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Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetate-phenyltriethoxysilane fibers
Accepted Manuscript Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetate-phenyltriethoxysilane fibers
Habib Bagheri, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi PII: DOI: Reference:
S0026-265X(18)30364-3 doi:10.1016/j.microc.2018.07.006 MICROC 3247
To appear in:
Microchemical Journal
Received date: Revised date: Accepted date:
19 March 2018 2 July 2018 6 July 2018
Please cite this article as: Habib Bagheri, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi , Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetate-phenyltriethoxysilane fibers. Microc (2018), doi:10.1016/j.microc.2018.07.006
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ACCEPTED MANUSCRIPT Title: Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetatephenyltriethoxysilane fibers
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Authors: Habib Bagheri, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi
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Affiliation: Environmental and Bio-Analytical Laboratories, Department of Chemistry
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Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
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Corresponding author:
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Professor Habib Bagheri
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E-mail address: [email protected]
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Tel.: +98-21-66005718; Fax: +98-21-66012983
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ACCEPTED MANUSCRIPT Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetate-phenyltriethoxysilane fibers Habib Bagheri1, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi Environmental and Bio-Analytical Laboratories, Department of Chemistry
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Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran Abstract
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In this research, three fibers including cellulose acetate (CA), CA–phenyltriethoxysilane
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(PTES) prepared via sol–gel electrospinning and sol–gel–based CA fibers immersed in PTES solution (dipped–CA–PTES) were prepared. The composition and morphology of the
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prepared fibers were evaluated by energy dispersive X–ray spectroscopy and field emission
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scanning electron microscopy. The prepared fibers were implemented in a home–made needle trap device, followed by thermal desorption of the selected chlorobenzenes (CBs) to a
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gas chromatography–flame ionization detector. Finally, parameters affecting the extraction
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methodology such as the amount of sorbent, extraction time and temperature, desorption time and temperature and the ionic strength were investigated. Among the fabricated extractive phases, the hybrid CA–PTES fibers exhibited higher extraction efficiency. Under the optimal
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condition, the limits of detection were lower than 0.42 μg L-1 and the relative standard
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deviations for intra– and inter–day precision for a single needle were in the range of 3–5% and 5–10%, respectively. In addition, the needle–to–needle reproducibility was from 9 to 12% (n=3). Finally, the method was applied to the analysis of samples from river water, sediment and sludge samples. Relative recoveries were in the range of 94-105%.
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Corresponding author. Tel.: +98-21-66005718; Fax: +98-21-66012983 E-mail address: [email protected] (H. Bagheri)
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ACCEPTED MANUSCRIPT Keywords: Sol–gel–based cellulose acetate fibers; Needle trap microextraction; Green
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chemistry; Environmental samples; Chlorobenzenes; Gas chromatography
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ACCEPTED MANUSCRIPT 1. Introduction The growing utilization of toxic artificial compounds has extensive harmful effects on the environment and human health. The consumption of many toxic compounds is prohibited in many countries and maximum contaminant level for the high–risk materials has been set by
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some international agencies such as the United States Environmental Protection Agency (US EPA) [1]. The use of precise and sensitive techniques to measure low amounts of toxic
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materials in various samples is essential.. During the last few decades, most of the
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developments in analytical chemistry have been devoted to rapid improvements in instrumentations. However, despite the availability of advanced instruments, sample
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preparation has remained an important aspect of chemical analyses. Methods such as liquid– liquid extraction and solid phase extraction, due to their large solvent consumption and/or
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their relatively high expenses, are certainly far from the green chemistry criteria. Lately, more attention has been focused on the development of inexpensive and environmentally friendly
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procedures in analytical chemistry. The development of green analytical chemistry was based on the reduction of the analytical methods side effects, especially in the extraction techniques. The reduction in toxic solvents and reagents consumptions and the extraction
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stages are major features in green chemistry [2-4]. The recent interest in possessing
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environmentally friendly, simplified and miniaturized sample preparation techniques has led to the development of rapid, solventless and directly compatible methods with analytical instrumentations. Among the various successful methodologies, solid phase microextraction (SPME) and needle trap microextraction (NTME) are typical miniaturized techniques which are amenable to the green chemistry demands [5, 6]. In SPME, extraction is based on the use of a coated fiber. This sampling approach has become popular for analyzing food samples and environmental monitoring [7].. The methods based on NTME offer increased robustness in comparison with SPME, as the extractive phase is packed inside the needle rather than 4
ACCEPTED MANUSCRIPT being used as a thin layer coating on a fragile fiber [8, 9]. NTME has been successfully used for the analysis of volatile and semi volatile pollutants from environmental samples. By adaption of this methodology, the extraction is carried out by transferring the analytes from the sample headspace to the extractive phase body, located in needle. Subsequent thermal desorption of analytes is accomplished by entering the needle trap device (NTD) inside the
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injection port of a gas chromatography system. The extractive phase capacity is determined
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by the sorbent quantity and the sample flow rate passing through the sorbent [10].
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The extractive phase in various sampling techniques has a vital role in achieving ultimate performance. Several research groups have worked on the development of various extractive
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phases for NTME techniques. Some sorbents such as divinylbenzene (DVB), carboxen particles, polydimethylsiloxane (PDMS) [11,12] and melamine formaldehyde foam [13] were
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used to extract BTEX. Other extractive phases such as carbon nanotubes (CNTs)/silica were applied for extraction of perchloroethylene in air [14] and halogenated volatile organic
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compounds were analyzed by multiwall carbon nanotubes (MWCNTs)/silica [15]. The amino–silica/graphene oxide nanocomposite coated cotton [16] and polythiophene/Ag nanocomposite as extractive phase applied for sampling polycyclic aromatic hydrocarbon
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(PAHs) [17] while silica aerogel used for extracting chlorobenzene from water samples [18].
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Among the versatile and well–known extractive phases, fibrous–based materials are quite popular. So far, various fibers have been prepared from different synthetic polymers, alone or in combination with other chemicals, and employed as extractive phases in micro solid phase extraction (μ-SPE) [19], thin film microextraction (TFME) [20] and SPME [21]. The use of biopolymers among the scientific community has become an alternative for conventional synthetic polymers. Cellulose is almost the most abundant natural polymer, which contains the key inherent benefits such as its biodegradability, high mechanical
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ACCEPTED MANUSCRIPT strength and chemical resistance, good flexibility and non–toxicity, makes it a promising extractive phase [22, 23]. This natural polymer is not soluble in most organic solvents and this drawback limits its application in electrospinning. In order to overcome this issue, great attentions have been given to the use of its derivatives such as CA. The solubility of CA in
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most organic solvents makes it amenable for fibers production [24-27]. The CA nanofibers have impressive properties such as high surface area and porosity, good
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thermal stability, biocompatibility and biodegradability [28-30] that could be considered as
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green media in microextraction methods. An essential feature for selection of an appropriate sorbent lies on its thermal and mechanical stability and this is not an exception for the
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electrospun fibers.
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In this work, three CA–based extractive phases were prepared and structurally characterized. Then, their capabilities for isolation of CBs using headspace needle trap device (HS–NTD)
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was evaluated. To the best of our knowledge, CA fibers, dipped–CA–PTES fibers and CA–
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PTES fibers have been used for the first time as an extractive phase in the NTME technique for extraction of CBs from water, sediment, and sludge samples followed by gas
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chromatography–flame ionization detector (GC–FID). As expected, the contribution of PTES within the fibrous structure improved the extraction efficiency.
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2. Experimental
2.1. Chemicals and materials The selected CBs such as monochlorobenzene (MCB), 1,4-dichlorobenzene (1,4-DCB), 1,2dichlorobenzene
(1,2-DCB),
1,2,4-trichlorobenzene
(1,2,4-TCB),
and
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tetrachlorobenezne (1,2,3,4-TeCB)) were purchased from Merck (Darmstadt, Germany). Standard solution (1000 mg L−1) of CBs mixture was prepared in methanol (MeOH) obtained from Merck (Darmstadt, Germany) and stored in the refrigerator. Working solution are 6
ACCEPTED MANUSCRIPT obtained by diluting the standard solutions with double distilled water. Phenyltriethoxysilane (PTES), tetraethylorthosilicate (TEOS) (98%), hydrochloric acid (HCl), sodium chloride (NaCl), dichloromethane (DCM) and acetone (Ace) were obtained from Merck (Darmstadt, Germany). The polycyclic aromatic hydrocarbon (PAH) compounds such as naphtalene, acenaphtylene, acenaphtene, fluorene and anthracene (all >99.0% analytical standards) were
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purchased from Sigma-Aldrich (Germany). The stock standard solution (1000 mg L-1) of
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PAHs mixture was prepared in MeOH. The working standard solutions of the selected PAHs were prepared by appropriate dilution of the stock solution with MeOH. All PAHs stock and
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working standard solutions were stored at 4 ˚C. The volatile organic compounds including
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benzene, ethylbenzene, o-xylene, m-xylene, p-xylene (>99%) and toluene (99.5%) (BTEX) were obtained from Fluka. A mixture of standard solution of these analytes prepared at the
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concentration of 1000 mg L-1 in MeOH. The working solutions of BTEX were prepared in pure water prior to their use.
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Water, sediment and sludge samples were collected from a few districts around Karaj River (Alborz, Iran). To extract CBs from sediment and sludge samples, 0.1 g from each individual
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was added to the double distillated water prior to be analyzed by HS-NTD. 2.2. Instrumentation
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An Agilent 6820 gas chromatograph with a split–splitless injection port and flame ionization detection (FID) system was employed for optimization and validation of the method. The analytes were separated using a wide bore HP–5 MS column (30 m, 0.53 mm i.d.) with 0.25 mm film thickness (Hewlett-Packard, Palo Alto, CA, USA). The carrier gas was nitrogen (99.999%) at a flow rate of 4 mL min-1. The gas chromatograph was operated in the splitless mode and the split valve was kept closed for 1 min. The injector and detector temperatures were set at 210 and 290 ˚C respectively. The temperature program of column was set at 50˚C
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ACCEPTED MANUSCRIPT for 1 min, increased to 180˚C at a rate of 40˚C min-1 and was kept at this temperature for 5 min. All samples were extracted from glass vials with a PTFE-faced septum and aluminum cap and were heated in a homemade glass water bath connected to a circulating water bath (RTG–8 NESLAB, USA). Samples were stirred using ZAG Shimi (Tehran-Iran) magnetic stirrer. An Ismatec BVP peristaltic pump (Switzerland) was used for aspirating the headspace
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analytes into the needle. Needles with the length of 88 mm (o.d. = 0.65, i.d. = 0.35 mm) were
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used to fabricate the needle trap device (NTD).
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The electrospinning technique was used to prepare the desired fibers. To carry out this process, a high voltage power supply (West Midlands, England) and a KDS100 syringe pump
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(KdScientific Co., Holliston, MA, US) were used for the polymer solution delivery in the electrospinning process. The field emission scanning electron microscopy (FE-SEM) images
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and energy dispersive x-ray spectroscopy (EDS) results were obtained by a TESCAN Mira3 LMU (Kohoutovice, Czech Republic). A Netzsch–TGA 209 F1 Libra thermal gravimetric
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analyzer was used to characterize the thermal degradation and stability of the fibers using a
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temperature program from room temperature to 600 °C at a rate of 20 °C min-1 under the nitrogen atmosphere. The Brunauer–Emmett–Teller (BET) study was carried out on the PHS-
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CA–based fibers.
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1020 (PHSCHINA) device for determination of the surface area and pore size distribution of
2.3. Preparation of the CA–based fibers To prepare the fibers, CA (7.5 wt%) was dissolved in DCM:Ace (3:1 v/v) binary solvent system for 3 h. Afterwards, the solution was drawn into the syringe which was subsequently transferred to the syringe pump, operating at a flow rate of 0.40 mL h-1 and under the voltage of 12 kV, applied between the syringe and the collector.
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ACCEPTED MANUSCRIPT Two approaches were adapted for functionalizing the electrospun CA–based fibers. In the first approach to prepare the CA–PTES fibers, combination of the sol–gel and electrospinning technique was implemented as reported recently [32]. Firstly, the CA polymer solution with concentration of 7.5 wt% was dissolved in DCM:Ace solvents (3:1, v/v). After obtaining a homogenous solution, 200 µL PTES and 10 µL HCl (0.1 M) were added (Scheme 1). The
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prepared CA-PTES solution was loaded into the syringe pump to deliver the polymeric
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solution. A piece of aluminum foil was positioned at a ~10–cm distance from the needle as
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the collector electrode. The collector and the syringe needle were connected to a high voltage power supply. The electrospinning of the polymeric solution was performed by applying 13
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kV between the needle and the collector and the solution flow rate of 0.40 mL h-1. Then, the electrospun nanofibers were heated at 120 ◦C for 1 h for completion of sol–gel reaction.
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By adapting the second approach, the electrospun CA fibers were covered with the sol solution including PTES in order the sol–gel reaction occurs [33]. The coating process was
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carried out by placing the electrospun CA fibers in an acidic condition (HCl, 1 M) containing TEOS: PTES:CH3OH: H2O with molar ratio of 0.5:0.1:20:11. The process started with, hydrolysis of precursors of TEOS and PTES. Then their polycondensation in solution
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continued at room temperature for 24 h (Scheme 2). Eventually, the electrospun fibers were
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immersed into the sol–gel solution for 2 min. Moreover, the PTES film–coated fibers were heated at 120 °C for 1 h till sol–gel reaction was completed. 2.4. Preparation of the NTD The home–made NTD was prepared by packing the fibers into a stainless–steel needle (with the gauge of 22 and the length of 88 mm). The CA–based fibers can be easily placed in needle while there is no need to use any additional material such as glass wool for its fixation in the needle. Depending on the amount of extractive phase which varies from 0.5 to 2 mg,
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ACCEPTED MANUSCRIPT 0.5 to 2 cm of the needle length is packed. A side–hole, about 4 cm from the tip of needle, was drilled for facilitating the sorption/desorption process. The side hole of needle was sealed with a septum during sampling to prevent the analytes loss. But in the desorption step, the side hole was exposed to the carrier gas. It is important to note that due to the porous fibers structure the needle blockage is prevented. After packing, the NTD was conditioned in a GC
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injector at 230 ◦C for 2 h; then the NTD was ready for extraction process
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2.5. NTME procedure
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The extraction was performed in the headspace mode using 5 mL aqueous standard solution
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spiked with CBs at the final concentration of 1 µg mL−1 for all analytes. The sample vial was sealed with septum and an aluminum seal. In extraction stage, NTD was attached to a
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peristaltic pump and placed in the headspace of samples. The 22–gauge needle was also inserted into the sample solution to purge the circulating headspace into the sample (Fig. 1).
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During the extraction, the hole of needle was closed and subsequently, the NTD was
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immediately inserted into the GC injector at 210˚C for 4 min to perform the desorption process.
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3. Results and discussion
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Recently, functional nanofibers, due to their intrinsic characteristics such as high surface area and porosity, have received great deals of attention. It is rather simple to improve the functionality of the nanofibers by incorporating functional additives such as silica [34]. In this work, two different approaches were applied to the functionalization of CA fibers containing PTES. By adapting the first approach, the hybrid CA–PTES fibers were prepared via a one–step electrospinning process while the second approach was focused on dipping the CA fibers in the sol–gel solution containing the PTES precursor. The available –OH groups on the CA structure allows the sol–gel reaction to initiate by the PTES precursor in which is 10
ACCEPTED MANUSCRIPT hydrolyzed and condensed at the presence of the acidic catalyst. After synthesizing the CA, CA–PTES and dipped–CA–PTES fibers, their efficiencies toward pollutant such as CBs were compared. 3.1. Comparing the CA–based fibers
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The use of inorganic–organic hybrid structures is usually an efficient approach to improve their overall properties. Modification of fibrous polymers by silica is an interesting strategy to
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achieve a suitable extractive phase with the enhanced extraction efficiency [35]. Among the
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tested precursors, PTES as a silica–based modifier was superior and incorporated within the CA fibers. In order to examine the extraction behavior of the three CA–based fibers, they
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were employed as the extractive phases in a home–made NTD for isolation of CBs, as model
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analytes. The initial extraction conditions consisted of using a desorption temperature and time of 210 °C and 4 min, extraction time and temperature of 15 min and 25 °C. The sample
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flow rate was set at 2.4 ml min-1 and 1 mg of extractive phase was chosen. As the results in
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Fig. 2 show, the CA–PTES fibers exhibit the highest extraction efficiencies for CBs. The presence of –OH groups in the CA structure can only interact with the desired analytes via the hydrogen bonding. After functionalization with PTES by the sol–gel reaction, besides
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hydrogen bonding, the non–polar and π–π interactions between CBs and PTES lead to the
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enhanced efficiency. Among the functionalized fibers, CA–PTES, due to their higher porosity, are more favorable and efficient for extracting the desired analytes. The electrospun fibers were also used to extract other pollutants such as PAHs, benzene, toluene, ethylbenzene, o–xylene, m–xylene, p–xylene (BTEX). As expected, due to the non– polar nature of the analytes, their interactions with the CA fibers are rather poor. Functionalizing the CA fibers with PTES induce the hydrophobic– and π–π interactions with these analytes. In the case of PAHs and BTEX, CA-PTES has also higher performance than
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ACCEPTED MANUSCRIPT dipped-CA-PTES. Generally speaking, the extraction efficiencies of these three fibers toward PAHs and BTEX are lower than those obtained for CBs. 3.2. Optimization Several parameters affect the extraction of CBs using the NTME technique. These parameters
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are classified into two general categories, those affecting the desorption conditions and the ones which are associated with the extraction conditions. In the first group, the effects of
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desorption temperature and time were investigated and for the second group, the effects of
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the sample flow rate, extraction temperature and time and salt presence were studied. The aim of optimizing these parameters was to achieve increased sensitivity and improve the method
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overall performance. Prior to optimize the whole procedure, it was essential to find the
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amount of the CA–PTES fibers as the extractive phase. As shown in Fig. 3a, the efficiency is increased with the rise of fibers quantities, although the use of higher amounts of fibers leads
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to lower efficiency which is due to the occupying large volumes of the needle and subsequent
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reducing the air flow. The highest signal was obtained when 1.5 mg CA–PTES fibers was used.
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3.2.1. Desorption temperature
Any increase in desorption temperature leads to reduction of distribution constant between
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the fibers and the carrier gas, allowing efficient desorption of analytes. The desorption temperature rise is limited by the thermal stability of the sorbent. At high temperatures, the lifetime of extractive phase is usually decreased while is favorable for the memory effect reduction. Given these constraints, the right temperature should be adapted to reduce the memory effect along with the minimal damage to CA–PTES fibers. Fig. 3b shows the effect of desorption temperature on extraction efficiency, ranged from 150 to 230 °C. In order to
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ACCEPTED MANUSCRIPT increase the lifetime of the fiber, an optimum temperature of 210 °C was an appropriate value. 3.2.2. Desorption time Desorption time is the period of time that the carrier gas passes through the extractive phase
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and carries the analytes into the column. The duration of the passage of the carrier gas must be sufficient to desorb all the analytes. The higher the desorption time, the greater the
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desorption quality. It should be noted that, the CA–PTES fibers are placed in the hot injector
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and the use of longer duration time reduces the sorbent lifetime. Indeed, the desorption time and the memory effect are two important factors which should be considered. A desorption
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time interval of 0.5–3 min was therefore monitored. According to the data in Fig. 3c, the
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relevant signals due to the desorption time remains significantly unchanged after 1 min. The use of 210 °C within 1 min, appears to be appropriate in order to have a rather safe
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environment for the CA–PTES fibers to be reused more frequently while no memory effect
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occurs. 3.2.3. Flow rate
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In NTME, the sample headspace passes through the needle containing CA–PTES fibers during the extraction process. The sample flow rate has an effective role in reaching
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equilibrium. At high flow rate sampling, the extraction efficiency is reduced as the species are in the pre–equilibrium condition and pass through the sorbent bed without being trapped. At very low flow rates, sufficient amounts of analytes are not exposed to sorbent and this lowers the efficiency. Therefore, optimizing the sample flow rate is crucial in NTME. Here, a flow rate range of 1.2–4.8 mL min-1 was investigated. As shown in Fig. 3d, a flow rate of 2.4 mL min-1 was chosen as the optimum value. 3.2.4. Extraction temperature 13
ACCEPTED MANUSCRIPT As Eq. 1 [36] indicates, by increasing the extraction temperature, the Henry constant (kH) is expected to rise and the mass transfer from water to the headspace is facilitated; this subsequently leads to the enhanced concentration of analytes in the headspace ( Ch ) as distribution constant of headspace and sample matrix (Khs) is increased.
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1
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are the gas and Henry constant while T is the temperature.
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In this equation, Cs represents the concentration of analyte in the sample matrix, R and K H
According to Eq. 2 [37], due to the fact that the adsorption phenomenon is exothermic, any
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temperature increase leads to the reduction of distribution constant between the extractive
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phase and sample matrix (Kfs). Increasing the temperature leads to higher Khs values from one side, and lower Kfs quantities from other side. In fact, the outcome of these two factors
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determines the extraction efficiency. In NTME, one reason for lowering the extraction
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efficiency at high temperatures is associated with the heat transfer from the stainless steel substrate to the extractive phase, which results in the desorption of analytes during extraction
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In Eq. 2, K0 expresses the constant distribution and ∆H represents enthalpy. In order to optimize the extraction temperature, a temperature range of 20–50 °C was considered (Fig. 3e) and due to the acceptable extraction efficiency, simplicity and convenience of extraction conditions, the temperature of 25 °C was selected as optimum temperature. 3.2.5. Extraction time
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ACCEPTED MANUSCRIPT For optimizing this parameter, two contrary effects should be considered. On the one hand short extraction time, always considered as the advantage of the method, is preferred. On the other hand, the extraction time interval should be sufficient for the species to be equilibrated between the extractive phase and the sample matrix. Reaching the equilibrium increases the repeatability of the method and the intensity of the signals. Therefore, due to the competition
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between kinetic and thermodynamic parameters, the conditions must be chosen to obtain the
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highest possible signals. Given that these two effects are in the opposite direction; it is
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important to find the shortest time when the equilibrium is rather established. For this purpose, a time range of 10–30 min was investigated and according to the results shown in
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Fig. 3f, after 15 min, the signals remained almost constant, indicating equilibrium is reached within 15 min.
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3.2.6. Salt effect
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Increasing the salt content in water samples often increases the extraction efficiency which is
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due to the enhancement soluble ionic strength. As ionic strength increases, the solubility of organic compounds is lowered by reducing the number of available water molecules in
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aquatic media. Therefore, the presence of analytes in the headspace becomes favorable and extraction efficiency increases. In Fig. 3g, the effect of salt content on the extraction of CBs
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is shown. As the extraction of the analytes is improved by the addition of salt, the highest efficiency attained at 30% (w/v) of NaCl. 3.3. Figures of merit evaluation The homemade NTD using the synthesized CA–PTES fibers after optimization at 210°C desorption temperature, 1 min desorption time, sample flow rate of 2.4 mL min-1, extraction time 15 min at 25°C and 30% salt content was implemented to the analysis of the spiked samples at different concentration levels. As it was noted the linearity ranged from 0.75-1000 15
ACCEPTED MANUSCRIPT µg L-1 with regression coefficient of (R2 > 0.99). Moreover, the values for limit of detection (LOD) (S/N = 3/1) and limit of quantification (LOQ) (S/N = 10/1) were lower than 0.42 and 1 µg L−1, respectively. The intra–day and inter–day relative standard deviations (RSD%, n=4) were in the range of 3–5% and 5–10%, respectively. The needle–to–needle repeatability was calculated by three replicate extractions of CBs using three different fibers prepared
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under similar conditions as is shown in (Table 1).
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The analytical data obtained from the developed NTME method using CA-PTES fibers as the extractive fibers with other relevant methodologies is listed in Table 2 and it was concluded
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that the results of this study were comparable with the methods used by other researchers. As a result, the proposed method was superior to the FID-oriented methodologies considering
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LOD, LOQ and relative recovery information. 3.4. Real sample analysis
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The method performance was evaluated by isolation and determination of CBs in water, sediment and sludge samples collected from Karaj River region. For the analysis of sediment and wet sludge, 0.1 g from each sample was poured in vial and then 5 mL double distillated
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water was added. The quantities of CBs in soil, sediment and sludge are reported in Table 3. For testing the accuracy of the proposed method, relative recovery was evaluated. For this purpose, various concentrations were spiked in water (µg L-1), soil and sediment (µg kg-1)
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samples. Relative recovery and RSD% are reported in Table 3. As is observed the relative
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recover was in the range of 94-105 % with standard division of 3-8 %. As a conclusion, the use of GC-FID was applicable due to high efficiency of fibers for retaining the analytes and significant presence of CBs in real samples. The Figure 4 shows the chromatogram obtained from analysis of water samples which could approve the capability of the CA-PTES fibers in analyzing of real samples. 4. Conclusions In this work, two approaches were applied for functionalization of CA fibers to ascertain the role of electrospinning for production of low-cost and green extractive phases. In the first 16
ACCEPTED MANUSCRIPT approach, the electrospun CA–PTES fibers were prepared and in the latter one, the dipped– CA–PTES fibers were synthesized. The use of PTES not only increases the thermal stability of CA fibers but also leads to the enhancement of surface area and extraction efficiency. Based on the obtained results, the CA–PTES fibers had higher extraction efficiencies than the dipped–CA–PTES fibers. By embedding PTES in the CA network the hydrophobic
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interactions are associated to the enhanced extraction efficiencies.
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Moreover, The NTME technique using CA-PTES fibers provides a very simple, rapid,
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efficient and convenient method. Finally, the high capacity of the CA-PTES fibers originated from their porous structure, makes them favorable for trace analysis of the majority of
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volatile compounds in real samples. As a result, the suitability of the proposed method for real sample analysis was approved by the results of analytical data analysis namely LOD,
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LOQ values as well as recovery and reproducibility.
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[8] H. Bagheri, Z. Ayazi, A. Aghakhani, A novel needle trap sorbent based on carbon nanotube-sol–gel for microextraction of polycyclic aromatic hydrocarbons from aquatic media, Anal. Chim. Acta, 683 (2011) 212-220. [9] M.R. Azari, A. Barkhordari, R. Zendehdel, M. Heidari, A novel needle trap device with nanoporous silica aerogel packed for sampling and analysis of volatile aldehyde compounds in air, Microchem. J., 134 (2017) 270-276.
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ACCEPTED MANUSCRIPT [10] X. Li, G. Ouyang, H. Lord, J. Pawliszyn, Theory and validation of solid-phase microextraction and needle trap devices for aerosol sample, Anal. Chem., 82 (2010) 95219527. [11] I.-Y. Eom, A.-M. Tugulea, J. Pawliszyn, Development and application of needle trap
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devices, J. Chromatogr. A, 1196 (2008) 3-9. [12] A. Wang, F. Fang, J. Pawliszyn, Sampling and determination of volatile organic
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compounds with needle trap devices, J. Chromatogr. A, 1072 (2005) 127-135.
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[13] H. Bagheri, S. Zeinali, M.Y. Baktash, A single–step synthesized supehydrophobic melamine formaldehyde foam for trace determination of volatile organic pollutants, J.
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Chromatogr. A, 1525 (2017) 10-16.
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[14] M. Heidari, S.G. Attari, M. Rafieiemam, Application of solid phase microextraction and needle trap device with silica composite of carbon nanotubes for determination of
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perchloroethylene in laboratory and field, Anal. Chim. Acta, 918 (2016) 43-49.
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[15] M. Heidari, A. Bahrami, A.R. Ghiasvand, F.G. Shahna, A.R. Soltanian, A needle trap device packed with a sol–gel derived, multi-walled carbon nanotubes/silica composite for
(2013) 67-74.
N. Heidari,
A. Ghiasvand, S. Abdolhosseini, Amino-silica/graphene oxide
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[16]
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sampling and analysis of volatile organohalogen compounds in air, Anal. Chim. Acta, 785
nanocomposite coated cotton as an efficient sorbent for needle trap device, Anal. Chim. Acta, 975 (2017) 11-19.
[17] H. Bagheri, S. Banihashemi, S. Jelvani, A polythiophene–silver nanocomposite for headspace needle trap extraction, J. Chromatogr. A, 1460 (2016) 1-8. [18] M.Y. Baktash, H. Bagheri, A superhydrophobic silica aerogel with high surface area for needle trap microextraction of chlorobenzenes, Microchim. Acta, 184 (2017) 2151-2156.
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ACCEPTED MANUSCRIPT [19] H. Bagheri, A. Aghakhani, M. Akbari, Z. Ayazi, Electrospun composite of polypyrrolepolyamide as a micro-solid phase extraction sorbent, Anal. Bioanal. Chem., 400 (2011) 36073613. [20] J. Huang, H. Deng, D. Song, H. Xu, Electrospun polystyrene/graphene nanofiber film as a novel adsorbent of thin film microextraction for extraction of aldehydes in human exhaled
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breath condensates, Anal. Chim. Acta, 878 (2015) 102-108.
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[21] J. Zou, X. Song, J. Ji, W. Xu, J. Chen, Y. Jiang, Y. Wang, X. Chen,
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Polypyrrole/graphene composite‐ coated fiber for the solid‐ phase microextraction of phenols, J. Sep. Sci., 34 (2011) 2765-2772.
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[22] F. Abujaber, M. Zougagh, S. Jodeh, Á. Ríos, F.J.G. Bernardo, R.C.R. MartínDoimeadios, Magnetic cellulose nanoparticles coated with ionic liquid as a new material for
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the simple and fast monitoring of emerging pollutants in waters by magnetic solid phase extraction, Microchem. J., 137 (2018) 490-495.
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[23] S. Hokkanen, A. Bhatnagar, M. Sillanpää, A review on modification methods to
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cellulose-based adsorbents to improve adsorption capacity, Water Res., 91 (2016) 156-173. [24] S.R. Dods, O. Hardick, B. Stevens, D.G. Bracewell, Fabricating electrospun cellulose
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nanofibre adsorbents for ion-exchange chromatography, J. Chromatogr. A, 1376 (2015) 74-
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[25] Y. Nishio, Material functionalization of cellulose and related polysaccharides via diverse microcompositions, Polysaccharides II, Springer2006, pp. 97-151. [26] S. Tungprapa, T. Puangparn, M. Weerasombut, I. Jangchud, P. Fakum, S. Semongkhol, C. Meechaisue, P. Supaphol, Electrospun cellulose acetate fibers: effect of solvent system on morphology and fiber diameter, Cellulose, 14 (2007) 563-575. [27] A. Celebioglu, T. Uyar, Electrospun porous cellulose acetate fibers from volatile solvent mixture, Mater. Lett., 65 (2011) 2291-2294.
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ACCEPTED MANUSCRIPT [28] T. Christoforou, C. Doumanidis, Biodegradable cellulose acetate nanofiber fabrication via electrospinning, J. Nanosci. Nanotechnol., 10 (2010) 6226-6233. [29] R. Konwarh, N. Karak, M. Misra, Electrospun cellulose acetate nanofibers: the present status and gamut of biotechnological applications, Biotechnol. Adv., 31 (2013) 421-437. [30] O. Suwantong, P. Supaphol, Applications of cellulose acetate nanofiber mats, Handbook
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of Polymer Nanocomposites. Processing, Performance and Application, Springer2015, pp.
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355-368.
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[31] T. Pirzada, S.A. Arvidson, C.D. Saquing, S.S. Shah, S.A. Khan, Hybrid silica–PVA nanofibers via sol–gel electrospinning, Langmuir, 28 (2012) 5834-5844.
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[32] O. Arslan, Z. Aytac, T. Uyar, Superhydrophobic, hybrid, electrospun cellulose acetate Nanofibrous Mats for oil/water separation by tailored surface modification, ACS Appl.
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Mater. Interfaces, 8 (2016) 19747-19754.
[33] B. Ding, C. Li, Y. Hotta, J. Kim, O. Kuwaki, S. Shiratori, Conversion of an electrospun
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Nanotechnology, 17 (2006) 4332.
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nanofibrous cellulose acetate mat from a super-hydrophilic to super-hydrophobic surface,
[34] H. Bagheri, A. Roostaie, Electrospun modified silica-polyamide nanocomposite as a
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novel fiber coating, J. Chromatogr. A, 1324 (2014) 11-20. [35] S. Chigome, G. Darko, N. Torto, Electrospun nanofibers as sorbent material for solid
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phase extraction, Analyst, 136 (2011) 2879-2889. [36] J. Pawliszyn, Handbook of solid phase microextraction, Elsevier2011. [37] J. Pawliszyn, Solid phase microextraction: theory and practice, John Wiley & Sons 1997. [38]
Y.-l.
Hu,
Y.-l.
Fu,
anilinemethyltriethoxysilane/polydimethylsiloxane
G.-K. sol–gel
Li, coatings
Preparation for
of
solid-phase
microextraction of aromatic compounds, Anal. Chim. Acta, 567 (2006) 211-217. [39] M. Alonso, L. Cerdan, A. Godayol, E. Anticó, J.M. Sanchez, Headspace needle-trap analysis of priority volatile organic compounds from aqueous samples: application to the analysis of natural and waste waters, J. Chromatogr. A, 1218 (2011) 8131-8139. 21
ACCEPTED MANUSCRIPT [40] M. Wu, L. Wang, B. Zeng, F. Zhao, Fabrication of poly (3, 4-ethylenedioxythiophene)ionic liquid functionalized graphene nanosheets composite coating for headspace solid-phase microextraction of benzene derivatives, J. Chromatogr. A, 1364 (2014) 45-52. [41] G. Zhang, Z. Li, X. Zang, C. Wang, Z. Wang, Solid‐ phase microextraction with a graphene‐ composite‐ coated fiber coupled with GC for the determination of some
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halogenated aromatic hydrocarbons in water samples, J. Sep. Sci., 37 (2014) 440-446.
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[42] X. Rong, F. Zhao, B. Zeng, Electrochemical preparation of poly (p-phenylenediamine-
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co-aniline) composite coating on a stainless steel wire for the headspace solid-phase microextraction and gas chromatographic determination of some derivatives of benzene,
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Talanta, 98 (2012) 265-271.
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Figure Captions
Fig. 1. Schematic diagram of the needle trap device (NTD) using the cellulose acetate–based
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fibers (cellulose acetate (CA), CA–phenyltriethoxysilane (PTES) prepared via sol–gel
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electrospinning and sol–gel–based CA fibers immersed in PTES solution (dipped–CA– PTES)).
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Fig. 2. Comparing the extraction efficiencies of the synthesized CA fibers, CA-PTES fibers
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and dipped–CA–PTES fibers toward CBs Fig. 3. Optimization of influencing parameters on extraction efficiency (a) amount of fibers, (b) desorption temperature, (c) desorption time, (d) sampling flow rate, (e) extraction temperature, (f) extraction time, (g) NaCl quantity. Fig. 4. A GC–FID Chromatogram obtained after NTD of a water sample obtained from Karaj River.
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Fig. 1
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Fig. 2
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Fig. 3
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Fig. 4
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ACCEPTED MANUSCRIPT Scheme 1 The reaction scheme for synthesizing the CA–PTES fibers
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Scheme 2 The reaction scheme for synthesizing the dipped CA–PTES fibers
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Scheme 1
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Scheme 2
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ACCEPTED MANUSCRIPT Table 1- Figures of merit obtained from the current method using the NTD and the hybrid CA-PTES fibers
Compound
LOD
LOQ
Inter-day
Intra-day
Needle to needle
LDR
(µg L-1)
(µg L-1)
RSD%
RSD%
RSD%
(µg L-1)
R2
0.25
0.75
7
5
10
0.75-1000
0.9988
1,2-DCB
0.23
0.75
5
3
9
0.75-1000
0.9990
1,4-DCB
0.24
0.75
9
5
10
0.75-1000
0.9991
1,2,4-TCB
0.42
1
8
4
12
1-1000
0.9987
1,2,3,4-TeCB
0.40
1
10
4
11
1-1000
0.9989
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MCB
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ACCEPTED MANUSCRIPT Table 2- Comparing the analytical performance of the hybrid CA-PTES fibers–based method with other relevant works LOD (µg L-1)
Method
Extractive phase
Extraction time (min)
Sample volume (mL)
NTME-GC-FID
CA-PTES fibers
15
10
0.23-0.42
5-10
SPME-GC-FID
AMTEOS/PDMSa
15
5
1.5-3.8
7.8-9.6
NTME-GC-MS
Carboxen
90
5
0.06
SPME-GC-FID
PEDOT-IL/GNsb
20
10
0.19
SPME-GC-FID
Graphene composite
15
20
SPME-GC-FID
poly(PPDA-co-ANI)c
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8
NTME-GC-MS
Silica Aerogel
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Recovery (%)
Reference
94-105
Current method
4-4000
121.8
[38]
0.01–50
65-71
[39]
4.1-5.3
0.03-500
95
[40]
3.7-14.9
2.5-800
76-104
[41]
0.88
2.7-12.7
0.98-500
97
[42]
0.004-0.022
4-8
0.002-0.1
88-104
[18]
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anilinemethyltriethoxysilane/polydimethylsiloxane
b
poly (3, 4-ethylenedioxythiophene)-ionic liquid functionalized graphene
c
poly (p-phenylenediamine-co-aniline)
C C
A
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0.75-1000
7–18
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I R
C S U
N A 0.5-1.0
a
LDR (µg L-1)
RSD%
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Amount
Amount
Relative
in the real sample a
added
Found
recovery (%)
MCB
640
190
840
105
5
1,2-DCB
1010
210
1230
105
4
River
1,4-DCB
1700
190
1880
95
6
water
1,2,4-TCB
2200
180
2390
1,2,3,4-TeCB
1910
210
2130
105
6
MCB
850
9500
10500
102
7
1,2-DCB
700
10500
11000
98
6
1,4-DCB
1950
9500
11500
100
8
1,2,4-TCB
600
9000
9250
96
5
1,2,3,4-TeCB
ND b
10500
11000
99
5
MCB
350
9500
9900
100
6
1,2-DCB
ND
10500
11000
105
7
1,4-DCB
450
9500
9750
98
5
ND
9000
9500
94
8
ND
10500
11000
105
7
Sediment
1,2,4-TCB
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1,2,3,4-TeCB
µg L−1 for water samples and µg kg−1 for sediment and sludge samples
b
Not detected
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Sludge
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Sample
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Amount measured
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Table 3- Relative recoveries obtained for the real spiked samples using the hybrid CA-PTES
RSD (%)
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ACCEPTED MANUSCRIPT Highlights Various sol–gel–based cellulose acetate fibers were synthesized
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Fibers were implemented to the needle–trap microextraction of organic pollutants
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The cellulose acetate–phenyltriethoxysilane fibers show superior extraction efficiency
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The method was applied to the analysis of chlorobenzenes in river water, sediment and sludge samples
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Habib Bagheri, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi PII: DOI: Reference:
S0026-265X(18)30364-3 doi:10.1016/j.microc.2018.07.006 MICROC 3247
To appear in:
Microchemical Journal
Received date: Revised date: Accepted date:
19 March 2018 2 July 2018 6 July 2018
Please cite this article as: Habib Bagheri, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi , Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetate-phenyltriethoxysilane fibers. Microc (2018), doi:10.1016/j.microc.2018.07.006
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ACCEPTED MANUSCRIPT Title: Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetatephenyltriethoxysilane fibers
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Authors: Habib Bagheri, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi
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Affiliation: Environmental and Bio-Analytical Laboratories, Department of Chemistry
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Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
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Corresponding author:
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Professor Habib Bagheri
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E-mail address: [email protected]
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Tel.: +98-21-66005718; Fax: +98-21-66012983
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ACCEPTED MANUSCRIPT Evaluation of prepared natural polymers in the extraction of chlorobenzenes from environmental samples: Sol–gel–based cellulose acetate-phenyltriethoxysilane fibers Habib Bagheri1, Tahereh Golzari Aqda, Marzieh Enteshari Najafabadi Environmental and Bio-Analytical Laboratories, Department of Chemistry
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Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran Abstract
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In this research, three fibers including cellulose acetate (CA), CA–phenyltriethoxysilane
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(PTES) prepared via sol–gel electrospinning and sol–gel–based CA fibers immersed in PTES solution (dipped–CA–PTES) were prepared. The composition and morphology of the
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prepared fibers were evaluated by energy dispersive X–ray spectroscopy and field emission
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scanning electron microscopy. The prepared fibers were implemented in a home–made needle trap device, followed by thermal desorption of the selected chlorobenzenes (CBs) to a
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gas chromatography–flame ionization detector. Finally, parameters affecting the extraction
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methodology such as the amount of sorbent, extraction time and temperature, desorption time and temperature and the ionic strength were investigated. Among the fabricated extractive phases, the hybrid CA–PTES fibers exhibited higher extraction efficiency. Under the optimal
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condition, the limits of detection were lower than 0.42 μg L-1 and the relative standard
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deviations for intra– and inter–day precision for a single needle were in the range of 3–5% and 5–10%, respectively. In addition, the needle–to–needle reproducibility was from 9 to 12% (n=3). Finally, the method was applied to the analysis of samples from river water, sediment and sludge samples. Relative recoveries were in the range of 94-105%.
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Corresponding author. Tel.: +98-21-66005718; Fax: +98-21-66012983 E-mail address: [email protected] (H. Bagheri)
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ACCEPTED MANUSCRIPT Keywords: Sol–gel–based cellulose acetate fibers; Needle trap microextraction; Green
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chemistry; Environmental samples; Chlorobenzenes; Gas chromatography
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ACCEPTED MANUSCRIPT 1. Introduction The growing utilization of toxic artificial compounds has extensive harmful effects on the environment and human health. The consumption of many toxic compounds is prohibited in many countries and maximum contaminant level for the high–risk materials has been set by
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some international agencies such as the United States Environmental Protection Agency (US EPA) [1]. The use of precise and sensitive techniques to measure low amounts of toxic
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materials in various samples is essential.. During the last few decades, most of the
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developments in analytical chemistry have been devoted to rapid improvements in instrumentations. However, despite the availability of advanced instruments, sample
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preparation has remained an important aspect of chemical analyses. Methods such as liquid– liquid extraction and solid phase extraction, due to their large solvent consumption and/or
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their relatively high expenses, are certainly far from the green chemistry criteria. Lately, more attention has been focused on the development of inexpensive and environmentally friendly
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procedures in analytical chemistry. The development of green analytical chemistry was based on the reduction of the analytical methods side effects, especially in the extraction techniques. The reduction in toxic solvents and reagents consumptions and the extraction
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stages are major features in green chemistry [2-4]. The recent interest in possessing
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environmentally friendly, simplified and miniaturized sample preparation techniques has led to the development of rapid, solventless and directly compatible methods with analytical instrumentations. Among the various successful methodologies, solid phase microextraction (SPME) and needle trap microextraction (NTME) are typical miniaturized techniques which are amenable to the green chemistry demands [5, 6]. In SPME, extraction is based on the use of a coated fiber. This sampling approach has become popular for analyzing food samples and environmental monitoring [7].. The methods based on NTME offer increased robustness in comparison with SPME, as the extractive phase is packed inside the needle rather than 4
ACCEPTED MANUSCRIPT being used as a thin layer coating on a fragile fiber [8, 9]. NTME has been successfully used for the analysis of volatile and semi volatile pollutants from environmental samples. By adaption of this methodology, the extraction is carried out by transferring the analytes from the sample headspace to the extractive phase body, located in needle. Subsequent thermal desorption of analytes is accomplished by entering the needle trap device (NTD) inside the
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injection port of a gas chromatography system. The extractive phase capacity is determined
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by the sorbent quantity and the sample flow rate passing through the sorbent [10].
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The extractive phase in various sampling techniques has a vital role in achieving ultimate performance. Several research groups have worked on the development of various extractive
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phases for NTME techniques. Some sorbents such as divinylbenzene (DVB), carboxen particles, polydimethylsiloxane (PDMS) [11,12] and melamine formaldehyde foam [13] were
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used to extract BTEX. Other extractive phases such as carbon nanotubes (CNTs)/silica were applied for extraction of perchloroethylene in air [14] and halogenated volatile organic
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compounds were analyzed by multiwall carbon nanotubes (MWCNTs)/silica [15]. The amino–silica/graphene oxide nanocomposite coated cotton [16] and polythiophene/Ag nanocomposite as extractive phase applied for sampling polycyclic aromatic hydrocarbon
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(PAHs) [17] while silica aerogel used for extracting chlorobenzene from water samples [18].
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Among the versatile and well–known extractive phases, fibrous–based materials are quite popular. So far, various fibers have been prepared from different synthetic polymers, alone or in combination with other chemicals, and employed as extractive phases in micro solid phase extraction (μ-SPE) [19], thin film microextraction (TFME) [20] and SPME [21]. The use of biopolymers among the scientific community has become an alternative for conventional synthetic polymers. Cellulose is almost the most abundant natural polymer, which contains the key inherent benefits such as its biodegradability, high mechanical
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ACCEPTED MANUSCRIPT strength and chemical resistance, good flexibility and non–toxicity, makes it a promising extractive phase [22, 23]. This natural polymer is not soluble in most organic solvents and this drawback limits its application in electrospinning. In order to overcome this issue, great attentions have been given to the use of its derivatives such as CA. The solubility of CA in
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most organic solvents makes it amenable for fibers production [24-27]. The CA nanofibers have impressive properties such as high surface area and porosity, good
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thermal stability, biocompatibility and biodegradability [28-30] that could be considered as
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green media in microextraction methods. An essential feature for selection of an appropriate sorbent lies on its thermal and mechanical stability and this is not an exception for the
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electrospun fibers.
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In this work, three CA–based extractive phases were prepared and structurally characterized. Then, their capabilities for isolation of CBs using headspace needle trap device (HS–NTD)
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was evaluated. To the best of our knowledge, CA fibers, dipped–CA–PTES fibers and CA–
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PTES fibers have been used for the first time as an extractive phase in the NTME technique for extraction of CBs from water, sediment, and sludge samples followed by gas
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chromatography–flame ionization detector (GC–FID). As expected, the contribution of PTES within the fibrous structure improved the extraction efficiency.
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2. Experimental
2.1. Chemicals and materials The selected CBs such as monochlorobenzene (MCB), 1,4-dichlorobenzene (1,4-DCB), 1,2dichlorobenzene
(1,2-DCB),
1,2,4-trichlorobenzene
(1,2,4-TCB),
and
1,2,3,4-
tetrachlorobenezne (1,2,3,4-TeCB)) were purchased from Merck (Darmstadt, Germany). Standard solution (1000 mg L−1) of CBs mixture was prepared in methanol (MeOH) obtained from Merck (Darmstadt, Germany) and stored in the refrigerator. Working solution are 6
ACCEPTED MANUSCRIPT obtained by diluting the standard solutions with double distilled water. Phenyltriethoxysilane (PTES), tetraethylorthosilicate (TEOS) (98%), hydrochloric acid (HCl), sodium chloride (NaCl), dichloromethane (DCM) and acetone (Ace) were obtained from Merck (Darmstadt, Germany). The polycyclic aromatic hydrocarbon (PAH) compounds such as naphtalene, acenaphtylene, acenaphtene, fluorene and anthracene (all >99.0% analytical standards) were
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purchased from Sigma-Aldrich (Germany). The stock standard solution (1000 mg L-1) of
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PAHs mixture was prepared in MeOH. The working standard solutions of the selected PAHs were prepared by appropriate dilution of the stock solution with MeOH. All PAHs stock and
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working standard solutions were stored at 4 ˚C. The volatile organic compounds including
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benzene, ethylbenzene, o-xylene, m-xylene, p-xylene (>99%) and toluene (99.5%) (BTEX) were obtained from Fluka. A mixture of standard solution of these analytes prepared at the
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concentration of 1000 mg L-1 in MeOH. The working solutions of BTEX were prepared in pure water prior to their use.
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Water, sediment and sludge samples were collected from a few districts around Karaj River (Alborz, Iran). To extract CBs from sediment and sludge samples, 0.1 g from each individual
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was added to the double distillated water prior to be analyzed by HS-NTD. 2.2. Instrumentation
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An Agilent 6820 gas chromatograph with a split–splitless injection port and flame ionization detection (FID) system was employed for optimization and validation of the method. The analytes were separated using a wide bore HP–5 MS column (30 m, 0.53 mm i.d.) with 0.25 mm film thickness (Hewlett-Packard, Palo Alto, CA, USA). The carrier gas was nitrogen (99.999%) at a flow rate of 4 mL min-1. The gas chromatograph was operated in the splitless mode and the split valve was kept closed for 1 min. The injector and detector temperatures were set at 210 and 290 ˚C respectively. The temperature program of column was set at 50˚C
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ACCEPTED MANUSCRIPT for 1 min, increased to 180˚C at a rate of 40˚C min-1 and was kept at this temperature for 5 min. All samples were extracted from glass vials with a PTFE-faced septum and aluminum cap and were heated in a homemade glass water bath connected to a circulating water bath (RTG–8 NESLAB, USA). Samples were stirred using ZAG Shimi (Tehran-Iran) magnetic stirrer. An Ismatec BVP peristaltic pump (Switzerland) was used for aspirating the headspace
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analytes into the needle. Needles with the length of 88 mm (o.d. = 0.65, i.d. = 0.35 mm) were
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used to fabricate the needle trap device (NTD).
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The electrospinning technique was used to prepare the desired fibers. To carry out this process, a high voltage power supply (West Midlands, England) and a KDS100 syringe pump
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(KdScientific Co., Holliston, MA, US) were used for the polymer solution delivery in the electrospinning process. The field emission scanning electron microscopy (FE-SEM) images
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and energy dispersive x-ray spectroscopy (EDS) results were obtained by a TESCAN Mira3 LMU (Kohoutovice, Czech Republic). A Netzsch–TGA 209 F1 Libra thermal gravimetric
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analyzer was used to characterize the thermal degradation and stability of the fibers using a
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temperature program from room temperature to 600 °C at a rate of 20 °C min-1 under the nitrogen atmosphere. The Brunauer–Emmett–Teller (BET) study was carried out on the PHS-
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CA–based fibers.
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1020 (PHSCHINA) device for determination of the surface area and pore size distribution of
2.3. Preparation of the CA–based fibers To prepare the fibers, CA (7.5 wt%) was dissolved in DCM:Ace (3:1 v/v) binary solvent system for 3 h. Afterwards, the solution was drawn into the syringe which was subsequently transferred to the syringe pump, operating at a flow rate of 0.40 mL h-1 and under the voltage of 12 kV, applied between the syringe and the collector.
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ACCEPTED MANUSCRIPT Two approaches were adapted for functionalizing the electrospun CA–based fibers. In the first approach to prepare the CA–PTES fibers, combination of the sol–gel and electrospinning technique was implemented as reported recently [32]. Firstly, the CA polymer solution with concentration of 7.5 wt% was dissolved in DCM:Ace solvents (3:1, v/v). After obtaining a homogenous solution, 200 µL PTES and 10 µL HCl (0.1 M) were added (Scheme 1). The
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prepared CA-PTES solution was loaded into the syringe pump to deliver the polymeric
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solution. A piece of aluminum foil was positioned at a ~10–cm distance from the needle as
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the collector electrode. The collector and the syringe needle were connected to a high voltage power supply. The electrospinning of the polymeric solution was performed by applying 13
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kV between the needle and the collector and the solution flow rate of 0.40 mL h-1. Then, the electrospun nanofibers were heated at 120 ◦C for 1 h for completion of sol–gel reaction.
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By adapting the second approach, the electrospun CA fibers were covered with the sol solution including PTES in order the sol–gel reaction occurs [33]. The coating process was
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carried out by placing the electrospun CA fibers in an acidic condition (HCl, 1 M) containing TEOS: PTES:CH3OH: H2O with molar ratio of 0.5:0.1:20:11. The process started with, hydrolysis of precursors of TEOS and PTES. Then their polycondensation in solution
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continued at room temperature for 24 h (Scheme 2). Eventually, the electrospun fibers were
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immersed into the sol–gel solution for 2 min. Moreover, the PTES film–coated fibers were heated at 120 °C for 1 h till sol–gel reaction was completed. 2.4. Preparation of the NTD The home–made NTD was prepared by packing the fibers into a stainless–steel needle (with the gauge of 22 and the length of 88 mm). The CA–based fibers can be easily placed in needle while there is no need to use any additional material such as glass wool for its fixation in the needle. Depending on the amount of extractive phase which varies from 0.5 to 2 mg,
9
ACCEPTED MANUSCRIPT 0.5 to 2 cm of the needle length is packed. A side–hole, about 4 cm from the tip of needle, was drilled for facilitating the sorption/desorption process. The side hole of needle was sealed with a septum during sampling to prevent the analytes loss. But in the desorption step, the side hole was exposed to the carrier gas. It is important to note that due to the porous fibers structure the needle blockage is prevented. After packing, the NTD was conditioned in a GC
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injector at 230 ◦C for 2 h; then the NTD was ready for extraction process
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2.5. NTME procedure
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The extraction was performed in the headspace mode using 5 mL aqueous standard solution
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spiked with CBs at the final concentration of 1 µg mL−1 for all analytes. The sample vial was sealed with septum and an aluminum seal. In extraction stage, NTD was attached to a
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peristaltic pump and placed in the headspace of samples. The 22–gauge needle was also inserted into the sample solution to purge the circulating headspace into the sample (Fig. 1).
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During the extraction, the hole of needle was closed and subsequently, the NTD was
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immediately inserted into the GC injector at 210˚C for 4 min to perform the desorption process.
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3. Results and discussion
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Recently, functional nanofibers, due to their intrinsic characteristics such as high surface area and porosity, have received great deals of attention. It is rather simple to improve the functionality of the nanofibers by incorporating functional additives such as silica [34]. In this work, two different approaches were applied to the functionalization of CA fibers containing PTES. By adapting the first approach, the hybrid CA–PTES fibers were prepared via a one–step electrospinning process while the second approach was focused on dipping the CA fibers in the sol–gel solution containing the PTES precursor. The available –OH groups on the CA structure allows the sol–gel reaction to initiate by the PTES precursor in which is 10
ACCEPTED MANUSCRIPT hydrolyzed and condensed at the presence of the acidic catalyst. After synthesizing the CA, CA–PTES and dipped–CA–PTES fibers, their efficiencies toward pollutant such as CBs were compared. 3.1. Comparing the CA–based fibers
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The use of inorganic–organic hybrid structures is usually an efficient approach to improve their overall properties. Modification of fibrous polymers by silica is an interesting strategy to
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achieve a suitable extractive phase with the enhanced extraction efficiency [35]. Among the
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tested precursors, PTES as a silica–based modifier was superior and incorporated within the CA fibers. In order to examine the extraction behavior of the three CA–based fibers, they
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were employed as the extractive phases in a home–made NTD for isolation of CBs, as model
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analytes. The initial extraction conditions consisted of using a desorption temperature and time of 210 °C and 4 min, extraction time and temperature of 15 min and 25 °C. The sample
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flow rate was set at 2.4 ml min-1 and 1 mg of extractive phase was chosen. As the results in
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Fig. 2 show, the CA–PTES fibers exhibit the highest extraction efficiencies for CBs. The presence of –OH groups in the CA structure can only interact with the desired analytes via the hydrogen bonding. After functionalization with PTES by the sol–gel reaction, besides
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hydrogen bonding, the non–polar and π–π interactions between CBs and PTES lead to the
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enhanced efficiency. Among the functionalized fibers, CA–PTES, due to their higher porosity, are more favorable and efficient for extracting the desired analytes. The electrospun fibers were also used to extract other pollutants such as PAHs, benzene, toluene, ethylbenzene, o–xylene, m–xylene, p–xylene (BTEX). As expected, due to the non– polar nature of the analytes, their interactions with the CA fibers are rather poor. Functionalizing the CA fibers with PTES induce the hydrophobic– and π–π interactions with these analytes. In the case of PAHs and BTEX, CA-PTES has also higher performance than
11
ACCEPTED MANUSCRIPT dipped-CA-PTES. Generally speaking, the extraction efficiencies of these three fibers toward PAHs and BTEX are lower than those obtained for CBs. 3.2. Optimization Several parameters affect the extraction of CBs using the NTME technique. These parameters
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are classified into two general categories, those affecting the desorption conditions and the ones which are associated with the extraction conditions. In the first group, the effects of
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desorption temperature and time were investigated and for the second group, the effects of
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the sample flow rate, extraction temperature and time and salt presence were studied. The aim of optimizing these parameters was to achieve increased sensitivity and improve the method
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overall performance. Prior to optimize the whole procedure, it was essential to find the
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amount of the CA–PTES fibers as the extractive phase. As shown in Fig. 3a, the efficiency is increased with the rise of fibers quantities, although the use of higher amounts of fibers leads
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to lower efficiency which is due to the occupying large volumes of the needle and subsequent
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reducing the air flow. The highest signal was obtained when 1.5 mg CA–PTES fibers was used.
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3.2.1. Desorption temperature
Any increase in desorption temperature leads to reduction of distribution constant between
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the fibers and the carrier gas, allowing efficient desorption of analytes. The desorption temperature rise is limited by the thermal stability of the sorbent. At high temperatures, the lifetime of extractive phase is usually decreased while is favorable for the memory effect reduction. Given these constraints, the right temperature should be adapted to reduce the memory effect along with the minimal damage to CA–PTES fibers. Fig. 3b shows the effect of desorption temperature on extraction efficiency, ranged from 150 to 230 °C. In order to
12
ACCEPTED MANUSCRIPT increase the lifetime of the fiber, an optimum temperature of 210 °C was an appropriate value. 3.2.2. Desorption time Desorption time is the period of time that the carrier gas passes through the extractive phase
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and carries the analytes into the column. The duration of the passage of the carrier gas must be sufficient to desorb all the analytes. The higher the desorption time, the greater the
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desorption quality. It should be noted that, the CA–PTES fibers are placed in the hot injector
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and the use of longer duration time reduces the sorbent lifetime. Indeed, the desorption time and the memory effect are two important factors which should be considered. A desorption
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time interval of 0.5–3 min was therefore monitored. According to the data in Fig. 3c, the
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relevant signals due to the desorption time remains significantly unchanged after 1 min. The use of 210 °C within 1 min, appears to be appropriate in order to have a rather safe
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environment for the CA–PTES fibers to be reused more frequently while no memory effect
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occurs. 3.2.3. Flow rate
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In NTME, the sample headspace passes through the needle containing CA–PTES fibers during the extraction process. The sample flow rate has an effective role in reaching
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equilibrium. At high flow rate sampling, the extraction efficiency is reduced as the species are in the pre–equilibrium condition and pass through the sorbent bed without being trapped. At very low flow rates, sufficient amounts of analytes are not exposed to sorbent and this lowers the efficiency. Therefore, optimizing the sample flow rate is crucial in NTME. Here, a flow rate range of 1.2–4.8 mL min-1 was investigated. As shown in Fig. 3d, a flow rate of 2.4 mL min-1 was chosen as the optimum value. 3.2.4. Extraction temperature 13
ACCEPTED MANUSCRIPT As Eq. 1 [36] indicates, by increasing the extraction temperature, the Henry constant (kH) is expected to rise and the mass transfer from water to the headspace is facilitated; this subsequently leads to the enhanced concentration of analytes in the headspace ( Ch ) as distribution constant of headspace and sample matrix (Khs) is increased.
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1
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are the gas and Henry constant while T is the temperature.
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In this equation, Cs represents the concentration of analyte in the sample matrix, R and K H
According to Eq. 2 [37], due to the fact that the adsorption phenomenon is exothermic, any
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temperature increase leads to the reduction of distribution constant between the extractive
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phase and sample matrix (Kfs). Increasing the temperature leads to higher Khs values from one side, and lower Kfs quantities from other side. In fact, the outcome of these two factors
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determines the extraction efficiency. In NTME, one reason for lowering the extraction
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efficiency at high temperatures is associated with the heat transfer from the stainless steel substrate to the extractive phase, which results in the desorption of analytes during extraction
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.
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2
In Eq. 2, K0 expresses the constant distribution and ∆H represents enthalpy. In order to optimize the extraction temperature, a temperature range of 20–50 °C was considered (Fig. 3e) and due to the acceptable extraction efficiency, simplicity and convenience of extraction conditions, the temperature of 25 °C was selected as optimum temperature. 3.2.5. Extraction time
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ACCEPTED MANUSCRIPT For optimizing this parameter, two contrary effects should be considered. On the one hand short extraction time, always considered as the advantage of the method, is preferred. On the other hand, the extraction time interval should be sufficient for the species to be equilibrated between the extractive phase and the sample matrix. Reaching the equilibrium increases the repeatability of the method and the intensity of the signals. Therefore, due to the competition
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between kinetic and thermodynamic parameters, the conditions must be chosen to obtain the
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highest possible signals. Given that these two effects are in the opposite direction; it is
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important to find the shortest time when the equilibrium is rather established. For this purpose, a time range of 10–30 min was investigated and according to the results shown in
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Fig. 3f, after 15 min, the signals remained almost constant, indicating equilibrium is reached within 15 min.
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3.2.6. Salt effect
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Increasing the salt content in water samples often increases the extraction efficiency which is
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due to the enhancement soluble ionic strength. As ionic strength increases, the solubility of organic compounds is lowered by reducing the number of available water molecules in
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aquatic media. Therefore, the presence of analytes in the headspace becomes favorable and extraction efficiency increases. In Fig. 3g, the effect of salt content on the extraction of CBs
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is shown. As the extraction of the analytes is improved by the addition of salt, the highest efficiency attained at 30% (w/v) of NaCl. 3.3. Figures of merit evaluation The homemade NTD using the synthesized CA–PTES fibers after optimization at 210°C desorption temperature, 1 min desorption time, sample flow rate of 2.4 mL min-1, extraction time 15 min at 25°C and 30% salt content was implemented to the analysis of the spiked samples at different concentration levels. As it was noted the linearity ranged from 0.75-1000 15
ACCEPTED MANUSCRIPT µg L-1 with regression coefficient of (R2 > 0.99). Moreover, the values for limit of detection (LOD) (S/N = 3/1) and limit of quantification (LOQ) (S/N = 10/1) were lower than 0.42 and 1 µg L−1, respectively. The intra–day and inter–day relative standard deviations (RSD%, n=4) were in the range of 3–5% and 5–10%, respectively. The needle–to–needle repeatability was calculated by three replicate extractions of CBs using three different fibers prepared
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under similar conditions as is shown in (Table 1).
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The analytical data obtained from the developed NTME method using CA-PTES fibers as the extractive fibers with other relevant methodologies is listed in Table 2 and it was concluded
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that the results of this study were comparable with the methods used by other researchers. As a result, the proposed method was superior to the FID-oriented methodologies considering
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LOD, LOQ and relative recovery information. 3.4. Real sample analysis
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The method performance was evaluated by isolation and determination of CBs in water, sediment and sludge samples collected from Karaj River region. For the analysis of sediment and wet sludge, 0.1 g from each sample was poured in vial and then 5 mL double distillated
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water was added. The quantities of CBs in soil, sediment and sludge are reported in Table 3. For testing the accuracy of the proposed method, relative recovery was evaluated. For this purpose, various concentrations were spiked in water (µg L-1), soil and sediment (µg kg-1)
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samples. Relative recovery and RSD% are reported in Table 3. As is observed the relative
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recover was in the range of 94-105 % with standard division of 3-8 %. As a conclusion, the use of GC-FID was applicable due to high efficiency of fibers for retaining the analytes and significant presence of CBs in real samples. The Figure 4 shows the chromatogram obtained from analysis of water samples which could approve the capability of the CA-PTES fibers in analyzing of real samples. 4. Conclusions In this work, two approaches were applied for functionalization of CA fibers to ascertain the role of electrospinning for production of low-cost and green extractive phases. In the first 16
ACCEPTED MANUSCRIPT approach, the electrospun CA–PTES fibers were prepared and in the latter one, the dipped– CA–PTES fibers were synthesized. The use of PTES not only increases the thermal stability of CA fibers but also leads to the enhancement of surface area and extraction efficiency. Based on the obtained results, the CA–PTES fibers had higher extraction efficiencies than the dipped–CA–PTES fibers. By embedding PTES in the CA network the hydrophobic
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interactions are associated to the enhanced extraction efficiencies.
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Moreover, The NTME technique using CA-PTES fibers provides a very simple, rapid,
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efficient and convenient method. Finally, the high capacity of the CA-PTES fibers originated from their porous structure, makes them favorable for trace analysis of the majority of
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volatile compounds in real samples. As a result, the suitability of the proposed method for real sample analysis was approved by the results of analytical data analysis namely LOD,
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LOQ values as well as recovery and reproducibility.
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ACCEPTED MANUSCRIPT References [1] H. Cheng, Y. Hu, M. Reinhard, Environmental and health impacts of artificial turf: a review, Environ. Sci. Technol., 48 (2014) 2114-2129. [2] S. Armenta, S. Garrigues, M. de la Guardia, The role of green extraction techniques in
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Green Analytical Chemistry, Trends Anal. Chem., 71 (2015) 2-8. [3] S. Armenta, S. Garrigues, M. De la Guardia, Green analytical chemistry, Trends Anal.
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[4] M. Koel, Do we need green analytical chemistry?, Green Chem., 18 (2016) 923-931. [5] J. Cai, G. Ouyang, Y. Gong, J. Pawliszyn, Simultaneous sampling and analysis for vapor
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spectrometry, J. Chromatogr. A, 1213 (2008) 19-24.
[6] J. Cen, S. Wei, H. Nan, J. Xu, Z. Huang, S. Liu, Q. Hu, J. Yan, G. Ouyang, Incorporation
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of carbon nanotubes into graphene for highly efficient solid-phase microextraction of
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[8] H. Bagheri, Z. Ayazi, A. Aghakhani, A novel needle trap sorbent based on carbon nanotube-sol–gel for microextraction of polycyclic aromatic hydrocarbons from aquatic media, Anal. Chim. Acta, 683 (2011) 212-220. [9] M.R. Azari, A. Barkhordari, R. Zendehdel, M. Heidari, A novel needle trap device with nanoporous silica aerogel packed for sampling and analysis of volatile aldehyde compounds in air, Microchem. J., 134 (2017) 270-276.
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ACCEPTED MANUSCRIPT [10] X. Li, G. Ouyang, H. Lord, J. Pawliszyn, Theory and validation of solid-phase microextraction and needle trap devices for aerosol sample, Anal. Chem., 82 (2010) 95219527. [11] I.-Y. Eom, A.-M. Tugulea, J. Pawliszyn, Development and application of needle trap
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[13] H. Bagheri, S. Zeinali, M.Y. Baktash, A single–step synthesized supehydrophobic melamine formaldehyde foam for trace determination of volatile organic pollutants, J.
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[14] M. Heidari, S.G. Attari, M. Rafieiemam, Application of solid phase microextraction and needle trap device with silica composite of carbon nanotubes for determination of
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perchloroethylene in laboratory and field, Anal. Chim. Acta, 918 (2016) 43-49.
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[15] M. Heidari, A. Bahrami, A.R. Ghiasvand, F.G. Shahna, A.R. Soltanian, A needle trap device packed with a sol–gel derived, multi-walled carbon nanotubes/silica composite for
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nanocomposite coated cotton as an efficient sorbent for needle trap device, Anal. Chim. Acta, 975 (2017) 11-19.
[17] H. Bagheri, S. Banihashemi, S. Jelvani, A polythiophene–silver nanocomposite for headspace needle trap extraction, J. Chromatogr. A, 1460 (2016) 1-8. [18] M.Y. Baktash, H. Bagheri, A superhydrophobic silica aerogel with high surface area for needle trap microextraction of chlorobenzenes, Microchim. Acta, 184 (2017) 2151-2156.
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ACCEPTED MANUSCRIPT [19] H. Bagheri, A. Aghakhani, M. Akbari, Z. Ayazi, Electrospun composite of polypyrrolepolyamide as a micro-solid phase extraction sorbent, Anal. Bioanal. Chem., 400 (2011) 36073613. [20] J. Huang, H. Deng, D. Song, H. Xu, Electrospun polystyrene/graphene nanofiber film as a novel adsorbent of thin film microextraction for extraction of aldehydes in human exhaled
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cellulose-based adsorbents to improve adsorption capacity, Water Res., 91 (2016) 156-173. [24] S.R. Dods, O. Hardick, B. Stevens, D.G. Bracewell, Fabricating electrospun cellulose
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ACCEPTED MANUSCRIPT [28] T. Christoforou, C. Doumanidis, Biodegradable cellulose acetate nanofiber fabrication via electrospinning, J. Nanosci. Nanotechnol., 10 (2010) 6226-6233. [29] R. Konwarh, N. Karak, M. Misra, Electrospun cellulose acetate nanofibers: the present status and gamut of biotechnological applications, Biotechnol. Adv., 31 (2013) 421-437. [30] O. Suwantong, P. Supaphol, Applications of cellulose acetate nanofiber mats, Handbook
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of Polymer Nanocomposites. Processing, Performance and Application, Springer2015, pp.
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[31] T. Pirzada, S.A. Arvidson, C.D. Saquing, S.S. Shah, S.A. Khan, Hybrid silica–PVA nanofibers via sol–gel electrospinning, Langmuir, 28 (2012) 5834-5844.
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nanofibrous cellulose acetate mat from a super-hydrophilic to super-hydrophobic surface,
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Y.-l.
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ACCEPTED MANUSCRIPT [40] M. Wu, L. Wang, B. Zeng, F. Zhao, Fabrication of poly (3, 4-ethylenedioxythiophene)ionic liquid functionalized graphene nanosheets composite coating for headspace solid-phase microextraction of benzene derivatives, J. Chromatogr. A, 1364 (2014) 45-52. [41] G. Zhang, Z. Li, X. Zang, C. Wang, Z. Wang, Solid‐ phase microextraction with a graphene‐ composite‐ coated fiber coupled with GC for the determination of some
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[42] X. Rong, F. Zhao, B. Zeng, Electrochemical preparation of poly (p-phenylenediamine-
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co-aniline) composite coating on a stainless steel wire for the headspace solid-phase microextraction and gas chromatographic determination of some derivatives of benzene,
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Talanta, 98 (2012) 265-271.
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Figure Captions
Fig. 1. Schematic diagram of the needle trap device (NTD) using the cellulose acetate–based
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fibers (cellulose acetate (CA), CA–phenyltriethoxysilane (PTES) prepared via sol–gel
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electrospinning and sol–gel–based CA fibers immersed in PTES solution (dipped–CA– PTES)).
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Fig. 2. Comparing the extraction efficiencies of the synthesized CA fibers, CA-PTES fibers
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and dipped–CA–PTES fibers toward CBs Fig. 3. Optimization of influencing parameters on extraction efficiency (a) amount of fibers, (b) desorption temperature, (c) desorption time, (d) sampling flow rate, (e) extraction temperature, (f) extraction time, (g) NaCl quantity. Fig. 4. A GC–FID Chromatogram obtained after NTD of a water sample obtained from Karaj River.
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Fig. 1
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Fig. 2
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Fig. 3
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ACCEPTED MANUSCRIPT Scheme 1 The reaction scheme for synthesizing the CA–PTES fibers
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Scheme 2 The reaction scheme for synthesizing the dipped CA–PTES fibers
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Scheme 1
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Scheme 2
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ACCEPTED MANUSCRIPT Table 1- Figures of merit obtained from the current method using the NTD and the hybrid CA-PTES fibers
Compound
LOD
LOQ
Inter-day
Intra-day
Needle to needle
LDR
(µg L-1)
(µg L-1)
RSD%
RSD%
RSD%
(µg L-1)
R2
0.25
0.75
7
5
10
0.75-1000
0.9988
1,2-DCB
0.23
0.75
5
3
9
0.75-1000
0.9990
1,4-DCB
0.24
0.75
9
5
10
0.75-1000
0.9991
1,2,4-TCB
0.42
1
8
4
12
1-1000
0.9987
1,2,3,4-TeCB
0.40
1
10
4
11
1-1000
0.9989
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ACCEPTED MANUSCRIPT Table 2- Comparing the analytical performance of the hybrid CA-PTES fibers–based method with other relevant works LOD (µg L-1)
Method
Extractive phase
Extraction time (min)
Sample volume (mL)
NTME-GC-FID
CA-PTES fibers
15
10
0.23-0.42
5-10
SPME-GC-FID
AMTEOS/PDMSa
15
5
1.5-3.8
7.8-9.6
NTME-GC-MS
Carboxen
90
5
0.06
SPME-GC-FID
PEDOT-IL/GNsb
20
10
0.19
SPME-GC-FID
Graphene composite
15
20
SPME-GC-FID
poly(PPDA-co-ANI)c
30
8
NTME-GC-MS
Silica Aerogel
10
D E 10
Recovery (%)
Reference
94-105
Current method
4-4000
121.8
[38]
0.01–50
65-71
[39]
4.1-5.3
0.03-500
95
[40]
3.7-14.9
2.5-800
76-104
[41]
0.88
2.7-12.7
0.98-500
97
[42]
0.004-0.022
4-8
0.002-0.1
88-104
[18]
M
T P E
anilinemethyltriethoxysilane/polydimethylsiloxane
b
poly (3, 4-ethylenedioxythiophene)-ionic liquid functionalized graphene
c
poly (p-phenylenediamine-co-aniline)
C C
A
31
0.75-1000
7–18
T P
I R
C S U
N A 0.5-1.0
a
LDR (µg L-1)
RSD%
ACCEPTED MANUSCRIPT
Amount
Amount
Relative
in the real sample a
added
Found
recovery (%)
MCB
640
190
840
105
5
1,2-DCB
1010
210
1230
105
4
River
1,4-DCB
1700
190
1880
95
6
water
1,2,4-TCB
2200
180
2390
1,2,3,4-TeCB
1910
210
2130
105
6
MCB
850
9500
10500
102
7
1,2-DCB
700
10500
11000
98
6
1,4-DCB
1950
9500
11500
100
8
1,2,4-TCB
600
9000
9250
96
5
1,2,3,4-TeCB
ND b
10500
11000
99
5
MCB
350
9500
9900
100
6
1,2-DCB
ND
10500
11000
105
7
1,4-DCB
450
9500
9750
98
5
ND
9000
9500
94
8
ND
10500
11000
105
7
Sediment
1,2,4-TCB
CE
1,2,3,4-TeCB
µg L−1 for water samples and µg kg−1 for sediment and sludge samples
b
Not detected
AC
a
32
105
RI
SC
NU
Sludge
MA
Compound
D
Sample
PT
Amount measured
PT E
Table 3- Relative recoveries obtained for the real spiked samples using the hybrid CA-PTES
RSD (%)
3
ACCEPTED MANUSCRIPT Highlights Various sol–gel–based cellulose acetate fibers were synthesized
PT
Fibers were implemented to the needle–trap microextraction of organic pollutants
SC
RI
The cellulose acetate–phenyltriethoxysilane fibers show superior extraction efficiency
AC
CE
PT E
D
MA
NU
The method was applied to the analysis of chlorobenzenes in river water, sediment and sludge samples
33