Novel dextran/graphene oxide composite material as a sorbent for solid-phase microextraction of polar aromatic compounds

Abstract

A novel solid-phase microextraction (SPME) fiber for extraction of polar aromatic compounds was prepared by chemically bonding a dextran/graphene oxide (GO) composite material on stainless steel wire. Coupled with gas chromatography (GC), the fiber was used to extract phenols and halogenated aromatic compounds in aqueous samples. The analytical performances of the proposed fiber were evaluated under optimized extraction conditions. The wide linear ranges were 0.10–200 μg L⁻¹, 0.20–200 μg L⁻¹ for different target compounds; the detection limits ranged from 0.015 μg L⁻¹ to 0.050 μg L⁻¹; single-fiber repeatability and fiber-to-fiber reproducibility were in the range of 2.7–10.6% and 5.5–13.7%, respectively. The outstanding stability of the prepared fiber was demonstrated by its ability to sustain more than 100 times usage with relative standard deviations for extraction efficiency less than 13.7%. The dextran/GO-coated SPME fiber was applied to determine phenols and halogenated aromatics in two real water samples, and satisfactory results were obtained.

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1 Introduction

Phenols and halogenated aromatics as the typical species of polar benzene derivatives widely exist in the environment. While the amounts of phenols have been commonly considered as pollution indicators of the environment, halogenated aromatic compounds are other important pollutants. Due to the trace presence and complex matrix of these toxic compounds, it is necessary to carry out sample pre-treatment in order to detect them. Recently, He et al. coupled dispersive liquid–liquid microextraction with capillary electrophoresis to analyze phenols from water samples.¹ The SPME method has been also used to extract polar aromatic compounds. Multi-walled carbon nanotubes (MWCNTs) and metal–organic frameworks (MOFs) have been synthesized and modified on the supporting substrates for the extraction of phenols.^2–4 For chlorinated benzene compounds, researchers adopted graphene nanosheets with poly(3,4-ethylenedioxythiophene) ionic liquid and MOF MIL-88B film-coated SPME fibers.^5,6 However, owing to the limited technology and materials for extracting polar compounds, the extraction of phenols and halogenated aromatics has been scarcely reported currently.

SPME, first introduced in 1990s by Pawliszyn,⁷ has become a popular sample preparation method and gained much attention. As a simple separation and enrichment technique, SPME possesses the advantages of simplicity, high rapidity, sensitivity and being solvent free, so coupled with GC,⁸ liquid chromatography,⁹ and capillary electrochromatography,¹⁰ SPME has been extensively used in the extraction of trace analytes in water samples. Compared with solid-phase extraction, the SPME needs less adsorbent, which can avoid the excessive adsorption of undesirable compounds. Besides, the microextraction system commonly adopts pre-equilibrium and equilibrium methods, the extraction process is highly time-efficient. As for SPME, the extraction capacity mainly depends on the properties of the extraction fiber, therefore, to select a suitable absorbing material is a critical factor to obtain the satisfactory extraction efficiency. Recently, composite materials such as TiO₂–ceramics nanofibers,¹¹ polymeric ionic liquids–graphene,⁵ polypyrrole–graphene,¹² MOF hybridized with other compounds,^13–16 have been applied as the fiber coatings, which simultaneously combine the inherent and special characteristics of different materials. To achieve the stable immobilization of coating materials on the substrate, versatile methods have been introduced, including chemical vapor deposition,¹⁷ electrospun,¹¹ sol–gel technique,^18,19 in situ polymerization,²⁰ in situ oxidation of metal wires,²¹ electroless plating,²² layer-to-layer assemble.²³ Nowadays, the application of SPME has been mainly focused on the extraction of nonpolar compounds, leaving much room for exploration of novel polar coating materials and immobilization methods.

Graphene (G) with a two-dimensional nanostructure, was identified in a simple stripped experiment in 2004.²⁴ As a novel class of carbon allotrope, G has attracted tremendous interest and possessed the extensive applications in many fields.²⁵ The single-layer graphene with a large surface area, high mechanical strength and stability, is considered to be a potential sorbent material in SPME. Chen et al. firstly prepared a G-coated SPME fiber by repeatedly immersing a stainless steel wire (SSW) into a G suspension.²⁶ Thereafter, various G-based composites have been also prepared and evaluated to make the full use of the excellent properties of graphene.^12,15,27 Except for the development of the fiber coating, the methods of G-based coating immobilized on SSW surface, a widely accessible substrate, have been developed diversely. Specifically, there are magnetron sputtering Si interlayer, physical adhesion, electrodeposition and covalent immobilization by polydopamine.^5,28–30

Dextran, made of many glucose molecules, is a complex, branched polysaccharide composed of linear chains of varying lengths, which has been firstly discovered by Pasteur in wine.³¹ Dextran is used in various fields such as pharmaceutical, photographic, agricultural and chemical industries.^32,33 The versatile applications are attributed to the favorable properties of neutral and water soluble, biocompatible, and highly stable. The application of dextran in the separation and analysis is mainly its crosslinked product, Sephadex. Generally, in view of the abundant hydroxyl functional groups in dextran chains, the dextran molecules can be promising candidate for extraction material.

In this paper, a dextran/GO hybrid functional material which had strong hydrogen bonding and van der Waals force between them, was prepared and used as the fiber coating for SPME. The introduction of dextran increased the amount of hydroxy groups on the coating, thus enhancing the polarity of the fiber. Two different water samples were collected to test the real application of the novel SPME fiber and acceptable results were obtained.

2 Experimental

2.1 Chemicals and reagents

The stainless steel wire (SUS304, Φ 112.5 μm) was purchased from Yixing Shenglong Metal Wire Net. Co. (Jiangsu, China). Phenols used as the standards: 2,4-dimethyl phenol (2,4-DMP), 4-tert-butylphenol (4-TBP), 2,4-di-tert-butylphenol (2,4-TBP), 2,6-di-tert-butyl-p-cresol (2,6-TBP) and 4-tert-octylphenol (4-TOP), were purchased from the Shanghai Chemical Rea. Co. (Shanghai, China). Chlorobenzene was purchased from Tianjin Chemical Reagent no. 2 Plant (Tianjing, China). 1,3-Dichlorobenzene and α-chloronaphthalene were purchased from Bright Reagent Factory of Shanghai. α-Bromonaphthalene, dextran-40 000 and trifluoroacetic acid (TFA) were purchased from the Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). 1,4-Dibromobenzene was obtained from Beijing Chemical Plant. Glycidy-oxypropyltrimethoxysilane (GPTMS, 97%) was obtained from Aladdin Chemistry Co. Ltd. (Shanghai, China). Tetraethyl orthosilicate (TEOS) was obtained from the Chemical Reagent no. 1 Plant of Tianjin. 3-Aminopropyltriethoxysilane was purchased from the Gaizhou Chemical Industrial Corporation. All the reagents were of analytical grade.

2.2 Instruments

An Agilent 7890 GC (Agilent Technologies, USA) with a split/splitless injector and flame ionization detector (FID) was performed for the analysis and measure the standards and samples. The SE-54 (30 m long × 0.32 mm i.d. × 0.33 μm film thickness) capillary column was used for the separation. In the experiment, the injector adopted the splitless mode. Nitrogen (>99.999% purity, Guolei Kefa Equipment Co. Ltd. of Lanzhou, China) was used as the carrier gas and make-up gas with flows of 1 mL min⁻¹ and 25 mL min⁻¹, respectively. The analytical temperatures were as follows: the injector temperature, 300 °C; the column temperature, initially adjusted at 90 °C, and programmed to 160 °C at the rate of 10 °C min⁻¹, holding for 5 min, then programmed to 300 °C at the same rate of 10 °C min⁻¹; the detector temperature, 300 °C. The extraction temperature was regulated by the oil bath with dimethylsilicone oil. The synthetic dextran/GO coating was verified by elemental analysis performed on an Elementar Vario EL cube (Hanau, Germany). Scanning electron microscope (SEM) images of the fiber were obtained on a field emission scanning electron microscope (JSM-6701F, Japan). IR spectra were obtained on the Nicolet iS10 Fourier transform infrared spectrometer (Thermo Fisher scientific, USA). The thermogravimetric analysis was obtained on a Thermal Analyzer (STA 449C, Germany).

2.3 Preparation of environmental samples

The water samples were collected from the Yellow River and the ground potholes just after raining (Lanzhou, China). These samples solution were extracted immediately without any pre-treatment and preparation process.

2.4 Synthesis of GO

The modified Hummers method was used for the synthesis of GO from the natural graphite.^34,35 The preparation process was in accordance with the description in the previous work reported by Zhang et al.²³

2.5 Preparation of the SPME fibers

One end (approximately 2 cm) of the SSW was precleaned with distilled water and ethanol. The cleaned part was immersed into a HCl solution (1.0 mol L⁻¹) at room temperature overnight, then was rinsed with ultrapure water and dried for further use. For the comparative analysis, three different fibers, the GO-coated fiber, dextran-coated fiber and dextran/GO-coated fiber, were prepared.

2.5.1 Preparation of dextran/GO-coated fiber. 100 mg of dextran-40 000 was dissolved in 1 mL of ultrapure water. Then a 1 mL of GO solution (0.1%, w/v) was dropped into the 1 mL of as-prepared dextran solution (100 g L⁻¹) to give the dextran/GO composite material (the dextran concentration in mixed solution is 50 g L⁻¹) through the hydrogen bonding between dextran and GO. As shown in Fig. 1, brief and detailed preparation steps of dextran/GO-coated SPME fiber were as follows: (a) the etching part was put into a 10 mL glass vial with APTES for 12 h at room temperature, which mainly activate the SSW; (b) after being dried, the SSW was inserted into the prepared dextran/GO dispersion solution and reacted at 70 °C for 30 min to obtain a thin layer (about 6 μm) of the dextran/GO coating; then placed in a 120 °C vacuum oven. The two operations (a) and (b) described above were repeated four times to give a homogeneous coating of about 25 μm in thickness.

Fig. 1 Schematic preparation process of the dextran/GO coated SPME fiber.

2.5.2 Preparation of dextran-coated and GO-coated fibers. Although the dissolved dextran solution was slightly viscous, the solution was not enough to interact with SSW steadily and abundantly. So a sol–gel method was used for the preparation of the dextran fiber coating. Firstly, 100 mg of dextran-40 000 was dissolved in 1 mL of dichloromethane. Then 200 μL of TEOS, 200 μL of GPTMS and 1 mL of TFA were added into the dextran/dichloromethane mixed solution successively. The etched SSW was immersed into the colloid solution at a constant temperature for 12 h in the fume hood. And the immobilization procedure of the GO adsorbent on SSW surface was the same as that for the dextran/GO fiber.

2.6 Procedure of solid-phase microextraction

All used laboratory vials were rinsed with ethanol and distilled water. Stock solutions of model compounds were prepared in ethanol at concentrations of 1.0 mg mL⁻¹, and were stored at 4 °C. According to the experimental requirement, the stock solution was diluted to the working solution with various concentrations. The SPME device was homemade by using a 5 μL microsyringe which can be conveniently coupled with the GC-FID equipment. Prior to use, the as-prepared fiber was mounted into the microsyringe and introduced into the GC injector at 300 °C for 2 h under ultrapure nitrogen to be aged. All SPME extractions were conducted in the direct immersion mode and performed with 20 mL of aqueous solution in a 25 mL vial. The oil bath equipped with a magnetic stirring system was used to control the extraction temperature. After the extraction, the syringe with SPME fiber was transformed to the GC inlet to desorb the analytes, and continued to perform the following separation and detection.

2.7 Determination of enrichment factor

The enrichment factor (EF) was defined as the ratio of the analyte concentration after extraction and the original concentration in aqueous solution. The relationship between chromatographic peak areas and the concentration of standard solutions, used in the EF calculation, was obtained through the injection of the gradient concentrations using a 1 μL injector needle.³⁶

3 Results and discussion

3.1 Preparation of dextran/GO-coated fiber

The dextran/GO-coated SPME fiber for extraction of polar-oriented aromatics mainly made use of the large specific surface area, π electrons of GO and the –OHs of dextran. Thus the ratio of GO and dextran concentrations during the synthesized process should be optimized in order to obtain higher extraction efficiency. 50, 75, 100, 125 mg of dextran were dissolved in 1 mL of ultrapure water, respectively. The prepared dextran solutions were mixed with 1 mL of 0.1% GO solution. As shown in Fig. 2a, the peak areas rose up apparently until 100 mg of dextran amount. Before the turning point, the addition of dextran could contribute to extract target compounds, so the synergistic effect of dextran and GO gave the increasing response. But after 100 mg, excessive dextran blocked the effect of GO leading to the decrease of extraction efficiency. So 100 mg was selected as the optimal dextran amount, benefiting to the synergistic effect of the composite material on extraction.

Fig. 2 Effect of dextran contents (a) and assembly times (b) on extraction capacity.

The dextran/GO coating was immobilized on SSW by the layer-by-layer assemble steps. Fig. 2b demonstrated that it was necessary to highlight the difference in assembly times because higher coating thickness was usually accompanied by higher extraction efficiency. Peak areas increased greatly with repeat times from one to four and after four times, extraction efficiency increased slightly. To save the preparation time, the fiber coating was completed after four times assembly.

3.2 Characterization of dextran/GO-coated fiber

Morphology structure of the SPME fiber was investigated by SEM. As shown in Fig. 3A, the low-magnification surface SEM image revealed a structure with striped appearance mainly from GO. From Fig. 3B, the high-magnification SEM image showed a winkled and rugged structure with polymer clusters. Through the SEM images of dextran/GO-coated fiber and unmodified fiber (Fig. S-1, seeing the ESI†), the thickness of the composite coating was approximately 25 μm. Furthermore, in order to testify the synthesis of dextran/GO composite material, elemental analysis was used for the characterization of synthesized material. Because dextran molecules possess the groups of CH and CH₂, the proportion of hydrogen element of the dextran/GO composite coating would increase compared with GO. As can be seen in Table 1, 4.58% of hydrogen element in dextran/GO was obviously higher than that of 1.89% in GO powders. Besides, according to the IR spectrum of GO in Fig. S-2,† the most characteristic features were the O–H stretching vibration at 3421 cm⁻¹ and the C=O of carboxyl stretching at 1620 cm⁻¹. As a result of the CH and CH₂ from dextran molecules, the signal peak appeared at 2986 cm⁻¹ in dextran/GO composite, demonstrating that dextran/GO composite was successfully synthesized.

Fig. 3 Scanning electron micrographs of a dextran/GO-coated fiber. The surface images at magnifications of (A) 500× and (B) 10 000×.

Table 1 The elemental analysis of GO and dextran/GO coating

	GO (%)	Dextran/GO (%)
C	39.90	38.96
H	1.89	4.58

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3.3 Stability and lifetime of the dextran/GO fiber

To testify the durability of the proposed fiber to organic solvent, acid and alkali, the dextran/GO fibers were immersed in benzene, HCl (0.1 M), NaOH (0.1 M) for 12 h, respectively. The as-prepared dextran/GO-coated SPME fiber was compared with the above treated fibers to determine its chemical stability (Fig. S-3†). The experimental result showed no significant differences in the extraction efficiency. In general, coatings may be damaged at high temperature, so the thermal stability was also evaluated. The proposed fiber was treated at 300 °C for more than 6 h, after that, the extraction efficiency had still no change. The thermal stability of the dextran/GO coating was also investigated by the thermogravimetric analysis (Fig. S-4†). The weight loss near 400 °C was 3.99% and after that, it became much apparent. But the composite material had so little change at 300 °C that satisfied the desorption condition (300 °C). The fiber was stable enough for use more than 100 times without any obvious decrease in extraction performance. These could be due to the inherent stability and strong interaction of composite material.

3.4 Optimization of extraction parameters

The SPME is a multiphase transferring and equilibrium process. Combining with the conservation of mass, the formula of extraction amounts is calculated.³⁷where c_o is the initial concentration of the analyte in the sample solution, K_fs is the distribution coefficient of the analyte between coating and samples, V_s and V_f are the sample volume and coating volume, respectively. Comparing with the sample volume, the volume of the thin layer coating is very small, which can be neglected. The simplified equation of eqn (1) is

n = c_oK_fsV_f (2)

From eqn (2), high extraction amounts can be obtained by increasing the distribution coefficient, which is affected by dynamics and thermodynamics factors. All the extraction conditions may have effects on the SPME efficiency. Subsequently, it is essential to conduct the optimization of extraction conditions, including extraction time, extraction temperature and salt content etc. Optimization of extraction parameters were performed with a “one-variable-at-a-time” procedure.

Temperature has a dual-effect on extraction efficiency. On the one hand, higher temperature can increase the mobile speed of molecules in solution, thus accelerating the mass transference and increasing the extraction efficiency. On the other hand, higher temperature has a negative effect on partition coefficients of analytes between the fiber coating and solution because the extraction equilibrium is an exothermic process. The temperature profiles ranging from 30 °C to 70 °C were investigated, and the influence of them on the peak areas was shown in Fig. 4a. The extraction efficiency increased with the temperature rising up to 50 °C, then decreased from 50 °C to 60 °C. Thereby, 50 °C was chosen as the optimal extraction temperature.

Fig. 4 Effect of extraction conditions on extraction efficiency. Conditions: stirring rate, 1000 rpm; concentration, 200 μg L⁻¹; extraction time, 40 min; extraction temperature, 50 °C; content of NaCl, 20%; desorption temperature, 300 °C; desorption time, 4 min.

The absorption of sample compounds on the SPME fiber is a dynamic equilibrium. Generally speaking, the longer time is advantageous to reach the best equilibrium. The effect of extraction time was studied by extracting analytes from 10 to 50 min. As can be seen in Fig. 4b, peak areas increased as the extraction time increased from 10 to 40 min and reached a relatively stable stage after a 40 min extraction. So 40 min was granted to the suitable extraction time.

Ionic strength also has a twofold impact on the extraction. Salt in the aqueous solution may contribute to the extraction of analytes due to the decrease of solubility, whereas along with the increase of salt content, the competitive effect maybe occur resulting in decreasing distribution coefficient. From Fig. 4c, it was obviously found that peak areas increased with the content of NaCl from 0 to 20% and after 20%, the competitive effect played an important role so that the extraction efficiency decreased. Therefore, 20% was chosen as the optimal concentration of NaCl.

3.5 Extraction selectivity studies

During the sampling of analytes, the analytical sensitivity and sampling efficiency are related to the extraction selectivity of the extraction fiber coating. In this study, the extraction performance of dextran/GO-coated SPME fiber was compared with dextran and GO-coated fibers via the extraction of a series of typical aromatic compounds. All the extraction processes were performed under the optimal conditions and the results were shown in Fig. 5. As shown in Fig. 5a, the extractions for polycyclic aromatic hydrocarbons (PAHs) were performed using the GO-coated and dextran/GO-coated SPME fibers. The lower extraction capacity of dextran/GO-coated fiber compared with GO-coated fiber maybe attribute to that the dextran chains with abundant –OHs blocked the π–π interaction between benzene rings. So in this work, the novel fiber wasn't suitable to extract PAHs. To exhibit the excellent application of the composite-coated fiber, phenols and halogenated aromatics were investigated. From Fig. 5b, the extraction efficiency of the dextran/GO-coated fiber for polar benzene derivatives was enhanced apparently compared with that of dextran and GO-coated fibers, which demonstrated the cooperative effect of two different materials. For phenols, the increase of extraction efficiency was related to the large adsorption area, π system of GO easily forming the π–π stacking with benzene ring, and the rich oxygen-containing groups of dextran and GO which can adsorb phenols through the interaction of hydrogen bonding. For halogenated aromatics, the rich –OHs of dextran increased the polarity of the fiber coating, thus contributing to the adsorption of polar compounds so that dextran/GO-coated SPME exhibited excellent extraction efficiency. It was found that the peak areas of CNAP and BNAP were greatly larger than that of 1,3-DCPH and 1,4-DBPH, which could be mainly ascribed to the dominant role of the π–π stacking interaction between analytes and GO because of the former ones with more benzene rings. To sum up, the dextran/GO fiber exhibited superb selectivity for phenols and halogenated aromatics, which were favorable to its practical utilization.

Fig. 5 Comparison of the peak areas for PAHs (a) and phenols, halogenated aromatics (b) extracted by three different fibers under the optimal conditions.

3.6 Assessment of the method

The analytical parameters including linear range with correlation coefficient, limit of detection (LOD), single fiber repeatability and fiber-to-fiber reproducibility were evaluated under the optimal extraction conditions. The linearity of the method was determined by a series of standard solutions with different concentrations. As can be seen in Table 2, the as-prepared dextran/GO-coated SPME-GC showed wide linear ranges of 0.10–200 μg L⁻¹, 0.20–200 μg L⁻¹ for different analytes with good correlation coefficients ranged from 0.9957 to 0.9990. LODs defined as three times the signal to noise ratio, were investigated by extracting aqueous solution spiked at different levels. Values of LODs were varying from 0.015 μg L⁻¹ to 0.050 μg L⁻¹, which could satisfy the trace determination of analytes in real samples. Furthermore, the fibers were confirmed by the repeatability and reproducibility. Single-fiber repeatability was investigated by five replicate extractions of analytes. Relative standard deviations (RSDs) for different analytes were from 2.7 to 10.6%. Fiber-to-fiber repeatability was evaluated by controlling the preparation process and performing the extraction procedure under the same conditions. RSDs obtained from five different fibers were in the range of 5.5–13.7%.

Table 2 Analytical parameters of the dextran/GO-SPME-GC method for the determination of analytes and comparison of the LODs with other methods

Compounds	EFs^a	Linear range (μg L^−1)	R^b	LOD^c (μg L^−1)	Repeatability (n = 5 (%))	Reproducibility (n = 5 (%))	LODs of 30 μm PDMS fiber^38	LODs of PILs-coated fiber^38
a Enrichment factors.b Correlation coefficient.c LOD, limit of detection for S/N = 3.
4-TBP	535	0.20–200	0.9973	0.050	6.4	7.3	8.3	1.2
2,4-DTBP	916	0.10–200	0.9985	0.025	9.4	11.5	—	—
2,6-DTBP	575	0.10–200	0.9976	0.020	3.7	6.6	—	—
4-TOP	1228	0.10–200	0.9968	0.020	6.9	8.7	0.38	0.055
1,3-DCPH	510	0.20–200	0.9986	0.050	9.1	10.4	—	—
1,4-DBPH	954	0.20–200	0.9964	0.050	8.3	13.7	—	—
α-CNAP	2090	0.10–200	0.9990	0.015	6.1	8.9	—	—
α-BNAP	1942	0.10–200	0.9957	0.020	10.6	12.4	—	—

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3.7 Application of the real samples

Phenols and halogenated aromatic compounds, as a class of pollutants, were easily introduced into the water environment through various channels. The established direct immersion SPME-GC method was applied to determine them in the real samples without any pretreatment. The final concentrations of each analytes in two water samples were the average values for consecutive analysis by three times. Furthermore, to evaluate the reliability of the proposed method in real samples, spiked recovery experiments were carried out. The water samples were spiked with 10 μg L⁻¹. Fig. 6 presented the GC chromatograms of the samples extracted by dextran/GO-coated SPME fiber. The detailed results were described in Table 3, which exhibited good recoveries for analytes. According to the analysis results of real samples, it was obvious that the proposed SPME-GC method had a potential application for the extraction of polar aromatic compounds in real samples.

Fig. 6 GC-FID chromatograms of real samples and the samples spiked at 10 μg L⁻¹: river water (A) and rain water (B); 1,3-DCPH (1), 1,4-DBPH (2), 4-TBP (3), α-CNAP (4), α-BNAP (5), 2,4-DTBP (6), 2,6-DTBP (7), 4-TOP (8).

Table 3 Analytical results and recoveries for dextran/GO-SPME-GC determination of analytes in water samples

Analytes	River water		Rain water
	Concentration (μg L^−1)	Recovery^b (n = 3, RSD%)	Concentration (μg L^−1)	Recovery (n = 3, RSD%)
a Not detected.b Standard addition level: 10 μg L^−1.
4-TBP	N.D.^a	98.0 ± 9.6	N.D.	92.2 ± 9.8
2,4-DTBP	N.D.	95.1 ± 6.8	2.6	84 ± 2.5
2,6-DTBP	2.7	94.5 ± 5.4	N.D.	99.6 ± 7.3
4-TOP	N.D.	98.7 ± 9.4	N.D.	110.6 ± 8.6
1,3-DCPH	N.D.	91.4 ± 11.3	N.D.	98.4 ± 2.7
1,4-DBPH	4.5	104.6 ± 9.8	3.2	94.5 ± 4.7
α-CNAP	3.2	106.1 ± 1.3	N.D.	87.6 ± 9.6
α-BNAP	N.D.	93.5 ± 3.4	1.9	105.4 ± 5.6

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4 Conclusion

In this work, a dextran/GO composite material was synthesized and used as the SPME fiber coating for extraction of trace phenols and polar halogenated aromatics. The novel fiber had the wrinkled and rugged structure enhancing the adsorption sites and extraction efficiency. Besides, huge amounts of –OH groups on the coating surface contributed to increase the polarity, resulting in the increase of extraction capacity for polar aromatic compounds. The inherent stability and strong interaction of composite material made the SPME fiber exhibit excellent stability and long lifetime. The SPME-GC-FID method showed high sensitivity, wide linear range, low LOD and good reproducibility, which was applied successfully to determine specific analytes in real samples. The as-established fiber proved to be a suitable candidate for the extraction of polar aromatic analytes.

Acknowledgements

Financial supports from the National Natural Science Foundation of China (21105107, 21175143 and 21475143) are gratefully acknowledged.

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Footnote

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c4ra15853a

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