Molecularly imprinted solid-phase extraction combined with high-performance liquid chromatography for analysis of trace olaquindox residues in chick feeds

BACKGROUND: Olaquindox, one of the antimicrobial growth accelerants, is usually used as a feed additive in livestock production to improve feed efficiency. Due to health concerns over possible carcinogenic, mutagenic and photoallergenic effects of olaquindox on animals, the development of a simple, rapid and sensitive analytical method for determination of olaquindox is crucial and necessary. RESULTS: In this paper, a novel and hydrophilic functionalised material of olaquindox‐imprinted polymer was synthesised in aqueous solution by a surface molecular imprinting in combination with a sol–gel process. This imprinted material was characterised by Fourier transform infrared, scanning electron microscopy, and static and kinetic adsorption experiments, and results showed that it had good recognition and selective ability, and fast adsorption‐desorption dynamics for olaquindox. Applying the prepared material as sorbent, a method of molecularly imprinted solid‐phase extraction (MISPE) for separation and analysis of olaquindox residues in feeds coupled with HPLC was presented. Under the selected MISPE condition, the detection limit (S/N = 3) for olaquindox was 68.0 ng L^?1, the RSD for five replicate extractions of 50 µg L^?1 olaquindox was 9.8%. The blank chick feed samples spiked with olaquindox at 0.0025 and 0.010 mg g^?1 levels were extracted and determined by the developed method, with recoveries ranging from 90% to 96%. CONCLUSION: This method was applied for enrichment and analysis of olaquindox in animal feed samples with good accuracy and repeatability. This study will provide a sensitive and fast method for the monitoring of olaquindox residues in foods. Copyright © 2011 Society of Chemical Industry     

Development of an on-line molecularly imprinted chemiluminescence sensor for determination of trace olaquindox in chick feeds

BACKGROUND: Olaquindox, as one of the antimicrobial growth accelerants, is usually used in livestock production to improve feed efficiency. Due to health concerns over possible carcinogenic, mutagenic and photoallergenic effects of olaquindox on animals, the development of simple, rapid and sensitive analytical method for determination of olaquindox is crucial and necessary. RESULTS: In this study, a surface molecularly imprinted polymer was prepared by a molecular imprinting technique in combination with a sol‐gel process using activated silica gel as a support material. This imprinted material exhibited with good recognition and selective ability, and fast adsorption‐desorption dynamics toward olaquindox. Using it as the recognition element, a new on‐line molecularly imprinted solid phase extraction coupled with chemiluminescence sensor for the determination of olaquindox was developed. The factors affecting preconcentration of the analytes and sensitivity of the method were all investigated. Under the optimal condition, the linear range of the calibration graph was between 2 × 10^?8 and 1 × 10^?6 g mL^?1, and the detection limit of this method was 7 × 10^?9 g mL^?1. The blank chick feed samples spiked with olaquindox at 0.3, 0.9 and 1.5 µg g^?1 levels were extracted and determined by this presented method with recoveries ranging from 87% to 94%. This method was validated by high‐performance liquid chromatography and the results correlated well with those obtained by both methods. Moreover, this method was quantitatively analysed with two contaminated chick feed samples. CONCLUSION: This study will provide a sensitive and fast method for the monitoring of olaquindox residues in foods. Copyright © 2012 Society of Chemical Industry     

Preparation of Ofloxacin Poly(Glycidyl Methacrylate-Co-Ethylenedimethacrylate) (PGMA/EDMA) Molecularly Imprinted Microspheres and Their Application to the Analysis of Quinolones in Milk

A series of novel ofloxacin-imprinted polymers have been prepared using poly(glycidyl methacrylate-co-ethylenedimethacrylate) (P_GMA/EDMA) particles as a support and their recognition abilities evaluated. Several factors that are known to influence the rebinding of the imprinted polymers were investigated, including the pH and water content of the adsorbed solutions. The binding capabilities of the materials were also evaluated. The resulting P_GMA/EDMA molecularly imprinted polymers were used as selective solid phase extraction sorbents for the simultaneous determination of three different quinolones in milk, with the results revealing high levels of selectivity. The use of 10 % methanol–water as washing solution together with 2 % trifluoroacetic acid–acetonitrile as an elution solution allowed for the three different quinolones to be selectively extracted from the milk samples. Furthermore, all of the matrix interference factors were eliminated simultaneously, whereas the enrichment factors were >234. The quantification limit was determined to be 1.00 ng/mL using an ultraviolet detector, and the recovery was in the range of 81.8–102.0 % with a relative deviation of <9.6 %.     

A Novel Molecularly Imprinted Polymer Based on Carbon Nanotubes for Selective Determination of Dioctyl Phthalate from Beverage Samples Coupled with GC/MS

Phthalates represent a potential risk for humans, since they are ubiquitous environmental contaminants. Efficient extraction and purification procedures are demanded for the detection of low concentration levels of phthalates. In this work, a novel type of molecularly imprinted polymers coated onto the surface of vinyl functionalized multi-walled carbon nanotubes was synthesized and coupled with gas chromatography–mass spectrometry (GC/MS) for the selective separation and determination of dioctyl phthalate (DOP) in beverage samples. The morphology, structure property, and thermostability of the resultant polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The adsorption properties of the prepared polymers were investigated by equilibrium rebinding and competitive experiments. The resultant imprinted nanomaterials exhibited high capacity and favorable selectivity. In addition, the feasibility of the developed method using the obtained imprinted polymers as a solid-phase sorbent coupled with GC/MS for the selective isolation and determination of DOP in different beverage samples was demonstrated. Under optimal conditions, the limit of detection of the proposed method for DOP was 2.3 ng L^?1. DOP spiked at three levels of concentration in beverage samples was extracted and determined through the application of the present method, with recoveries ranging from 88.6 to 93.0 % with relative standard deviations less than 5.6 %.     

Solid-Phase Extraction of Florfenicol from Meat Samples by a Newly Synthesized Surface Molecularly Imprinted Sol–Gel Polymer

A new molecularly imprinted polymer (MIP) as a solid-phase sorbent for selective extraction of florfenicol (FF) was prepared by combination of the surface molecular imprinting technique with the sol–gel process. The FF-imprinted silica sorbent was prepared using FF as template, 3-aminopropyltriethoxysilane as functional monomer and tetraethoxysilicate as cross-linker on the silica gel support. The non-imprinted silica (NIP) was synthesized in the same way without addition of FF. The MIP was evaluated as a sorbent in column extraction approach for extraction of FF from aqueous solutions followed by spectrofluorometric determination. The influence of certain variables including the sample pH, the sample volume, the sample flow rate, the type of eluent, and its flow rate on the extraction efficiency of FF was assessed. The prepared FF-MIP silica sorbent showed higher adsorption capacity (64.9 mg g^?1) and significant selectivity than the corresponding NIP (11.5 mg g^?1). The FF-MIP-based solid phase extraction method was successfully applied to the separation and determination of FF from fish and chiken meat samples under the optimized extraction conditions.     

Synthesis and utilisation of molecular imprinting polymer for clean-up of propachlor in food and environmental media

The molecularly imprinted polymers (MIPs) are used as the base material of solid phase extraction (SPE) for the separation and concentration of the propachlor herbicide (Prop) in different environmental matrix. Accordingly, we prepared MIPs on the surface of modified silica gel using propachlor as a template, acrylamide (AA) as functional monomers, ethylene glycol dimethacrylate (EGDMA) as a cross-linker and 2,2-azo-bis-isobutyronitrile (AIBN) as an initiator. The MIP structure was characterised using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Synthesised MIPs had a specific ability to detect the template Prop. The high selectivity solid phase extraction cartridges of molecularly imprinted polymers (MISPE) containing MIP Prop particles were prepared. The optimised Prop-MISPE procedure was developed for enrichment or clean-up of propachlor residues in water, soil and rice samples. Concentrations of propachlor in the samples were analysed by high performance liquid chromatography. Overall, the newly developed technique provides an analytical platform to quantify the trace amount of propachlor residues in multi or complex environmental and food media.     

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.     

有机磷分子印迹聚合物的制备及其吸附性能评价

目的 制备出有机磷类分子印迹聚合物(molecular imprinted polymers,MIPs)并对其进行吸附性能评价.方法 选用氯代磷酸二苯酯为虚拟模板、以甲基丙烯酸(methacrylic acid,MAA)为功能单体、三羟甲基丙烷三甲基丙烯酸酯(trimethylolpropane trimethacry...     

双填料固相萃取-紫外分光光度法检测茶汤中农药残留

以沉淀聚合法制备溴氰菊酯和吡虫啉分子印迹聚合物,然后干法裝柱制备双填料固相萃取柱考察其吸附性能,利用紫外分光光度计确定溴氰菊酯和吡虫啉的最大吸收波长,采用扫描电子显微镜对聚合物进行表征。实验结果表明溴氰菊酯在220 nm处吸收峰较大,而吡虫啉在270 nm处有最大吸收峰,且两种聚合物均具有较好的吸附能力。溴氰菊酯和吡虫啉在10~60 mg/L浓度范围内线性关系良好(R2>0.99),当以甲醇为活化溶剂、1 mL/min的流速上样、10%乙酸甲醇溶液作为洗脱剂时,该萃取柱对不同茶汤中溴氰菊酯和吡虫啉的加标回收率分别为83.15%~110.19%和80.61%~90.73%。对萃取柱8次重复利用结果证明该双填料萃取柱具有较好的再生性,可应用于茶叶中溴氰菊酯和吡虫啉农药的定量检测。     

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 solid phase extraction coupled to high-performance liquid chromatography for determination of trace dichlorvos residues in vegetables

In this paper, we prepared a highly selective imprinted polymer by a room temperature ionic liquid-mediated bulk polymerization technique, using dichlorvos as the template, methacrylic acid as the functional monomers, and trimethylolpropane trimethacrylate as the cross-linker. This functionalized material was characterized by FT-IR, static and kinetic adsorption experiments, and the results showed that this imprinted sorbent exhibited good recognition and selective ability, and offered fast kinetics for the adsorption and desorption of dichlorvos. Using the prepared material as a solid phase extraction sorbent, a novel sample pre-treatment technique that can be coupled to high-performance liquid chromatography (HPLC) had been developed for determination of trace dichlorvos residues in foods. Under the selected experimental condition, the detection limit (S/N = 3) of dichlorvos was 94.8 ng L⁻¹, and the peak area precision (RSD) for five replicate detections of 10 μg L⁻¹ dichlorvos was 4.41%. The blank samples of cucumber and lettuce spiked with dichlorvos at 0.005 and 0.02 μg g⁻¹ levels were determined with recoveries ranging from 82.1% to 94.0%.     

Extraction and detection of morin from Sanghuangporus lonicericola by magnetic molecularly imprinted polymers coupled with HPLC analysis

In this study, morin magnetic molecularly imprinted polymers (Morin-MMIPs) were synthesized based on magnetic nanoparticles and surface molecularly imprinted technology with superparamagnetism and extraction selectivity. The polymers allowed the separating of morin from complex matrices in the presence of an external magnetic field with no need for centrifugation or filtration. The microstructure of the polymers was characterized by scanning electron microscopy and transmission electron microscopy. Meanwhile, the functional group and magnetic properties of the polymers were characterized using Fourier transform infrared spectroscopy (FT-IR) and magnetic vibration meter (VSM). The maximum adsorption capacity of MMIPs was 3.24 mg/g, which was 2.55 times higher than that of MNIPs (1.27 mg/g). Morin was quantified by HPLC-DAD, which showed good linearity in the concentration range of 0.05–60 µg/ml with the correlation coefficient R² = 0.9993. The limit of detection (LOD) was 0.08 µg/ml, and the spiked recoveries were 87.5–106.8%. The calculation of the adsorption isotherm and kinetic model revealed the adsorption mechanisms, and the adsorption process was consistent with the Langmuir adsorption isotherm and pseudo-secondary kinetic models. Likewise, the material has been successfully used to extract and separate morin from food samples. The method reported in this paper has the advantages of fast adsorption speed, high selectivity, and environmental friendliness. It provided a reliable method for the separation and detection of morin or other natural products.     

In vivo studies to highlight possible illegal treatments of rabbits with carbadox and olaquindox

For the treatment of rabbit dysentery and bacterial enteritis, veterinary practitioners often adopt veterinary medicinal products authorised for other food-producing species, but in some cases non-authorised drugs frequently used in the past, such as carbadox and olaquindox, might be illegally adopted. To verify the carbadox and olaquindox distribution and persistence in rabbit tissues, two independent in vivo studies were carried out. In the first study, 24 healthy rabbits received water medicated with carbadox at 100 mg l^?1 over a period 28 days, whereas in the second one, 24 healthy rabbits were administered water containing olaquindox at 100 mg l^?1. In each study rabbits were randomly assigned to four groups to be sacrificed respectively at 0, 5, 10 and 20 days from treatment withdrawal, for depletion studies. A control group of six animals was adopted for control and as a reservoir of blank tissues. Muscle and liver samples collected from each treated animal were stored at ?20°C pending the analysis. Sensitive and robust liquid chromatography-tandem mass spectrometry analytical methods were set up for the parent compounds and their main metabolites quinoxaline-2-carboxylic acid, desoxycarbadox and 3-methylquinoxaline-2-carboxylic acid to verify their residual. Data collected demonstrate that the combination of liver as target matrix, quinoxaline-2-carboxylic acid and 3-methylquinoxaline-2-carboxylic acid as marker residue and enzymatic digestion is strategic to evidence carbadox and/or olaquindox illegal treatments in rabbits, even 20 days after treatment withdrawal at concentration levels higher than 0.5 µg kg^?1. This findings suggests that liver should be proposed as target matrix for official control in national monitoring plan.     

Determination of olaquindox,carbadox and cyadox in animal feeds by ultra-performance liquid chromatography tandem mass spectrometry

Olaquindox, carbadox, and cyadox are chemically synthesised antibacterial and growth-promoting agents for animals. At high doses they may exert mutagenicity and hepatic and adrenal toxicities in animals. Regrettably, these substances are frequently abused or misused when added into animal feeds. Thus, developing a sensitive and reliable method for simultaneous determination of olaquindox, carbadox, and cyadox in different kinds of animal feeds is crucially important for food safety monitoring. In this paper we optimised instrumental conditions, extraction solvents, solid phase extraction cartridges, and pH of the loading solvents on the Oasis HLB cartridge. Under the optimal conditions, mean recoveries ranged from 74.1 to 111%, and intra-day and inter-day variations were lower than 14.6% and 10.8%, respectively. The limits of quantification for olaquindox, carbadox, and cyadox were 0.05 mg kg^?1, 0.10 mg kg^?1, and 0.025 mg kg^?1, respectively. The proposed method uses ultra-performance liquid chromatography tandem mass spectrometry and is sensitive and reliable for the simultaneous determination of olaquindox, carbadox, and cyadox in three kinds of animal feeds (specifically, mixed feed, concentrated feed, and additive premixed feed). This method has good precision, high sensitivity, and good reproducibility, and thus it can be used for convenient and accurate determination of olaquindox, carbadox, and cyadox in different kinds of animal feeds.     

Multi-Residue Determination of Pesticides in Açai Tropical Fruit (Euterpe oleracea) by Matrix Solid-Phase Dispersion Combined with Liquid Chromatography

An extraction method based on matrix solid phase dispersion was developed to determine bromuconazole, fenbuconazole, parathion-methyl, kresoxim-methyl, and teflubenzuron in açai using liquid chromatography with ultraviolet diode array detector. The best results were obtained using 1.0 g of açai, 3.0 g of neutral alumina as the dispersant sorbent, and cyclohexane/ethyl acetate (1:1, v/v, 20 mL) as an eluting solvent. The method was validated using açai samples fortified with pesticides at three concentration levels (0.25, 0.5, and 1.0 mg kg^?1). Average recoveries (seven replicates) ranged from 66 to 119 %, with relative standard deviations between 1.4 and 20 %. The detection and quantification limits for açai ranged from 0.02 to 0.05 mg kg^?1 and from 0.05 to 0.1 mg kg^?1, respectively.     

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.     

磁固相萃取在食品分析中的研究进展

磁固相萃取(Magnetic solid phase extraction,MSPE)是使用磁性吸附剂富集待测物,在磁场作用下分离待测物的样品前处理方法。相比于传统的样品前处理方法,MSPE具有吸附快速、效率高、易分离等优点。MSPE磁性吸附剂由磁性纳米颗粒和其表面的非磁性功能材料修饰组成。本文主要综述碳化合物、表面活性剂、离子液体、金属-有机骨架化合物、氧化物、高分子、分子印迹聚合物这几类材料表面修饰的MSPE磁性吸附剂的研究进展。选择不同表面修饰材料的MSPE技术可以对不同的食品添加剂、农药残留、抗生素等化合物有理想的吸附效果,有广泛的应用前景。     

花椒麻味物质分子印迹聚合物的制备及吸附特性

为实现对花椒麻味物质经济高效的纯化制备,本实验采用分子印迹技术,以甲基丙烯酸为功能单体,花椒麻味物质为模板分子,合成对花椒麻味物质具有特异性识别和吸附能力的分子印迹聚合物(molecularly imprinted polymers,MIPs),并用MIPs制成固相萃取柱用于分离纯化花椒油树脂中的花椒麻味物质。吸附动力学实验结果显示,MIPs与花椒麻味物质接触约12 h后就达到吸附平衡,对花椒麻味物质识别因子α达到3.05;等温吸附实验表明,MIPs对花椒麻味物质的吸附量高于空白聚合物,在吸附过程中模板分子花椒麻味物质与MIPs形成两种结合位点,两种结合位点的解离常数分别为1.172×10~(-2) mg/m L和3.585×10~(-2) mg/m L,对花椒麻味物质最大表观吸附量分别为11.133 mg/g和15.802 mg/g;固相萃取实验表明,该固相萃取柱可以分离出相对纯度为94.09%的花椒麻味物质。     

(壳聚糖/γ-Fe_2O_3)@C磁性复合材料表面印迹聚合物选择性吸附2,4,5-TCP的研究

本文采用乳液聚合法合成碳基磁性碳球(壳聚糖/γ-Fe2O3)@C,并在其表面上引入乙烯基,以2,4,5-三氯酚(2,4,5-TCP)为模板分子、甲基丙烯酸(MAA)为功能单体、乙二醇二甲基丙烯酸酯(EGDMA)为交联剂制备磁性碳球表面印迹聚合物。并利用扫描电子显微镜、紫外分光光度计、振动样品磁强计和热重分析仪等表征手段对其形貌、结构等物理化学性能进行表征,研究其热稳定性和磁稳定性,考察其作为吸附剂对2,4,5-三氯酚的吸附性能及选择性能。研究结果表明,磁性碳球和磁性碳球表面印迹聚合物(MMIPs)的饱和磁强度分别为4.3 emu/g和1.7 emu/g。吸附平衡数据表明其符合Freundlich吸附等温模型,平衡吸附量大约为200mg/g,吸附符合准二级动力学方程,平衡吸附时间大约为10 min,印迹吸附剂对模板分子吸附量最佳,且存在明显特异性吸附。     

A Novel Electrochemical Sensor Based on Graphene Oxide Decorated with Silver Nanoparticles–Molecular Imprinted Polymers for Determination of Sunset Yellow in Soft Drinks

In this study, a new imprinted electrochemical sensor for selectively detecting sunset yellow was developed based on glassy carbon electrode (GCE) modified by graphene oxide decorated with silver nanoparticles–molecular imprinted polymers (GO/AgNPs–MIPs). GO/AgNPs were firstly synthesized using self-assembly technology, and GO/AgNPs–MIPs were synthesized through surface imprinted technology by using GO/AgNPs as the substrate and sunset yellow as the template, respectively. The sensor was prepared by a drop-casting method. The synthetic materials were characterized by transmission electron microscope (TEM), Fourier transmission infrared spectra (FT-IR), and X-ray diffraction (XRD). The sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The usage amount of GO/AgNPs–MIPs suspensions, solution pH, and accumulation time made an important difference in the process of detecting sunset yellow. Under optimal conditions, the peak current is linear to concentration of sunset yellow in the ranges of 0.1–0.6 and 0.6–12 μM, and the limit of detection was estimated to be 0.02 μM (S/N = 3). Finally, the proposed sensor was applied to detect sunset yellow in soft drinks with acceptable recovery, which demonstrated that the sensor could be used as a reliable and simple method for practical detection of sunset yellow.