Synthetic approaches to parabens molecularly imprinted polymers and their applications to the solid-phase extraction of river water samples

In this paper we describe the synthesis, characterisation and use of two distinct molecularly imprinted polymers (MIPs) prepared using esters of p-hydroxybenzoic acid (parabens) as templates: one MIP was synthesised by precipitation polymerisation using a semi-covalent molecularly imprinting strategy with methyl paraben as the template/target (MIP 1); the second MIP was prepared in monolithic form through a conventional non-covalent molecular imprinting strategy, with butyl paraben as the template (MIP 2). MIP 1 recognized methyl paraben, showed cross-selectivity for other parabens analytes used in the study and higher affinity towards these compounds than did a non-imprinted control polymer. Similarly, MIP 2 demonstrated higher affinity towards paraben analytes than a non-imprinted control polymer.For the analysis of environmental water samples, a solid-phase extraction (SPE) protocol was developed using MIP 2 as sorbent, and results were compared to a SPE using a commercial sorbent (Oasis HLB). With MIP 2 as sorbent and butyl paraben as target, when percolating 500 mL of river water spiked at 1 μg L⁻¹ through the SPE cartridge, and using 1 mL of isopropanol as cleaning solvent, a higher recovery of butyl 4-hydroxybenzoate (butyl paraben) and a cleaner chromatogram where achievable when using the MIP compared to the commercial sorbent.     

Synthesis and application of a T-2 toxin imprinted polymer

The synthesis of a T-2 toxin imprinted polymer and its application in food analysis are reported for the first time. A molecularly imprinted polymer (MIP) for the selective recognition of T-2 toxin (T-2) was synthesized by bulk polymerization. Methacrylamide and ethyleneglycol dimethacrylate were applied as functional monomer and cross-linker, respectively. Molecularly imprinted solid-phase extraction (MISPE) procedures were optimized for further application in the analysis of T-2. Scatchard plot analysis revealed that two classes of imprinted binding sites were formed in the imprinted polymer. The dissociation constant (K_D) of the higher affinity binding sites was 7.0 μmol/l, while the K_D of the lower affinity binding sites was 54.7 μmol/l. The performance of the MIP throughout the clean-up of spiked maize, barley and oat sample extracts was compared with the results obtained when using non-imprinted polymer, OASIS HLB^® and immunoaffinity columns (IAC). Depending on the food matrix and the spiked concentration, recoveries after MISPE and non-imprinted solid-phase extraction varied respectively from 60% to 73% and from 21% to 57%. Recoveries obtained after clean-up using OASIS HLB^® and IAC were in the range of 74–104% and 60–85%, respectively. Although highest recoveries were obtained with OASIS HLB^® sorbents, the designed MIP and the IAC were superior regarding selectivity, cross-reactivity, matrix effect, limits of detection (LOD) and limits of quantification (LOQ). Depending on the matrix, LOD after MISPE ranged from 0.4 μg/kg to 0.6 μg/kg and LOQ from 1.4 μg/kg to 1.9 μg/kg. LOD and LOQ after OASIS HLB^® clean-up varied from 0.9 μg/kg to 3.5 μg/kg and from 3.1 μg/kg to 11.7 μg/kg, respectively. The LOD and LOQ values obtained with IAC were in the range of 0.3–2.3 μg/kg and 1.0–7.7 μg/kg, respectively. Analysis of 39 naturally contaminated samples (maize, barley and oat) by liquid chromatography tandem mass spectrometry revealed that the MIP could be an excellent alternative for clean-up of contaminated food samples.     

Pseudo-template molecularly imprinted polymer for selective screening of trace β-lactam antibiotics in river and tap water

To assess the potential risks associated with the environmental exposure of β-lactam antibiotics (BLAs), the monitoring of the occurrence, distribution, and fate of these emerging contaminants in the environment is required. Herein, we demonstrate a molecularly imprinted solid-phase extraction (MISPE) method for selective and reliable screening of trace BLAs in river and tap water. By developing a low-temperature photopolymerization, highly selective molecularly imprinted polymers (MIPs) for five BLAs (penicillin G, amoxicillin, ampicillin, nafcillin and mezlocillin) were synthesized. Nafcillin was chosen as a pseudo template to make the MIP sorbent (Nafc-MIP), which was used in pseudo-template MISPE for preconcentration of the other four BLAs from river and tap water. The application of pseudo-template MISPE overcomes the template bleeding, which significantly elevates the sample background and restricts the application of MIP for detection of the target BLA below 2 μg/L. The average recoveries of BLAs are in the range of 60–90% when Nafc-MIP was adopted as the selective MISPE sorbent. The developed method was validated, and applied to the screening of trace β-lactam antibiotics in river and tap water. The linearity of the calibration curve for each BLA was observed over the range of 0.1–20 μg/L (r > 0.998). The β-lactam antibiotics were found within the range of 0–9.56 μg/L in river water at the downstream of antibiotics manufacturers, and none were detected in the tap water.     

Determination of 76 pharmaceutical drugs by liquid chromatography–tandem mass spectrometry in slaughterhouse wastewater

A multi-residue method for the analysis of 76 pharmaceutical agents of nine classes of drugs (tetracyclines, macrolides, fluoroquinolones, β-agonists, β-blockers, diuretics, sedatives, sulfonamides and chloramphenicol) in slaughterhouse wastewater and a receiving river is presented. After simultaneous extraction with an Oasis HLB solid-phase extraction (SPE) cartridge and further purification using an amino SPE cartridge, analytes were detected by liquid chromatography–electrospray ionization-tandem mass spectrometry in positive or negative ion mode. Standard addition was used for quantification to overcome unavoidable matrix effects during ESI-MS analysis. Recoveries for most analytes based on matrix-matched calibration in different test matrices were >60%. The method quantification limits of 76 pharmaceuticals were in the range 0.2–30 ng/L. Nineteen compounds of 76 drugs were found in raw and treated slaughterhouse wastewater from four main slaughterhouses in Beijing. Sulfanamides (sulfanilamide, sulfameter), fluoroquenones (ofloxacin, pefloxacin, norfloxacin, ciprofloxacin, enrofloxacin), tetracyclines (tetracycline, oxytetracycline) and macrolides (kitasamycin, tylosin, erythromycin) were most frequently detected, with the highest levels up to ∼3 μg/L in slaughterhouse wastewater and ∼1 μg/L in treated wastewater. Illicit drugs for animal feeding such as clenbuterol and diazepam were commonly detected in slaughterhouse wastewater. These analytes were also observed in a river receiving slaughterhouse wastewater, with a highest level of up to 0.2 μg/L.     

Synthesis and application of a carbamazepine-imprinted polymer for solid-phase extraction from urine and wastewater

A molecularly imprinted polymer (MIP) designed to enable the selective extraction of carbamazepine (CBZ) from effluent wastewater and urine samples has been synthesised using a non-covalent molecular imprinting approach. The MIP was evaluated chromatographically in the first instance and its affinity for CBZ also confirmed by solid-phase extraction (SPE). The optimal conditions for SPE consisted of conditioning of the cartridge using acidified water purified from a Milli-Q system, loading of the sample under basic aqueous conditions, clean-up using acetonitrile and elution with methanol. The attractive molecular recognition properties of the MIP gave rise to good CBZ recoveries (80%) when 100 mL of effluent water spiked with 1 μg L⁻¹ was percolated through the polymer. For urine samples, 2 mL samples spiked with 2.5 μg L⁻¹ CBZ were extracted with a recovery of 65%. For urine, the linear range was 0.05-24 mg L⁻¹, the limit of detection was 25 μg L⁻¹ and precision, expressed as relative standard deviation at 0.5 mg L⁻¹ (n = 3), was 3.1% and 12.6% for repeatability and reproducibility between days, respectively.     

Novel cyromazine imprinted polymer applied to the solid-phase extraction of melamine from feed and milk samples

A water compatible molecularly imprinted polymer (MIP) using cyromazine as a mimic template, methacrylic acid as the functional polymer and ethylene glycol dimethacrylate as the cross-linker was synthesized and used to extract melamine from feed and milk samples via a molecularly imprinted solid-phase extraction (MISPE) protocol. Optimum retention of melamine on the MISPE cartridge was achieved using methanol, and the interferences in the samples were effectively washed out. The binding capacity of the polymer toward melamine was found to be about 500 μg of melamine/g of polymer. The recoveries of 2 μg and 20 μg melamine standard spiked into water extract of blank feeds and milk samples were between 83.4% and 103%, with relative standard deviation <5.6%. The cyromazine-MIP demonstrated high cross-reactivity for melamine and low affinity to cyanuric acid. The ionic bond interaction was regarded as the main factors that dominated the retention of the melamine on the MISPE cartridge.     

橄榄醇分子印迹聚合物的制备及评价(英文)

以橄榄醇为模板分子,α-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,甲苯和十二醇为溶剂,通过本体聚合法制备了橄榄醇分子印迹聚合物。利用平衡结合实验、扫描电镜(SEM)及红外光谱(FTIR)对分子印迹聚合物(MIP)进行了表征,并用该聚合物进行了加标麦麸中橄榄醇的固相萃取(SPE)研究。平衡结合实验表明MIP对模板分子具有更好的识别性。Scatchard分析表明对橄榄醇分子的吸附存在2类不同结合位点,其中高亲和力结合位点和低亲和力结合位点的解离常数分别为0.021和1.002 mmol/L,相应的最大表观结合量分别为18.74和135.9 μmol/g。在优化的固相萃取条件下,MIP固相萃取柱对加标麦麸中橄榄醇的回收率达到97.8%~98.8%,相对标准偏差为2.8%~4.2%(n=5),线性范围为0.1~100 mg/L,检出限(S/N=3)为0.062 mg/L。与非印迹聚合物(NIP)柱及市售聚苯乙烯/二乙烯基苯(PLS)柱相比,MIP柱的选择性更强,回收率更高,纯化效果更好。     

Selective solid-phase extraction of amoxicillin and cephalexin from urine samples using a molecularly imprinted polymer

In this paper we describe, for the first time, a molecularly imprinted polymer (MIP) for the antibiotic amoxicillin (AMX), synthesised by a noncovalent molecular imprinting approach and used to extract AMX selectively from urine samples. The MIP was applied as a molecularly selective sorbent in molecularly imprinted SPE (MISPE) in an off-line mode, where it showed useful cross-selectivity for a structurally related antibiotic, cephalexin (CPX). By using a MISPE protocol, the MIP was able to selectively extract both AMX and CFX from 5 mL of water spiked with 10 mg/L with recoveries of 75 and 78% for AMX and CFX, respectively. When applied to real samples (urine) at clinically relevant concentrations, recoveries from 2 mL of human urine spiked with 20 mg/L decreased slightly to 65 and 63% for AMX and CFX, respectively. To demonstrate further the selectivity of the MIP obtained, a comparison with commercially available SPE cartridges was performed. Improvements in the retention of both AMX and CFX on the MIP were obtained relative to the commercially available cartridges, and the MISPE extracts were considerably cleaner, due to molecularly selective analyte binding by the MIP.     

A new sample preparation method for determination of acidic drugs in sewage sludge applying microwave assisted solvent extraction followed by gas chromatography-mass spectrometry

This paper presents a new sample preparation procedure for determination of selected acidic pharmaceuticals (ibuprofen, naproxen, ketoprofen, and diclofenac) in sewage sludge using microwave assisted solvent extraction, dispersive matrix extraction (DME) followed by the conventionally applied solid phase extraction (SPE), derivatization, and gas chromatography-mass spectrometry. The recoveries calculated from analytical data of spiked sludge samples changed in the range of 80-105% ± 15% for the four pharmaceuticals in mixed and activated sludge depending on the efficiency of the clean-up procedure. The measured concentration values of ibuprofen and naproxen were identical in the mixed and the activated sludge samples. However, ketoprofen and diclofenac showed about twice as high concentration in activated sludge than in the mixed one independently of the applied extraction method. The typical concentration ranges of ibuprofen, naproxen, ketoprofen and diclofenac in sewage sludge were 10-30 ng/g, 30-50 ng/g, 50-130 ng/g, and 50-140 ng/g respectively.     

邻苯二甲酸二（2-丙基庚）酯分子印迹固相萃取剂的制备及其应用

以邻苯二甲酸二辛酯（DOP）为虚拟模板分子,α-甲基丙烯酸（MAA）为功能单体,乙二醇二甲基丙烯酸酯（EDMA）为交联剂,采用沉淀聚合法制备了对邻苯二甲酸二（2-丙基庚）酯（DPHP）具有高选择性的分子印迹聚合物（MIP）。用紫外分光光度法探索了不同功能单体与模板分子的结合能力,与功能单体丙烯酸（AA）相比,MAA与DOP的结合能力更强,其最佳结合的物质的量比为6：1。考察MIP对DOP、DPHP、邻苯二甲酸二甲酯（DMP）、邻苯二甲酸二丁酯（DBP）的选择吸附性能,发现该聚合物对DPHP具有更高的选择吸附性。以制备的聚合物为固相萃取填料,结合HPLC分析,考察了淋洗剂与洗脱剂的种类和用量对DPHP回收率的影响。将DPHP甲醇溶液加载至萃取柱后用1 mL甲醇-水（1：9,v/v）淋洗,5 mL甲醇-乙酸（9：1,v/v）洗脱,DPHP在分子印迹固相萃取（MISPE）柱上的回收率达到96.8%,而在非印迹固相萃取（NISPE）柱上的回收率仅为52.9%。将建立的MISPE-HPLC方法应用于测定兔口服DPHP后不同时间点兔血清中DPHP的浓度,发现其血药浓度的最大值为5.88 μg/mL,达峰值时间为4 h,DPHP加标回收率为90.0%~92.0%,相对标准偏差小于5%。     

Molecularly imprinted solid phase extraction for rapid screening of cephalexin in human plasma and serum

A molecularly imprinted solid phase extraction (MISPE) method was developed for the rapid screening of cephalexin in human plasma and serum. The method employed a micro-column packed with molecularly imprinted polymer (MIP) particles for the selective solid phase extraction (SPE) of cephalexin. Since the MIP interacted indiscriminately with two other α-aminocephalosporins, cefradine and cefadroxil, their removal was ultimately achieved using differential pulsed elution (DPE) with acetonitrile+12% acetic acid. Cephalexin was then determined in a final pulsed elution (FPE) with methanol+1% trifluoroacetic (CF₃COOH, TFA) acid. This excellent selectivity represents a significant advance in analytical separation, demonstrating how a MIP can differentiate between molecules that are structurally dissimilar only in their non-hydrogen-bonding moieties, even if their hydrogen-bonding moieties are identical to each other. With UV detection, a concentration detection limit of 0.1 μg/ml (or 2 ng in 20 μl) was afforded for cephalexin. By increasing the CHCl₃ flow rate to 1.25 ml/min, each MISPE-DPE-FPE analysis required only 2 min to complete. Rapid screening was demonstrated in a modified MISPE-PE method, which used 14% CH₃COOH+CH₃CN as the mobile phase, followed by direct PE with 1% TFA+CH₃OH.     

Synthesis by precipitation polymerisation of molecularly imprinted polymer microspheres for the selective extraction of carbamazepine and oxcarbazepine from human urine

Two molecularly imprinted polymers (MIPs), in the physical form of well-defined polymer microspheres, were synthesised via precipitation polymerisation (PP) using an antiepileptic drug, carbamazepine (CBZ), as template molecule, methacrylic acid as functional monomer and either divinylbenzene 80 (DVB-80) or a mixture of DVB-80 and ethylene glycol dimethacrylate (EGDMA) as crosslinking agents. The MIP obtained using DVB-80 alone as crosslinking agent (MIP A) had a narrow particle size distribution (9.5 ± 0.5 μm) and a well-developed permanent pore structure (specific surface area in the dry state = 758 m² g⁻¹), whereas when a mixture of DVB-80 and EGDMA (MIP B) were used as crosslinking agents, the polymer obtained had a broader particle size distribution (6.4 ± 1.8 μm) and a relatively low specific surface area (23 m² g⁻¹). The molecular recognition character of both polymers was evaluated by means of LC and then a molecularly imprinted solid-phase extraction (MISPE) protocol; CBZ was recognised by both polymers, and useful cross-selectivity for oxcarbazepine (OCBZ), which is the main metabolite of CBZ, also observed. In a detailed bioanalytical study, MIP A was selected in preference to MIP B since MIP A enabled a high volume of sample to be extracted such that lower limits of detection were achievable using this polymer. High recoveries of CBZ and OCBZ were obtained in a MISPE protocol when 50 mL of human urine spiked at 0.2 mg L⁻¹ were percolated through MIP A (90% and 83%, respectively).     

Simultaneous determination of acidic,neutral and basic pharmaceuticals in urban wastewater by ultra high-pressure liquid chromatography-tandem mass spectrometry

In this work, an ultra high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method has been developed for the simultaneous quantification and confirmation of the 20 most consumed pharmaceuticals in Spain in urban wastewater and surface water samples. The scope of the method included acidic, neutral and basic compounds belonging to different therapeutic classes and allows their simultaneous determination in just a single injection, giving realistic information of the most widely consumed pharmaceuticals in only one analysis. An enrichment step based on solid-phase extraction using Oasis HLB cartridges was carried out, followed by UHPLC-MS/MS measurement with a fast-acquisition triple quadrupole mass analyzer. It allowed working with short dwell times and made possible to acquire three simultaneous SRM transitions per compound to assure a reliable identification. Several isotope-labelled internal standards were used as surrogates to correct SPE losses, as well as matrix effects that notably affect quantification of analytes. The method was validated in surface water and effluent and influent urban wastewater at different concentrations from 0.005 μg/L (surface water) to 1.25 μg/L (influent wastewater). The optimized method was applied to the analysis of 84 urban wastewater samples (influent and effluent), with the result that 17 out of 20 compounds monitored were detected in the samples. Analgesics and anti-inflamatories, cholesterol lowering statin drugs and lipid regulators were the major groups found, with diclofenac, ketoprofen, naproxen, 4-aminoantipyrine, bezafibrate, gemfibrozil and venlafaxine being the most frequently detected. The highest concentration level reached was 277 μg/L for salicylic acid in influent wastewater.     

The use of coenzyme Q0 as a template in the development of a molecularly imprinted polymer for the selective recognition of coenzyme Q10

In this work, a novel molecularly imprinted polymer (MIP) for use as a solid phase extraction sorbent was developed for the determination of coenzyme Q10 (CoQ10) in liver extract. CoQ10 is an essential cofactor in mitochondrial oxidative phosphorylation and a powerful antioxidant agent found in low concentrations in biological samples. This fact and its high hydrophobicity make the analysis of CoQ10 technically challenging. Accordingly, a MIP was synthesised using coenzyme Q0 as the template, methacrylic acid as the functional monomer, acetonitrile as the porogen, ethylene glycol dimethacrylate as the crosslinker and benzoyl peroxide as the initiator. Various parameters affecting the polymer preparation and extraction efficiency were evaluated. Morphological characterisation of the MIP and its proper comparison with C18 as a sorbent in solid phase extraction were performed. The optimal conditions for the molecularly imprinted solid phase extraction (MISPE) consisted of 400 μL of sample mixed with 30 mg of MIP and 600 μL of water to reach the optimum solution loading. The loading was followed by a washing step consisting of 1 mL of a 1-propanol solution (1-propanol:water, 30:70,v/v) and elution with 1 mL of 1-propanol. After clean-up, the CoQ10 in the samples was analysed by high performance liquid chromatography. The extraction recoveries were higher than 73.7% with good precision (3.6–8.3%). The limits of detection and quantification were 2.4 and 7.5 μg g⁻¹, respectively, and a linear range between 7.5 and 150 μg g⁻¹ of tissue was achieved. The new MISPE procedure provided a successful clean-up for the determination of CoQ10 in a complex matrix.     

Multiresidue analysis of pollutants as their trimethylsilyl derivatives,by gas chromatography–mass spectrometry

This paper reports a multiresidue analysis procedure which permits the identification and quantification of sixty-three water-soluble pollutants. Subsequent to their solid-phase extraction (SPE) enrichment, analyses of species have been carried out from one solution, by a single injection, as their trimethylsilyl-oxime ether/ester derivatives, by gas chromatography–mass spectrometry, within 31 min. Based on our optimized extraction, derivatization and mass fragmentation studies separation have been performed in the total ion current mode, identification and quantification of compounds have been carried out on the basis of their selective fragment ions. Including various pharmaceuticals, benzoic acid, its substituted species, different aromatic carboxylic acids, cholic acids, unsaturated and saturated fatty acids, aliphatic dicarboxylic acids, as well as synthetic pollutants of various origins (2,4-di-tert-butylphenol, different phthalates). Standard compounds were added to 500 mL effluent wastewater samples, at three concentrations (1–5 μg/L, 5–10 μg/L and 10–20 μg/L). Recoveries, using the Waters Oasis cartridges performing extractions at pH 2, pH 4 and pH 7 proved to be the optimum at pH 4 (average recoveries (94.5%), except for cholesterol (10%), paracetamol (18%) and 2,5-dihydroxybenzoic acid (25%). Carbamazepine could be recovered at pH 7, only. Responses, obtained with derivatized standards proved to be linear in the range of 4–80 μg/L levels. Limit of quantitation values varied between 0.92 ng/L (4-hydroxyphenylacetic acid) and 600 ng/L (dehydrocholic acid) concentrations. One of the most important messages of this work is the confirmation of the origin of blank values. It was shown that contaminants, mainly 2,4-di-tert-butylphenol, different phthalates and fatty acids, are sourced both from the reagents and mainly from the SPE procedure, independent on the cartridge applied. Reproducibilities, characterized with the relative standard deviations (RSDs) of measurements, varied between 0.71% and 10%, with an average of 4.38% RSD. The practical utility of the method was shown by the identification and quantification of the pollutant contents of Hungarian influent and effluent wastewaters (for six consecutive months and that of the Danube River for 2 months).     

On-line solid-phase extraction-HPLC-fluorescence detection for simultaneous determination of puerarin and daidzein in human serum

Response surface methodology (RSM) was applied to the optimization of on-line solid-phase extraction (SPE) parameters, and an automated system of on-line SPE coupled with high-performance liquid chromatography (HPLC) with fluorescence detection was developed for the determination of puerarin and daidzein in human serum. The human serum sample of 50 μL was injected into a conditioned C18 SPE cartridge, and the matrix was washed out with acetonitrile-KH₂PO₄-triethylamine buffer (0.01 M, pH 7.4) (3:97, v/v) for 3 min at a flow rate of 0.25 mL/min. Then the target analytes were eluted and transferred to the analytical column. A chromatographic gradient elution was programmed with the mobile phase consisting of acetonitrile and KH₂PO₄-triethylamine buffer, and the analytes were determined with a fluorescence detector at excitation wavelength of 350 nm and emission wavelength of 472 nm, respectively. The proposed method presented good linear relations (0.85-170 μg/mL for puerarin and 0.2-40 μg/mL for daidzein), satisfactory precision (RSD < 8%), and accredited recovery (92.5-107.8%).     

Simultaneous sample preparation for high-performance liquid chromatographic determination of Vitamin A and β-carotene in emulsified nutritional supplements after solid-phase extraction

Determination of small amounts of the fat-soluble species Vitamin A (VA) (2.5 μg/g) and β-carotene (9 μg/g) from emulsified nutritional supplements containing 50 kinds of co-existing compounds and a fat content between 2000 and 8000 times higher was performed by solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with fluorescence detection set at ex. 350 nm and em. 480 nm, and visible detection at 450 nm using an Inertsil ODS 80A (5 μm) analytical column. Mobile phases of methanol-ethanol (50:50) and acetonitrile-ethanol (70:30) were used for the both vitamins. A Bond Elut C₁₈ cartridge was chosen for SPE after comparison with eight other types of SPE cartridge. Retention time of VA and β-carotene was 7 and 8 min, respectively, giving a limit of detection of ca. 0.1 ng per injection at a signal-to-noise ratio 3:1. Recoveries of VA and β-carotene were over 90% by the standard addition method. Relative standard deviation of VA and β-carotene were ca. 2.9 (n=5) and 2.3% (n=5), respectively.     

Molecularly imprinted stir bar sorptive extraction coupled with high performance liquid chromatography for trace analysis of sulfa drugs in complex samples

A novel sulfamethazine molecularly imprinted polymer (MIP)-coated stir bar for sorptive extraction of eight sulfa drugs from biological samples was prepared. The MIP-coating was about 20 μm thickness with the relative standard deviation (RSD) of 6.7% (n = 10). It was characterized by scanning electron microscope, infrared spectrum, thermogravimetric analysis, and solvent-resistant investigation, respectively. The non-imprinted polymer (NIP)-coating was used for comparison. The adsorptive capacity and selectivity of MIP-coating were evaluated in detail. The MIP-coating showed higher adsorption capability and selectivity than the NIP-coating. The saturated adsorption amount of the MIP-coating was 4.6 times over that of the NIP-coating in toluene. Sulfamethazine could be detected after the MIP-coated stir bar sorptive extraction even at a low concentration of 0.2 μg/L. The MIP-coating also exhibited selective adsorption ability to analogues of the template. A method for the determination of eight sulfa drugs in biological samples by MIP coated stir bar sorptive extraction coupled with high performance liquid chromatography (HPLC) was developed. The extraction conditions, including extraction solvent, extraction time, desorption solvent, desorption time and stirring speed, were optimized. The linear ranges were 1.0-100 μg/L and 2.0-100 μg/L for eight sulfonamides, respectively. The detection limits were within the range of 0.20-0.72 μg/L. The method was successfully applied to simultaneous multi-residue analysis of eight sulfonamides in spiked pork, liver and chicken samples with the satisfactory recoveries.     

Determination of trace bisphenol A in complex samples using selective molecularly imprinted solid-phase extraction coupled with capillary electrophoresis

The highly selective, fast and effective sample pretreatment technique molecularly imprinted solid-phase extraction (MISPE) can overcome the low sensitivity of the highly efficient capillary electrophoresis-UV method (CE-UV). In this work, narrowly dispersible bisphenol A (BPA)-imprinted polymeric microspheres with a high capacity factor of k′ = 6.8 and an imprinted factor of I = 6.53 were investigated as selective solid-phase extraction (SPE) sorbents for use in extraction of BPA from different sample matrices (tap water, wastewater, Yangtze River water, soil from the Yangtze River, shrimp and human urine). Washing and eluting protocols of MISPE were optimized. Under optimal conditions, recoveries of MISPE were investigated. Recoveries were basically constant and the relative standard deviation (RSD) was lower than 5.8% when loading volumes changed from 1 to 50 mL. Recoveries ranged from 71.20% to 86.23% for different sample matrices. Compared with C18 SPE, MISPE had higher selectivity and recovery for BPA. BPA was determined with good accuracy and precision in different complex samples using CE-UV coupled with MISPE. Spiked recoveries ranged from 95.20% to 105.40%, and the RSD was less than 7.2%. Because a large loading volume was achieved, the enrichment efficiency of pretreatment and the sensitivity of this method were improved. The limits of detection of this MISPE-CE-UV method for BPA in tap water, wastewater, Yangtze River water, soil from the Yangtze River, shrimp and human urine were 3.0 μg L^− 1, 5.4 μg L^− 1, 6.9 μg L^− 1, 2.1 μg L^− 1, 1.8 μg L^− 1 and 84 μg L^− 1, respectively.     

HPLC based method using sample precolumn cleanup for the determination of triazines and thiolcarbamates in hemodialysis saline solutions

Solid-phase extraction (SPE) procedures for cleanup and preconcentration followed by HPLC-UV method were investigated for the simultaneous determination of seven low-dosed pesticides in saline concentrates for hemodialysis. The target compounds were ametryn, desmetryn, prometryn, terbutryn, molinate, triallate and butylate. Polyethylene (three different types), teflon, polyurethane and polystyrene, in powder form, were investigated as adsorbents for solid-phase extraction of the analytes from the saline samples. Quantification was performed at 222 nm and the analytes were separated on a LiChrosorb RP-18 (5 μm, 125 mm × 4 mm i.d.) column using gradient elution with water/acetonitrile as mobile phase. The duration each chromatographic run was 18 min including column reconditioning. The efficiency of the different SPE substrates for retaining the analytes from the highly concentrated saline (HCS) samples was discussed. The best performance was achieved with polystyrene as SPE material considering preconcentration factor, precolumn clogging, reusing capability and similarity between the mobile phases for SPE and HPLC procedures. Analyte concentrations as low as 1 μg L⁻¹ could be determined in spiked HCS samples after preconcentration on polystyrene SPE precolumns. Recoveries between 98.7 and 102.2% were obtained from commercial spiked samples. Detection limits ranging from 4.8 (for prometryn) to 46 μg L⁻¹ (for butylate) were calculated (without preconcentration). The within-day relative standard deviations (n = 9) ranged from 2.3 to 4.8%.