Study of an Online Molecularly Imprinted Solid Phase Extraction

Article pubs.acs.org/JAFC

Study of an Online Molecularly Imprinted Solid Phase Extraction Coupled to Chemiluminescence Sensor for the Determination of Trichlorfon in Vegetables Ling Meng,† Xuguang Qiao,† Jiaming Song,†,§ Zhixiang Xu,*,† Junhong Xin,† and Yue Zhang† †

College of Food Science and Engineering, Shandong Agricultural University, Tai’an 271018, People's Republic of China College of Food Science and Engineering, Qingdao Agricultural University, Qingdao 266109, People's Republic of China

§

ABSTRACT: This study reports a new online molecularly imprinted solid phase extraction coupled to chemiluminescence for the determination of trichlorfon. This molecularly imprinted polymer (MIP) was prepared through bulk polymerization, in which methacrylic acid (MAA) was used as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. This novel functionalized material was characterized by FT-IR spectra and adsorption, and it exhibited good recognition and selective ability and fast adsorption−desorption dynamics toward trichlorfon. The factors affecting preconcentration of the analytes and sensitivity of the method are discussed in detail. Under the optimal condition, the linear range of the calibration graph was between 0.02 and 1.0 ng L−1, and the detection limit was 1 × 103 ng L−1. The blank cucumber samples spiked with trichlorfon at three levels were extracted and determined by the presented method with recoveries ranging from 83.5 to 94.5%, and the results were correlated well with those obtained using gas chromatography. Moreover, this developed method was successfully applied to the quantitative detection of trichlorfon residues in leek samples. KEYWORDS: trichlorfon, molecularly imprinted polymer, online solid phase extraction, chemiluminescence, vegetables

■

samples prior to analysis. Online solid phase extraction coupled with chemiluminescence (SPE-CL) is a versatile method for the analysis of traces of organic compounds.21 This method has the advantages of both solid phase extraction and CL. However, they can also concentrate other compounds presented in the matrix because of their poor selectivity, which may interfere with the analysis. The preparation of selective sorbent is crucial. Among the approaches applied, one of the most interesting and promising methods is molecular imprinting technology. The resulting molecularly imprinted polymers (MIPs) not only possess high selectivity and specificity for template molecules but also exhibit far greater physiochemical stability and applicability in harsh chemical media. Applications of MIPs in affinity separation, immunoassays, microreactors, enzymes mimics, and biomimetic sensors have been reported.22−26 However, use as a recognition element in CL is one of the most interesting and important applications of MIPs. The specific function of MIP can improve the selectivity of CL analysis. CL based on the reaction of luminol with H2O2 has been described for the direct determination of dichlorvos pesticide. 13 Our research showed that the addition of trichlorfon can enhance the CL reaction in alkaline buffer solution, and the trichlorfon concentration is linear with the CL intensity. Therefore, this system can be used for the determination of trichlorfon. The aim of this paper was to fabricate a MIP material with specific binding sites for trichlorfon. Using the MIP as solid phase extraction sorbent, a new method of online

INTRODUCTION

Organophosphorus pesticides have been widely used in a wide range to improve the production of crops and vegetables, and their residues have become a serious phenomenon, to which people and researchers have paid close attention because many of these compounds display a high acute toxicity.1,2 To prevent these uncontrolled effects on human health and provide safe products to consumers, it is vital to control pesticide residues. Therefore, development of a sensitive and effective separation and analysis method is required and of great importance. In the past decades, many methods have been used in the detection of organophosphorus compounds, such as chromatography,3−8 chromatography−mass spectrometry,9 electrochemiluminescence,10 acetylcholinesterase biosensors,11 and immunoassays.12 Among them, gas chromatography (GC), gas chromatography−mass spectrometry (GC-MS), and liquid chromatography (LC) are widely adopted for their sensitivity. However, these methods require expensive instruments and long analytical time. Chemiluminescence (CL) has become one of the usual methods for biomedical, pharmaceutical, clinical, and food analysis due to its low detection limit, wide linear range, and short analysis time.13−18 Unfortunately, there are many other substances that will interfere with CL, and the selectivity of the CL method itself is relatively low., so it cannot be used to determine an analyte directly in complicated samples. Furthermore, the trichlorfon is generally presented in samples at a low concentration. To achieve the necessary levels of sensitivity, an extraction and separation step is needed. Many pretreatments, such as solid phase extraction (SPE), liquid chromatography,19 and capillary electrophoresis,20 have been utilized. SPE, as a well-established technique, has been used to substitute for liquid−liquid extraction (LLE) in biological © 2011 American Chemical Society

Received: Revised: Accepted: Published: 12745

July 16, 2011 November 15, 2011 November 22, 2011 November 22, 2011 dx.doi.org/10.1021/jf203801n | J. Agric.Food Chem. 2011, 59, 12745−12751

Journal of Agricultural and Food Chemistry

Article

CL with a luminol−H2O2 system for direct determination of trace trichlorfon was developed. The factors affecting the preconcentration of the analytes and the sensitivity of the method are discussed in detail, and the applicability and advantages of the presented method are evaluated.

■

MATERIALS AND METHODS

Materials and Reagents. The cucumber and leek samples were purchased randomly from the market of Taian in January 2011 (Shandong, China). Chemicals. The analytical standard trichlorfon, omethoat, and acephate (99%) were obtained from the Institute for the Control of Agrochemicals of Ministry of Agriculture (Beijing, China). Methacrylic acid (MAA) and 2,2-azobis(isobutyronitrile) (AIBN) were purchased from Tianjin Chemical Reagent Factory (Tianjin, China); the MAA was vacuum distilled, and AIBN was recrystallized before use. Ethylene glycol dimethacrylate (EGDMA) was supplied by Sigma-Aldrich. Chromatography grade acetone was obtained from Yongda Chemical Reagent Co., Ltd. (Tianjin, China). All other solvents and reagents used in this study were of the highest available purity and at least of analytical grade. Doubly deionized water (DDW) obtained from a Water Pro water system (Labconco Corp., Kansas City, MO) was used throughout the experiments. Working solutions were prepared fresh for daily use. Stock solutions of luminol, H2O2, and buffer were prepared by dissolving appropriate amounts of luminol, H 2O2, NaOH, and NaHCO3 in DDW, respectively. Apparatus. A model IFFM-E flow injection chemiluminescence system (Xi’an Remex Electronic High-Tech Ltd., China) was used to evaluate the applicability of the imprinted polymer sorbent for online preconcentration of the trichlorfon. PTFE tubing (0.8 mm i.d.) was used to connect all components in the flow injection system. FT-IR spectra (4000−400 cm−1) in KBr were recorded using a Vector 22 spectrometer (Bruker). For characterization of the MIP, a Cary 50-Bio UV spectrometer (Victoria, Australia) was used in this study. A Shimadzu 2010 gas chromatograph equipped with a flame photometric detector was used for the separation and determination of organophosphate pesticides. Separation was carried out on an RTX1701 capillary column (30 m × 250 μm i.d. × 0.25 μm particle size). Nitrogen was used as the carrier gas at the constant flow rate of 1.0 mL min−1, and the injection volume was 1.0 μL. The injection port temperature was held at 200 °C at the split mode with the split ratio 10: 1. The detector temperature was held at 250 °C. The analysis was performed with an initial column temperature of 90 °C held for 1 min followed by heating to 150 °C at 30 °C min−1 and held for 3 min. Finally, it was heated to 160 °C at 1.0 °C min−1 and held for 2 min, with an overall run time of 18 min. Preparation of the MIP. The imprinted polymer was prepared as follows: 0.2574 g of trichlorfon (1 mmol) and 0.1722 g of MAA (2 mmol) were dissolved in 0.6 mL of chloroform. After stirring by a magnetic stirrer at room temperature for 30 min, 0.754 mL of EGDMA (4 mmol) and 20 mg of AIBN were added. The mixture was purged with nitrogen for 15 min. The flask was then sealed and placed in a water bath at 58 °C for 18 h. After that, the rigid polymer was crushed and sieved. The MIP particles were extracted by methanol/ acetic acid (9:1, v/v) for 48 h and then by methanol for 8 h to be free of trichlorfon (Figure 1). Finally, the polymer was dried in a vacuum oven at 60 °C for 12 h. For comparison, an imprinted polymer was prepared following the same procedure but without the extraction process, and a nonimprinted polymer (NIP) was polymerized in the same way except for the addition of the template. Characterization of the MIP. To measure its adsorption capacity, 20 mg of imprinted or nonimprinted polymer and 10 mL of a standard aqueous solution containing trichlorfon at 100−500 mg L−1 concentrations were added to the 25 mL flask, respectively. The mixtures were shaken (200 times/min) with a horizontal shaker at room temperature for 4.0 h and then centrifugated (4000 rpm) for 20 min. The concentration of unextracted trichlorfon in the solution

Figure 1. Schematic representation of the molecularly imprinted polymer used in this study. was determined by UV spectrometry at 195 nm, and the adsorption capacity (Q) was calculated. The uptake kinetics of MIP toward trichlorfon was examined as follows: 20 mg of MIP was added to 10 mL of a 300 mg L −1 aqueous solution of trichlorfon. The mixture was mechanically shaken (200 times/min) for 5, 30, 60, 90, 120, 180, and 240 min, respectively, at room temperature and then centrifuged for 20 min. The unextracted trichlorfon was determined by UV spectrometry. The selective properties of the MIP toward trichlorfon and the structurally related compounds omethoat and acephate at 300 mg L −1 were studied. The supernatants were analyzed for the unextracted trichlorfon, omethoat, and acephate at 195, 210, and 220 nm, respectively. Procedures of Online Molecularly Imprinted Solid Phase Extraction Coupled with Chemiluminescence (MISPE-CL). A V-shaped tube (6 mm i.d. × 5 cm) packed with 100 mg of MIP . Both ends of the tube were plugged with a small amount of glass wool. The schematic diagram (Figure 2) for the enrichment and determination of trichlorfon through online MISPE-CL was used in this study. First, trichlorfon solution was injected into the MIP cell through pipeline d by pump 2. As a result, trichlorfon was selectively adsorbed onto the MIP. Second, to take the interfering substances away, DDW was injected into the MIP channel continuously for 2.0 min by pump 2 through pipeline d. Third, pipeline d was stopped, the luminol, H2O2, and buffer solution were delivered, respectively, into the MIP cell and reacted with the absorbed trichlorfons, producing stronger CL signals. During this procedure, the affinity binding between MIP and trichlorfon was destroyed, and the cavities of binding sites were left. Finally, DDW was injected continuously for 60 s through pipeline d, 12746

dx.doi.org/10.1021/jf203801n | J. Agric.Food Chem. 2011, 59, 12745−12751


Article

To check the accuracy of the developed method, the spiked sample were prepared and extracted according to the same procedure. The resulting extractions were collected into a test tube and condensed to dryness under a gentle flow of nitrogen and then accurately redissolved with 0.2 mL of acetone. After filtration, 1.0 μL of the filtrate was injected into a gas chromatograph for analysis. The leek sample was extracted according to the same process, the filtrate was injected into the MISPE cell, and the content of trichlorfon was determined.

■

RESULTS AND DISCUSSION

FT-IR Spectra Analysis. The FT-IR spectra of imprinted polymer without extraction (a), imprinted polymer after extraction (b), nonimprinted polymer (c), and trichlorfon (d) are compared in Figure 3. For imprinted polymer without extraction and imprinted polymer after extraction, the observed feature around 2996 cm−1 indicated a CH stretch, and that around 1720 cm−1 indicated a CO stretch. For the FT-IR spectra of trichlorfon and polymer without extraction, the features around 1268 and 1253 cm−1 indicated the presence of a PO bond, and the stretch shift in the position of spectrum a can be attributed to the hydrophobic interaction between the PO group of trichlorfon and the −OH group of MAA.5 These results demonstrated that trichlorfon had been reacted with MAA, and the imprinted polymers had been synthesized. The FT-IR spectra b and c with similar locations and appearances of the major bands suggested that the trichlorfon

Figure 2. Schematic diagram of the MIP-CL sensor flow system: (a) luminol solution; (b) H2O2; (c) buffer; (d) trichlorfons (or vegetable sample); (v) six-way injection valve; (W) waste; (D) detector. and the MIP cell was cleaned for the next procedure. Thus, a complete cycle of the online MISPE-CL for determination of trichlorfon was finished. Sample Preparation. To check the accuracy of the developed online MISPE-CL method, blank cucumber samples were spiked with trichlorfon at three levels and determined. Briefly, 2.0 g of cucumber was separately weighed into a 100 mL conical flask, spiked with 1.0 mL of standard solution (0.6, 1.8, and 3.0 mg L−1) containing 0.6, 1.8, and 3.0 μg of trichlorfon, respectively. After incubation for 1 h, the spiked samples were ultrasonicated with 3 × 10 mL of DDW for 30 min. The resulting extractions were collected and centrifuged at 5000 rpm for 10 min. The supernatants were filtered and then passed through the online MISPE cell, and the CL signals were recorded.

Figure 3. FT-IR spectra of (a) imprinted polymer without extraction, (b) imprinted polymer after extraction, (c) nonimprinted polymer, and (d) trichlorfon. 12747



Article

was completely removed from the imprinted polymer after Soxhlet extraction. Evaluation of Adsorption and Selectivity of the Imprinted Polymer. The adsorption capacity Q of the MIP or NIP was calculated according to the equation 27

Table 1. Adsorption Capacity of MIP toward Different Target Molecules at 300 mg L−1

where C0 and C1 are the concentrations of the target molecule in solution before and after absorption, respectively, V is the volume of the solution, and M is the mass of the polymer. The adsorption isotherms of the MIP and NIP are displayed in Figure 4. The data showed that with the initial concentration

omethoat and acephate, which demonstrated that the imprinted polymer was able to recognize the structural differences between trichlorfon and its analogues. This might result from the imprinting effect, the difference of the molecular interactions, and the structures. During polymerization, the template of trichlorfon was incorporated with a functional monomer. Subsequent removal of the template molecule resulted in imprinted cavities having shape, size, and spatial arrangement complementary to the trichlorfon. Conditions of CL Reaction. To achieve the best performance, the optimal CL reaction system of luminol−H2O2 and pH value were investigated at the trichlorfon concentration of 5 × 10−5 g mL−1. The effect of luminol concentration on the CL emission intensity was studied. Luminol solutions at 1.0 × 10−6−1.0 × 10−4 mol L−1 were injected into the CL reaction system, and results showed that the CL emission intensity was increased with luminol concentration increasing; the maximum was achieved when the concentration was 5.0 × 10−5 mol L−1. Thus, 5.0 × 10−5 mol L−1 luminol was selected as the reaction condition. Because the trichlorfon can enhance the CL reaction in alkaline condition, the pH of the NaHCO3−NaOH buffer solution was investigated over the range 7.5−14.0. Results indicated that the CL emission intensity was increased with increasing pH; the maximum CL emission intensity was achieved when the pH was 12.0, and then it weakened in the pH range of 12.0−14.0. It is known that trichlorfon is unstable in strong alkaline condition and may decompose into dichlorvos. However, the whole process lasted just several minutes, so it had little effect on the trichlorfon. With the selected concentration of luminol solution and pH, the effect of H2O2 concentration on this reaction system was investigated in the range of 0.1−0.5 mol L−1, and the maximum CL signal was achieved when 0.3 mol L−1 H2O2 was selected. Thus, 5 × 10−5 mol L−1 luminol and 0.3 mol L−1 H2O2 at pH 12 were used as the CL system conditions for subsequent experiments. Online MISPE-CL Optimization. To achieve the maximum CL emission and good sensitivity for the online MISPECL sensor to satisfy trace trichlorfon determination, a series of experimental conditions, such as flow rate, adsorption time, washing time, and reaction time, were optimized in this study. The effect of flow rate varied from 0.5 to 2.0 mL min−1 on the CL emission intensity was investigated, and a flow rate of 1.5 mL min−1 for all solutions was recommended because of greater precision and economy in the use of reagents. Adsorption time was critical in the MISPE procedure, which would affect the sample volume, the amount of trichlorfon absorbed on the MIP sorbent, and the sensitivity of the developed method. If the adsorption time was too short or too long, CL maximum could not been obtained. The adsorption time was studied from 1.0 to 6.0 min by injection of 1 × 10−7 g mL−1 trichlorfon at 1.5 mL min−1. It was noted that too long an

Figure 4. Adsorption isotherms of the imprinted and nonimprinted polymers.

of trichlorfon increasing, the adsorption capacities of MIP or NIP toward template molecules increased. The MIP exhibited a higher adsorption capacity for trichlorfon, which was >1.5-fold that of NIP at 500 mg L−1 concentration. The uptake kinetics of MIP toward trichlorfon was tested (Figure 5). It was shown that the MIP had fast uptake kinetics.

Figure 5. Kinetic uptake plot of the imprinted polymer.

After shaking a period of 30 min, the adsorption capacity was 12.26 mg g−1, which was 72.16% of the maximum adsorption capacity, and the adsorption equilibrium was almost reached within 180 min. The selective recognition property of the imprinted polymer was tested, as displayed in Table 1. It was found that the MIP had a larger adsorption capacity toward trichlorfon than 12748

target molecule

Q (mg g−1)

trichlorfon omethoat acephate

16.93 2.81 1.79



Article

deviation for 5 × 10−6 g mL−1 trichlorfon was 4.5% (n = 5). The detection limit (LOD) was 7 × 104 ng L−1 (3σ), which was 70-fold higher than that of the online MISPE-CL. The CL diagram of 1.0 × 10−6 g m L −1 trichlorfon solution after online flow injection for 3.0 min with or without MIP as selective sorbent is depicted in Figure 6. In comparison to CL

adsorption time would consume more time and reagent, and the best result was obtained when 3.0 min was employed. A suitable washing time was needed to remove other residues completely without the loss of the trichlorfon adsorbed by specific binding. For selection of the optimum washing time applied in the eluting step, the washing time was tested at 1.5 mL min−1 in the range of 30−180 s. The results showed that with a washing time of 120 s, the interfering substances could be completely removed. The reaction time was one of the important parameters, and it would affect the CL signal. The optimization of reaction time was investigated from 10 to 120 s. It was known that when the time was short, the adsorbed trichlorfon could not completely react with the luminol−H2O2 system and the CL signal was weak. The best result was obtained when the reaction process lasted 60 s. Then, the CL signal declined to a stable baseline. Therefore, on the basis of the above results, a 3.0 min adsorption time at 1.5 mL min−1 flow rate, a 120 s washing time, and 60 s of reaction time were chosen as the experimental conditions in the following study. Interference Study. To apply the online MISPE-CL sensor for detection of trichlorfon in vegetable samples, the interferences that are commonly present in vegetables were tested using MIP or NIP as sorbent by analyzing a standard trichlorfon solution of 1 × 10 −7 g mL−1, which is depicted in Table 2. It was shown that by using MIP as selective Table 2. Tolerable Concentration Ratios with Respect to Trichlorfons for Some Interfering Substances Using MIP or NIP as Sorbent substance

NIP sorbent

MIP sorbent

Ba2+, Ca2+, Al3+ Zn2+ starch, Cr3+, glucose F−, NO3−

1000 600 100 1000

5000 3000 500 5000

Figure 6. CL diagrams of 1.0 × 10−7 g mL −1 trichlorfon after online flow injection for 3.0 min: (a) with MIP as sorbent; (b) without MIP as sorbent.

diagram b without MIP as sorbent, the CL signal of trichlorfon in diagram a was higher, which indicated that trichlorfon was selectively extracted onto the imprinted sorbent. These results showed that the online MISPE coupled to CL sensor could obviously improve the sensitivity of CL for the determination of trichlorfon. Application of the Presented Method. The proposed online MISPE-CL method was successfully applied for the determination of trichlorfon in vegetable samples using the standard addition experiment. The blank cucumbers spiked with trichlorfon at 0.0003, 0.0009, and 0.0015 mg g −1 were analyzed by the developed method. At each concentration, five measurements were performed. The analytical data are shown in Table 3. Recoveries between 83.5 and 94.5% were obtained.

recognition element, a >5000-fold excess of Ba2+, Ca2+, and Al3+, a 3000-fold excess of Zn2+, a 500-fold excess of starch, Cr3+, and glucose, and a 5000-fold excess of F− and NO3− could not interfere with the sensitivity of the developed method. Interference using NIP as sorbent was also investigated under the same conditions. The results showed that a 1000-fold excess of Ba2+, Ca2+, and Al3+, a 600-fold excess of Zn2+, a 100-fold excess of starch, Cr3+, and glucose, and a 1000-fold excess of F− and NO3− could not interfere with the trichlorfon analysis. These results indicated that MIP had a stronger antiinterference ability than the NIP, and its use as the selective recognition material in CL analysis can simplify the pretreatment procedure. Analytical Performance and Selectivity of the Online MISPE-CL Sensor. The analytical figures of the present online MISPE-CL sensor for the determination of trace trichlorfon were evaluated under optimal conditions. The linear relationship between the imaging intensity and the concentration of trichlorfon was in the range of 2 × 10−8−1 × 10−6 g mL−1, and the relative standard deviation for 1 × 10−7 g mL−1 trichlorfon was 4.6% (n = 5). The detection limit was 1 × 103 ng L−1 (3σ), which was described by the linear fit equation (ΔI = 700.19c + 1032.9, r = 0.9964), where I is the relative CL intensity and c is the concentration of trichlorfons (10−7 g mL−1). In comparison with the method of online MISPE-CL, the linear range of CL was 1 × 10−7−1 × 10−5 g mL−1, and the relative standard

Table 3. Determination of Spiked Trichlorfons in Actual Cucumber Samples by GC and Online MISPE-CL Methods (Mean ± SD, n = 5) spiked level (μg g−1)

GC (μg g−1)

MISPE-CL (μg g−1)

0.3 0.9 1.5

0.27 ± 0.0018 0.85 ± 0.0032 1.44 ± 0.0030

0.25 ± 0.0098 0.81 ± 0.0275 1.42 ± 0.0440

The accuracy of this online MISPE-CL method was validated by comparative analysis of the spiked samples with GC (Table 2), 12749



Article

Table 4. Comparison of Previously Used Methods to the One Described Here ref

a

detection method

pesticides

LOD

9

accelerated solvent extraction solid phase extraction

pretreatment

GC-MS LC-MS-MS

405 pesticides

0.5−300 μg kg1− (μg L−1)

2

matrix solid phase dispersion

GC-NPD

5 pesticides

0.2−2.0 μg kg1− (μg L−1)

8

continuous flow microextraction

HPLC-UV

5 pesticides

4 ng L −1

5

molecularly imprinted solid phase extraction

HPLV-UV

dichlorvos

94.8 ng L −1

a

online molecularly imprinted solid phase extraction

CL

trichlorfon

1 × 103 ng L−1

This work.

■

and no significant differences were observed between the results obtained by both methods. The performance of the developed method was used to check the leek sample, and trichlorfon at a level of 0.03 mg L −1 was detected. The validation of the presented method for determination of a high number of samples will be tested in a further study. These good results indicated that this developed method can be used for practical applications. Advantage of the Developed Online MISPE-CL Sensor. Some usual methods including LC with UV detection and GC coupled to mass spectrometry (GC-MS, LC-MS/MS) have been used for the determination of organophosphorus pesticides, which are summarized in Table 4. It was shown that each method has its advantages and limitations in terms of specificity, sensitivity, and interference of matrix compounds. Generally, the LOD values of these methods can reach μg kg−1 or ng L−1 levels. Compared to other methods, the results obtained in this study suggest that the developed online MISPE-CL sensor exhibited many advantages, although the sensitivity is lower than those of the other methods. First, using MIP as recognition element coupled with CL, the analysis procedure was simplified and the sensitivity of the CL reaction could be improved due to the good selectivity of the MIP. Second, a cycle of this method lasted only 8 min, whereas a complete procedure of LC, GC, or LC/GC-MS is >1.0 h. It was important that the working life of the novel imprinted polymer had a reusability of 80 times without loss of sensitivity. Furthermore, the templates could be easily washed from the MIP by aqueous solution, so the use of organic reagents and buffer solutions to extract the trichlorfon, which may possibly affect the CL reaction, was avoided. Thus, the cost per analysis of the developed method was drastically reduced, and it was more suitable for the rapid detection of pesticide residues. Conclusion. In this study, a novel functional material for selective recognition of trichlorfon was prepared. Using it as sorbent, a simple and sensitive system of online MISPE-CL sensor has been developed. This method had good precision and accuracy for screening trichlorfon in vegetable sample due to its high recovery and low relative standard deviation. This paper provided a fast method for monitoring organophosphorus pesticide residues in agriculture and foods.

AUTHOR INFORMATION Corresponding Author *Phone: (86 538) 824 6021. Fax: (86 538) 824 2482. E-mail: [email protected]. Funding We are grateful for financial support from the Department of Science and Technology of Shandong Province, China (Project 2009GG10009058), and the Shandong Postdoctoral Science Foundation Project (Project 200902012).

■

ABBREVIATIONS USED MIP, molecularly imprinted polymer; MAA, methacrylic acid; EGDMA, ethylene glycol dimethacrylate; GC, gas chromatography; LC, liquid chromatography; CL, chemiluminescence; SPE, solid phase extraction; LLE, liquid−liquid extraction; SPECL, solid phase extraction coupled with chemiluminescence; MISPE, molecularly imprinted solid phase extraction; AIBN, 2,2-azobis(isobutyronitrile); DDW, doubly deionized water; NIP, nonimprinted polymer; MISPE-CL, molecularly imprinted solid phase extraction coupled with chemiluminescence; Q, adsorption capacity; GC-MS, gas chromatography coupled to mass spectrometry; LC-MS/MS, liquid chromatography coupled to tandem mass spectrometry.

■

REFERENCES

(1) Peter, J. V.; Prabhakar, A. T.; Pichamuthu, K. Delayed-onset encephalopathy and coma in acute organophosphate poisoning in humans. Neurotoxicology 2008, 29, 335−342. (2) Sun, F. Y.; Betzendahl, I.; Wemmel, K. V.; Cortvrindt, R.; Smitz, J.; Pacchierotti, F.; Eichenlaub-Ritter, U. Trichlorfon-induced polyploidy and nondisjunction in mouse oocytes from preantral follicle culture. Mutat. Res. 2008, 651, 114−124. (3) Shen, X.; Su, Q. D. Determination of pesticide residues in soil by modified matrix solid-phase dispersion and gas chromatography. Ann. Chim. 2007, 97, 647−653. (4) He, Y.; Lee, H. K. Continuous flow microextraction combined with high-performance liquid chromatography for the analysis of pesticides in natural waters. J. Chromatogr., A 2006, 1122, 7−12. (5) Xu, Z. X.; Fang, G. Z.; Wang, S. Molecularly imprinted solid phase extraction coupled to high-performance liquid chromatography for determination of trace dichlorvos residues in vegetables. Food Chem. 2010, 119, 845−850. (6) Li, L.; Zhou, S. S.; Jin, L. X.; Zhang, C.; Liu, W. P. Enantiomeric separation of organophosphorus pesticides by high-performance liquid chromatography, gas chromatography and capillary electrophoresis and their applications to environmental fate and toxicity assays. J. Chromatogr., B 2010, 878, 1264−1276. 12750



Article

(24) Martin-Esteban, A. Molecular imprinting technology: a simple way of synthesizing biomimetic polymeric receptors. Anal. Bioanal. Chem. 2004, 378, 1875. (25) Molinelli, A.; Weiss, R.; Mizaikoff, B. Advanced solid phase extraction using molecularly imprinted polymers for the determination of quercetin in red wine. J. Agric. Food Chem. 2002, 50, 1804−1808. (26) Haginaka, J. Molecularly imprinted polymers for solid-phase extraction. Anal. Bioanal. Chem. 2004, 379, 332−334. (27) Gong, S. L.; Yu, Z. J.; Meng, L. Z.; Hu, L.; He, Y. B. Dye molecular-imprinted polusiloxanes. II. Preparation, characterization, and recognition behavior. J. Appl. Polym. Sci. 2004, 93, 637−643.

(7) Berijani, S.; Assadi, Y.; Anbia, M.; Hosseini, M. M.; Aghaee, E. Dispersive liquid−liquid microextraction combined with gas chromatography-flame photometric detection: very simple, rapid and sensitive method for the determination of organophosphorus pesticides in water. J. Chromatogr., A 2006, 1123, 1−9. (8) He, L. J.; Luo, X. L.; Xie, H. X.; Wang, C. J.; Jiang, X. M.; Lu, K. Ionic liquid-based dispersive liquid-liquid microextraction followed high-performance liquid chromatography for the determination of organophosphorus pesticides in water sample. Anal. Chim. Acta 2009, 655, 52−59. (9) Pang, G. F.; Liu, Y. M.; Fan, C. L.; Zhang, J. J.; Cao, Y. Z.; Li, X. M.; Li, Z. Y.; et al. Simultaneous determination of 405 pesticide residues in grain by accelerated solvent extraction then gas chromatography-mass spectrometry or liquid chromatographytandem mass spectrometry. Anal. Chim. Acta 2006, 384, 1366−1408. (10) Chen, X. M.; Lin, Z. J.; Cai, Z. M.; Chen, X.; Wang, X. R. Electrochemiluminescence detection of dichlorvos pesticide in luminal-CTAB medium. Talanta 2008, 76, 1083−1087. (11) Sun, X.; Wang, X. Y. Acetylcholinesterase biosensor based on prussian blue-modified electrode for detecting organophosphorous pesticides. Biosens. Bioelectron. 2010, 25, 2611−2614. (12) Lee, E. K.; Kim, Y. J.; Park, W. C.; Chung, T.; Lee, Y. T. Monoclonal antibody-based enzyme-linked immunosorbent assays for the detection of the organophosphorus insecticide isofenphos. Anal. Chim. Acta 2006, 557, 169−178. (13) Wang, J. N.; Zhang, C.; Wang, H. X.; Yang, F. Z.; Zhang, X. R. Development of a luminol-based chemiluminescence flow-injection method for the determination of dichlorvos pesticide. Talanta 2001, 54, 1185−1193. (14) Li, B. X.; He, Y. Z.; Xu, C. L. Simultaneous determination of three organophosphorus pesticides residues in vegetables using continuous-flow chemiluminescence with artificial neural network calibration. Talanta 2007, 72, 223−230. (15) Gámiz-Gracia, L.; García-Campaña, A. M.; Soto-Chinchilla, J. J.; Huertas-Pérez, J. F.; González-Casado, A. Analysis of pesticides by chemiluminescence detection in the liquid phase. Trends Anal. Chem. 2005, 24, 927−942. (16) Adcock, J. L.; Francis, P. S.; Barnett, N. W. Acidic potassium permanganate as a chemiluminescence reagent − a review. Anal. Chim. Acta 2007, 601, 36−67. (17) Liang, Y. D.; Song, J. F.; Yang, X. F.; Guo, W. Flow-injection chemiluminescence determination of chloroquine using peroxynitrous acid as oxidant. Talanta 2004, 62, 757−763. (18) Lu, C.; Qu, F.; Lin, J. M.; Yamada, M. Flow-injection chemiluminescent determination of nitrite in water based on the formation of peroxynitrite from the reaction of nitrite and hydrogen peroxide. Anal. Chim. Acta 2002, 474, 107−114. (19) Liu, H. Y.; Ren, J. J.; Hao, Y. H.; He, P. G.; Fang, Y. Z. Flow injection-chemiluminescence determination of sulfadiazine in compound naristillae. Talanta 2007, 72, 1036−1041. (20) Wada, M.; Inoue, K.; Ihara, A.; Kishikawa, N.; Nakashima, K.; Kuroda, N. Determination of organic peroxides by liquid chromatography with on-line post-column ultraviolet irradiation and peroxyoxalate chemiluminescence detection. J. Chromatogr., A 2003, 987, 198−195. (21) Fang, G. Z.; He, J. X.; Wang, S. Multiwalled carbon nanotubes as sorbent for on-line coupling of solid phase extraction to highperformance liquid chromatography for simultaneous determination of 10 sulfonamides in eggs and pork. J. Chromatogr., A 2006, 1127, 12−17. (22) Turiel, E.; Martin-Esteban, A. Molecularly imprinted polymers: towards highly selective stationary phases in liquid chromatography and capillary electrophoresis. Anal. Bioanal. Chem. 2004, 378, 1876− 1886. (23) Bui, B. T. S.; Haupt, K. Molecularly imprinted polymers: synthetic receptors in bioanalysis. Anal. Bioanal. Chem. 2010, 398, 2481−2492. 12751


Study of an Online Molecularly Imprinted Solid Phase Extraction

Recommend Documents