Mater. 200 (1
3) (1999) 359
372. [153] S. Sadeghi, H. Azhdari, H. Arabi, A.Z. Moghaddam, Surface modified magnetic Fe3O4 nanoparticles as a selective sorbent for solid phase extraction of uranyl ions from water samples, J. Hazard. Mater. 215 (2012) 208
216. [154] S. Christophoridou, P. Dais, L.H. Tseng, M. Spraul, Separation and identification of phenolic compounds in olive oil by coupling high-performance liquid chromatography with postcolumn solid-phase extraction to nuclear magnetic resonance spectroscopy (LC-SPE-NMR), J. Agric. Food. Chem. 53 (12) (2005) 4667
4679.

412

Handbook of Nanomaterials in Analytical Chemistry

[155] C. Clarkson, D. Stærk, S.H. Hansen, J.W. Jaroszewski, Hyphenation of solid-phase extraction with liquid chromatography and nuclear magnetic resonance: application of HPLC-DAD-SPE-NMR to identification of constituents of Kanahia laniflora, Anal. Chem. 77 (11) (2005) 3547
3553. [156] D. Xiao, C. Zhang, D. Yuan, J. He, J. Wu, K. Zhang, et al., Magnetic solid-phase extraction based on Fe3O4 nanoparticle retrieval of chitosan for the determination of flavonoids in biological samples coupled with high performance liquid chromatography, RSC Adv. 4 (110) (2014) 64843
64854. [157] G. Miliauskas, T.A. van Beek, P. de Waard, R.P. Venskutonis, E.J. Sudho¨lter, Comparison of analytical and semi-preparative columns for high-performance liquid chromatography
solid-phase extraction
nuclear magnetic resonance, J. Chromatogr. A 1112 (1
2) (2006) 276
284. [158] J.J. Xu, L.H. Ye, J. Cao, W. Cao, Q.Y. Zhang, Ultramicro chitosan-assisted in-syringe dispersive micro-solid-phase extraction for flavonols from healthcare tea by ultra-high performance liquid chromatography, J. Chromatogr. A 1409 (2015) 11
18. [159] E. Tahmasebi, Y. Yamini, Facile synthesis of new nano sorbent for magnetic solidphase extraction by self assembling of bis-(2,4,4-trimethyl pentyl)-dithiophosphinic acid on Fe3O4@Ag core@shell nanoparticles: characterization and application, Anal. Chim. Acta 756 (2012) 13
22. [160] A. Asfaram, M. Ghaedi, H. Javadian, A. Goudarzi, Cu- and S-@SnO2 nanoparticles loaded on activated carbon for efficient ultrasound assisted dispersive μSPE-spectrophotometric detection of quercetin in Nasturtium officinale extract and fruit juice samples: CCD-RSM design, Ultrason. Sonochem. 47 (2018) 1
9. [161] A. Michalkiewicz, M. Biesaga, K. Pyrzynska, Solid-phase extraction procedure for determination of phenolic acids and some flavonols in honey, J. Chromatogr. A 1187 (1
2) (2008) 18
24. [162] Y. Tahtah, S.G. Wubshet, K.T. Kongstad, A.M. Heskes, I. Pateraki, B.L. Møller, et al., High-resolution PTP1B inhibition profiling combined with high-performance liquid chromatography
high-resolution mass spectrometry
solid-phase extraction
nuclear magnetic resonance spectroscopy: proof-of-concept and antidiabetic constituents in crude extract of Eremophila lucida, Fitoterapia 110 (2016) 52
58. [163] C. Clarkson, M. Sibum, R. Mensen, J.W. Jaroszewski, Evaluation of on-line solidphase extraction parameters for hyphenated, high-performance liquid chromatography
solid-phase extraction
nuclear magnetic resonance applications, J. Chromatogr. A 1165 (1
2) (2007) 1
9. [164] M. Safarikova, I. Safarik, Magnetic solid-phase extraction of target analytes from large volumes of urine, Eur. Cells Mater. 3 (Suppl. 2) (2002) 192
195. [165] M. Safarikova, I. Kibrikova, L. Ptackova, T. Hubka, K. Komarek, I. Safarik, Magnetic solid phase extraction of non-ionic surfactants from water, J. Magn. Magn. Mater. 293 (1) (2005) 377
381. [166] C. Huang, B. Hu, Silica-coated magnetic nanoparticles modified with γ-mercaptopropyltrimethoxysilane for fast and selective solid phase extraction of trace amounts of Cd, Cu, Hg, and Pb in environmental and biological samples prior to their determination by inductively coupled plasma mass spectrometry, Spectrochim. Acta, B: At. Spectrosc. 63 (3) (2008) 437
444. [167] H.M. Kim, M. Uh, D.H. Jeong, H.Y. Lee, J.H. Park, S.K. Lee, Localized surface plasmon resonance biosensor using nanopatterned gold particles on the surface of an optical fiber, Sens. Actuators, B: Chem. 280 (2019) 183
191.

Functionalized nanomaterials for sample preparation methods

413

[168] H. Li, H. Li, Z. Chen, J. Lin, On-chip solid phase extraction coupled with electrophoresis using modified magnetic microspheres as stationary phase, Sci. China Ser. B: Chem. 52 (12) (2009) 2287. [169] Q. Cheng, F. Qu, N.B. Li, H.Q. Luo, Mixed hemimicelles solid-phase extraction of chlorophenols in environmental water samples with 1-hexadecyl-3-methylimidazolium bromide-coated Fe3O4 magnetic nanoparticles with high-performance liquid chromatographic analysis, Anal. Chim. Acta 715 (2012) 113
119. [170] H.M. Jiang, Z.P. Yan, Y. Zhao, X. Hu, H.Z. Lian, Zincon-immobilized silica-coated magnetic Fe3O4 nanoparticles for solid-phase extraction and determination of trace lead in natural and drinking waters by graphite furnace atomic absorption spectrometry, Talanta 94 (2012) 251
256. [171] C. Cui, M. He, B. Chen, B. Hu, Chitosan modified magnetic nanoparticles based solid phase extraction combined with ICP-OES for the speciation of Cr(III) and Cr(VI), Anal. Methods 6 (21) (2014) 8577
8583. [172] Y. Wang, J. Xie, Y. Wu, X. Hu, A magnetic metal-organic framework as a new sorbent for solid-phase extraction of copper(II), and its determination by electrothermal AAS, Microchim. Acta 181 (9
10) (2014) 949
956. [173] S. Azodi-Deilami, A.H. Najafabadi, E. Asadi, M. Abdouss, D. Kordestani, Magnetic molecularly imprinted polymer nanoparticles for the solid-phase extraction of paracetamol from plasma samples, followed its determination by HPLC, Microchim. Acta 181 (15
16) (2014) 1823
1832.

Further reading S. Goyanes, G.R. Rubiolo, A. Salazar, A. Jimeno, M.A. Corcuera, I. Mondragon, Carboxylation treatment of multiwalled carbon nanotubes monitored by infrared and ultraviolet spectroscopies and scanning probe microscopy, Diamond Relat. Mater. 16 (2) (2007) 412
417. ´ . Me´ndez, J.B. Garcı´a, S.G. Martı´n, R.P. Crecente, Carbon nanotubes as C.H. Latorre, J.A solid-phase extraction sorbents prior to atomic spectrometric determination of metal species: a review, Anal. Chim. Acta 749 (2012) 16
35.