Molecularly Imprinted Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography for the Determination of Trace Trichlorfon and Monocrotophos Residues in Fruits

In this study, a novel molecularly imprinted polymer (MIL@MIP) that could selectively recognize the trichlorfon and monocrotophos was synthesized using metal-organic framework MIL-101 as support material. The prepared MIL@MIP was characterized by Fourier transform infrared, thermogravimetric analysis, scanning electron microscope, static adsorption, kinetic adsorption, and competitive adsorption analyses. Using this material as sorbent, a new method of molecularly imprinted solid-phase extraction coupled with high performance liquid chromatography for simultaneous determination of trichlorfon and monocrotophos was established. Under optimal conditions, the limit of detection (LOD) of this method for trichlorfon and monocrotophos detection was 0.011 and 0.015 mg/kg, respectively. The relative standard deviation (RSD) for five replicates of 0.05 mg/L trichlorfon and monocrotophos mixed solutions was within the range of 1.8 to 3.7 %. Apple and pear samples spiked with the two kinds of organophosphate pesticides were extracted and determined by using this method with good recoveries ranging from 86.5 to 91.7 %. Moreover, this method was successfully applied for the detection of the two organophosphate pesticides in strawberry samples.     

Molecularly Imprinted Polymer as Sorbent for Solid-Phase Extraction Coupling to Gas Chromatography for the Simultaneous Determination of Trichlorfon and Monocrotophos Residues in Vegetables

In this study, a molecularly imprinted polymer (MIP) was prepared using the mixture of trichlorfon and monocrotophos as the mixed template. The imprinted polymer was characterized and exhibited good recognition ability and fast adsorption–desorption dynamic toward the trichlorfon and monocrotophos. Using this imprinted polymer as sorbent, a new method of molecularly imprinted solid-phase extraction coupled to gas chromatography for the simultaneous determination of two organophosphate pesticides residues was developed. Under optimal condition, the linear range was 0.005–10.0 mg/l. At a loading flow rate of 2.0 ml/min for loading 100 ml, the detection limits were 0.28 μg/l for trichlorfon and 0.090 μg/l for monocrotophos, the peak area precision (RSD) for five replicates was 4.23–4.50 %. The blank rape samples spiked with two organophosphate pesticides at 0.05 and 0.1 mg/l levels were determined by this method with recoveries ranging from 89.41 % to 95.12 %. Moreover, this method was successfully applied to the quantitative detection of the trichlorfon and monocrotophos residues in leek samples.     

Evaluation of a Selective Approach for the Determination of 5-Nitroimidazoles in Aquaculture Products by Capillary Liquid Chromatography Using Molecularly Imprinted Solid-Phase Extraction

Capillary liquid chromatography with UV detection is proposed for the determination of 5-nitroimidazole residues in aquaculture products. The separation was carried out in a C18 column at 20 °C, using a mobile phase consisting of water and acetonitrile, at 7 μL/min and 320 nm as detection wavelength. Furthermore, full loop injection mode (8 μL) was selected and water was considered as injection solvent. The optimized method was applied to the monitoring of nine 5-nitroimidazoles, including three metabolites, in crab, salmon, prawn, and velvet swimming crab. Molecularly imprinted solid-phase extraction has been evaluated for sample cleanup. The method was characterized in all the matrices in terms of linearity (R ² ≥ 0.9964), precision (repeatability, RSD ≤ 7.9%, and reproducibility, RSD ≤ 11.1%) and trueness (recoveries between 80.4 and 108.7%). Decision limits, CCα, ranging from 0.2 to 1.5 μg/kg and detection capabilities, CCβ, from 0.2 to 1.8 μg/kg, were obtained.     

Preparation of a Hydrophilic Molecularly Imprinted Polymer and Its Application in Solid-Phase Extraction to Determine of Trace Acrylamide in Foods Coupled with High-Performance Liquid Chromatography

A hydrophilic molecularly imprinted polymer was synthesized using acrylamide (C₃H₅ON) as the template and 2-acrylamido-2-methylpropane sulfonic acid as the functional monomer. This imprinted polymer was characterized by static and kinetic adsorption experiments, and results showed that it exhibited with good recognition ability and fast adsorption–desorption dynamics toward acrylamide in an aqueous environment. Using the prepared material as sorbent, a method of molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography for analysis of acrylamide in foods was developed. Under the optimized conditions, the limit of detection (S/N?=?3) of this method for acrylamide was 72.0 ng/L, and the RSD for five replicate extractions of 10 μg/L acrylamide was 4.7 %. The blank potato samples spiked with acrylamide at different levels of 0.125, 0.250, and 0.50 μg/g were extracted and determined respectively by this developed method, and recoveries ranging from 91.5 to 95.1 % were obtained. Finally, commercial samples of twisted cruller and potato chip were quantitatively analyzed by this method.     

Molecularly Imprinted Nanosilica Solid-Phase Extraction for Bisphenol A in Fish Samples

This paper reports a method using molecularly imprinted nanosilica as the solid-phase extraction sorbent to extract bisphenol A (BPA) from fish samples. The selective extraction efficiency of BPA from its structure-analogous by molecularly imprinted solid-phase extraction (MISPE) was compared with commercial C18 SPE column. The reproducibility of MISPE and optimal flow rate of sample were studied. There was a linear correlation in the concentration range of 0.7–114.1 μg l^?1 of BPA (r?=?0.997). The limit of detection (LOD) based on three times ratio of signal to noise was 0.11 μg l^?1. Under optimal conditions, the proposed method was applied to the analysis of BPA in fish samples. The amount of BPA in bream was 4.00 μg kg^?1, and both concentrations of BPA in crucian and weever were below the LOD. The recoveries of BPA standard solution spiked with fish samples were in the range of 92.56–102.3 % with the relative standard deviation less than 10 %.     

分子印迹固相萃取-高效液相色谱法检测奶粉中的双氰胺

通过一步聚合法制备以双氰胺为模板分子,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸为交联剂,偶氮二异丁腈为引发剂的分子印迹聚合物。通过扫描电子显微镜、红外光谱、紫外光谱等对材料的物理及化学性能进行表征。采用分子印迹固相萃取结合高效液相色谱法检测实际奶粉样品中的双氰胺残留。该方法的线性范围为0.01~2.00 mg/L,线性相关系数R~2为0.999 4,呈现良好的线性关系,检出限(R_(SN)=3)为0.57×10~(-2) mg/L,样品加标回收率为102.5%~104%,相对标准偏差在0.21%~0.86%之间。     

Development of a Direct Competitive Biomimetic Enzyme-Linked Immunosorbent Assay Based on a Hydrophilic Molecularly Imprinted Membrane for the Determination of Trichlorfon Residues in Vegetables

In recent years, there has been an increasing demand on the determination of trace trichlorfon residues in fresh vegetables. In this study, a sensitive direct competitive biomimetic enzyme-linked immunosorbent assay (BELISA) method was developed for the determination of trichlorfon based on a hydrophilic imprinted membrane, which was directly synthesized on the well surface of MaxiSorp polystyrene 96-well plate through bulk polymerization technology. This novel imprinted membrane was characterized with high binding ability and specificity. Under the optimal conditions, the sensitivity (IC₅₀, half maximal inhibitory concentration) and the limit of detection (LOD, IC₁₅) of this method were 6800 ± 60 μg/L and 6.8 ± 0.20 μg/L, respectively. This BELISA method had been applied to the determination of trichlorfon with good recoveries ranging from 106.0 to 110.5%, and the results were correlated with that obtained by the gas chromatography method. Moreover, this method was applied to quantitative detection of trichlorfon residues in the leek samples.     

Determination of Diazinon Pesticide Residue in Tomato Fruit and Tomato Paste by Molecularly Imprinted Solid-Phase Extraction Coupled with Liquid Chromatography Analysis

Food Analytical Methods - In the present study, an optimized molecularly imprinted polymer (MIP) was prepared and evaluated as a selective sorbent in solid-phase extraction and analysis in tomato...     

Matrix Solid-Phase Dispersion Extraction and Capillary Electrophoresis Determination of Tetracycline Residues in Milk

A capillary zone electrophoresis method was proposed for simultaneous detection and quantification of three tetracycline antibiotics in commercial milk samples, i.e., tetracycline, oxytetracycline, and doxycycline. The influences of the electrolyte composition, pH, as well as temperature and applied voltage on separation were investigated. The optimal running buffer was 30 mM Na₂HPO₄ and 1 mM EDTA at pH 11.5, with 3 s hydrodynamic injection, 25 kV applied voltage, and UV detection at 268 nm. Matrix solid-phase dispersion procedure was used for sample pretreatment. Several solid support materials were investigated, and silica with bonded C₁₈ chains (C₁₈) was used as sorbent. Electrophoretic analysis was completed in less than 6 min, with LODs ranging from 0.0745 μg/mL for oxytetracycline to 0.0808 μg/mL for doxycycline. The recoveries obtained were between 93.4% and 102%.     

Determination of Trace Para Red Residues in Foods through On-Line Molecularly Imprinted Solid Phase Extraction Coupled with High-Performance Liquid Chromatography

ABSTRACT:  In this article, we prepared a novel imprinted polymer by a room temperature ionic liquid-mediated surface molecular imprinting technique in combination with a sol–gel process. This polymer was characterized by static and kinetic adsorption experiments and exhibited good recognition ability and offered fast kinetics for the adsorption of Para Red. A simple and sensitive analytical method, based on the coupling of molecularly imprinted solid phase extraction with high-performance liquid chromatography (HPLC), had been developed for determination of trace Para Red. With a loading flow rate of 0.42 mL min⁻¹ for 25 mL, an enrichment factor of 1061 was achieved. Under the selected experimental condition, the detection limit (S/N = 3) of Para Red was 6.6 ng L⁻¹, and the peak area precision (RSD) for 5 replicate detections of 0.15 μg L⁻¹ Para Red was 4.1%. The applicability of this method for determination of the blank chili sauce sample, spiked with Para Red at 5 to 25 ng g⁻¹ levels, was demonstrated, with recoveries ranging from 86% to 95%.
Practical Application: In this paper, a simple and sensitive analytical method, based on the coupling of molecularly imprinted solid phase extraction with high performance liquid chromatography, had been developed for determination of trace Para Red. It was applied to the analysis of spiking Para Red in chili sauce sample with satisfactory recovery and repeatability. This proposed method has the potential to be used for monitoring the illegal addition of Para Red in foods in the future due to its simple, reliable, rapid, and excellent precision.     

Preparation and Evaluation of Histamine Imprinted Polymer as a Selective Sorbent in Molecularly Imprinted Solid-Phase Extraction Coupled with High Performance Liquid Chromatography Analysis in Canned Fish

A series of molecularly imprinted polymers (MIPs) were prepared against histamine. Different template/monomer ratios were applied to optimize the imprinting condition. Methacrylic acid (MAA) as a functional monomer and Chloroform as a solvent were applied in polymerization process. The binding properties of MIPs were studied in comparison with a blank non-imprinted polymer. The optimized polymer, with a histamine/MAA ratio of 1/4, was selected as a sorbent in molecularly imprinted solid-phase extraction (MISPE) of histamine from canned fish. Scatchard analysis of MIP-histamine interactions revealed two types of binding sites for MIP: high affinity (K_D?=?11.11 μM) and low affinity (K_D?=?333.3 μM). The MISPE procedure was calibrated and a recovery of 76.5–97.6 % was obtained. The intra-and inter-day precision values were less than 5.70 % and 10.1 %, respectively. The selectivity of MISPE for histamine was also studied in comparison with some other structurally similar amines, which could be simultaneously present in canned fish. The performance of the imprinted polymer was examined and the results indicated that its good selectivity and affinity for histamine was very promising. Therefore, the proposed calibrated method could be applied in selective extraction and analysis of histamine in canned fish.     

Sensitive Determination of Bromate in Water Samples by Capillary Electrophoresis Coupled with Electromembrane Extraction

Electromembrane extraction (EME) as a novel sample preparation technique was firstly applied for the purification and enrichment of bromate (BrO₃ ^?) in drinking water prior to capillary zone electrophoresis with capacitively coupled contactless conductivity detection (CZE-C⁴D). BrO₃ ^?, as the primary disinfection by-product of ozonation, could be well separated with the major inorganic anions coexisting in water samples using a 300 mmol L^?1 acetic acid solution as the running buffer. Under the optimum conditions, the calibration curve showed good linearity (r ²?=?0.996), and the limit of detection was down to 0.12 ng mL^?1 with the enrichment factor at 267. The relative standard deviation (RSD) values for peak area and migration time at a spiked concentration of 10 ng mL^?1 of bromate were below 8.8 and 2.5 %, respectively. This proposed EME-CZE-C⁴D method has been successfully applied to analyze bottled drinking water and tap water samples with recoveries in the range of 85~98 %, providing an alternative to the determination of bromate in drinking water.     

Determination of Sulfonamides in Chicken Meat by Magnetic Molecularly Imprinted Polymer Coupled to HPLC-UV

In this work, Fe₃O₄ magnetic nanoparticles were synthesized and modified by a molecularly imprinted polymer for easy and selective extraction and determination of sulfonamides in chicken meat samples. Imprinted polymer magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction pattern, thermal analysis, and scanning electron microscope micrograph. The template was removed by methanol elution. The effective parameters on extraction and determination of sulfonamides on the sorbent such as eluent type, extraction solvent, and adsorption and desorption times were optimized. Sulfonamide separation and determination were performed by high-performance liquid chromatography–UV. The linear ranges for sulfonamides were 0.5–150 μg/L and the limits of detection were 0.1–0.5 μg/L. Relative standard deviations were within 4.3–5.4 %. The method showed good selectivity for extraction of sulfonamides in real samples.     

基于分子印迹富集及HPLC-ICP-MS检测海产品中三丁基锡的研究

本文以甲基丙烯酸为功能单体,三丁基锡为模板分子,二甲基丙烯酸乙二醇酯为交联剂,乙腈为致孔剂,采用分子印迹技术并联合高效液相色谱电感耦合等离子质谱(HPLC-ICP-MS)成功地制备了能特异性识别TBT的MIPs。所合成的MIPS经过选择识别、吸附动力学及再生性能等检测,对三丁基锡具有良好的吸附能力和高选择识别能力。并以分子印迹聚合物作为固相萃取吸附剂分离富集TBT,联合高效液相色谱-电感耦合等离子质谱(HPLC-ICP-MS)检测海水及海产品中的三丁基锡。结果表明,用传统分子印迹聚合物作为吸附剂富集分离,在海水、贻贝和大黄鱼样品中检测限(LOD)分别为0.06μg/L、4.0 ng/g和5.0 ng/g,加标回收率分别是61.5%~84.5%、76.2%~93.9%和74.2%~93.3%,线性范围分别是0.1μg/L~30μg/L、5 ng/g~50 ng/g和5 ng/g~500 ng/g。为海产品中有机锡等有机金属的检测提供方法。     

Molecularly Imprinted Layer-Coated Silica Gel Particles for Selective Solid-Phase Extraction of Pefloxacin and Enrofloxacin from Milk Samples

This study describes the synthesis of a molecularly imprinted polymer (MIP) as a novel solid-phase extraction adsorbent. The MIP consisted of pefloxacin (PEF) as a template, methacrylic acid (MAA) as a functional monomer, and silica gel particles as a support. The MIP was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and static adsorption. The MIP allowed the selective extraction of the fluoroquinolones PEF and enrofloxacin (ENR) and the simultaneous elimination of interfering components from milk matrices. Good linearity was obtained in a range of 2.5–500 ng?mL^?1, with correlation coefficients (R ²) >0.999. The average recovery rates of PEF and ENR ranged from 92.04 to 98.31 %, and the detection limits were 0.8–1.5 ng?mL^?1. This work provides a sensitive and selective tool for the detection of PEF and ENR residues in milk and potentially in other foods.     

多环芳烃分子印迹柱-高效液相色谱荧光检测法快速测定烤肉中15 种多环芳烃

建立一种高效液相色谱-荧光检测（high performance liquid chromatography-fluorescence detection,HPLC-FLD）法同时测定烤肉中15 种多环芳烃（polycyclic aromatic hydrocarbons,PAHs）的方法。样品经超声提取,多环芳烃分子印迹柱（molecular imprinting column of PAHs,MIP-PAHs）净化,通过HPLC分离,外标法定量。结果表明：15 种PAHs在质量浓度1～50 ng/mL范围内与色谱峰面积呈良好的线性关系,r＞0.999 5;在5.0、10.0、25.0 μg/kg 3 个加标水平下,平均回收率为71.1%～98.8%,相对标准偏差为1.0%～5.8%;方法检出限（RS/N=3）为0.33～3.30 μg/kg,定量限（RS/N=10）为1.0～10.0 μg/kg。     

痕量食品外源药毛细管电泳检测方法研究进展

介绍毛细管电泳两种分离模式的基本原理和特点。论述毛细管电泳在线富集技术的优点及胶束电动毛细管色谱在线堆积、推扫富集技术检测原理。综述两种分离模式、两种在线富集技术在食品痕量外源药检测中的研究进展,并对毛细管电泳在线富集技术应用前景进行展望。     

Simultaneous Determination of Erythromycin,Tetracycline, and Chloramphenicol Residue in Raw Milk by Molecularly Imprinted Polymer Mixed with Solid-Phase Extraction

A rapid, simple, and efficient method was described for the simultaneous determination of three common antibiotic residues including erythromycin, tetracycline, and chloramphenicol in raw milk. A molecular imprinting technique combined with solid-phase extraction (SPE) was used to pretreat the test samples and then simultaneously detected with HPLC. The whole process, only including one step of pretreatment, was able to detect the entire target molecule using specific enrichment and analysis method. The detection was verified by comparison with Chinese standard methods of GB/T 22988-2008, GB/T 22990-2008, and GB/T 29688-2013. The testing lines, accuracy, reproducibility, specificity, and recoveries were evaluated, and calculated values were in line with established standards. The recoveries of erythromycin, tetracycline, and chloramphenicol were 77.82~87.08, 81.02~88.17, and 72.94~83.57%, respectively. By using of this novel solid-phase extraction substrate, the detection limits for erythromycin, tetracycline, and chloramphenicol were 10, 20, and 10 μg kg^?1, respectively. The method was suitable for routine analysis, and the experimental procedure was simplified, with the detection time greatly reduced. This method showed broad application prospects for the detection of antibiotic residues in raw milk.     

分子印迹固相萃取-高效液相色谱法检测鸡肉中的四环素类抗生素残留

采用本体聚合法,以盐酸四环素为模板分子,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,偶氮二异丁腈为引发剂,合成了针对四环素类抗生素具有选择性的分子印迹聚合物。并以此材料作为固相吸附剂与高效液相色谱联用,建立了固相萃取-高效液相色谱技术检测鸡肉中的3种四环素类抗生素痕量残留的方法。实验结果表明,该材料具有较强的吸附性和特异识别性。在0.1 mg/L~1.0 mg/L范围内3种四环素类药物的线性关系良好(R20.99),土霉素、四环素、强力霉素的最低检出限分别为0.13μg/L、0.12μg/L、0.14μg/L,5次重复实验的精密度分别为1.27%、1.31%、1.94%。在鸡肉中添加3个浓度(50μg/kg、100μg/kg、200μg/kg)的四环素类抗生素,回收率分别为88.33%~94.95%、80.94%~88.02%、87.69%~93.08%,RSD分别为2.08%~3.63%、1.46%~2.37%、1.04%~3.03%。这项研究的结果表明目前建立的方法可以用于鸡肉中四环素类抗生素的残留检测。