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Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples
Accepted Manuscript Title: Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples Author: Shu-Wen Xue Min-Qiong Tang Li Xu Zhi-guo Shi PII: DOI: Reference:
S0021-9673(15)01112-7 http://dx.doi.org/doi:10.1016/j.chroma.2015.07.104 CHROMA 356731
To appear in:
Journal of Chromatography A
Received date: Revised date: Accepted date:
16-4-2015 28-7-2015 31-7-2015
Please cite this article as: S.-W. Xue, M.-Q. Tang, L. Xu, Z.-g. Shi, Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples, Journal of Chromatography A (2015), http://dx.doi.org/10.1016/j.chroma.2015.07.104 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from
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environmental water samples
Shu-Wen Xuea, Min-Qiong Tanga, Li Xua, Zhi-guo Shib,* a
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Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan
Department of Chemistry, Wuhan University, Wuhan 430072, China
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b
430030, China
Abstract
Email address: [email protected] (Z.-g. Shi).
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*Corresponding author. Tel: +86 27 68752701; Fax: +86 27 68754067
Magnetic nanoparticles (MNPs) featured with divinylbenzene (DVB) and sulfonate functionalities (Fe3O4-DVB-SO3-) were prepared via “thiol-ene” click chemistry. The hydrophobic DVB moieties were dedicated for extraction while the hydrophilic sulfonate groups were designed for dispersing the MNPs in aqueous sample solution. Thus, the special designed material could ensure operational convenience and improve
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reproducibility during extraction. The application of the material was demonstrated by the extraction of polycyclic aromatic hydrocarbons (PAHs)
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from environmental water samples followed by gas chromatography-mass spectrometric analysis. The main factors influencing the extraction, including the type of the desorption solvent, the agitation mode, the amount of MNPs, extraction and desorption time and salt addition in sample
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solution, were investigated in detail. Under the optimized conditions, the proposed method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations less than 16.5% and 21.2%, and low limits of detection of 1.1 pg mL-1, 0.8 pg mL-1, 1.1 pg mL-1, 1.4
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pg mL-1, 0.6 pg mL-1, 2.1 pg mL-1 and 0.7 pg mL-1 for naphthalene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene and pyrene,
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respectively. The developed method was also successfully used for determination of the PAHs in genuine lake and river environmental water samples by standard addition method. All the studied PAHs were detected in these waters with comparable results by the standard liquid-liquid
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extraction method. The developed MNPs with dual property of hydrophobicity and hydrophilicity were suitable for the treatment of water samples. The magnetic solid phase extraction based on this material was reliable and convenient. It has great potential in the preconcentration of trace analytes in complex matrix. Keywords: magnetic solid-phase extraction; click chemistry; hydrophobicity; aqueous dispersibility; polycyclic aromatic hydrocarbons.
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1 Introduction
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Recently, magnetic solid-phase extraction (MSPE) has attracted increasing interest worldwide [1-4]. Owing to the nanoscale particle size, the MNPs commonly possess large surface area and short diffusion pathway, which may result in large extraction capacity and high extraction
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efficiency. Additionally, the MNPs can be quickly isolated from matrix solution via an external magnetic field after extraction. Thus, compared with traditional column SPE, the MSPE affords enhanced extraction efficiency, and avoids column packing as well as possible blockage in the
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column [5, 6].
In MSPE, Fe3O4 and γ-Fe2O3 are the most frequently used kernel materials of the sorbents. Generally they should be functionalized with special
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ligands for target analytes [7, 8]. For example, MNPs functionalized with C18, C8 and cyclodextrin were applied for the extraction of organophosphorous pesticides [9], peptides [10] and biphenolic pollutants [11], respectively. However, the functionalized MNPs are usually difficult to disperse well in aqueous sample owing to their high hydrophobicity, especially for the particles below 50 nm [12]. On the other hand, these MNPs aggregate easily, which may decrease their stability and be detrimental to the extraction performance [13]. For these reasons, a hydrophilic layer constructed on the surface of hydrophobic MNPs is essential to improve the aqueous dispersibility, and thus enhance the
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extraction reproducibility and operation convenience. As a typical example, Cai et al. synthesized a novel MNP sorbent with an interior C18
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group and an exterior chitosan polymer coating, to extract perfluorinated and phthalate ester compounds from environmental water samples [12]. Following that, Geng et al. prepared chitosan coated carbon-functionalized MNPs for extraction of bisphenol A from tap water [14]. In addition,
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Ye et al. coated non-ionic surfactants, i.e. Span and Tween, on the surface of C12-MNPs to extract steroid hormones from environmental and biological samples [5]. Besides, Bai et al. synthesized carbon-ferromagnetic nanocomposite with enriched hydroxyl groups via specially
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designed carbonization strategy [15] for extracting polycyclic aromatic hydrocarbons (PAHs). Another example was methylcellulose coated
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phenyl functionalized MNPs, to extract sildenafil and desmethyl sildenafil from human urine and plasma samples [16]. Nevertheless, most of these hydrophilic layer groups were physically coated instead of chemically modified on the MNPs [5, 13, 14, 16]. In another word, they may be
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not stable enough in some circumstances.
In the present work, new MNPs, which simultaneously contained hydrophobic divinylbenzene (DVB) and hydrophilic sulfonate (Fe3O4-DVB-SO3-), were elaborately designed. It was prepared via a two-step approach involving “thiol-ene” click chemistry. The prepared Fe3O4-DVB-SO3- was used as the MSPE sorbent.
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As is known to all, PAHs are recognized as potential carcinogens, which have been listed as priority pollutants by the European Union and U.S. Environmental Protection Agency. Considering that the hydrophobic DVB on the Fe3O4-DVB-SO3- MNPs would feature its reservation of
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hydrophobic compounds, among which PAHs are one kind of the representative, several PAHs were chosen to test the extraction ability of the
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prepared MNPs. The developed method was then applied to genuine environmental water samples.
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2 Experimental 2.1 Chemicals and Reagents
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Seven PAHs, naphthalene (Np), acenaphthene (Ace), fluorene (F), phenanthrene (Ph), anthracene (An), fluoranthene (FI) and pyrene (Py), were purchased from Aladdin Chemical Reagent Co., Ltd. (Shanghai, China). Methanol was supplied by Merck (Darmstadt, Hessen, Germany). Azodiisobutyronitrile (AIBN), ethanol, toluene, ethyl acetate (HPLC grade), acetone (HPLC grade), n-hexane (HPLC grade), DVB, acetic acid, sodium acetate, ethylene glycol, polyvinyl alcohol, ammonia, sodium 3-mercapto-1-propanesulfonate and iron(III) chloride hexahydrate were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Tetraethoxysilane and 3-(mercaptopropyl)trimethoxysilane were
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obtained from Hubei Wuhan University Silicone New Material Co., Ltd. (Wuhan, China). Isooctane (HPLC grade) was purchased from Xiya
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2.2 Preparation of Fe3O4-DVB-SO3- MNPs
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Reagent Research Center (Linshu, China). Ultrapure water was produced by a Heal Fore NW system (Shanghai, China).
The procedures for preparation of Fe3O4-DVB-SO3- MNPs are depicted in Fig. 1. Firstly, Fe3O4 MNPs were prepared by solvothermal method
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and coated with silica as previously reported [17]. Secondly, Fe3O4-SiO2 (8.0 g), 3-(mercaptopropyl)- trimethoxysilane (2.0 mL) and toluene
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(15.0 mL) were mixed and heated at 130℃ for 4 h. The obtained product, Fe3O4-SiO2-SH, was isolated and washed carefully by toluene and methanol for 3 times, respectively. Then it was dried at 120℃ for 4 h. Thirdly, the as-prepared Fe3O4-SiO2-SH (2.0 g) was mixed with ethanol
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(15.0 mL) containing DVB (0.5 mL) and H2O (1.0 mL). Five minutes later, AIBN (25 mg) and sodium 3-mercapto-1-propanesulfonate (0.45 g) were added simultaneously. Under vigorous mechanical stirring and nitrogen atmosphere, the reaction proceeded at 70℃ for 8 h. Thereafter, the product was washed with ethanol and pure water consecutively, and then dried at 80℃ for 12 h. Finally, Fe3O4-DVB-SO3- MNPs was available.
2.3 Characterization of Fe3O4-DVB-SO3- MNPs
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Magnetism of the material was studied by a PPMS-9 vibrating sample magnetometer (QUANTOM, USA). The hydrophobic and hydrophilic
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properties of the prepared material were studied by contact angle measurement (Drop Shape Analysis System DSA 100) (Kruss, Germany). Transmission electron microscopy (TEM) image was recorded on a H-7500 transmission electronic microscopy (Hitachi, Tokyo, Japan) Fourier
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transform infrared (FTIR) spectroscopic experiment was carried out on a Nicolet (Madison, WI, USA) Impact 420 apparatus. Thermogravimetric
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analysis (TGA) was carried out on a Setaram (France) TG-DTA analyzer.
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2.4 Gas chromatography-mass spectrometric (GC-MS) analysis The analysis of the seven PAHs was performed on a TriPlus-RSH autosampler -Trace1300-ISQ GC-MS instrument from Thermo Scientific
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(West Palm Beach, FL, USA). The following GC temperature program was used: the initial oven temperature 70℃ for 2 min; increased to 180 ℃ at a rate of 15℃ min-1 and held at 180℃ for 10 min; then increased to 240℃ at a rate of 10℃ min-1, and finally up to 280℃ at a rate of 20℃ min-1 and held at 280℃ for 2 min. A DB-5MS capillary column (30 m ×0.25 mm ×0.25 μm) from Agilent Technology, Inc. (Santa Clara, CA, USA) was used. The carrier gas was helium at a flow rate of 1.2 mL min-1. The injector was operated at 280℃ in splitless mode for 2 min. The electron ionization mass spectrometer was operated with energy of 70 eV. The ion source temperature was 280℃, and the GC-MS interface
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temperature was 300℃. The analysis was performed in full scan mode (mass range: 50-450 m/z) to confirm the retention time of PAHs. The
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quantification was achieved by selected ion monitoring (SIM) mode using the characteristic ions as listed in Table 1. The collection of raw data was performed using an X-Calibur 1.4 software system from Thermo Scientific (West Palm Beach, FL, USA). All the experiments were
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2.5 Sample preparation
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performed at least in triplicate.
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The stock solutions of PAHs were prepared as follows. Accurately weighed 2 mg of An and 10 mg of the others were separately dissolved in methanol, yielding stock solutions of 0.2 mg mL-1 for An and 1 mg mL-1 for the others. Working solutions containing the required concentration
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of each analyte were freshly prepared daily by diluting stock solutions with double distillated water, which were used for evaluating extraction performance under different conditions. All solutions prepared were stored at 4℃ and protected from light in brown glass bottles.
2.6 MSPE procedure The MSPE procedure was carried out as follows. Prescribed amount of Fe3O4-DVB-SO3- was added into a vial (maximum volume of 25 mL),
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which contained 20 mL sample solution. After being oscillated for certain time, the MNPs were separated from the sample solution by attaching
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a Nd-Fe-B magnet (50 mm ×50 mm ×10 mm) to the bottom of the vial. The sample solution was decanted and ultrapure water (500 μL) was added into the vial to wash the MNPs. After the water was decanted, filter paper was carefully dispatched to absorb the residual water.
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Subsequently, 100 μL of isooctane was introduced to desorb the adsorbed analytes from the MNPs by oscillation for the prescribed time. The
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eluate was separated from the suspension with the magnet. Finally, 1 μL of the eluate was injected into the GC-MS system for analysis.
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2.7 Liquid-liquid extraction (LLE)
For comparison, the LLE procedure, based on US EPA Method 3510C [18], was adopted for the genuine samples. Briefly, 20 mL of water
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sample was placed in a 25 mL separatory funnel. The extraction was carried out three times with 2 mL of dichloromethane. The extracts were combined and evaporated under a gentle nitrogen stream (N2, purity >99.9%) until dryness. The residue was then dissolved in 100 μL of isooctane and collected for GC-MS analysis.
2.8 Application to genuine samples
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The genuine water samples were collected from Changjiang River and East Lake (Wuhan, Hubei, China). They were stored at the temperature of
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4℃, and protected from light in brown glass bottles. Standard addition method was employed to determine target PAHs in these water samples. Standard PAHs stock solutions were added to real water samples to obtain the different spiked concentrations, 10, 5, 1, 0.5, 0.1, 0.05 and 0.01 ng
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3 Results and discussion
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mL-1. Each water sample was first filtered, and then subjected to the MSPE and LLE under the optimal condition.
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3.1 Preparation and characterization of Fe3O4-DVB-SO3- MNPs The “thiol-ene” click reaction is the hydrothiolation of a C=C bond, which is conducted under radical conditions [19, 20]. In this experiment,
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Fe3O4-SiO2 was first chemically bonded with -SH group to generate Fe3O4-SiO2-SH. With the promotion of AIBN, the -SH groups on Fe3O4-SiO2-SH and 3-mercapto-1-propanesulfonate formed thiol radicals, which attacked the C=C bond of DVB to yield intermediate carboncentred radicals followed by chain transfer to a second molecule of thiol to give the thiol-ene addition product. This reaction generally proceeded in a mild condition, and was extremely rapid and complete in several hours.
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The magnetic property of Fe3O4-DVB-SO3- MNPs was investigated by a vibrating sample magnetometer. As shown in Fig. 2, the curve had no
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magnetic hysteresis loop and the saturation magnetization value was 61 emu/g. The result demonstrated that the MNPs were super paramagnetic.
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The TEM image, as shown in Fig. 3, disclosed that the material was spherical, with average diameter of ~70 nm.
FT-IR spectroscopy was employed to verify the functional moieties of the MNPs. As shown in Fig. 4, the DVB component of Fe3O4-DVB-SO3-
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MNPs can be confirmed by the peaks around 1600 cm-1, corresponding to the stretching vibration of the vinyl and phenyl groups. The strong
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peaks around 1200 and 1100 cm-1 should be ascribed to the stretching vibration of sulfonic acid group, indicating -SO3- was present in the MNPs. The organic content of the MNPs was evaluated by TGA method. The weight loss ranging from 200
to 800
was calculated to be 3.80% and
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5.33% for Fe3O4-SiO2-SH and Fe3O4-DVB-SO3-, respectively. All of these results indicated that both DVB and sulfonate groups were successfully modified onto the Fe3O4-SiO2 MNPs.
A contact angle analysis was carried out to evaluate the hydrophilicity of Fe3O4-DVB-SO3-. As depicted in Fig. 5 (i), the water drop dispersed quickly when it contacted the material and the contact angle was found to be almost 0º, which demonstrated that Fe3O4-DVB-SO3- had superb
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hydrophilicity. In addition, as shown in Fig. 5 (ii), the Fe3O4-DVB-SO3- MNPs were well dispersed in aqueous solution (a) and they could be
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quickly isolated from the solution through an external magnetic field (b), which would be a preferred merit for extraction application. In contrast, the dispersibility of the Fe3O4-SiO2-SH MNPs in aqueous solution was bad, as shown in Fig. 5 (ii) (c), which further demonstrated that sulfonate
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groups featured the material excellent aqueous dispersibility.
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3.2 Optimization of MSPE conditions
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The performance of MSPE was influenced by multiple factors. In our preliminary experiments, the type of desorption solvent was first studied to ensure its compatibility with the GC-MS system and the elution of the PAHs from MNPs. Ethyl acetate, acetone, n-hexane and isooctane, all of
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which were documented to have low boiling points, great solubility of PAHs and superb compatibility with GC-MS system [18, 21], were herein studied. Isooctane was finally chosen as it afforded the strongest analytical signals, least interference to signals and symmetric peaks with high column efficiency [22, 23]. Moreover, the volume of isooctane for elution was also optimized. It was found that 100 μL of isooctane was the best choice.
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Agitation is commonly applied to promote the extraction process in MSPE. Herein, two agitation modes, ultrasonication and oscillation, were
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compared. The results demonstrated that the oscillation mode can provide better reproducibility and higher extraction efficiency. Therefore, this
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mode was adopted for the following experiments.
The sample pH was also evaluated and it was found to be irrelevant to the extraction efficiency. This observation could be explained as below.
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As the sulphonate groups of Fe3O4-DVB-SO3- MNPs were fully ionized under the investigated pH range (2-10), it did not influence the
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dispersive status of the MNPs in the sample solution. Furthermore, since the extraction was based on the hydrophobic interaction between the
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target analytes (PAHs) and the MNPs, little influence by the sample pH could be also predicted.
In addition to these parameters, the amount of Fe3O4-DVB-SO3- MNPs, extraction time, desorption time and salt addition were optimized in detail by a one-variant-at-one-time approach.
3.2.1 The influence of Fe3O4-DVB-SO3- MNPs amount
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The sorbent amount played a significant role in MSPE performance. The influence of Fe3O4-DVB-SO3- amount on the extraction was studied in
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the range of 10-70 mg. As shown in Supplement material Fig. S1, peak area of the analytes climbed up notably with the increasing amount of MNPs from 10 to 50 mg. It reflected that the more amount of MNPs was used, the better extraction performance was achieved. However, the
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peak area declined or slightly went up with the particle amount further increasing to 70 mg, which would be ascribed to the inadequate elution of
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the adsorbed analytes by the fixed desorption volume of eluant. As a compromise, 50 mg of MNPs were chosen for the subsequent experiments.
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3.2.2 The influence of extraction time
Preliminary experiments showed that poor reproducibility was obtained in the case of short extraction time, i.e. <5 min. Therefore, the extraction
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time was investigated in the range of 5-20 min. As shown in Supplement material Fig. S2, the maximum peak area for all the studied analytes occurred at 10 min, which indicated that the extraction equilibrium reached quite quickly. The result might benefit from the merits of the MNPs, including high surface area, short diffusion route for extraction and particularly good dispersibility of the Fe3O4-DVB-SO3- MNPs. Hence, 10 min was chosen as the optimal extraction time.
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3.2.3 The influence of desorption time
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To achieve satisfactory extraction efficiency, the influence of desorption time was investigated at time duration of 5, 10 and 15 min. It can be found from Supplement material Fig. S3 that all peak areas evidently increased with increasing desorption time from 5 to 10 min. After 10 min,
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the peak area slightly varied or remained unchanged. Therefore, 10 min of desorption time was chosen based on the experimental results.
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3.2.4 The influence of salt addition in the sample solution
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To investigate salt influence, NaCl was added into the sample solution at the concentration of 50 and 300 mg mL-1, respectively. As shown in Supplement material Fig. S4, the analytical signals varied irregularly with the addition of different amount of NaCl. For Np, Ace and F, the
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addition of NaCl facilitated the extraction (salting-out effect); while for Ph, An, FI and Py, the addition of NaCl was unfavorable to the extraction (salting-in effect). Anyway, neither the salting-out nor salting-in effect was significant. Considering the convenience of the operation, no salt addition was preferred herein.
In summary, the optimal extraction conditions for MSPE of PAHs were 50 mg of MNPs, 20 mL of sample solution without salt addition, 100
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μLisooctane as the elution solvent, and 10 min for both extraction and desorption under oscillation. The conditions were used afterwards.
3.3 Method evaluation
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To evaluate the proposed method, the ultrapure water samples were spiked at eight concentration levels of test analytes from 0.01 to 50 ng mL-1, followed by MSPE under the above optimized conditions and GC-MS analysis. All the validation data for the seven studied PAHs are presented
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in Table 2. The linearity ranges were calculated by plotting corresponding peak areas (y) versus concentrations of analytes (x, ng mL-1). Intra-day
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and inter-day relative standard deviations (RSDs) were both examined at three concentration levels, and each level was repeated three times.
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Limit of detection (LOD) and limit of quantification (LOQ) were calculated based on S/N=3 and S/N=10, respectively.
As shown in Table 2, the linearity ranges of the test PAHs were wide with satisfactory regression (r2>0.988). Intra-day and inter-day RSDs of peak areas were 3.3-16.5% and 0.7-21.2%. LODs and LOQs for the test analytes were ranging from 0.6 to 2.1 pg mL-1 and 2.0 to 7.0 pg mL-1, respectively. Although the enrichment factors were relatively low for the PAHs of low molecular weight, i.e. Np and Ace, the majority was satisfactory, especially for the PAHs of middle molecular weight, i.e. Ph and An. This may be due to the better interaction of these analytes and
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DVB herein [24]. The extraction recoveries were acceptable in the range of 79.9-115.3%. The evaluation data fully demonstrated that the
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developed method had wide linearity, low LODs and LOQs, and acceptable RSDs.
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3.4 Method applications
The practical suitability of the proposed MSPE was evaluated by determining PAHs in genuine water samples collected from Changjiang River
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and East Lake. In our preliminary experiment, it was found that matrix effect was obvious in the case of genuine environmental water. The
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relative extraction recovery was relatively low. Thus, standard addition was considered for quantification of the real water sample. To validate this method, the traditional LLE method as described in section 2.7 was used for comparison. As listed in Table 3, the two methods had
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comparable linearity range with satisfactory regression, and comparable intra-day and inter-day RSDs. However, MSPE was a one-step procedure with much less solvent consumption, fast and convenient operation.
As listed in Table 4, the determined concentrations of target PAHs ranged from 0.0684-1.0295 ng mL-1 for Changjiang river water and 0.2323-1.3561 ng mL-1 for East lake water by MSPE method, which was a little different from the results by LLE method. However, it was in an
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acceptable deviation range. The results demonstrated that the lake water was more seriously contaminated by PAHs than the river water. The
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detect PAHs in real environment samples.
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chromatograms of spiked water, river and lake waters were compared in Fig. 6. All the data revealed that the proposed method was suitable to
3.5 Comparison of the MSPE method based on Fe3O4-DVB-SO3- with other magnetic materials
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As shown in Table 5, the performance of the MSPE method based on Fe3O4-DVB-SO3- sorbent was superior to other magnetic materials for
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PAHs extraction from the view point of wide linearity, low LODs and low sample volume consumption [24-30]. There were some differences in MSPE operation between the present and the reported methods. First, the agitation mode was different. Sonication was the general way for
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MSPE agitation [24, 25, 28, 29]; while, as discussed in Section 3.2, oscillation was found to be more effective than ultrasonication in our study. Secondly, the type of the elution solvent was different. Hexane was used in most cases for PAH desorption when combined with GC-MS analysis [24, 25]. However, isooctane was herein demonstrated to be more suitable than hexane. In addition, a nitrogen stream concentration step was performed after desorption in some cases [24, 26, 28, 29], which is tedious and may bring possible loss of the target PAHs because of their semi-volatile nature. Therefore, satisfactory sensitivity was obtained for the present method.
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4 Conclusions
In this study, Fe3O4-DVB-SO3- magnetic nanoparticles (MNPs) were successfully prepared via “thiol-ene” click chemistry. The MNPs is made
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up with a hydrophobic underlayer for extraction and a hydrophilic surface layer for dispersion in aqueous solution. The particles afforded superb dispersibility and stabilization in aqueous solution, quick extraction and convenient operation. They were successfully used to extract PAHs from
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environmental water samples. Satisfactory results including low limits of detection and acceptable reproducibility were achieved. Therefore, this
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proposed method is possible to be applied in preconcentration of trace analytes in complex matrix.
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Acknowledgements
The authors gratefully acknowledge the financial support of this research by the Nature Science Foundation of China (No. 21177099), the Fundamental Research Funds for the Central Universities (No. 2042014kf0262), and Program for New Century Excellent Talents in University (No. NCET-12-0213).
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Ac
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coated-Fe3O4-SiO2-phenyl for HPLC-DAD analysis of sildenafil and its metabolite in biological samples, Talanta 130 (2014) 427-432. [17]
H. Deng, X. Li, Q. Peng, X. Wang, J. Chen, Y. Li, Monodisperse magnetic single-crystal ferrite microspheres, Angew. Chem. Int. Edit. 44 (2005) 2782-2785.
[18]
S. Ozcan, A. Tor, M.E. Aydin, Determination of polycyclic aromatic hydrocarbons in waters by ultrasound-assisted
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emulsification-microextraction and gas chromatography mass spectrometry, Anal. Chim. Acta 665 (2010) 193-199. A.B. Lowe, Thiol-ene "click" reactions and recent applications in polymer and materials synthesis, Polym. Chem. 1 (2010) 17-36.
[20]
C.E. Hoyle, C.N. Bowman, Thiol-Ene Click Chemistry, Angew. Chem. Int. Edit. 49 (2010) 1540-1573. B.S. Crimmins, J.E. Baker, Improved GC/MS methods for measuring hourly PAH and nitro-PAH concentrations in urban particulate
ed
[21]
M
[19]
matter, Atmos. Environ. 40 (2006) 6764-6779. M.C. Pietrogrande, M.G. Perrone, G. Sangiorgi, L. Ferrero, E. Bolzacchini, Data handling of GC/MS signals for characterization of PAH
pt
[22]
[23]
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sources in Northern Italy aerosols, Talanta 120 (2014) 283-288. M. Possanzini, V. Di Palo, P. Gigliucci, M. Concetta, T. Sciano, A. Cecinato, Determination of phase-distributed PAH in Rome ambient
Ac
air by denuder/GC-MS method, Atmos. Environ. 38 (2004) 1727-1734. [24] Y. Liu, H. Li, J.M. Lin, Magnetic solid-phase extraction based on octadecyl functionalization of monodisperse magnetic ferrite microspheres for the determination of polycyclic aromatic hydrocarbons in aqueous samples coupled with gas chromatography-mass spectrometry, Talanta 77 (2009) 1037-1042. [25]
F. Galán-Cano, M.C. Alcudia-León, R. Lucena, S. Cárdenas, M. Valcárcel, Ionic liquid coated magnetic nanoparticles for the gas
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an
chromatography/mass spectrometric determination of polycyclic aromatic hydrocarbons in waters, J. Chromatogr. A 1300 (2013)
[26]
M
134-140.
Q. Han, Z. Wang, J. Xia, S. Chen, X. Zhang, M. Ding, Facile and tunable fabrication of Fe3O4/graphene oxide nanocomposites and their
(2012) 388-395.
S. Zhang, H. Niu, Y. Cai, Y. Shi, Barium alginate caged Fe3O4@C18 magnetic nanoparticles for the pre-concentration of polycyclic
pt
[27]
ed
application in the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples, Talanta 101
[28]
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aromatic hydrocarbons and phthalate esters from environmental water samples, Anal. Chim. Acta 665 (2010) 167-175. S. Zhang, H. Niu, Z. Hu, Y. Cai, Y. Shi, Preparation of carbon coated Fe3O4 nanoparticles and their application for solid-phase extraction
[29]
Ac
of polycyclic aromatic hydrocarbons from environmental water samples, J. Chromatogr. A 1217 (2010) 4757-4764. Y. Long, Y. Chen, F. Yang, C. Chen, D. Pan, Q. Cai, S. Yao, Triphenylamine-functionalized magnetic microparticles as a new adsorbent coupled with high performance liquid chromatography for the analysis of trace polycyclic aromatic hydrocarbons in aqueous samples, Analyst 137 (2012) 2716-2722. [30]
A. Ballesteros-Gómez, S. Rubio, Hemimicelles of alkyl carboxylates chemisorbed onto magnetic nanoparticles: study and application to
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ed
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an
the extraction of carcinogenic polycyclic aromatic hydrocarbons in environmental water samples, Anal. Chem. 81 (2009) 9012-9020.
Figure captions
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Fig. 1 Preparation scheme of Fe3O4-DVB-SO3- MNPs.
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Fig. 2 The magnetic curve of Fe3O4-DVB-SO3- MNPs. Fig. 3 TEM image of Fe3O4-DVB-SO3- MNPs.
Ac
Fig. 4 FT-IR spectrum of Fe3O4-DVB-SO3- MNPs. Fig. 5 (i) Optical image of water droplets on the surface of Fe3O4-DVB-SO3- MNPs by contact angle analysis. (ii) Fe3O4-DVB-SO3- MNPs dispersed in sample solution (a), Fe3O4-DVB-SO3- MNPs isolated by a magnet (b) and Fe3O4-SiO2-SH MNPs dispersed in sample solution (c). Fig. 6 Chromatograms of (a) the spiked water at the PAH concentration of 0.01 ng mL-1, (b) the original Changjiang River and (c) the original East Lake after Fe3O4-DVB-SO3- MSPE at the optimal conditions. Peak assignment: (1) Np; (2) Ace; (3) F; (4) Ph; (5) An; (6) FI; (7) Py.
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Table 1 Retention time and characteristic ions of PAHs employed for GC/MS analysis.
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Mass List (amu) 128, 127, 129 153, 152, 154 166, 165, 167 178, 179, 176 178, 179, 176 202, 101, 100 202, 101, 100
pt
ed
Retention Time (min) 7.3 10.3 11.6 15.7 16.0 23.6 24.6
Ac
Np Ace F Ph An FI Py
Mol Mass 128 153 166 178 178 202 202
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Analyte
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Table 2 Regression data, enrichment factor, LODs, LOQs, intra-day and inter-day RSDs of PAHs extracted with Fe3O4 -DVB -SO3- MNPs.
2.6 9.0 20.2
1.1 0.8 1.1
3.7 2.8 3.6
104.0 105.6 111.1 115.3 91.6 103.0
0.01-100 0.01-50 0.05-50 0.01-50
y=4.0*106x-14026 y=5.9*106x+7.4*105 y=2.4*106x+3.4*105 y=3.2*106x+1.5*106
113.6 155.4 77.6 67.4
1.4 0.6 2.1 0.7
4.7 2.0 7.0 2.3
79.9 105.3 96.8 95.7
ed
y=1.3*106x+4.1*106 0.9884 y=3.7*106x+2.7*106 0.9978 y=4.6*106x+1.7*106 0.9993 0.9997 0.9994 0.9990 0.9977
pt
FI Py
0.01-50 0.01-50 0.01-50
ce
Ace F Ph An
r
Recovery (%) Intra-day RSD (%, n=4) LOQ Enrichment LOD 1 ng 0.05 ng 50 ng 1 ng 0.05 ng Factor (pg mL−1) (pg mL−1) 50 ng mL−1 mL−1 mL−1 mL−1 mL−1 mL−1
Inter-day RSD (%, n=3) 50 ng mL−1
1 ng mL−1
0.05 ng mL−1
84.5 86.1 80.9
6.1 5.0 5.2
6.1 8.0 7.8
10.8 10.2 9.8
3.5 1.8 2.1
4.8 5.0 3.8
8.4 12.2 10.2
103.6 92.9 81.5 110.2 92.7 91.4 98.1 90.4
6.0 6.3 7.4 6.9
3.9 3.3 5.5 8.0
11.3 14.1 16.5 14.7
5.1 14.4 4.8 0.7
5.0 8.4 13.2 9.7
11.9 14.2 5.0 21.2
Ac
Np
2
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Linear range Calibration Equation Analyte (ng mL-1)
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MSPE
East Lake
r
Np
0.01-5
0.9939
Ace
0.01-5
0.9992
F
0.01-10
0.9924
Ph
0.01-10
An
M
Linear range (ng mL-1)
2
LLE
Inter-day RSD (%, n=3)
5 ng 0.5 ng 0.05 ng 5 ng 0.5 ng 0.05 ng mL−1 mL−1 mL−1 mL−1 mL−1 mL−1
Intra-day RSD (%, n=4)
Calibration r2
5 ng 0.5 ng 0.05 ng 5 ng 0.5 ng 0.05 ng mL−1 mL−1 mL−1 mL−1 mL−1 mL−1
5.4
6.8
6.5
6.6
5.5
0.01-5
0.9093
3.1
14.2
1.3
7.2
17.9
12.4
7.9
5.9
1.9
9.8
5.9
9.3
0.01-5
0.9970
6.2
6.3
15.9
6.8
17.4
5.3
5.3
2.0
4.2
10.0
6.9
4.7
0.01-10
0.9941
6.7
5.0
14.8
9.3
18.6
4.5
0.9925
4.5
1.8
5.6
14.4
10.5
19.2
0.01-10
0.9804
12.3
18.5
18.8
2.0
15.9
6.3
0.01-10
0.9914
3.0
4.1
4.6
12.7
5.2
0.3
0.01-10
0.9970
7.4
4.2
16.0
12.1
4.2
3.8
FI
0.05-5
0.9956
5.6
6.5
15.2
7.4
5.9
8.5
0.05-5
0.9745
9.6
14.9
17.7
11.8
6.4
4.2
Py
0.01-10
0.9984
6.5
7.2
4.6
7.0
4.8
13.1
0.01-10
0.9787
9.5
6.8
19.7
6.2
8.3
11.0
ce
6.3
pt
Linear range (ng mL-1)
Inter-day RSD (%, n=3)
Ac
Changjiang River
Intra-day RSD (%, n=4)
Calibration
ed
Genuine Analyte samples
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Table 3 Linearity range, regression data, intra-day and inter-day RSDs of PAHs in real samples extracted with MSPE and LLE.
Np
0.01-10
0.9850
4.9
11.3
6.2
2.7
10.7
5.6
0.01-10
0.9498
4.9
6.4
4.1
38.3
9.4
4.5
Ace
0.01-10
0.9920
5.4
2.9
10.9
7.4
8.4
0.7
0.01-10
0.9997
5.6
8.1
14.4
13.3
15.6
16.3
F
0.01-10
0.9908
5.7
4.9
9.8
7.8
19.7
0.4
0.01-10
0.9963
6.7
11.2
14.5
11.9
5.7
21.1
Ph
0.01-10
0.9913
3.3
3.5
7.0
4.8
16.8
15.6
0.01-10
0.9921
9.1
18.1
15.3
7.4
19.9
21.5
An
0.01-10
0.9917
3.9
3.8
5.2
5.3
14.3
4.4
0.01-10
0.9972
1.5
7.9
15.6
13.0
15.4
2.3
FI
0.05-10
0.9923
3.6
7.3
5.3
16.2
12.8
3.5
0.05-10
0.9876
4.1
8.8
12.4
18.0
12.0
11.4
Py
0.01-10
0.9923
4.6
8.0
5.0
10.8
9.9
8.4
0.01-10
0.9902
6.1
5.8
13.0
6.1
21.9
5.7
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0.9900 0.2034 0.3057 0.7277 0.3378 0.4848 0.0827 1.1113 0.3731 1.0410 1.5186 0.2469 0.4603 0.2706
East Lake
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1.0295 0.2662 0.2609 0.5656 0.3420 0.4179 0.0684 1.3196 0.3261 0.8674 1.3561 0.2323 0.4179 0.2466
Error (%)
3.8 23.6 -17.2 -28.7 1.2 -16.0 -20.9 15.8 -14.4 -20.0 -12.0 -6.3 -10.1 -9.7
ed
LLE
pt
Np Ace F Ph An FI Py Np Ace F Ph An FI Py
MSPE
Ac
Changjiang River
Analyte
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Genuine samples
Concentration in genuine samples (ng mL-1)
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Table 4 The determined PAH concentration in genuine samples by MSPE and LLE
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1
40-1110
7
Fe3O4/GO Fe3O4@C18@Ba2+-ALG Fe3O4/C
HPLC-UV UHPLC-FLD HPLC-FLD
0.5-100 0.01-2 0.01-1
120-190 2-5 0.2-0.6
10 30 30
Fe3O4/SiO2/TPA
HPLC-FLD
0.5-400
0.25-0.5
10
C14/Fe3O4
HPLC-FLD
0.02-10
0.2-0.4
15
ip t
0.25-25
us
cr
GC-MS
GC-MS 0.01-100 0.6-2.1 Fe3O4-DVB-SO3Na IL- Fe3O4, ionic liquid-coated Fe3O4; C18-Fe3O4, C18 bonded Fe3O4; Fe3O4/GO, graphene oxide modified Fe3O4; Fe3O4@C18@Ba2+-ALG, Fe3O4@C18@barium alginate polymers; Fe3O4/C, carbon coated Fe3O4; Fe3O4/SiO2/TPA, triphenylamine-functionalized Fe3O4; C14/Fe3O4, C14 bonded Fe3O4.
10
Fig. 1
Ac ce p
te
d
9
IL/Fe3O4
Extraction time (min) 5
an
4 5 6 7 8
Table 5 Comparison of Fe3O4-DVB-SO3- with other published MSPE of PAHs from water samples. LOD Linearity MNP material Detection -1 (pg mL-1) (ng mL ) C18/Fe3O4 GC-MS 10-800 800-4200
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2 3
10 11 12 13 14 15 16 30
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Fig. 2
37 38 39 40 41 42 43 44 45
Ac ce p
te
d
36
ip t
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
31
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Fig. 3
66 67 68 69 70 71 72 73 74
Ac ce p
te
d
65
ip t
46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
32
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ip t cr us an M
Fig. 4
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110
Ac ce p
te
d
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
33
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ip t cr us an M
Fig. 5 (i)
133 134 135 136
Ac ce p
te
d
111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
(ii)
34
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Fig. 6
te
d
M
an
us
cr
ip t 153
Ac ce p
137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152
154 35
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► Fe3O4-divinylbenzene-SO3- magnetic nanoparticle was prepared via “thiol-ene” click reaction. ► The sulfonate groups featured the material excellent aqueous dispersibility.
159
► It was used for PAH extraction from environmental samples.
160
► Satisfactory reproducibility, low LODs and good linearity were obtained.
ip t
155 156 157 158
Ac ce p
te
d
M
an
us
cr
161 162
36
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S0021-9673(15)01112-7 http://dx.doi.org/doi:10.1016/j.chroma.2015.07.104 CHROMA 356731
To appear in:
Journal of Chromatography A
Received date: Revised date: Accepted date:
16-4-2015 28-7-2015 31-7-2015
Please cite this article as: S.-W. Xue, M.-Q. Tang, L. Xu, Z.-g. Shi, Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples, Journal of Chromatography A (2015), http://dx.doi.org/10.1016/j.chroma.2015.07.104 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from
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environmental water samples
Shu-Wen Xuea, Min-Qiong Tanga, Li Xua, Zhi-guo Shib,* a
ed
Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan
Department of Chemistry, Wuhan University, Wuhan 430072, China
pt
b
430030, China
Abstract
Email address: [email protected] (Z.-g. Shi).
Ac
ce
*Corresponding author. Tel: +86 27 68752701; Fax: +86 27 68754067
Magnetic nanoparticles (MNPs) featured with divinylbenzene (DVB) and sulfonate functionalities (Fe3O4-DVB-SO3-) were prepared via “thiol-ene” click chemistry. The hydrophobic DVB moieties were dedicated for extraction while the hydrophilic sulfonate groups were designed for dispersing the MNPs in aqueous sample solution. Thus, the special designed material could ensure operational convenience and improve
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reproducibility during extraction. The application of the material was demonstrated by the extraction of polycyclic aromatic hydrocarbons (PAHs)
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from environmental water samples followed by gas chromatography-mass spectrometric analysis. The main factors influencing the extraction, including the type of the desorption solvent, the agitation mode, the amount of MNPs, extraction and desorption time and salt addition in sample
ed
solution, were investigated in detail. Under the optimized conditions, the proposed method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations less than 16.5% and 21.2%, and low limits of detection of 1.1 pg mL-1, 0.8 pg mL-1, 1.1 pg mL-1, 1.4
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pg mL-1, 0.6 pg mL-1, 2.1 pg mL-1 and 0.7 pg mL-1 for naphthalene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene and pyrene,
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respectively. The developed method was also successfully used for determination of the PAHs in genuine lake and river environmental water samples by standard addition method. All the studied PAHs were detected in these waters with comparable results by the standard liquid-liquid
Ac
extraction method. The developed MNPs with dual property of hydrophobicity and hydrophilicity were suitable for the treatment of water samples. The magnetic solid phase extraction based on this material was reliable and convenient. It has great potential in the preconcentration of trace analytes in complex matrix. Keywords: magnetic solid-phase extraction; click chemistry; hydrophobicity; aqueous dispersibility; polycyclic aromatic hydrocarbons.
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1 Introduction
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Recently, magnetic solid-phase extraction (MSPE) has attracted increasing interest worldwide [1-4]. Owing to the nanoscale particle size, the MNPs commonly possess large surface area and short diffusion pathway, which may result in large extraction capacity and high extraction
ed
efficiency. Additionally, the MNPs can be quickly isolated from matrix solution via an external magnetic field after extraction. Thus, compared with traditional column SPE, the MSPE affords enhanced extraction efficiency, and avoids column packing as well as possible blockage in the
ce
pt
column [5, 6].
In MSPE, Fe3O4 and γ-Fe2O3 are the most frequently used kernel materials of the sorbents. Generally they should be functionalized with special
Ac
ligands for target analytes [7, 8]. For example, MNPs functionalized with C18, C8 and cyclodextrin were applied for the extraction of organophosphorous pesticides [9], peptides [10] and biphenolic pollutants [11], respectively. However, the functionalized MNPs are usually difficult to disperse well in aqueous sample owing to their high hydrophobicity, especially for the particles below 50 nm [12]. On the other hand, these MNPs aggregate easily, which may decrease their stability and be detrimental to the extraction performance [13]. For these reasons, a hydrophilic layer constructed on the surface of hydrophobic MNPs is essential to improve the aqueous dispersibility, and thus enhance the
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extraction reproducibility and operation convenience. As a typical example, Cai et al. synthesized a novel MNP sorbent with an interior C18
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group and an exterior chitosan polymer coating, to extract perfluorinated and phthalate ester compounds from environmental water samples [12]. Following that, Geng et al. prepared chitosan coated carbon-functionalized MNPs for extraction of bisphenol A from tap water [14]. In addition,
ed
Ye et al. coated non-ionic surfactants, i.e. Span and Tween, on the surface of C12-MNPs to extract steroid hormones from environmental and biological samples [5]. Besides, Bai et al. synthesized carbon-ferromagnetic nanocomposite with enriched hydroxyl groups via specially
pt
designed carbonization strategy [15] for extracting polycyclic aromatic hydrocarbons (PAHs). Another example was methylcellulose coated
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phenyl functionalized MNPs, to extract sildenafil and desmethyl sildenafil from human urine and plasma samples [16]. Nevertheless, most of these hydrophilic layer groups were physically coated instead of chemically modified on the MNPs [5, 13, 14, 16]. In another word, they may be
Ac
not stable enough in some circumstances.
In the present work, new MNPs, which simultaneously contained hydrophobic divinylbenzene (DVB) and hydrophilic sulfonate (Fe3O4-DVB-SO3-), were elaborately designed. It was prepared via a two-step approach involving “thiol-ene” click chemistry. The prepared Fe3O4-DVB-SO3- was used as the MSPE sorbent.
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As is known to all, PAHs are recognized as potential carcinogens, which have been listed as priority pollutants by the European Union and U.S. Environmental Protection Agency. Considering that the hydrophobic DVB on the Fe3O4-DVB-SO3- MNPs would feature its reservation of
ed
hydrophobic compounds, among which PAHs are one kind of the representative, several PAHs were chosen to test the extraction ability of the
pt
prepared MNPs. The developed method was then applied to genuine environmental water samples.
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2 Experimental 2.1 Chemicals and Reagents
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Seven PAHs, naphthalene (Np), acenaphthene (Ace), fluorene (F), phenanthrene (Ph), anthracene (An), fluoranthene (FI) and pyrene (Py), were purchased from Aladdin Chemical Reagent Co., Ltd. (Shanghai, China). Methanol was supplied by Merck (Darmstadt, Hessen, Germany). Azodiisobutyronitrile (AIBN), ethanol, toluene, ethyl acetate (HPLC grade), acetone (HPLC grade), n-hexane (HPLC grade), DVB, acetic acid, sodium acetate, ethylene glycol, polyvinyl alcohol, ammonia, sodium 3-mercapto-1-propanesulfonate and iron(III) chloride hexahydrate were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Tetraethoxysilane and 3-(mercaptopropyl)trimethoxysilane were
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obtained from Hubei Wuhan University Silicone New Material Co., Ltd. (Wuhan, China). Isooctane (HPLC grade) was purchased from Xiya
ed
2.2 Preparation of Fe3O4-DVB-SO3- MNPs
M
Reagent Research Center (Linshu, China). Ultrapure water was produced by a Heal Fore NW system (Shanghai, China).
The procedures for preparation of Fe3O4-DVB-SO3- MNPs are depicted in Fig. 1. Firstly, Fe3O4 MNPs were prepared by solvothermal method
pt
and coated with silica as previously reported [17]. Secondly, Fe3O4-SiO2 (8.0 g), 3-(mercaptopropyl)- trimethoxysilane (2.0 mL) and toluene
ce
(15.0 mL) were mixed and heated at 130℃ for 4 h. The obtained product, Fe3O4-SiO2-SH, was isolated and washed carefully by toluene and methanol for 3 times, respectively. Then it was dried at 120℃ for 4 h. Thirdly, the as-prepared Fe3O4-SiO2-SH (2.0 g) was mixed with ethanol
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(15.0 mL) containing DVB (0.5 mL) and H2O (1.0 mL). Five minutes later, AIBN (25 mg) and sodium 3-mercapto-1-propanesulfonate (0.45 g) were added simultaneously. Under vigorous mechanical stirring and nitrogen atmosphere, the reaction proceeded at 70℃ for 8 h. Thereafter, the product was washed with ethanol and pure water consecutively, and then dried at 80℃ for 12 h. Finally, Fe3O4-DVB-SO3- MNPs was available.
2.3 Characterization of Fe3O4-DVB-SO3- MNPs
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Magnetism of the material was studied by a PPMS-9 vibrating sample magnetometer (QUANTOM, USA). The hydrophobic and hydrophilic
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properties of the prepared material were studied by contact angle measurement (Drop Shape Analysis System DSA 100) (Kruss, Germany). Transmission electron microscopy (TEM) image was recorded on a H-7500 transmission electronic microscopy (Hitachi, Tokyo, Japan) Fourier
ed
transform infrared (FTIR) spectroscopic experiment was carried out on a Nicolet (Madison, WI, USA) Impact 420 apparatus. Thermogravimetric
pt
analysis (TGA) was carried out on a Setaram (France) TG-DTA analyzer.
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2.4 Gas chromatography-mass spectrometric (GC-MS) analysis The analysis of the seven PAHs was performed on a TriPlus-RSH autosampler -Trace1300-ISQ GC-MS instrument from Thermo Scientific
Ac
(West Palm Beach, FL, USA). The following GC temperature program was used: the initial oven temperature 70℃ for 2 min; increased to 180 ℃ at a rate of 15℃ min-1 and held at 180℃ for 10 min; then increased to 240℃ at a rate of 10℃ min-1, and finally up to 280℃ at a rate of 20℃ min-1 and held at 280℃ for 2 min. A DB-5MS capillary column (30 m ×0.25 mm ×0.25 μm) from Agilent Technology, Inc. (Santa Clara, CA, USA) was used. The carrier gas was helium at a flow rate of 1.2 mL min-1. The injector was operated at 280℃ in splitless mode for 2 min. The electron ionization mass spectrometer was operated with energy of 70 eV. The ion source temperature was 280℃, and the GC-MS interface
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temperature was 300℃. The analysis was performed in full scan mode (mass range: 50-450 m/z) to confirm the retention time of PAHs. The
M
quantification was achieved by selected ion monitoring (SIM) mode using the characteristic ions as listed in Table 1. The collection of raw data was performed using an X-Calibur 1.4 software system from Thermo Scientific (West Palm Beach, FL, USA). All the experiments were
pt
2.5 Sample preparation
ed
performed at least in triplicate.
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The stock solutions of PAHs were prepared as follows. Accurately weighed 2 mg of An and 10 mg of the others were separately dissolved in methanol, yielding stock solutions of 0.2 mg mL-1 for An and 1 mg mL-1 for the others. Working solutions containing the required concentration
Ac
of each analyte were freshly prepared daily by diluting stock solutions with double distillated water, which were used for evaluating extraction performance under different conditions. All solutions prepared were stored at 4℃ and protected from light in brown glass bottles.
2.6 MSPE procedure The MSPE procedure was carried out as follows. Prescribed amount of Fe3O4-DVB-SO3- was added into a vial (maximum volume of 25 mL),
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which contained 20 mL sample solution. After being oscillated for certain time, the MNPs were separated from the sample solution by attaching
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a Nd-Fe-B magnet (50 mm ×50 mm ×10 mm) to the bottom of the vial. The sample solution was decanted and ultrapure water (500 μL) was added into the vial to wash the MNPs. After the water was decanted, filter paper was carefully dispatched to absorb the residual water.
ed
Subsequently, 100 μL of isooctane was introduced to desorb the adsorbed analytes from the MNPs by oscillation for the prescribed time. The
pt
eluate was separated from the suspension with the magnet. Finally, 1 μL of the eluate was injected into the GC-MS system for analysis.
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2.7 Liquid-liquid extraction (LLE)
For comparison, the LLE procedure, based on US EPA Method 3510C [18], was adopted for the genuine samples. Briefly, 20 mL of water
Ac
sample was placed in a 25 mL separatory funnel. The extraction was carried out three times with 2 mL of dichloromethane. The extracts were combined and evaporated under a gentle nitrogen stream (N2, purity >99.9%) until dryness. The residue was then dissolved in 100 μL of isooctane and collected for GC-MS analysis.
2.8 Application to genuine samples
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The genuine water samples were collected from Changjiang River and East Lake (Wuhan, Hubei, China). They were stored at the temperature of
M
4℃, and protected from light in brown glass bottles. Standard addition method was employed to determine target PAHs in these water samples. Standard PAHs stock solutions were added to real water samples to obtain the different spiked concentrations, 10, 5, 1, 0.5, 0.1, 0.05 and 0.01 ng
pt
3 Results and discussion
ed
mL-1. Each water sample was first filtered, and then subjected to the MSPE and LLE under the optimal condition.
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3.1 Preparation and characterization of Fe3O4-DVB-SO3- MNPs The “thiol-ene” click reaction is the hydrothiolation of a C=C bond, which is conducted under radical conditions [19, 20]. In this experiment,
Ac
Fe3O4-SiO2 was first chemically bonded with -SH group to generate Fe3O4-SiO2-SH. With the promotion of AIBN, the -SH groups on Fe3O4-SiO2-SH and 3-mercapto-1-propanesulfonate formed thiol radicals, which attacked the C=C bond of DVB to yield intermediate carboncentred radicals followed by chain transfer to a second molecule of thiol to give the thiol-ene addition product. This reaction generally proceeded in a mild condition, and was extremely rapid and complete in several hours.
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The magnetic property of Fe3O4-DVB-SO3- MNPs was investigated by a vibrating sample magnetometer. As shown in Fig. 2, the curve had no
M
magnetic hysteresis loop and the saturation magnetization value was 61 emu/g. The result demonstrated that the MNPs were super paramagnetic.
ed
The TEM image, as shown in Fig. 3, disclosed that the material was spherical, with average diameter of ~70 nm.
FT-IR spectroscopy was employed to verify the functional moieties of the MNPs. As shown in Fig. 4, the DVB component of Fe3O4-DVB-SO3-
pt
MNPs can be confirmed by the peaks around 1600 cm-1, corresponding to the stretching vibration of the vinyl and phenyl groups. The strong
ce
peaks around 1200 and 1100 cm-1 should be ascribed to the stretching vibration of sulfonic acid group, indicating -SO3- was present in the MNPs. The organic content of the MNPs was evaluated by TGA method. The weight loss ranging from 200
to 800
was calculated to be 3.80% and
Ac
5.33% for Fe3O4-SiO2-SH and Fe3O4-DVB-SO3-, respectively. All of these results indicated that both DVB and sulfonate groups were successfully modified onto the Fe3O4-SiO2 MNPs.
A contact angle analysis was carried out to evaluate the hydrophilicity of Fe3O4-DVB-SO3-. As depicted in Fig. 5 (i), the water drop dispersed quickly when it contacted the material and the contact angle was found to be almost 0º, which demonstrated that Fe3O4-DVB-SO3- had superb
Page 11 of 36
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hydrophilicity. In addition, as shown in Fig. 5 (ii), the Fe3O4-DVB-SO3- MNPs were well dispersed in aqueous solution (a) and they could be
M
quickly isolated from the solution through an external magnetic field (b), which would be a preferred merit for extraction application. In contrast, the dispersibility of the Fe3O4-SiO2-SH MNPs in aqueous solution was bad, as shown in Fig. 5 (ii) (c), which further demonstrated that sulfonate
ed
groups featured the material excellent aqueous dispersibility.
pt
3.2 Optimization of MSPE conditions
ce
The performance of MSPE was influenced by multiple factors. In our preliminary experiments, the type of desorption solvent was first studied to ensure its compatibility with the GC-MS system and the elution of the PAHs from MNPs. Ethyl acetate, acetone, n-hexane and isooctane, all of
Ac
which were documented to have low boiling points, great solubility of PAHs and superb compatibility with GC-MS system [18, 21], were herein studied. Isooctane was finally chosen as it afforded the strongest analytical signals, least interference to signals and symmetric peaks with high column efficiency [22, 23]. Moreover, the volume of isooctane for elution was also optimized. It was found that 100 μL of isooctane was the best choice.
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Agitation is commonly applied to promote the extraction process in MSPE. Herein, two agitation modes, ultrasonication and oscillation, were
M
compared. The results demonstrated that the oscillation mode can provide better reproducibility and higher extraction efficiency. Therefore, this
ed
mode was adopted for the following experiments.
The sample pH was also evaluated and it was found to be irrelevant to the extraction efficiency. This observation could be explained as below.
pt
As the sulphonate groups of Fe3O4-DVB-SO3- MNPs were fully ionized under the investigated pH range (2-10), it did not influence the
ce
dispersive status of the MNPs in the sample solution. Furthermore, since the extraction was based on the hydrophobic interaction between the
Ac
target analytes (PAHs) and the MNPs, little influence by the sample pH could be also predicted.
In addition to these parameters, the amount of Fe3O4-DVB-SO3- MNPs, extraction time, desorption time and salt addition were optimized in detail by a one-variant-at-one-time approach.
3.2.1 The influence of Fe3O4-DVB-SO3- MNPs amount
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The sorbent amount played a significant role in MSPE performance. The influence of Fe3O4-DVB-SO3- amount on the extraction was studied in
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the range of 10-70 mg. As shown in Supplement material Fig. S1, peak area of the analytes climbed up notably with the increasing amount of MNPs from 10 to 50 mg. It reflected that the more amount of MNPs was used, the better extraction performance was achieved. However, the
ed
peak area declined or slightly went up with the particle amount further increasing to 70 mg, which would be ascribed to the inadequate elution of
pt
the adsorbed analytes by the fixed desorption volume of eluant. As a compromise, 50 mg of MNPs were chosen for the subsequent experiments.
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3.2.2 The influence of extraction time
Preliminary experiments showed that poor reproducibility was obtained in the case of short extraction time, i.e. <5 min. Therefore, the extraction
Ac
time was investigated in the range of 5-20 min. As shown in Supplement material Fig. S2, the maximum peak area for all the studied analytes occurred at 10 min, which indicated that the extraction equilibrium reached quite quickly. The result might benefit from the merits of the MNPs, including high surface area, short diffusion route for extraction and particularly good dispersibility of the Fe3O4-DVB-SO3- MNPs. Hence, 10 min was chosen as the optimal extraction time.
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3.2.3 The influence of desorption time
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To achieve satisfactory extraction efficiency, the influence of desorption time was investigated at time duration of 5, 10 and 15 min. It can be found from Supplement material Fig. S3 that all peak areas evidently increased with increasing desorption time from 5 to 10 min. After 10 min,
ed
the peak area slightly varied or remained unchanged. Therefore, 10 min of desorption time was chosen based on the experimental results.
pt
3.2.4 The influence of salt addition in the sample solution
ce
To investigate salt influence, NaCl was added into the sample solution at the concentration of 50 and 300 mg mL-1, respectively. As shown in Supplement material Fig. S4, the analytical signals varied irregularly with the addition of different amount of NaCl. For Np, Ace and F, the
Ac
addition of NaCl facilitated the extraction (salting-out effect); while for Ph, An, FI and Py, the addition of NaCl was unfavorable to the extraction (salting-in effect). Anyway, neither the salting-out nor salting-in effect was significant. Considering the convenience of the operation, no salt addition was preferred herein.
In summary, the optimal extraction conditions for MSPE of PAHs were 50 mg of MNPs, 20 mL of sample solution without salt addition, 100
Page 15 of 36
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μLisooctane as the elution solvent, and 10 min for both extraction and desorption under oscillation. The conditions were used afterwards.
3.3 Method evaluation
ed
To evaluate the proposed method, the ultrapure water samples were spiked at eight concentration levels of test analytes from 0.01 to 50 ng mL-1, followed by MSPE under the above optimized conditions and GC-MS analysis. All the validation data for the seven studied PAHs are presented
pt
in Table 2. The linearity ranges were calculated by plotting corresponding peak areas (y) versus concentrations of analytes (x, ng mL-1). Intra-day
ce
and inter-day relative standard deviations (RSDs) were both examined at three concentration levels, and each level was repeated three times.
Ac
Limit of detection (LOD) and limit of quantification (LOQ) were calculated based on S/N=3 and S/N=10, respectively.
As shown in Table 2, the linearity ranges of the test PAHs were wide with satisfactory regression (r2>0.988). Intra-day and inter-day RSDs of peak areas were 3.3-16.5% and 0.7-21.2%. LODs and LOQs for the test analytes were ranging from 0.6 to 2.1 pg mL-1 and 2.0 to 7.0 pg mL-1, respectively. Although the enrichment factors were relatively low for the PAHs of low molecular weight, i.e. Np and Ace, the majority was satisfactory, especially for the PAHs of middle molecular weight, i.e. Ph and An. This may be due to the better interaction of these analytes and
Page 16 of 36
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DVB herein [24]. The extraction recoveries were acceptable in the range of 79.9-115.3%. The evaluation data fully demonstrated that the
M
developed method had wide linearity, low LODs and LOQs, and acceptable RSDs.
ed
3.4 Method applications
The practical suitability of the proposed MSPE was evaluated by determining PAHs in genuine water samples collected from Changjiang River
pt
and East Lake. In our preliminary experiment, it was found that matrix effect was obvious in the case of genuine environmental water. The
ce
relative extraction recovery was relatively low. Thus, standard addition was considered for quantification of the real water sample. To validate this method, the traditional LLE method as described in section 2.7 was used for comparison. As listed in Table 3, the two methods had
Ac
comparable linearity range with satisfactory regression, and comparable intra-day and inter-day RSDs. However, MSPE was a one-step procedure with much less solvent consumption, fast and convenient operation.
As listed in Table 4, the determined concentrations of target PAHs ranged from 0.0684-1.0295 ng mL-1 for Changjiang river water and 0.2323-1.3561 ng mL-1 for East lake water by MSPE method, which was a little different from the results by LLE method. However, it was in an
Page 17 of 36
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acceptable deviation range. The results demonstrated that the lake water was more seriously contaminated by PAHs than the river water. The
ed
detect PAHs in real environment samples.
M
chromatograms of spiked water, river and lake waters were compared in Fig. 6. All the data revealed that the proposed method was suitable to
3.5 Comparison of the MSPE method based on Fe3O4-DVB-SO3- with other magnetic materials
pt
As shown in Table 5, the performance of the MSPE method based on Fe3O4-DVB-SO3- sorbent was superior to other magnetic materials for
ce
PAHs extraction from the view point of wide linearity, low LODs and low sample volume consumption [24-30]. There were some differences in MSPE operation between the present and the reported methods. First, the agitation mode was different. Sonication was the general way for
Ac
MSPE agitation [24, 25, 28, 29]; while, as discussed in Section 3.2, oscillation was found to be more effective than ultrasonication in our study. Secondly, the type of the elution solvent was different. Hexane was used in most cases for PAH desorption when combined with GC-MS analysis [24, 25]. However, isooctane was herein demonstrated to be more suitable than hexane. In addition, a nitrogen stream concentration step was performed after desorption in some cases [24, 26, 28, 29], which is tedious and may bring possible loss of the target PAHs because of their semi-volatile nature. Therefore, satisfactory sensitivity was obtained for the present method.
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4 Conclusions
In this study, Fe3O4-DVB-SO3- magnetic nanoparticles (MNPs) were successfully prepared via “thiol-ene” click chemistry. The MNPs is made
ed
up with a hydrophobic underlayer for extraction and a hydrophilic surface layer for dispersion in aqueous solution. The particles afforded superb dispersibility and stabilization in aqueous solution, quick extraction and convenient operation. They were successfully used to extract PAHs from
pt
environmental water samples. Satisfactory results including low limits of detection and acceptable reproducibility were achieved. Therefore, this
ce
proposed method is possible to be applied in preconcentration of trace analytes in complex matrix.
Ac
Acknowledgements
The authors gratefully acknowledge the financial support of this research by the Nature Science Foundation of China (No. 21177099), the Fundamental Research Funds for the Central Universities (No. 2042014kf0262), and Program for New Century Excellent Talents in University (No. NCET-12-0213).
Page 19 of 36
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air by denuder/GC-MS method, Atmos. Environ. 38 (2004) 1727-1734. [24] Y. Liu, H. Li, J.M. Lin, Magnetic solid-phase extraction based on octadecyl functionalization of monodisperse magnetic ferrite microspheres for the determination of polycyclic aromatic hydrocarbons in aqueous samples coupled with gas chromatography-mass spectrometry, Talanta 77 (2009) 1037-1042. [25]
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S. Zhang, H. Niu, Y. Cai, Y. Shi, Barium alginate caged Fe3O4@C18 magnetic nanoparticles for the pre-concentration of polycyclic
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application in the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples, Talanta 101
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aromatic hydrocarbons and phthalate esters from environmental water samples, Anal. Chim. Acta 665 (2010) 167-175. S. Zhang, H. Niu, Z. Hu, Y. Cai, Y. Shi, Preparation of carbon coated Fe3O4 nanoparticles and their application for solid-phase extraction
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of polycyclic aromatic hydrocarbons from environmental water samples, J. Chromatogr. A 1217 (2010) 4757-4764. Y. Long, Y. Chen, F. Yang, C. Chen, D. Pan, Q. Cai, S. Yao, Triphenylamine-functionalized magnetic microparticles as a new adsorbent coupled with high performance liquid chromatography for the analysis of trace polycyclic aromatic hydrocarbons in aqueous samples, Analyst 137 (2012) 2716-2722. [30]
A. Ballesteros-Gómez, S. Rubio, Hemimicelles of alkyl carboxylates chemisorbed onto magnetic nanoparticles: study and application to
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Figure captions
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Fig. 1 Preparation scheme of Fe3O4-DVB-SO3- MNPs.
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Fig. 2 The magnetic curve of Fe3O4-DVB-SO3- MNPs. Fig. 3 TEM image of Fe3O4-DVB-SO3- MNPs.
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Fig. 4 FT-IR spectrum of Fe3O4-DVB-SO3- MNPs. Fig. 5 (i) Optical image of water droplets on the surface of Fe3O4-DVB-SO3- MNPs by contact angle analysis. (ii) Fe3O4-DVB-SO3- MNPs dispersed in sample solution (a), Fe3O4-DVB-SO3- MNPs isolated by a magnet (b) and Fe3O4-SiO2-SH MNPs dispersed in sample solution (c). Fig. 6 Chromatograms of (a) the spiked water at the PAH concentration of 0.01 ng mL-1, (b) the original Changjiang River and (c) the original East Lake after Fe3O4-DVB-SO3- MSPE at the optimal conditions. Peak assignment: (1) Np; (2) Ace; (3) F; (4) Ph; (5) An; (6) FI; (7) Py.
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Table 1 Retention time and characteristic ions of PAHs employed for GC/MS analysis.
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Mass List (amu) 128, 127, 129 153, 152, 154 166, 165, 167 178, 179, 176 178, 179, 176 202, 101, 100 202, 101, 100
pt
ed
Retention Time (min) 7.3 10.3 11.6 15.7 16.0 23.6 24.6
Ac
Np Ace F Ph An FI Py
Mol Mass 128 153 166 178 178 202 202
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Analyte
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Table 2 Regression data, enrichment factor, LODs, LOQs, intra-day and inter-day RSDs of PAHs extracted with Fe3O4 -DVB -SO3- MNPs.
2.6 9.0 20.2
1.1 0.8 1.1
3.7 2.8 3.6
104.0 105.6 111.1 115.3 91.6 103.0
0.01-100 0.01-50 0.05-50 0.01-50
y=4.0*106x-14026 y=5.9*106x+7.4*105 y=2.4*106x+3.4*105 y=3.2*106x+1.5*106
113.6 155.4 77.6 67.4
1.4 0.6 2.1 0.7
4.7 2.0 7.0 2.3
79.9 105.3 96.8 95.7
ed
y=1.3*106x+4.1*106 0.9884 y=3.7*106x+2.7*106 0.9978 y=4.6*106x+1.7*106 0.9993 0.9997 0.9994 0.9990 0.9977
pt
FI Py
0.01-50 0.01-50 0.01-50
ce
Ace F Ph An
r
Recovery (%) Intra-day RSD (%, n=4) LOQ Enrichment LOD 1 ng 0.05 ng 50 ng 1 ng 0.05 ng Factor (pg mL−1) (pg mL−1) 50 ng mL−1 mL−1 mL−1 mL−1 mL−1 mL−1
Inter-day RSD (%, n=3) 50 ng mL−1
1 ng mL−1
0.05 ng mL−1
84.5 86.1 80.9
6.1 5.0 5.2
6.1 8.0 7.8
10.8 10.2 9.8
3.5 1.8 2.1
4.8 5.0 3.8
8.4 12.2 10.2
103.6 92.9 81.5 110.2 92.7 91.4 98.1 90.4
6.0 6.3 7.4 6.9
3.9 3.3 5.5 8.0
11.3 14.1 16.5 14.7
5.1 14.4 4.8 0.7
5.0 8.4 13.2 9.7
11.9 14.2 5.0 21.2
Ac
Np
2
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Linear range Calibration Equation Analyte (ng mL-1)
Page 27 of 36
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MSPE
East Lake
r
Np
0.01-5
0.9939
Ace
0.01-5
0.9992
F
0.01-10
0.9924
Ph
0.01-10
An
M
Linear range (ng mL-1)
2
LLE
Inter-day RSD (%, n=3)
5 ng 0.5 ng 0.05 ng 5 ng 0.5 ng 0.05 ng mL−1 mL−1 mL−1 mL−1 mL−1 mL−1
Intra-day RSD (%, n=4)
Calibration r2
5 ng 0.5 ng 0.05 ng 5 ng 0.5 ng 0.05 ng mL−1 mL−1 mL−1 mL−1 mL−1 mL−1
5.4
6.8
6.5
6.6
5.5
0.01-5
0.9093
3.1
14.2
1.3
7.2
17.9
12.4
7.9
5.9
1.9
9.8
5.9
9.3
0.01-5
0.9970
6.2
6.3
15.9
6.8
17.4
5.3
5.3
2.0
4.2
10.0
6.9
4.7
0.01-10
0.9941
6.7
5.0
14.8
9.3
18.6
4.5
0.9925
4.5
1.8
5.6
14.4
10.5
19.2
0.01-10
0.9804
12.3
18.5
18.8
2.0
15.9
6.3
0.01-10
0.9914
3.0
4.1
4.6
12.7
5.2
0.3
0.01-10
0.9970
7.4
4.2
16.0
12.1
4.2
3.8
FI
0.05-5
0.9956
5.6
6.5
15.2
7.4
5.9
8.5
0.05-5
0.9745
9.6
14.9
17.7
11.8
6.4
4.2
Py
0.01-10
0.9984
6.5
7.2
4.6
7.0
4.8
13.1
0.01-10
0.9787
9.5
6.8
19.7
6.2
8.3
11.0
ce
6.3
pt
Linear range (ng mL-1)
Inter-day RSD (%, n=3)
Ac
Changjiang River
Intra-day RSD (%, n=4)
Calibration
ed
Genuine Analyte samples
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Table 3 Linearity range, regression data, intra-day and inter-day RSDs of PAHs in real samples extracted with MSPE and LLE.
Np
0.01-10
0.9850
4.9
11.3
6.2
2.7
10.7
5.6
0.01-10
0.9498
4.9
6.4
4.1
38.3
9.4
4.5
Ace
0.01-10
0.9920
5.4
2.9
10.9
7.4
8.4
0.7
0.01-10
0.9997
5.6
8.1
14.4
13.3
15.6
16.3
F
0.01-10
0.9908
5.7
4.9
9.8
7.8
19.7
0.4
0.01-10
0.9963
6.7
11.2
14.5
11.9
5.7
21.1
Ph
0.01-10
0.9913
3.3
3.5
7.0
4.8
16.8
15.6
0.01-10
0.9921
9.1
18.1
15.3
7.4
19.9
21.5
An
0.01-10
0.9917
3.9
3.8
5.2
5.3
14.3
4.4
0.01-10
0.9972
1.5
7.9
15.6
13.0
15.4
2.3
FI
0.05-10
0.9923
3.6
7.3
5.3
16.2
12.8
3.5
0.05-10
0.9876
4.1
8.8
12.4
18.0
12.0
11.4
Py
0.01-10
0.9923
4.6
8.0
5.0
10.8
9.9
8.4
0.01-10
0.9902
6.1
5.8
13.0
6.1
21.9
5.7
Page 28 of 36
i cr us
0.9900 0.2034 0.3057 0.7277 0.3378 0.4848 0.0827 1.1113 0.3731 1.0410 1.5186 0.2469 0.4603 0.2706
East Lake
M
1.0295 0.2662 0.2609 0.5656 0.3420 0.4179 0.0684 1.3196 0.3261 0.8674 1.3561 0.2323 0.4179 0.2466
Error (%)
3.8 23.6 -17.2 -28.7 1.2 -16.0 -20.9 15.8 -14.4 -20.0 -12.0 -6.3 -10.1 -9.7
ed
LLE
pt
Np Ace F Ph An FI Py Np Ace F Ph An FI Py
MSPE
Ac
Changjiang River
Analyte
ce
Genuine samples
Concentration in genuine samples (ng mL-1)
an
Table 4 The determined PAH concentration in genuine samples by MSPE and LLE
Page 29 of 36
1
40-1110
7
Fe3O4/GO Fe3O4@C18@Ba2+-ALG Fe3O4/C
HPLC-UV UHPLC-FLD HPLC-FLD
0.5-100 0.01-2 0.01-1
120-190 2-5 0.2-0.6
10 30 30
Fe3O4/SiO2/TPA
HPLC-FLD
0.5-400
0.25-0.5
10
C14/Fe3O4
HPLC-FLD
0.02-10
0.2-0.4
15
ip t
0.25-25
us
cr
GC-MS
GC-MS 0.01-100 0.6-2.1 Fe3O4-DVB-SO3Na IL- Fe3O4, ionic liquid-coated Fe3O4; C18-Fe3O4, C18 bonded Fe3O4; Fe3O4/GO, graphene oxide modified Fe3O4; Fe3O4@C18@Ba2+-ALG, Fe3O4@C18@barium alginate polymers; Fe3O4/C, carbon coated Fe3O4; Fe3O4/SiO2/TPA, triphenylamine-functionalized Fe3O4; C14/Fe3O4, C14 bonded Fe3O4.
10
Fig. 1
Ac ce p
te
d
9
IL/Fe3O4
Extraction time (min) 5
an
4 5 6 7 8
Table 5 Comparison of Fe3O4-DVB-SO3- with other published MSPE of PAHs from water samples. LOD Linearity MNP material Detection -1 (pg mL-1) (ng mL ) C18/Fe3O4 GC-MS 10-800 800-4200
M
2 3
10 11 12 13 14 15 16 30
Page 30 of 36
cr us an M
Fig. 2
37 38 39 40 41 42 43 44 45
Ac ce p
te
d
36
ip t
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
31
Page 31 of 36
cr us an M
Fig. 3
66 67 68 69 70 71 72 73 74
Ac ce p
te
d
65
ip t
46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
32
Page 32 of 36
ip t cr us an M
Fig. 4
96 97 98 99 100 101 102 103 104 105 106 107 108 109 110
Ac ce p
te
d
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
33
Page 33 of 36
ip t cr us an M
Fig. 5 (i)
133 134 135 136
Ac ce p
te
d
111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
(ii)
34
Page 34 of 36
Fig. 6
te
d
M
an
us
cr
ip t 153
Ac ce p
137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152
154 35
Page 35 of 36
► Fe3O4-divinylbenzene-SO3- magnetic nanoparticle was prepared via “thiol-ene” click reaction. ► The sulfonate groups featured the material excellent aqueous dispersibility.
159
► It was used for PAH extraction from environmental samples.
160
► Satisfactory reproducibility, low LODs and good linearity were obtained.
ip t
155 156 157 158
Ac ce p
te
d
M
an
us
cr
161 162
36
Page 36 of 36