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Novel molecularly-imprinted solid-phase microextraction fiber coupled with gas chromatography for analysis of furan
Author’s Accepted Manuscript Novel molecularly-imprinted microextraction fiber coupled chromatography for analysis of furan
solid-phase with gas
Hamid Hashemi-Moghaddam, Mojtaba Ahmadi www.elsevier.com
PII: DOI: Reference:
S0039-9140(15)30264-2 http://dx.doi.org/10.1016/j.talanta.2015.08.044 TAL15904
To appear in: Talanta Received date: 11 June 2015 Revised date: 20 August 2015 Accepted date: 21 August 2015 Cite this article as: Hamid Hashemi-Moghaddam and Mojtaba Ahmadi, Novel molecularly-imprinted solid-phase microextraction fiber coupled with gas chromatography for analysis of furan, Talanta, http://dx.doi.org/10.1016/j.talanta.2015.08.044 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Novel molecularly-imprinted solid-phase microextraction fiber coupled with gas chromatography for analysis of furan Hamid Hashemi-Moghaddam*, Mojtaba Ahmadi Department of Chemistry, Damghan Branch, Islamic Azad University, PO Box 3671639998, Damghan, Iran, E-mail: [email protected]
Abstract This study combined a molecularly-imprinted polymer with headspace solid-phase microextraction (HS-SPME). Preparation of molecularly-imprinted polymer is not effective for volatile compounds. To overcome this limitation, pyrrole was chosen as a template for the preparation of the furan-imprinted polymer. The holes in the synthesized polymer were suitable for furan adsorption because the chemical structure of pyrrole is similar to that of furan. The extraction properties of the fiber to furan were examined using an HS-SPME device coupled with gas chromatography–flame ionization detection (GC-FID) and gas chromatography–mass spectrometry (GC-MS). The effects of the extraction parameters of exposure time, sampling temperature, and salt concentration on extraction efficiency were studied. Satisfactory reproducibility was obtained for extractions from spiked water samples at RSD < 7.5% (n = 5). The calibration graphs were linear at 0.5 to 100 ng ml−1 and the detection limit for furan was 0.042 ng ml−1. The fabricated fiber was successfully applied for headspace extraction of furan from tap water and canned tuna as shown by GC-MS analysis.
Keywords: Furan; Molecularly imprinted polymer; Headspace solid-phase microextraction; Gas chromatography; Canned tuna 1
1. Introduction Furan is a colorless five-member ring compound having high volatility and a boiling point of 31°C. Furan can form in food during a Maillard reaction and has been of concern because it is classified by the International Agency for Research on Cancer as potentially carcinogenic to humans. The US Department of Health and Human Services includes furan on the human pathogen list. Furan is known to cause tumors, more than 90% of which are adenocarcinoma with the remaining being squamous cell carcinoma [1]. The analysis of furan in food samples is complicated because of its extremely high volatility. The US FDA has selected automated headspace sampling gas chromatographymass spectrometry (GC-MS) using the standard addition method for accurate analysis of furan in food samples. This method is time and labor intensive because several sample preparation steps are required for each sample [2]. Headspace solid-phase microextraction (HS-SPME) is used to determine furan in samples [3-9]. HS-SPME is a simple, solvent-free extraction technique with high sensitivity, excellent reproducibility that is low in cost. In this technique, phase-coated fused silica fiber is exposed to the headspace above the liquid or solid sample. Analytes adsorb onto the phase, thermally desorb in the injection port of a GC, and are transferred to a capillary column. Selectivity can be altered by changing the phase type or thickness according to the characteristics of the analytes [10]. The main disadvantage of this method is poor selectivity, which is a significant drawback for analysis of complicated real samples. Moreover, commercially-available fibers suffer from low selectivity, stability and strength, and high cost [11].
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Molecular imprinting is an attractive technique for synthesizing highly-selective polymeric receptors [12-18]. The inherent selectivity associated with molecularly-imprinted polymers (MIPs) has made these materials efficient for SPME; this combination has been successfully employed for extraction and preconcentration of analytes from different samples [19-23]. Given the vaporization of furan in the polymerization step, preparation of furanimprinted polymers is not possible. Pyrrole was, thus, chosen as template molecule. The chemical structure of pyrrole is similar to that of furan, but it has a higher boiling point. The holes in the synthesized polymer are suitable for furan adsorption and the synthesized polymer has been used successfully for HS-SPME of furan in real samples. This fiber is monolithic and flexible enough to be placed in a homemade syringe and inserted into a GC or GC-MS injection port. After equilibrium is established between furan and the fiber, it is inserted into a GC injection port for thermal desorption of furan and determination.
2. Experimental 2.1. Chemicals Methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), 2,2-azobisisobutyronitrile (AIBN), and acetonitrile were purchased from Merck (Germany). Furan and pyrrole were obtained from Sigma-Aldrich (UK). The SPME fiber, 100 µm carboxen polydimethylsiloxane (CAR/PDMS), was purchased from Supelco (USA) and conditioned prior to use according supplier instructions. Stock solutions of furan at a concentration of 5 mg l−1 were prepared weekly in cold methanol. Working solutions were prepared daily using 5 µl of refrigerated stock solution
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and 10 ml cold water. All vials of stock and working solution were sealed with siliconePTFE septa and aluminum seals and then stored at -18 and 4 °C, respectively, until analysis.
2.2. Instrumentation The furan was analyzed using GC-FID (Varian CP-3800). The samples were separated on a CP-Sil 5 CB capillary column (30 m × 0.25 mm × 0.25 μm film thickness). The injector temperature was 250°C. The GC oven was set to an initial temperature of 35°C for 4 min. The temperature program was set to increase from 3°C to 250°C at 25°C min−1 and held for 2 min. N2 flow was maintained at 1 ml min−1. The samples were injected in splitless mode. Desorption time from the fibers was 3 min. GCMS determination was performed on an HP-6890 GC system coupled with a 5973 network mass selective detector equipped with an HP-5MS capillary fused silica column (30 m × 0.25 mm I.D. × 0.32 μm film thickness). The operating conditions were the same as described previously and used helium as the carrier gas. Chromatographic data was recorded using an HP Chemsation controlled by Windows NT (Microsoft) and equipped with a Wiley mass spectral library. SEM images were captured using a DSM 960 electron microscope (Carl Zeiss; Germany). An SPME device (Azar Electrode; Iran) was used to hold the synthesized fiber and inject it into the GCMS injection port.
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2.3. Preparation of monolithic poly(methacrylic acid-co-ethylene glycol dimethacrylate) SPME fiber An 8 mmol sample of the template molecule (furan and pyrrole) was dissolved in 30 ml of methanol porogenic solvent. Then, 30 mmol of functional monomer (MAA) and 120 mmol of cross-linker (EGDMA) were added to the solution. The resulting mixture was ultrasonically stirred for 5 min. Approximately 280 mg of initiator (AIBN) was then added and the mixture was degassed with a stream of N2 gas for 10 min. The laboratories were glass capillary tubes 4 cm in length and 0.3 mm in internal diameter (as molds) inserted into test tubes containing prepolymer solution to fabricate the monolithic fibers. The glass capillary tubes were immediately filled with solution and the test tubes were immediately sealed with a rubber cap. The mixture was cured in a water bath for 12 h at 60°C. Non-imprinted polymers (NIPs) were also fabricated according to the above procedure in the absence of a template during polymerization.
2.4. Fiber conditioning The fabricated MIP or NIP monolithic fibers were immersed in a mixture containing methanol, acetic acid, and double-distilled water 4:1:1 (v/v/v) several times until the furan or pyrrole template, porogen solvent, and other impurities were removed as thoroughly as possible. The fibers were then modified by heating at 220°C in the presence of water vapor in a carbolite furnace for 15 min. All the modified fibers were conditioned at 280°C for 20 min in a GC injection port under N2 flow.
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2.5. Sample preparation Canned tuna samples were homogenized for 3 min using a homogenizer. Samples were immersed in an ice/water bath to prevent overheating of the sample and homogenizer. The homogenized samples were placed in a 20 ml headspace vial and 5 ml of chilled water was quickly added. The vials were completely filled and closed with silicone-PTFE septa and aluminum seals and stored at 4°C until analysis.
2.6. Headspace extraction procedure A 10 ml aliquot of aqueous solution spiked with furan was extracted with synthesized fiber housed in a manual SPME holder using HS-SPME mode. The fiber was conditioned prior to use by insertion into the GC injection port for 5 min. Water (10 ml) containing the furan was placed in a 25 ml glass vial with a PTFEsilicon septum. After the addition of sodium chloride and a magnetic stirring bar, the vial was tightly sealed with an aluminum cap to prevent sample loss by evaporation. During extraction, the vials were thermostated using a heated circulating water bath with the temperature maintained at the desired value. The synthesized fiber was exposed to the headspace over the stirred liquid sample for 10 to120 min depending on the experiment. After completion of the sampling step, the fiber was withdrawn into the needle and removed from the sample vial. The fiber was then immediately inserted into the GC injection port.
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3. Results and Discussion 3.1. Characterization and extraction performance of monolithic SPME fiber 3.1.1. Morphological structure of monolithic SPME fiber The SEM image of the monolithic MIP fiber shows the detailed morphology of the SPME fibers. The pyrrole-imprinted monolithic SPME fiber exhibited a highly porous structure on the surface. The nonporous structure of the furan-imprinted monolithic SPME fiber and NIP were confirmed by SEM. The results revealed that the pyrrole-imprinted monolithic SPME fiber can increase extraction performance. The SEM of the monolithic MIP SPME fiber under ×50000 magnification is shown in Figure 1.
Fig. 1. SEM image of monolithic SPME fiber under ×50000 magnification: (A) pyrroleimprinted monolithic SPME; (B) furan-imprinted monolithic SPME; (C) non-imprinted monolithic SPME
3.1.2. Infrared spectra of MIP coating The synthesized molecularly-imprinted and control polymers were subjected to characterization by FT-IR spectroscopy. Both polymers had similar IR spectra, indicating similarity in their backbone structure. In the IR spectra, absorption caused by the presence of carboxyl OH stretch (ca. 3548 cm−1), carbonyl group stretch (ca. 1721 cm−1), C-O stretch (ca. 1138 cm−1), and C-H vibrations (ca. 755, 1250, 1451 and 2954 cm−1) were observed. In addition to the similarity of the backbones of the MIP and NIP, the MIP absorbance attributed to the C-O stretch (present only in cross linker EGDMA) was significantly stronger than that of the NIP. The IR spectra of the synthesized non-imprinted and
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molecularly-imprinted fibers are shown in Figure 2.The presence of the imprint molecule (pyrrole) increased the incorporation of EGDMA into the preparation of polymers.
Fig. 2. FTIR spectra of synthesized: (A) non-imprinted; and (B) pyrrole-imprinted fiber.
3.1.3. Thermogravimetric analysis of MIP monolithic SPME fiber The thermal stability of monolithic SPME fiber is essential for the injection and desorption of MIP for GC analysis. Thermogravimetric analysis (TGA) of the polymer revealed that the polymer was thermally stable up to 400C. The injector temperature of GC or GC-MS is commonly controlled at or below 290C, so the MIP fiber has good thermal stability and is suitable for GC analysis. Figure 3 shows the TGA of the synthesized MIP fiber.
Fig. 3. Thermal analysis of pyrrole-imprinted monolithic SPME fiber: (A) quantity change curve (mg); (B) TGA curve (mg); (C) DTA curve.
3.1.4. Chemical stability of monolithic SPME fiber The monolithic SPME fibers were separately immersed in 1.00 mol l−1 HCl, 1.00 mol l−1 NaOH, hexane, toluene, chloroform, methanol, 10% acetic acid in methanol, and distilled water to investigate their chemical stability. After keeping the solutions at room temperature for 2 h, the MIP coatings retained good surface quality without desquamating, cracking, and swelling (as observed by naked eye). These fibers were used for extraction and desorption of furan in spiked water solutions. Each experiment was repeated five times. Statistically, no significant difference was noted between the obtained results; hence, no measurable
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degradation of extraction ability was observed. The proposed monolithic SPME fibers were chemically stable in strong acid, base, and organic solvents. This result further demonstrated the characteristics and superiority of MIP.
3.2. Optimization of extraction conditions The SPME of furan was performed from the headspace of the water solution spiked with furan. The effect of the main extraction parameters of exposure time, sampling temperature, and salt concentration of the sample were studied. The adsorption time profiles were also examined.
3.2.1. Optimization of extraction temperature The effect of solution temperature was investigated based on the extraction ability of furan using synthesized pyrrole and furan-imprinted SPME fibers. The peak area of furan solution at a concentration of 40 ng ml−1 was plotted as a function of temperature (30, 40, 50, 60, 70, 80 °C) at a fixed exposure time of 20 min. The extraction ability increased as the temperature increased up to 50°C because of the increase in the distribution constant of the analytes between the aqueous phase and headspace. A slight decrease in adsorption capacity was observed when the temperature increased up to 70°C. This could be attributed to the decreased partition coefficient of the analytes between the headspace and the fiber because adsorption is generally an exothermic process. The results showed that the furan-imprinted SPME fiber had very low ability for extraction of furan rather than pyrrole-imprinted SPME fiber, which was attributed to the lack of formation of an imprinted cavity in the synthesized polymer. In this study, an
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exposure temperature of 50°C was chosen. Figure 4 shows the peak area by fiber exposure temperature at a fixed exposure time of 20 min.
Fig. 4 Effect of fiber exposure temperature on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fibers.
3.2.2. Optimization of fiber exposure time Another important parameter considered was fiber exposure time. The time of extraction was optimized by monitoring the GC peak area as a function of exposure time. The synthesized pyrrole and furan-imprinted SPME fibers were exposed to standard solutions of furan for 10 to 60 min at a fixed temperature of 50°C (Figure 5). All results were obtained from three replicates to ensure reproducibility. The results show that 20 min was the optimum time for furan adsorption. This experiment showed that the extraction ability for furan-imprinted fiber is weak and variation of peak area is low.
Fig. 5 Effect of fiber exposure time on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fiber.
3.2.3. Influence of NaCl The influence of NaCl concentration on extraction efficiency was investigated by preparing solutions of furan at 0 to 4 M. The results indicated that extraction efficiency increased as NaCl concentration increased, reached a maximum in the presence of 2 M NaCl and
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remained constant thereafter. The best results were obtained from an aqueous sample containing 2 M NaCl. All further extractions were conducted using 2 M NaCl.
3.3. Quantitative analysis The figures of merit of the HS-SPME GC-MS method were investigated for dynamic linear range, correlation coefficient of calibration graph, and relative standard deviation. Calibration curves were drawn using 10 spiking levels of furan at concentrations of 0.5 to 100 ng ml−1 for synthesized pyrrole-imprinted SPME fibers. For each level, three replicate extractions and determinations were performed under optimal conditions. The correlation coefficient obtained was 0.965, which shows acceptable linearity in the dynamic range. Satisfactory reproducibility for extractions from the spiked water samples with RSD < 7.5% (n = 5) was achieved, it was tested repeatedly for 5 consecutive days. LOD and LOQ, expressed as concentration, were calculated based on a signal-to-noise ratio (S/N) of 3:1 and 10:1, respectively. The LOD and LOQ were 0.042 and 0.134 ng ml−1, respectively.
3.4. Application to real samples The applicability of the pyrrole-imprinted monolithic SPME fiber for extraction of furan from the samples was studied and compared with the CAR/PDMS fiber, which is the commercial fiber for the SPME of furan [2]. Tap water samples were collected in amber glass bottles (1000 ml). The bottles were rinsed several times with the water to be analyzed and then filled to overflowing to prevent loss of volatile compounds in the presence of headspace. The water samples were transported and stored at 4°C until analysis for furan without pre-treatment. No furan was
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found in the samples under GC-MS analysis; thus, the samples were spiked with 5 and 10 ng ml−1 furan. Five replicate HS-SPME analyses were performed for each water sample using the synthesized fiber under optimal conditions. In addition, canned tuna was analyzed for furan using the proposed method using GC-MS. The chromatograms for furan determination by synthesized SPME fiber and CAR/PDMS fiber are shown in Figure 6. A total of 16 compounds were adsorbed onto the fiber and identified using CAR/PDMS fiber: hydrogen sulfide; acetaldehyde; methane thiol; ethanol; furan; 1-methyl1-butene; pentane; dimethyl sulfide; 2-methyl propanol; hexane, benzene, 2-methyl butanal, 2,2-dimethyl propanol; unknown; 1-penten-3-ol; heptane. A total of 14 compounds were adsorbed using the pyrrole-imprinted monolithic SPME fiber; the intensity of the interference compounds was very low and the intensity of the furan peak was significantly higher than other compounds. The identified compounds were: hydrogen sulfide; acetaldehyde; methane thiol; ethanol; 5, butane; furan; dimethyl sulfide; 2-methyl propanal; hexane; benzene; 2-methyl butanal; 2,2-dimethyl propanol; unknown 1; 1-penten-3-ol.
Fig. 6. GC-MS total ion chromatogram corresponding to extraction of furan from canned tuna by: (A) fabricated pyrrole-imprinted monolithic SPME fiber; and (B) commercial CAR/PDMS fiber.
The results of analysis of real samples are summarized in Table 1. Average recoveries for synthesized SPME fiber and CAR/PDMS fiber were 91.5% and 85.7%, respectively. The results demonstrated good recovery by the proposed method.
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Table 1. Determination of furan in water and canned tuna samples
4. Conclusion A new molecularly-imprinted polymer fiber was synthesized using a novel technique using furan, a volatile compound. This study presented the first application of molecularlyimprinted polymer for HS-SPME. Preparation of the furan-imprinted polymers cannot be achieved with high efficiency because of vaporization of furan in the polymerization step; thus, pyrrole, which has a higher boiling point but a similar structure to the furan molecule, was chosen as a template. The experimental results clearly demonstrated that the synthesized pyrrole-imprinted monolithic SPME fiber was significantly more effective than the furan-imprinted monolithic SPME fiber for HS-SPME of furan analytes. The combination of HS-SPME with molecularly-imprinted SPME fiber can achieve low LODs and be applied to determine furan in real samples.
Acknowledgments We are grateful to the Laboratory Complex of Damghan Branch Islamic Azad University and to Pars Material Research and Testing for their valuable technical assistance.
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References [1] A. Sarafraz-Yazdi, M. Abbasian, A. Amiri, Determination of furan in food samples using two solid phase microextraction fibers based on sol–gel technique with gas chromatography–flame ionisation detector, Food Chem. 131 (2012) 698-704. [2] T.-K. Kim, S. Kim, K.-G. Lee, Analysis of furan in heat-processed foods consumed in Korea using solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS), Food Chem. 123 (2010) 1328-1333. [3] A. Becalski, S. Seaman, Furan precursors in food: a model study and development of a simple headspace method for determination of furan, J. AOAC Int. 88 (2005) 102-106. [4] A. Becalski, D. Forsyth, V. Casey, B.-Y. Lau, K. Pepper, S. Seaman, Development and validation of a headspace method for determination of furan in food, Food Addit. Contam. 22 (2005) 535-540. [5] P.J. Nyman, K.M. Morehouse, G.A. Perfetti, G.W. Diachenko, J.R. Holcomb, Single-laboratory validation of a method for the determination of furan in foods by using headspace gas chromatography/mass spectrometry, Part 2 low-moisture snack foods, J. AOAC Int. 91 (2008) 414421. [6] C. Bicchi, M.R. Ruosi, C. Cagliero, C. Cordero, E. Liberto, P. Rubiolo, B. Sgorbini, Quantitative analysis of volatiles from solid matrices of vegetable origin by high concentration capacity headspace techniques: determination of furan in roasted coffee, J. Chromatogr. A 1218 (2011) 753762.
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[7] M. Bononi, F. Tateo, Determination of furan by headspace solid-phase microextraction–gas chromatography–mass spectrometry in balsamic vinegars of Modena (Italy), J. Food Comp. Anal. 22 (2009) 79-82. [8] F. Bianchi, M. Careri, A. Mangia, M. Musci, Development and validation of a solid phase microextraction–gas chromatography–mass spectrometry method for the determination of furan in babyfood, J. Chromatogr. A 1102 (2006) 268-272. [9] T. Goldmann, A. Périsset, F. Scanlan, R.H. Stadler, Rapid determination of furan in heated foodstuffs by isotope dilution solid phase micro-extraction-gas chromatography–mass spectrometry (SPME-GC-MS), Analyst 130 (2005) 878-883. [10] Z. Zhang, M.J. Yang, J. Pawliszyn, Solid-phase microextraction. A solvent-free alternative for sample preparation, Anal. Chem. 66 (1994) 844A-853A. [11] D. Djozan, M.A. Farajzadeh, S.M. Sorouraddin, T. Baheri, Synthesis and application of high selective monolithic fibers based on molecularly imprinted polymer for SPME of trace methamphetamine, Chromatographia 73 (2011) 975-983. [12] H.F. Wang, Y.Z. Zhu, X.P. Yan, R.Y. Gao, J.Y. Zheng, A room temperature ionic liquid (RTIL)‐mediated, non‐hydrolytic sol–gel methodology to prepare molecularly imprinted, silica‐based hybrid monoliths for chiral separation, Adv. Mater. 18 (2006) 3266-3270. [13] H.F. Wang, Y.Z. Zhu, J.P. Lin, X.P. Yan, Fabrication of molecularly imprinted hybrid monoliths via a room temperature ionic liquid‐mediated nonhydrolytic sol–gel route for chiral separation of zolmitriptan by capillary electrochromatography, Electrophoresis 29 (2008) 952-959. [14] C. Crews, L. Castle, A review of the occurrence, formation and analysis of furan in heatprocessed foods, Trends in Food Sci. Tech. 18 (2007) 365-372.
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[15] J. Li, Z. Zhang, S. Xu, L. Chen, N. Zhou, H. Xiong, H. Peng, Label-free colorimetric detection of trace cholesterol based on molecularly imprinted photonic hydrogels, J. Mater. Chem. 21 (2011) 19267-19274. [16] H. Hashemi-Moghaddam, M. Rahimian, B. Niromand, Molecularly imprinted polymers for solid-phase extraction of sarcosine as prostate cancer biomarker from human urine, Bull. Korean Chem. Soc. 34 (2013) 2331. [17] H. Hashemi-Moghaddam, M. Shakeri, Removal of potentioally genotoxic impurity from fluroxamine maleate crude drug by molecularly imprinted polymer, Korean J. Chem. Eng. 31 (2014) 1898-1902. [18] H. Hashemi-Moghaddam, F. Yahyazadeh, M.T. Vardini, Synthesis of a new molecularly imprinted polymer for sorption of the silver ions from geological and antiseptic samples for determination by flame atomic absorption spectrometry, J. AOAC Inter. 97 (2014) 1434-1438. [19] K. Haupt, K. Mosbach, Molecularly imprinted polymers and their use in biomimetic sensors, Chem. Rev., 100 (2000) 2495-2504. [20] K. Haupt, Peer reviewed: molecularly imprinted polymers: the next generation, Anal. Chem. 75 (2003) 376 A-383 A. [21] L.I. Andersson, Molecular imprinting for drug bioanalysis: a review on the application of imprinted polymers to solid-phase extraction and binding assay, J. Chromatogr. B 739 (2000) 163173. [22] H. Hashemi‐Moghaddam, M.R. Alaeian, Synthesis of molecularly imprinted polymer for removal of effective impurity (benzhydrol) from diphenhydramine hydrochloride drug, J. Chin. Chem. Soc-Taip 61 (2014) 643-648.
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[23] H. Hashemi-Moghaddam, D.J. Jedi, Solid-phase microextraction of chlorpyrifos in fruit samples by synthesised monolithic molecularly imprinted polymer fibres, Inter. J. Environ. Anal. Chem. 95 (2014) 33-44.
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Figure captions: Fig. 1. SEM image of monolithic SPME fiber under ×50000 magnification: (A) pyrroleimprinted monolithic SPME; (B) furan-imprinted monolithic SPME; (C) non-imprinted monolithic SPME Fig. 2. FTIR spectra of synthesized: (A) non-imprinted; and (B) pyrrole-imprinted fiber. Fig. 3. Thermal analysis of pyrrole-imprinted monolithic SPME fiber: (A) quantity change curve (mg); (B) TGA curve (mg); (C) DTA curve. Fig. 4 Effect of fiber exposure temperature on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fibers. Fig. 5 Effect of fiber exposure time on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fiber. Fig. 6. GC-MS total ion chromatogram corresponding to extraction of furan from canned tuna by: (A) fabricated pyrrole-imprinted monolithic SPME fiber; and (B) commercial CAR/PDMS fiber.
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Fig. 1. SEM image of monolithic SPME fiber under ×50000 magnification: (A) pyrroleimprinted monolithic SPME; (B) furan-imprinted monolithic SPME; (C) non-imprinted monolithic SPME
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A
B
Fig. 2. FTIR spectra of synthesized: (A) non-imprinted; and (B) pyrrole-imprinted fiber.
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Fig. 3. Thermal analysis of pyrrole-imprinted monolithic SPME fiber: (A) quantity change curve (mg); (B) TGA curve (mg); (C) DTA curve.
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A
B
Fig. 4 Effect of fiber exposure temperature on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fibers.
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A
B
Fig. 5 Effect of fiber exposure time on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fiber.
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Fig. 6. GC-MS total ion chromatogram corresponding to extraction of furan from canned tuna by: (A) fabricated pyrrole-imprinted monolithic SPME fiber; and (B) commercial CAR/PDMS fiber.
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Table1. Determination of furan in tap water and canned tuna samples Sample
Tap water
Canned tuna
Added MIP )ng mL-1/ ng g-1) ND 5 4.58 ± 5.0 10 4.0 ± 5.0 40.80 ± 5.6 5 20.76 ± 5.. 10 24.42 ± 5.8
Extraction % 92 40 44.0 88.3
CAR/PDMS Extraction% ND 4.28 ± 5.. 6.. ± 5.6 48.60 ± 5.. 44.80 ± 5.0 86..0 ± 5.4
6..8 6. 68.4 6..8
Significance of the work
This new monolithic molecular imprinted polymer fiber could answer to the call for selective and fast analysis of furan in real samples.
High Selectivity
Low price
High stability in different condition
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tpartsra aciGparG
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solid-phase with gas
Hamid Hashemi-Moghaddam, Mojtaba Ahmadi www.elsevier.com
PII: DOI: Reference:
S0039-9140(15)30264-2 http://dx.doi.org/10.1016/j.talanta.2015.08.044 TAL15904
To appear in: Talanta Received date: 11 June 2015 Revised date: 20 August 2015 Accepted date: 21 August 2015 Cite this article as: Hamid Hashemi-Moghaddam and Mojtaba Ahmadi, Novel molecularly-imprinted solid-phase microextraction fiber coupled with gas chromatography for analysis of furan, Talanta, http://dx.doi.org/10.1016/j.talanta.2015.08.044 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Novel molecularly-imprinted solid-phase microextraction fiber coupled with gas chromatography for analysis of furan Hamid Hashemi-Moghaddam*, Mojtaba Ahmadi Department of Chemistry, Damghan Branch, Islamic Azad University, PO Box 3671639998, Damghan, Iran, E-mail: [email protected]
Abstract This study combined a molecularly-imprinted polymer with headspace solid-phase microextraction (HS-SPME). Preparation of molecularly-imprinted polymer is not effective for volatile compounds. To overcome this limitation, pyrrole was chosen as a template for the preparation of the furan-imprinted polymer. The holes in the synthesized polymer were suitable for furan adsorption because the chemical structure of pyrrole is similar to that of furan. The extraction properties of the fiber to furan were examined using an HS-SPME device coupled with gas chromatography–flame ionization detection (GC-FID) and gas chromatography–mass spectrometry (GC-MS). The effects of the extraction parameters of exposure time, sampling temperature, and salt concentration on extraction efficiency were studied. Satisfactory reproducibility was obtained for extractions from spiked water samples at RSD < 7.5% (n = 5). The calibration graphs were linear at 0.5 to 100 ng ml−1 and the detection limit for furan was 0.042 ng ml−1. The fabricated fiber was successfully applied for headspace extraction of furan from tap water and canned tuna as shown by GC-MS analysis.
Keywords: Furan; Molecularly imprinted polymer; Headspace solid-phase microextraction; Gas chromatography; Canned tuna 1
1. Introduction Furan is a colorless five-member ring compound having high volatility and a boiling point of 31°C. Furan can form in food during a Maillard reaction and has been of concern because it is classified by the International Agency for Research on Cancer as potentially carcinogenic to humans. The US Department of Health and Human Services includes furan on the human pathogen list. Furan is known to cause tumors, more than 90% of which are adenocarcinoma with the remaining being squamous cell carcinoma [1]. The analysis of furan in food samples is complicated because of its extremely high volatility. The US FDA has selected automated headspace sampling gas chromatographymass spectrometry (GC-MS) using the standard addition method for accurate analysis of furan in food samples. This method is time and labor intensive because several sample preparation steps are required for each sample [2]. Headspace solid-phase microextraction (HS-SPME) is used to determine furan in samples [3-9]. HS-SPME is a simple, solvent-free extraction technique with high sensitivity, excellent reproducibility that is low in cost. In this technique, phase-coated fused silica fiber is exposed to the headspace above the liquid or solid sample. Analytes adsorb onto the phase, thermally desorb in the injection port of a GC, and are transferred to a capillary column. Selectivity can be altered by changing the phase type or thickness according to the characteristics of the analytes [10]. The main disadvantage of this method is poor selectivity, which is a significant drawback for analysis of complicated real samples. Moreover, commercially-available fibers suffer from low selectivity, stability and strength, and high cost [11].
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Molecular imprinting is an attractive technique for synthesizing highly-selective polymeric receptors [12-18]. The inherent selectivity associated with molecularly-imprinted polymers (MIPs) has made these materials efficient for SPME; this combination has been successfully employed for extraction and preconcentration of analytes from different samples [19-23]. Given the vaporization of furan in the polymerization step, preparation of furanimprinted polymers is not possible. Pyrrole was, thus, chosen as template molecule. The chemical structure of pyrrole is similar to that of furan, but it has a higher boiling point. The holes in the synthesized polymer are suitable for furan adsorption and the synthesized polymer has been used successfully for HS-SPME of furan in real samples. This fiber is monolithic and flexible enough to be placed in a homemade syringe and inserted into a GC or GC-MS injection port. After equilibrium is established between furan and the fiber, it is inserted into a GC injection port for thermal desorption of furan and determination.
2. Experimental 2.1. Chemicals Methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), 2,2-azobisisobutyronitrile (AIBN), and acetonitrile were purchased from Merck (Germany). Furan and pyrrole were obtained from Sigma-Aldrich (UK). The SPME fiber, 100 µm carboxen polydimethylsiloxane (CAR/PDMS), was purchased from Supelco (USA) and conditioned prior to use according supplier instructions. Stock solutions of furan at a concentration of 5 mg l−1 were prepared weekly in cold methanol. Working solutions were prepared daily using 5 µl of refrigerated stock solution
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and 10 ml cold water. All vials of stock and working solution were sealed with siliconePTFE septa and aluminum seals and then stored at -18 and 4 °C, respectively, until analysis.
2.2. Instrumentation The furan was analyzed using GC-FID (Varian CP-3800). The samples were separated on a CP-Sil 5 CB capillary column (30 m × 0.25 mm × 0.25 μm film thickness). The injector temperature was 250°C. The GC oven was set to an initial temperature of 35°C for 4 min. The temperature program was set to increase from 3°C to 250°C at 25°C min−1 and held for 2 min. N2 flow was maintained at 1 ml min−1. The samples were injected in splitless mode. Desorption time from the fibers was 3 min. GCMS determination was performed on an HP-6890 GC system coupled with a 5973 network mass selective detector equipped with an HP-5MS capillary fused silica column (30 m × 0.25 mm I.D. × 0.32 μm film thickness). The operating conditions were the same as described previously and used helium as the carrier gas. Chromatographic data was recorded using an HP Chemsation controlled by Windows NT (Microsoft) and equipped with a Wiley mass spectral library. SEM images were captured using a DSM 960 electron microscope (Carl Zeiss; Germany). An SPME device (Azar Electrode; Iran) was used to hold the synthesized fiber and inject it into the GCMS injection port.
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2.3. Preparation of monolithic poly(methacrylic acid-co-ethylene glycol dimethacrylate) SPME fiber An 8 mmol sample of the template molecule (furan and pyrrole) was dissolved in 30 ml of methanol porogenic solvent. Then, 30 mmol of functional monomer (MAA) and 120 mmol of cross-linker (EGDMA) were added to the solution. The resulting mixture was ultrasonically stirred for 5 min. Approximately 280 mg of initiator (AIBN) was then added and the mixture was degassed with a stream of N2 gas for 10 min. The laboratories were glass capillary tubes 4 cm in length and 0.3 mm in internal diameter (as molds) inserted into test tubes containing prepolymer solution to fabricate the monolithic fibers. The glass capillary tubes were immediately filled with solution and the test tubes were immediately sealed with a rubber cap. The mixture was cured in a water bath for 12 h at 60°C. Non-imprinted polymers (NIPs) were also fabricated according to the above procedure in the absence of a template during polymerization.
2.4. Fiber conditioning The fabricated MIP or NIP monolithic fibers were immersed in a mixture containing methanol, acetic acid, and double-distilled water 4:1:1 (v/v/v) several times until the furan or pyrrole template, porogen solvent, and other impurities were removed as thoroughly as possible. The fibers were then modified by heating at 220°C in the presence of water vapor in a carbolite furnace for 15 min. All the modified fibers were conditioned at 280°C for 20 min in a GC injection port under N2 flow.
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2.5. Sample preparation Canned tuna samples were homogenized for 3 min using a homogenizer. Samples were immersed in an ice/water bath to prevent overheating of the sample and homogenizer. The homogenized samples were placed in a 20 ml headspace vial and 5 ml of chilled water was quickly added. The vials were completely filled and closed with silicone-PTFE septa and aluminum seals and stored at 4°C until analysis.
2.6. Headspace extraction procedure A 10 ml aliquot of aqueous solution spiked with furan was extracted with synthesized fiber housed in a manual SPME holder using HS-SPME mode. The fiber was conditioned prior to use by insertion into the GC injection port for 5 min. Water (10 ml) containing the furan was placed in a 25 ml glass vial with a PTFEsilicon septum. After the addition of sodium chloride and a magnetic stirring bar, the vial was tightly sealed with an aluminum cap to prevent sample loss by evaporation. During extraction, the vials were thermostated using a heated circulating water bath with the temperature maintained at the desired value. The synthesized fiber was exposed to the headspace over the stirred liquid sample for 10 to120 min depending on the experiment. After completion of the sampling step, the fiber was withdrawn into the needle and removed from the sample vial. The fiber was then immediately inserted into the GC injection port.
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3. Results and Discussion 3.1. Characterization and extraction performance of monolithic SPME fiber 3.1.1. Morphological structure of monolithic SPME fiber The SEM image of the monolithic MIP fiber shows the detailed morphology of the SPME fibers. The pyrrole-imprinted monolithic SPME fiber exhibited a highly porous structure on the surface. The nonporous structure of the furan-imprinted monolithic SPME fiber and NIP were confirmed by SEM. The results revealed that the pyrrole-imprinted monolithic SPME fiber can increase extraction performance. The SEM of the monolithic MIP SPME fiber under ×50000 magnification is shown in Figure 1.
Fig. 1. SEM image of monolithic SPME fiber under ×50000 magnification: (A) pyrroleimprinted monolithic SPME; (B) furan-imprinted monolithic SPME; (C) non-imprinted monolithic SPME
3.1.2. Infrared spectra of MIP coating The synthesized molecularly-imprinted and control polymers were subjected to characterization by FT-IR spectroscopy. Both polymers had similar IR spectra, indicating similarity in their backbone structure. In the IR spectra, absorption caused by the presence of carboxyl OH stretch (ca. 3548 cm−1), carbonyl group stretch (ca. 1721 cm−1), C-O stretch (ca. 1138 cm−1), and C-H vibrations (ca. 755, 1250, 1451 and 2954 cm−1) were observed. In addition to the similarity of the backbones of the MIP and NIP, the MIP absorbance attributed to the C-O stretch (present only in cross linker EGDMA) was significantly stronger than that of the NIP. The IR spectra of the synthesized non-imprinted and
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molecularly-imprinted fibers are shown in Figure 2.The presence of the imprint molecule (pyrrole) increased the incorporation of EGDMA into the preparation of polymers.
Fig. 2. FTIR spectra of synthesized: (A) non-imprinted; and (B) pyrrole-imprinted fiber.
3.1.3. Thermogravimetric analysis of MIP monolithic SPME fiber The thermal stability of monolithic SPME fiber is essential for the injection and desorption of MIP for GC analysis. Thermogravimetric analysis (TGA) of the polymer revealed that the polymer was thermally stable up to 400C. The injector temperature of GC or GC-MS is commonly controlled at or below 290C, so the MIP fiber has good thermal stability and is suitable for GC analysis. Figure 3 shows the TGA of the synthesized MIP fiber.
Fig. 3. Thermal analysis of pyrrole-imprinted monolithic SPME fiber: (A) quantity change curve (mg); (B) TGA curve (mg); (C) DTA curve.
3.1.4. Chemical stability of monolithic SPME fiber The monolithic SPME fibers were separately immersed in 1.00 mol l−1 HCl, 1.00 mol l−1 NaOH, hexane, toluene, chloroform, methanol, 10% acetic acid in methanol, and distilled water to investigate their chemical stability. After keeping the solutions at room temperature for 2 h, the MIP coatings retained good surface quality without desquamating, cracking, and swelling (as observed by naked eye). These fibers were used for extraction and desorption of furan in spiked water solutions. Each experiment was repeated five times. Statistically, no significant difference was noted between the obtained results; hence, no measurable
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degradation of extraction ability was observed. The proposed monolithic SPME fibers were chemically stable in strong acid, base, and organic solvents. This result further demonstrated the characteristics and superiority of MIP.
3.2. Optimization of extraction conditions The SPME of furan was performed from the headspace of the water solution spiked with furan. The effect of the main extraction parameters of exposure time, sampling temperature, and salt concentration of the sample were studied. The adsorption time profiles were also examined.
3.2.1. Optimization of extraction temperature The effect of solution temperature was investigated based on the extraction ability of furan using synthesized pyrrole and furan-imprinted SPME fibers. The peak area of furan solution at a concentration of 40 ng ml−1 was plotted as a function of temperature (30, 40, 50, 60, 70, 80 °C) at a fixed exposure time of 20 min. The extraction ability increased as the temperature increased up to 50°C because of the increase in the distribution constant of the analytes between the aqueous phase and headspace. A slight decrease in adsorption capacity was observed when the temperature increased up to 70°C. This could be attributed to the decreased partition coefficient of the analytes between the headspace and the fiber because adsorption is generally an exothermic process. The results showed that the furan-imprinted SPME fiber had very low ability for extraction of furan rather than pyrrole-imprinted SPME fiber, which was attributed to the lack of formation of an imprinted cavity in the synthesized polymer. In this study, an
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exposure temperature of 50°C was chosen. Figure 4 shows the peak area by fiber exposure temperature at a fixed exposure time of 20 min.
Fig. 4 Effect of fiber exposure temperature on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fibers.
3.2.2. Optimization of fiber exposure time Another important parameter considered was fiber exposure time. The time of extraction was optimized by monitoring the GC peak area as a function of exposure time. The synthesized pyrrole and furan-imprinted SPME fibers were exposed to standard solutions of furan for 10 to 60 min at a fixed temperature of 50°C (Figure 5). All results were obtained from three replicates to ensure reproducibility. The results show that 20 min was the optimum time for furan adsorption. This experiment showed that the extraction ability for furan-imprinted fiber is weak and variation of peak area is low.
Fig. 5 Effect of fiber exposure time on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fiber.
3.2.3. Influence of NaCl The influence of NaCl concentration on extraction efficiency was investigated by preparing solutions of furan at 0 to 4 M. The results indicated that extraction efficiency increased as NaCl concentration increased, reached a maximum in the presence of 2 M NaCl and
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remained constant thereafter. The best results were obtained from an aqueous sample containing 2 M NaCl. All further extractions were conducted using 2 M NaCl.
3.3. Quantitative analysis The figures of merit of the HS-SPME GC-MS method were investigated for dynamic linear range, correlation coefficient of calibration graph, and relative standard deviation. Calibration curves were drawn using 10 spiking levels of furan at concentrations of 0.5 to 100 ng ml−1 for synthesized pyrrole-imprinted SPME fibers. For each level, three replicate extractions and determinations were performed under optimal conditions. The correlation coefficient obtained was 0.965, which shows acceptable linearity in the dynamic range. Satisfactory reproducibility for extractions from the spiked water samples with RSD < 7.5% (n = 5) was achieved, it was tested repeatedly for 5 consecutive days. LOD and LOQ, expressed as concentration, were calculated based on a signal-to-noise ratio (S/N) of 3:1 and 10:1, respectively. The LOD and LOQ were 0.042 and 0.134 ng ml−1, respectively.
3.4. Application to real samples The applicability of the pyrrole-imprinted monolithic SPME fiber for extraction of furan from the samples was studied and compared with the CAR/PDMS fiber, which is the commercial fiber for the SPME of furan [2]. Tap water samples were collected in amber glass bottles (1000 ml). The bottles were rinsed several times with the water to be analyzed and then filled to overflowing to prevent loss of volatile compounds in the presence of headspace. The water samples were transported and stored at 4°C until analysis for furan without pre-treatment. No furan was
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found in the samples under GC-MS analysis; thus, the samples were spiked with 5 and 10 ng ml−1 furan. Five replicate HS-SPME analyses were performed for each water sample using the synthesized fiber under optimal conditions. In addition, canned tuna was analyzed for furan using the proposed method using GC-MS. The chromatograms for furan determination by synthesized SPME fiber and CAR/PDMS fiber are shown in Figure 6. A total of 16 compounds were adsorbed onto the fiber and identified using CAR/PDMS fiber: hydrogen sulfide; acetaldehyde; methane thiol; ethanol; furan; 1-methyl1-butene; pentane; dimethyl sulfide; 2-methyl propanol; hexane, benzene, 2-methyl butanal, 2,2-dimethyl propanol; unknown; 1-penten-3-ol; heptane. A total of 14 compounds were adsorbed using the pyrrole-imprinted monolithic SPME fiber; the intensity of the interference compounds was very low and the intensity of the furan peak was significantly higher than other compounds. The identified compounds were: hydrogen sulfide; acetaldehyde; methane thiol; ethanol; 5, butane; furan; dimethyl sulfide; 2-methyl propanal; hexane; benzene; 2-methyl butanal; 2,2-dimethyl propanol; unknown 1; 1-penten-3-ol.
Fig. 6. GC-MS total ion chromatogram corresponding to extraction of furan from canned tuna by: (A) fabricated pyrrole-imprinted monolithic SPME fiber; and (B) commercial CAR/PDMS fiber.
The results of analysis of real samples are summarized in Table 1. Average recoveries for synthesized SPME fiber and CAR/PDMS fiber were 91.5% and 85.7%, respectively. The results demonstrated good recovery by the proposed method.
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Table 1. Determination of furan in water and canned tuna samples
4. Conclusion A new molecularly-imprinted polymer fiber was synthesized using a novel technique using furan, a volatile compound. This study presented the first application of molecularlyimprinted polymer for HS-SPME. Preparation of the furan-imprinted polymers cannot be achieved with high efficiency because of vaporization of furan in the polymerization step; thus, pyrrole, which has a higher boiling point but a similar structure to the furan molecule, was chosen as a template. The experimental results clearly demonstrated that the synthesized pyrrole-imprinted monolithic SPME fiber was significantly more effective than the furan-imprinted monolithic SPME fiber for HS-SPME of furan analytes. The combination of HS-SPME with molecularly-imprinted SPME fiber can achieve low LODs and be applied to determine furan in real samples.
Acknowledgments We are grateful to the Laboratory Complex of Damghan Branch Islamic Azad University and to Pars Material Research and Testing for their valuable technical assistance.
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References [1] A. Sarafraz-Yazdi, M. Abbasian, A. Amiri, Determination of furan in food samples using two solid phase microextraction fibers based on sol–gel technique with gas chromatography–flame ionisation detector, Food Chem. 131 (2012) 698-704. [2] T.-K. Kim, S. Kim, K.-G. Lee, Analysis of furan in heat-processed foods consumed in Korea using solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS), Food Chem. 123 (2010) 1328-1333. [3] A. Becalski, S. Seaman, Furan precursors in food: a model study and development of a simple headspace method for determination of furan, J. AOAC Int. 88 (2005) 102-106. [4] A. Becalski, D. Forsyth, V. Casey, B.-Y. Lau, K. Pepper, S. Seaman, Development and validation of a headspace method for determination of furan in food, Food Addit. Contam. 22 (2005) 535-540. [5] P.J. Nyman, K.M. Morehouse, G.A. Perfetti, G.W. Diachenko, J.R. Holcomb, Single-laboratory validation of a method for the determination of furan in foods by using headspace gas chromatography/mass spectrometry, Part 2 low-moisture snack foods, J. AOAC Int. 91 (2008) 414421. [6] C. Bicchi, M.R. Ruosi, C. Cagliero, C. Cordero, E. Liberto, P. Rubiolo, B. Sgorbini, Quantitative analysis of volatiles from solid matrices of vegetable origin by high concentration capacity headspace techniques: determination of furan in roasted coffee, J. Chromatogr. A 1218 (2011) 753762.
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[7] M. Bononi, F. Tateo, Determination of furan by headspace solid-phase microextraction–gas chromatography–mass spectrometry in balsamic vinegars of Modena (Italy), J. Food Comp. Anal. 22 (2009) 79-82. [8] F. Bianchi, M. Careri, A. Mangia, M. Musci, Development and validation of a solid phase microextraction–gas chromatography–mass spectrometry method for the determination of furan in babyfood, J. Chromatogr. A 1102 (2006) 268-272. [9] T. Goldmann, A. Périsset, F. Scanlan, R.H. Stadler, Rapid determination of furan in heated foodstuffs by isotope dilution solid phase micro-extraction-gas chromatography–mass spectrometry (SPME-GC-MS), Analyst 130 (2005) 878-883. [10] Z. Zhang, M.J. Yang, J. Pawliszyn, Solid-phase microextraction. A solvent-free alternative for sample preparation, Anal. Chem. 66 (1994) 844A-853A. [11] D. Djozan, M.A. Farajzadeh, S.M. Sorouraddin, T. Baheri, Synthesis and application of high selective monolithic fibers based on molecularly imprinted polymer for SPME of trace methamphetamine, Chromatographia 73 (2011) 975-983. [12] H.F. Wang, Y.Z. Zhu, X.P. Yan, R.Y. Gao, J.Y. Zheng, A room temperature ionic liquid (RTIL)‐mediated, non‐hydrolytic sol–gel methodology to prepare molecularly imprinted, silica‐based hybrid monoliths for chiral separation, Adv. Mater. 18 (2006) 3266-3270. [13] H.F. Wang, Y.Z. Zhu, J.P. Lin, X.P. Yan, Fabrication of molecularly imprinted hybrid monoliths via a room temperature ionic liquid‐mediated nonhydrolytic sol–gel route for chiral separation of zolmitriptan by capillary electrochromatography, Electrophoresis 29 (2008) 952-959. [14] C. Crews, L. Castle, A review of the occurrence, formation and analysis of furan in heatprocessed foods, Trends in Food Sci. Tech. 18 (2007) 365-372.
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[15] J. Li, Z. Zhang, S. Xu, L. Chen, N. Zhou, H. Xiong, H. Peng, Label-free colorimetric detection of trace cholesterol based on molecularly imprinted photonic hydrogels, J. Mater. Chem. 21 (2011) 19267-19274. [16] H. Hashemi-Moghaddam, M. Rahimian, B. Niromand, Molecularly imprinted polymers for solid-phase extraction of sarcosine as prostate cancer biomarker from human urine, Bull. Korean Chem. Soc. 34 (2013) 2331. [17] H. Hashemi-Moghaddam, M. Shakeri, Removal of potentioally genotoxic impurity from fluroxamine maleate crude drug by molecularly imprinted polymer, Korean J. Chem. Eng. 31 (2014) 1898-1902. [18] H. Hashemi-Moghaddam, F. Yahyazadeh, M.T. Vardini, Synthesis of a new molecularly imprinted polymer for sorption of the silver ions from geological and antiseptic samples for determination by flame atomic absorption spectrometry, J. AOAC Inter. 97 (2014) 1434-1438. [19] K. Haupt, K. Mosbach, Molecularly imprinted polymers and their use in biomimetic sensors, Chem. Rev., 100 (2000) 2495-2504. [20] K. Haupt, Peer reviewed: molecularly imprinted polymers: the next generation, Anal. Chem. 75 (2003) 376 A-383 A. [21] L.I. Andersson, Molecular imprinting for drug bioanalysis: a review on the application of imprinted polymers to solid-phase extraction and binding assay, J. Chromatogr. B 739 (2000) 163173. [22] H. Hashemi‐Moghaddam, M.R. Alaeian, Synthesis of molecularly imprinted polymer for removal of effective impurity (benzhydrol) from diphenhydramine hydrochloride drug, J. Chin. Chem. Soc-Taip 61 (2014) 643-648.
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[23] H. Hashemi-Moghaddam, D.J. Jedi, Solid-phase microextraction of chlorpyrifos in fruit samples by synthesised monolithic molecularly imprinted polymer fibres, Inter. J. Environ. Anal. Chem. 95 (2014) 33-44.
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Figure captions: Fig. 1. SEM image of monolithic SPME fiber under ×50000 magnification: (A) pyrroleimprinted monolithic SPME; (B) furan-imprinted monolithic SPME; (C) non-imprinted monolithic SPME Fig. 2. FTIR spectra of synthesized: (A) non-imprinted; and (B) pyrrole-imprinted fiber. Fig. 3. Thermal analysis of pyrrole-imprinted monolithic SPME fiber: (A) quantity change curve (mg); (B) TGA curve (mg); (C) DTA curve. Fig. 4 Effect of fiber exposure temperature on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fibers. Fig. 5 Effect of fiber exposure time on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fiber. Fig. 6. GC-MS total ion chromatogram corresponding to extraction of furan from canned tuna by: (A) fabricated pyrrole-imprinted monolithic SPME fiber; and (B) commercial CAR/PDMS fiber.
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Fig. 1. SEM image of monolithic SPME fiber under ×50000 magnification: (A) pyrroleimprinted monolithic SPME; (B) furan-imprinted monolithic SPME; (C) non-imprinted monolithic SPME
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A
B
Fig. 2. FTIR spectra of synthesized: (A) non-imprinted; and (B) pyrrole-imprinted fiber.
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Fig. 3. Thermal analysis of pyrrole-imprinted monolithic SPME fiber: (A) quantity change curve (mg); (B) TGA curve (mg); (C) DTA curve.
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A
B
Fig. 4 Effect of fiber exposure temperature on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fibers.
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A
B
Fig. 5 Effect of fiber exposure time on extraction ability of furan by: (A) synthesized pyrrole; and (B) furan-imprinted SPME fiber.
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Fig. 6. GC-MS total ion chromatogram corresponding to extraction of furan from canned tuna by: (A) fabricated pyrrole-imprinted monolithic SPME fiber; and (B) commercial CAR/PDMS fiber.
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Table1. Determination of furan in tap water and canned tuna samples Sample
Tap water
Canned tuna
Added MIP )ng mL-1/ ng g-1) ND 5 4.58 ± 5.0 10 4.0 ± 5.0 40.80 ± 5.6 5 20.76 ± 5.. 10 24.42 ± 5.8
Extraction % 92 40 44.0 88.3
CAR/PDMS Extraction% ND 4.28 ± 5.. 6.. ± 5.6 48.60 ± 5.. 44.80 ± 5.0 86..0 ± 5.4
6..8 6. 68.4 6..8
Significance of the work
This new monolithic molecular imprinted polymer fiber could answer to the call for selective and fast analysis of furan in real samples.
High Selectivity
Low price
High stability in different condition
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tpartsra aciGparG
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