Molecular imprinting‐based micro‐stir bar sorptive extraction for specific analysis of Glibenclamide in herbal dietary supplements

A novel molecularly imprinted polymers (MIPs) coated micro‐stir bar (MSB) for Glibenclamide (GM) was developed. The MIPs, with GM as template molecular and methacrylic acid as functional monomer, were synthesized at the surface of the silylated MSB that was filled with magnetic core as substrate. Computational simulation was used for the optimal selection of functional monomers and porogen. The thickness of MIPs coating for MSB was about 10 μm, the adsorption and desorption time were about 40 and 20 min, respectively. The MIPs coated MSB possessed mechanical stability, high adsorption capacity, and good selectivity for GM. To achieve the optimum extraction performance, several parameters including extraction and desorption time, stirring rate, extraction and desorption solvent were investigated. A method for the determination of GM in herbal dietary supplements by MIPs coated MSB coupled with HPLC‐UV was established. The results exhibited good linear ranges of 10–6250 μg L^?1 with the low limit of detection of GM (3.05 μg L^?1) and the good recoveries (81.9–101.4%).     

Enantioselective recognition of glutamic acid enantiomers based on poly(aniline-co-m-aminophenol) electrode column

A copolymer, poly(aniline-co-m-aminophenol), was synthesized by copolymerization of aniline and m-aminophenol in the presence of l-glutamic acid (l-Glu) as template molecules. The copolymer was filled into a porous ceramic column as the conductive stationary phase. Enantioselective recognition of Glu enantiomers was achieved on this special electrode column by applying different potentials on copolymers in the ceramic column. l-Glu anions were ejected from the ceramic column after electrochemical reduction due to the reversible redox of the copolymer while complementary cavities were left. Then a positive potential was applied to the molecularly imprinted poly(aniline-co-m-aminophenol) for re-binging Glu enantiomers in the mobile phase. The results showed good enantioselectivity.     

Influence of chemical and structural properties of functionalized polythiophene-based layers on electrochemical sensing of atrazine

Sensitive layers based on conducting homopolymer [poly(3,4-ethylenedioxythiophene), denoted PEDOT] and copolymers [molecularly imprinted and non-imprinted poly(EDOT-co-3-thiophene acetic acid), denoted MICP and NICP, respectively] are electrosynthesized on gold substrates and used for the electrochemical detection of atrazine. These layers are characterized by cyclic voltammetry, ATR-FTIR spectroscopy, optical profilemetry, and AFM microscopy in order to study the effect of the chemical functionalities and of the structural properties of these conducting polymers on the physical chemistry of the interaction with atrazine targets and with the aim to improve the sensitivity of the recognition process. In particular, due to the presence in their backbones of preshaped functionalized cavities which keep the molecular memory of the targets, MICP layers show remarkable sensitivity, a low detection limit (10(-9) mol L(-1)), and a large linear range of detection (10(-8) to 10(-4) mol L(-1)), as demonstrated by square-wave voltammetry.     

功能性聚合物薄膜修饰电极

化学修饰电极是当前在电化学、电分析化学方面十分活跃的研究领域。功能性聚合物薄膜由于其特殊的化学结构赋予其许多独特的功能,诸如选择性、分子识别、pH敏感、光化学敏感等;功能性聚合物修饰电极可以赋予电极许多特殊功能,拓展电极的应用范畴,故而备受关注。本文分别从分子印迹聚合物传感器和生物酶传感器制备的角度,综述在电极表面构筑功能性聚合物薄膜的材料以及方法,重点论述电泳沉积技术在电极修饰中的新应用。这些功能性聚合物薄膜在电极表面的构筑方法可以广泛的拓展到其它传感器的制备中,并指导特殊的传感器的制备,具有重要的研究和应用价值。     

分子印迹固相萃取-高效液相色谱法测定蜂蜜中三种氟喹诺酮类抗生素残留

采用沉淀聚合法,以诺氟沙星为模板分子,合成了对氟喹诺酮类(FQs)抗生素特异性识别的分子印迹聚合物(MIPs),其印迹因子为3.17,亲和位点总数为3.27μmol/g。以该MIPs做为固相萃取柱填料,建立了分子印迹固相萃取-高效液相色谱检测蜂蜜中三种FQs抗生素残留的方法。与Oasis HLB固相萃取柱相比,该分子印迹固相萃取柱(MISPE)具有更好的净化能力和更高的富集效率。最佳条件下,三种FQs抗生素的线性范围为0.125～12.5mg/kg,相关系数均大于0.999。方法的检出限(S/N=3)为9～12μg/kg,三种FQs抗生素的加标回收率为96.5%～104.1%,相对标准偏差不高于6.2%(n=5)。该方法有望用于蜂蜜中FQs抗生素残留的常规检测。     

Online coupling of molecularly imprinted solid-phase extraction to HPLC for determination of trace tetracycline antibiotic residues in egg samples

An automated system has been developed for the determination of trace tetracycline antibiotics (TCs) in egg samples, based on online molecularly imprinted solid-phase extraction (MISPE) coupling with high-performance liquid chromatography (HPLC). Oxytetracycline and chlortetracycline were chosen as mixed templates to synthesize highly selective molecularly imprinted polymers for online extraction. Under the optimal online MISPE-HPLC condition, 10 mL egg samples were injected into the MISPE column and then the matrix was washed out. By rotating the switching valve, TCs were transferred to the analytical column and then separated by HPLC. Because sample pretreatment and chromatographic separation were carried out simultaneously, the whole analytical time (18 min) was significantly shortened compared with conventional offline techniques. The detection limits ranged from 0.8 to 1.3 ng/g. The enhancement factors were in the range of 159-410. The spiked recoveries of TCs in real egg samples ranged from 91.6 to 107.6% and the relative standard deviations (RSDs) were not higher than 4.0%.     

Synthesis of core-shell molecularly imprinted polymer microspheres by precipitation polymerization for the inline molecularly imprinted solid-phase extraction of thiabendazole from citrus fruits and orange juice samples

In this work, the synthesis of molecularly imprinted polymer microspheres with narrow particle size distributions and core-shell morphology by a two-step precipitation polymerization procedure is described. Polydivinylbenzene (poly DVB-80) core particles were used as seed particles in the production of molecularly imprinted polymer shells by copolymerization of divinylbenzene-80 with methacrylic acid in the presence of thiabendazole (TBZ) and an appropriate porogen. Thereafter, polymer particles were packed into refillable stainless steel HPLC columns used in the development of an inline molecularly imprinted SPE method for the determination of TBZ in citrus fruits and orange juice samples. Under optimized chromatographic conditions, recoveries of TBZ within the range 81.1-106.4%, depending upon the sample, were obtained, with RSDs lower than 10%. This novel method permits the unequivocal determination of TBZ in the samples under study, according to the maximum residue levels allowed within Europe, in less than 20 min and without any need for a clean-up step in the analytical protocol.     

Fast and selective extraction of chloramphenicol from soil by matrix solid‐phase dispersion using molecularly imprinted polymer as dispersant

The molecularly imprinted polymer (MIP) was synthesized and used as dispersant of matrix solid‐phase dispersion (MSPD) for the extraction of chloramphenicol (CAP) in soil samples. The satisfactory recovery of CAP was obtained by the optimized extraction conditions: 1:2 as the ratio of sample to MIPs; 5 min as the dispersion time; 30% aqueous methanol as washing solvent and methanol as elution solvent. The CAP extracted from soil was determined by LC‐MS/MS. The slight ion suppression phenomenon was observed for the CAP when the sample was cleaned up by MSPD with MIP as dispersant, when compared with C18 as MSPD dispersant, which caused significant ion suppression. LOD of CAP is 4.1 ng/g. RSDs of intra‐ and inter‐day tests ranging from 3.1 to 6.2% and from 3.9 to 8.3% are obtained. At all three fortified levels (20, 100 and 500 ng/g), recoveries of CAP are in the range of 86.9–92.6%. The effect of ageing time of spiked soil sample on the CAP recovery was examined. The CAP recovery decreased from 91.0 to 36.9% when the ageing time changed from 1 day to 4 wk.     

Molecularly imprinted solid-phase extraction coupled with HPLC for the selective determination of monobutyl phthalate in bottled water

A molecularly imprinted polymer (MIP) was prepared using monobutyl phthalate as template. The synthesis was optimized by using different porogens and functional monomers. The MIP was used as a selective sorbent in molecularly imprinted solid-phase extraction (MIP-SPE) for pre-concentration and determination of monobutyl phthalate (mBP) from the bottled water. The difference in recognition selectivity of the polymer columns was observed in HPLC system, and the effect of the mobile phase on the performance of MIP columns was also investigated. Control of the MIP-SPE process is seen as important in helping to facilitate the selective extraction of mBP from water samples. Thereafter, the choice of washing solvent, eluting solvent amount, pH of loading sample, flow rate of loading solution and the loading sample volume was presented. The optimized procedure was described as follows: 25 mL spiked aqueous solution was percolated through the MIP-SPE cartridge at the flow rate of 1.5 mL/min. After rinsing with acetonitrile/methanol mixture (1:1, v/v), the bound analyte was desorbed with 3 mL methanol. The developed MIP-SPE method was demonstrated to be applicable for the analysis of mBP in the bottled water.     

Selective sample pretreatment by molecularly imprinted polymer monolith for the analysis of fluoroquinolones from milk samples

Water-compatible pefloxacin-imprinted monoliths synthesized in a water-containing system were used for the selective extraction of fluoroquinolones (FQs). The MIP monolith was synthesized by using methacrylic acid as the functional monomer, di(ethylene glycol) dimethacrylate as a cross-linker and methanol–water (10:3, v/v) as the porogenic solvent. The ability of the derivated MIP for selective recognition of FQs (ciprofloxacin, difloxacin, danofloxacin and enrofloxacin) and quinolones (flumequine, and oxolinic acid) was evaluated. The derivated monolith showed high selectivity and was able to distinguish between FQs and quinolones. A simple rapid and sensitive method using polymer monolith microextraction (PMME) based on the MIP monolith combined with HPLC with fluorescence detection was developed for the determination of four FQs from milk samples. Owing to the unique porous structure and flow-through channels in the network skeleton of the MIP monolith, phosphate buffer diluted milk samples were directly supplied to PMME; allowing non-specific bound proteins and other biological matrix to be washed out, and FQs to be selectively enriched. The limit of detection of the method was 0.4–1.6 ng/mL and recovery was 92.4–98.2% with relative standard deviations less than 5.9%.