Dummy Molecularly Imprinted Polymers Research Articles

Novel dummy molecularly imprinted polymer for simultaneous solid-phase extraction of stanozolol metabolites from urine

Stanozolol, a synthetic derivative of testosterone, is one of the common doping drugs among athletes and bodybuilders. It is metabolized to a large extent and metabolites are detected in urine for a longer duration than the parent compound. In this study, a novel dummy molecularly imprinted polymer (DMIP) is developed as a sorbent for solid-phase extraction of stanozolol metabolites from spiked human urine samples. The optimized DMIP is composed of stanozolol as the dummy template, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker in a ratio of 1:10:80. The extracted analytes were quantitively determined using a newly developed and validated ultrahigh-performance liquid chromatography tandem mass spectrometry method, where the limits of detection and quantitation were 0.91 and 1.81 ng mL−1, respectively, fulfilling the minimum required performance limit decided on by the World Anti-Doping Agency. The mean percentage extraction recoveries for 3’-hydroxystanozolol, 4β-hydroxystanozolol, and 16β-hydroxystanozolol are 97.80% ± 13.80, 83.16% ± 7.50, and 69.98% ± 2.02, respectively. As such, the developed DMISPE can serve as an efficient cost-effective tool for doping and regulatory agencies for simultaneous clean-up of the stanozolol metabolites prior to their quantification.Graphical abstract

Rational design of molecularly imprinted polymers for the recognition of geosmin: A computer-aided and experimental study

Dummy molecularly imprinted polymers (DMIPs) were prepared by combining the molecular imprinting technique with computer simulation for the selective adsorption of geosmin (GSM). The most stable geometric configuration and single-point energy calculations of the molecules were determined by the density functional theory (DFT) method at the M06–2X/6–31 + G (d, p) and the M06–2X/def2-TZVP level, respectively. Meanwhile, the binding energy at different monomer ratios (1:1, 1:2, 1:3 and 1:4) between dummy template with monomer was calculated. According to the theoretical studies, DMIPs materials were synthesized using methacrylic acid (MAA) as the functional monomer, forming a stable molecular/monomer complex in a 1:3 ratio. The DMIPs were characterized using infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The theoretical adsorption capacity (Qmax) of the obtained DMIPs was 1.23 mg g −1, it was approximately twice that of non-imprinted polymers (NIPs). Additionally, the results of the kinetic experiments showed that the DMIPs achieved adsorption equilibrium within 90 min. The combination of computational simulation and experimental approach can shorten the preparation cycle of DMIPs and improve their performance, enabling its efficient application in the analysis of actual samples.

Dummy template molecularly imprinted polymers as potential sorbents in the separation and purification of active compounds in natural products

AbstractMolecular imprinting technology is a promising technique for separating, purifying, and enriching target compounds with high selectivity and sensitivity. The molecularly imprinted polymer (MIP) technique has developed rapidly in the separation and purification of chemical compounds and secondary metabolites of natural products. However, there are real challenges to the isolation of target compounds in natural products such as the unavailability of target compounds and high cost, so it is necessary to develop another approach to MIP synthesis. The dummy template is a solution to the unavailability of target compounds as it will produce a binding site that is specific enough for the target compound through covalent or non‐covalent bonds and the presence of the same functional groups between the target compound and the dummy will result in an interaction between the target compound and the binding site made using the dummy template. In addition, this dummy MIP (DMIP) is the best solution for overcoming the template leakage in traditional MIPs so that the DMIP technique is very good for removing and purifying compounds that are allergenic or toxic in natural product samples (high traceability). This review article will discuss the development of DMIPs in the separation and purification of compounds in natural products and the factors that affect their performance. Our discussion highlights the importance of selecting the right dummy template for optimal DMIP performance. This selection should be based on factors such as functional group similarity, being in the same bioactive compound group, and structural skeleton similarity. In addition, the selection and composition of other DMIP components can also affect the analytical performance of the DMIP.

Dummy molecularly imprinted polymers-agarose gel mixed matrix membrane for extraction of amphetamine-type stimulants in wastewater and urine

Dummy molecularly imprinted polymers (DMIPs) with high selectivity for amphetamine-type stimulants (ATSs) were synthesized using synephrine molecule as a dummy template. The polymers were irregularly massive with a specific surface area of 330 m2g−1. Adsorption experiments found that the imprinting factors for five ATSs (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, and 3,4-methylenedioxy-N-ethylamphetamine) were 2.3∼3.7. The DMIPs-agarose gel mixed matrix membranes (MMMs) were further prepared by incorporating DMIPs in the agarose matrix. MMMs were used to extract five ATSs from wastewater and urine samples. Extraction conditions such as membrane matrix, sample pH, dissolved organic matter content, extraction time, and elution reagent were optimized. Under optimal conditions, the developed MMMs-HPLC-MS/MS method exhibited low limits of detection (0.1∼3.0ng L−1), satisfactory recoveries (91.7∼100%), and good repeatability (RSD<7%, n=3). It was then successfully applied to ATSs analysis in wastewater and urine samples. Recoveries of ATSs in spiked wastewater and urine were 82.0∼98.4% and 82.3∼95.7%, respectively. Moreover, compared with other methods, the present method possessed the advantages of high quantitative ability, suitable for typical environmental conditions, and low application cost. The above results suggested that the developed MMMs-HPLC-MS/MS method could be used as a feasible strategy to extract and determine trace ATSs in wastewater and urine samples.

Synthesis of molecularly-imprinted polymers towards a group of amphetamine-type stimulants by reflux precipitation polymerization with a pseudo template

Determination of amphetamine-type drugs (ATSs) in urine and wastewater is a simplified approach for the widespread monitoring of ATSs abuse. To improve the sensitivity of the analytical methods, molecularly imprinted polymers (MIPs) based solid-phase extraction (SPE) pretreatment attracted great attention in this field. Generally, smaller particle sizes and more uniform morphology of the MIPs could provide higher detection sensitivity. Our previous works showed reflux precipitation polymerization (RPP) is a method for synthesizing monodispersed MIPs with small particle size. However, synthesis of uniform spherical MIPs towards a group of targets has never been reported. Therefore, in the present work, MIPs towards a group of ATSs were synthesized via RPP with a pseudo template for the first time. After screening potential pseudo-templates, N-methylphenylethylamine (MPEA) was selected as the optimal pseudo-template. MPEA-MIPs were characterized by scanning electron microscope (SEM), FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS) spectra. Adsorption isotherms, adsorption kinetics and selectivity were evaluated, and the experimental results indicated that the MPEA-MIPs possessed good selectivity and adsorption property towards ATSs. After optimization of the MIP-SPE procedure, the MIP-SPE cartridges were then coupled with liquid chromatography and tandem mass spectrometry (LC-MS/MS) for determination of ATSs. The evaluation results showed that MIP-SPE-LC-MS/MS displayed good linearity (R2 >0.991) in the linear range (1.0–50.0 µg/L for urine and 0.5–50.0 µg/L for wastewater), and low matrix effect (85–112%). The limit of detection (LOD) was 0.05 -0.29 µg/L, and the accuracy (85–115%) and repeatability (RSD ≤ 15%) were satisfactory at low, medium and high concentrations. To the best of our knowledge, this is the first time that dummy MIPs towards a group of ATSs were synthesized by RPP polymerization, which showed great potential for the detection of ATSs in urine and wastewater.

Dummy molecularly imprinted solid-phase extraction-SERS determination of AFB1 in peanut

As a class I carcinogen, aflatoxin B1 (AFB1) contamination in foods and feeds accounts for 75 % of the total mycotoxin contamination. In this work, a simple and reliable surface-enhanced Raman spectroscopy (SERS) method for sensitive and selective detection of AFB1 in peanut samples integrated with dummy molecularly imprinted polymers (DMIPs) is developed. N-isopropylacrylamide (NIPAM) and 7-ethoxycoumarin (7-EOC) are chosen as monomer and dummy template, respectively and their ratio was screened through molecular design in both of kinetic and static adsorption views to form the optimal DMIPs. As-prepared dummy molecularly imprinted solid-phase extraction (DMISPE) could selectively enrich AFB1 from peanut samples. Finally, a liquid–liquid interface self-assembly constructed thioctic acid-decorated AgNPs monolayer film (TA-AgNPs MF) as a SERS-active substrate is employed to determine the amount of AFB1 eluted from DMISPE. SERS assay shows high detection sensitivity for AFB1 in peanut samples with limit of detection of 0.1 μg L−1 and a linear concentration relationship range from 0.1 to 10 μg L−1.

Selective extraction of synthetic cathinones new psychoactive substances from wastewater, urine and cocktail using dummy molecularly imprinted polymers

Dummy molecularly imprinted polymers (DMIPs) for selective extraction of five common synthetic cathinones (SCs) were prepared by bulk polymerization. DMIPs materials possessed narrow diameter distribution (30–60 µm) and large specific surface area (329.6 m2 g-1). Imprinting factors for cathinone, methcathinone, mephedrone, methylone and ethylone were 1.11–1.82. DMIPs could also quickly adsorb SCs from aqueous solutions within 5 min. Therefore, the materials were used as solid-phase extraction (SPE) sorbents to selectively extract five SCs in complex samples. An accurate and sensitive analytical method based on DMIPs-SPE combined with HPLC-MS/MS was established. Under optimal conditions, the established method showed low limits of detection (0.002–0.1 ng mL-1), satisfactory recoveries (84.1–97.7%) and good repeatability (relative standard deviation (RSD) below 9%). The method was successfully verified using wastewater, urine and cocktail samples. Recoveries of SCs at three spiking levels were in the range of 75.1–98.6%, with RSD values below 7.0%. Compared with commercial sorbents, DMIPs showed better clean-up ability with matrix effect values of −24.1%–8.3% for all SCs in wastewater, urine and cocktail samples. Therefore, the developed DMIPs-SPE-HPLC-MS/MS strategy could be used as a specific and cost-effective method for sensitive determination of SCs in complex samples.

Dummy molecularly imprinted polymers for class-selective extraction of amphetamine-type stimulants from alcoholic and nonalcoholic beverages

Molecularly imprinted polymer was constructed for the first time through dummy imprinting strategy with homopiperonylamine as dummy template. The prepared dummy molecularly imprinted polymer (DMIP) showed high class selectivity towards the most popular amphetamine-type stimulants (ATSs) such as methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxy-amphetamine, and 3,4-methylenedioxy-N-ethylamphetamine with the imprinting factors of 2.280∼3.698 and selectivity factors of 1.654∼3.698. Moreover, ATSs could be rapidly adsorbed from water with the equilibrium time within 5 min. Hydrogen-bonding interaction between the amino groups of ATSs and carboxy on DMIP could be dominated adsorption mechanism. DMIP was employed as solid phase extraction (SPE) sorbents. Under the optimum extraction conditions, the method using DMIP-based SPE and high performance liquid chromatography–tandem mass spectrometry showed good linearity in the range of 0.025∼1.00 μmol L−1, good repeatability (RSD 4.8∼8.6%, n = 5) and low limits of quantification (0.007∼0.200 ng mL−1, S/N = 10). Satisfactory recoveries (72.5∼120%) with low RSD values (<10%) were obtained for all targets viz. spiked coke carbonated drinks, beer and cocktail. Compared with other commercial SPE sorbents, DMIP exhibited lower matrix effect (ME) for coke, beer and cocktail with ME values of 101∼124%, 75.8∼80.2% and 103∼128%, respectively. The obtained results suggested that the developed DMIP materials could be a potential candidate for pretreatment of ATSs in alcoholic and nonalcoholic beverages.

Dummy molecularly imprinted polymer (DMIP) as a sorbent for bisphenol S and bisphenol F extraction from food samples

Dummy molecularly imprinted polymer (DMIP) was prepared towards bisphenol S and bisphenol F employing bisphenol A as a dummy template. Liquid chromatography with UV and fluorescence detection (LC-UV/FLD) was used for the separation and quantification of these analytes. The maximum adsorption capacity of DMIP was 20.9 mg g−1 and 18.6 mg g−1 for BPS and BPF, respectively. By applying solid phase extraction with DMIP prior to LC-UV/FLD, the limits of detections achieved in food samples can be lowered to 0.5 ng g−1 for BPF and 5 ng g−1 for BPS. Only 5 mg of DMIP sorbent was sufficient to achieve good recoveries (71–113%) and precision (RSD 0.1–3.2%, n = 3) for analyzed liquid food samples spiked at two concentration levels 0.25 mg L − 1 and 0.40 mg L − 1. For preconcentrated pineapple extract spiked with 0.5 mg•L − 1 of both analytes, also very good recovery was obtained (89% for BPS and 99% for BPF), significantly higher than for conventional SPE cartridges such as Oasis HLB and Affinimip®. The analytical characterization of the proposed method makes it suitable for monitoring programs, intended for the assessment of human exposure to bisphenol S in food samples, without using much expensive mass spectrometry detection.

Synthesis of dummy-template molecularly imprinted polymer adsorbents for solid phase extraction of aminoglycosides antibiotics from environmental water samples

A novel dummy molecularly imprinted polymers (DMIPs) for aminoglycoside antibiotics (AAs) was prepared for the first time by precipitation polymerization using raffinose as template molecule, methacrylic acid as functional monomer and trimethylolpropane triacrylate as cross-linker. The obtained DMIPs were characterized in detail, and their adsorbing and recognition performance were evaluated. The results showed that the DMIPs exhibited specific recognition towards six AAs with large adsorption capacity. The dummy molecularly imprinted solid phase extraction (DMISPE) conditions including elution/washing solutions and sample loading volumes were optimized. Under optimum conditions, a convenient and efficient method for the determination of AAs in environmental water samples based on DMISPE coupling with hydrophilic interaction-high performance liquid chromatography-tandem mass spectrometry was established. The developed method showed good linearity with correlation coefficients higher than 0.9921 for all the analytes and good recoveries (70.8–108.3%) with relative standard deviations from 2.6 to 11.4% spiked at three different concentration levels in water samples. The limit of detection (S/N = 3) ranged from 0.006 to 0.6 ng/mL. The results demonstrated good potential of DMIPs for sample pretreatment of trace AAs in environmental water samples.

Dummy Molecularly Imprinted Matrix Solid-Phase Dispersion for Selective Extraction of Seven Estrogens in Aquatic Products

A simple and sensitive method based on dummy molecular imprinting and matrix solid-phase dispersion (DMI–MSPD) was developed for the simultaneous detection of estrogens including estrone, 17β-estradiol, aestriol, ethinylestradiol, dienestrol, diethylstilbestrol, and hexestrol in aquatic products. The method was followed by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). In this method, the dummy molecularly imprinted polymers (DMIPs) were synthesized by Pickering emulsion polymerization, in which genistein was used as template molecular. According to the results of the experiment, the method of DMI–MSPD showed high affinity and a good selectivity for the seven estrogens in aquatic products. Compared with conventional MSPD sorbents, including C18, Florisil, and silica gel, the DMIPs could not only selectively elute the seven estrogens from aquatic products but also reduce matrix disruptions. The mean recovery rates of seven estrogens ranged from 89 to 103%, with relative standard deviations less than 5%. The limits of detection (LOD) and limits of quantitation (LOQ) were 1.6–2.8 ng g−1 and 5.4–7.6 ng g−1, respectively. Therefore, the proposed method can be well applied to the detection of estrogens in aquatic products.

Dummy molecularly imprinted solid phase extraction of climbazole from environmental water samples

Dummy molecularly imprinted polymer (DMIP) for climbazole (CBZ) was synthesized for the first time employing miconazole (MNZ) as the dummy template together with methacrylic acid (MAA) monomer, ethylene glycol dimethacrylate (EGDMA) cross-linker and acetonitrile (ACN) porogen. The selectivity and capacity of the prepared MNZ-DMIP was estimated for CBZ by high-performance liquid chromatography (HPLC) and equilibrium binding experiments. Imprinting factor (IF) with a value of 7.0 was achieved, much higher than the CBZ templated MIP (IF = 3.5). Heterogeneous binding sites were found in the MNZ-DMIP, the corresponding saturation capacity and dissociation constant for the high and low affinity binding sites were 6.761 μmol g–1 and 0.3027 mmol L–1, 43.60 μmol g–1 and 4.055 mmol L–1, respectively. High efficient method based on dummy molecularly imprinted solid phase extraction (DMISPE) coupled with HPLC was established for the selective enrichment of CBZ in river and tap water using MNZ-DMIP as sorbent. DMISPE conditions including sample loading pH/volume, selective washing and elution solvents were carefully optimized. The developed method showed good recoveries (82.3–96.2%) and repeatability (RSDs 0.6–4.9%, n = 5) for samples spiked at three different concentration levels (0.2, 1.0 and 5.0 μg L–1). The detection limit was determined as 0.012 μg L–1. The results demonstrated good potential of this method for sample pretreatment of CBZ in environmental water samples.

Preparation and evaluation of dummy-template molecularly imprinted polymer as a potential sorbent for solid phase extraction of imidazole fungicides from river water

Dummy molecularly imprinted polymer (DMIP) for imidazole fungicides was prepared for the first time using alpha-(2,4-Dichlorophenyl)-1H-imidazole-1-ethanol (DCE) as the fragment template. The imprinting selectivity of DCE-DMIP was evaluated for climbazole (CBZ), clotrimazole (CMZ) and miconazole (MNZ) by liquid chromatography, imprinting factors of 10.9, 10.8 and >10.7 were achieved, respectively. Heterogeneous binding sites were found in the DCE-DMIP, the corresponding saturation capacity and dissociation constant for the high affinity binding sites were 13.05 μmol g–1 and 0.4701 mmol L–1. High efficient method based on dummy molecularly imprinted solid phase extraction (DMISPE) coupled with HPLC was established for the selective enrichment of CBZ, CMZ and MNZ in river water using DCE-DMIP as sorbent. DMISPE conditions including sample loading pH/volume, selective washing and elution solvents were carefully optimized. The developed method showed good recoveries (84.2–95.0%) and precision (RSDs 1.7–5.0%, n = 5) for samples spiked at two different concentration levels (0.5 and 2.5 μg L–1). The detection limits were ranged from 0.023 to 0.031 μg L–1. The results demonstrated good potential of this method for sample pretreatment of azole fungicides in environmental water samples.

Dummy molecularly imprinted polymers based on a green synthesis strategy for magnetic solid-phase extraction of acrylamide in food samples

In this work, novel dummy molecularly imprinted polymers (DMIP) with propanamide as a dummy template molecule were prepared based on a green synthesis strategy of less consumption of hazardous/organic reagents and at mild conditions for magnetic solid-phase extraction (MSPE) of acrylamide in biscuit samples, followed by high performance liquid chromatography (HPLC) determination. The resultant DMIP was well characterized by FT-IR, SEM, TEM and VSM, exhibiting uniform nanoscale coreshell structure and good magnetic property in favor of simple rapid separation. Several main variables influencing MSPE efficiency were investigated, including DMIP dosage, sample solution pH, extraction time and desorption solvent; central composite design (CCD) and response surface methodology (RSM) were employed to assist in the MSPE condition optimization with rapidity and reliability. Under optimized conditions, excellent linearity for acrylamide was obtained in the range of 5.0–5000.0 µg kg−1, and low detection and quantification limits were 1.3 µg kg−1 and 4.4 µg kg−1, respectively. The method recoveries at five spiked concentrations were found within 86.0–98.3% with relative standard deviations (RSDs) of 1.2–4.1%. Furthermore, endogenous acrylamide was detected in five different biscuit samples and the RSDs values were lower than 3.3%. The present study suggested promising perspectives of water-compatible eco-friendly DMIP based MSPE-HPLC method for highly effective sample pretreatment and targeted analytes determination in complicated matrices.

Preparation and characterization of dummy-template molecularly imprinted polymers as potential sorbents for the recognition of selected polybrominated diphenyl ethers

The main aim of this work was to conduct the preliminary/basic research concerning the preparation process of a new dummy molecularly imprinted polymer (DMIP) materials. Developed DMIPs were proposed as a sorption material in solid-phase extraction (SPE) technique for recognition of selected low mass polybrominated diphenyl ethers (PBDEs) – PBDE-47 and PBDE-99. Four new DMIPs were synthesized employing bulky polymerization technique by application of structural analogue of low mass PBDEs - 4,4′-Dihydroxydiphenyl ether, as a dummy template. The DMIPs and corresponding non-imprinted polymers were prepared using different functional monomers: methacrylic acid; methyl methacrylate and different porogen agents: acetonitrile and tetrahydrofuran. The polymerization reaction was thermally initiated with 1,1′-azobis (cyclohexanecarbonitryle). Ethylene glycol dimethacrylate was applied as a cross-linker. To optimize geometries and to calculate energies of the respective template-monomer complexes, the computational molecular modeling method was employed. The particles morphology and physicochemical characteristics of developed DMIPs and their equivalent NIPs were performed using nitrogen sorption porosimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy. The sorption capacities of prepared DMIPs and corresponding NIPs were studied using standard binding test. The adsorption capability studies give a possibility to assess the imprinting factor (IF) values, which were in the range from 1.1 to 4.0, depending on the DMIP type. The recovery values of PBDE-47 and PBDE-99 from prepared organic solutions were in the range from 43 to 92%, depending on the studied DMIP. Performed basic laboratory studies give a possibility to select the optimal DMIP material which might be applied in the environmental samples preparation process as a potential sorbent for the recognition of low mass PBDEs.

Pipette tip dummy molecularly imprinted solid-phase extraction of Bisphenol A from urine samples and analysis by gas chromatography coupled to mass spectrometry.

Molecularly imprinted polymers (MIPs) were synthesized and used as sorbent for Bisphenol A (BPA) pipette tip solid-phase microextraction from urine samples and BPA analysis by gas chromatography coupled to mass spectrometry (GC-MS). The MIPs were synthesized by the sol-gel methodology. Aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) were used as functional monomer and cross-linking reagent, respectively. BPA and tetrabromobisphenol A (TBBPA) were evaluated as template during MIP synthesis. The BPA-based MIP displayed slightly higher extraction efficiency than the TBBPA-based dummy molecularly imprinted polymer (DMIP), but the TBBPA-based DMIP was selected as sorbent to minimize interference from leaked template. Comparison of the TBBPA-based DMIP, BPA-based MIP, and non-imprinted polymer (NIP) extraction efficiencies attested that the TBBPA-based DMIP was selective. The synthesized polymers were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The TBBPA-based DMIP was reused for over 100 times, which confirmed its robustness. The developed method was linear from 50 to 500ngmL-1. Precision values had coefficient of variation (CV) ranging from 4 to 14%. The accuracy relative standard deviation values (RSD) varied from -13.6 to 12.3%.

Fluorescent competitive assay for melamine using dummy molecularly imprinted polymers as antibody mimics

A fluorescent competitive assay for melamine was first developed utilizing dummy molecularly imprinted polymers (DMIPs) as artificial antibodies. This method is based on the competition between fluorescent substances and the unlabeled analyte for binding sites in synthesized DMIPs and the decreased binding of fluorescent substances to DMIPs due to increased concentrations of melamine in the solutions. DMIPs for melamine were synthesized under a hot water bath in the presence of the initiator azobisisobutyronitrile (AIBN) using 2,4-diamino-6-methyl-1,3,5-triazine (DAMT) as a dummy template, methacrylic acid (MAA) as a functional monomer, and ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent. The adsorption capacity and selectivity of DMIPs for melamine were evaluated by the isothermal adsorption curve and Scatchard analysis. The evaluation results showed that the synthesized DMIPs had specific recognition sites for melamine and the maximum adsorption amount was 1 066.33 μg g−1. Later, 5-(4,6-dichlorotriazinyl) amino fluorescein (DTAF) with a triazine ring, which slightly resembles melamine, was selected as the fluorescent substance. The fluorescent competitive assay using DMIPs as the antibody mimics was finally established by selecting and optimizing the reaction solvents, DMIPs amount, DTAF concentration, and incubation time. The optimal detection system showed a linear response within range of 0.05–40 mg L−1 and the limit of detection (LOD) was 1.23 μg L−1. It was successfully applied to the detection of melamine in spiked milk samples with satisfactory recoveries (71.9 to 86.3%). According to the comparative analysis, the result of optimized fluorescent competitive assay revealed excellent agreement with the HPLC-MS/MS result for melamine.

Determination of hydroxylated polychlorinated biphenyls by offline solid-phase extraction-liquid chromatography–tandem mass spectrometry using a molecularly imprinted polymer as a sorbent for sample preconcentration

Hydroxylated polychlorinated biphenyls (OH-PCBs) can be detected by liquid chromatography–mass spectrometry coupled to solid-phase extraction (SPE) using a dummy molecularly imprinted polymer (DMIP) as a sorbent. The DMIP is prepared by using an analogue of OH-PCBs (i.e., 4, 4-dihydroxybiphenyl) as a dummy template, to avoid the leakage of the target molecules. The DMIP-SPE sorbent shows good recoveries for OH-PCBs at pH 11 due to the charge-assisted hydrogen bondings between OH-PCBs and the DMIP. It has been found that the DMIP is much more effective and selective than the traditional C18-SPE method. The sample pH, polymer dosage, elution solvent and volume have been optimized for higher recoveries. Under the optimum experimental conditions, OH-PCBs can be detected in the linear concentration range of 0.05–1.0pM, with the detection limits ranging from 11fM to 82fM for 4′-OH-CB 9, 4′-OH-CB 30, 4′-OH-CB 61, 4′-OH-CB 106 and 4′-OH-CB 112. The proposed system has been successfully applied to the determination of trace OH-PCBs in spiked water samples with recoveries in the range of 89–110%.

Molecularly imprinted polymers with synthetic dummy template for simultaneously selective removal and enrichment of ginkgolic acids from Ginkgo biloba L. leaves extracts

Dummy molecularly imprinted polymers (DMIPs) for simultaneously selective removal and enrichment of ginkgolic acids (GAs) during the processing of Ginkgo biloba leaves have been prepared. Two dummy template molecule with similar structural skeleton to GAs, 6-methoxysalicylic acid (MOSA, DT-1) and 6-hexadecyloxysalicylic acid (HOSA, DT-2), have been designed and synthesized. The performance of the DMIPs and NIPs were evaluated including selective recognition capacity, adsorption isotherm, and adsorption kinetics. The selective recognition capacity of the three GAs with four analogues on the sorbents illustrated that the DMIPs sorbents have high specificity for GAs. An efficient method based on DMIP-HOSA coupled with solid-phase extraction (SPE) was developed for simultaneously selective removal and enrichment of ginkgolic acids (GAs) during the processing of Ginkgo biloba leaves. The method showed excellent recoveries (82.5–88.7%) and precision (RSD 0.5–2.6%, n=5) for licorice extracts, Gastrodia elata extracts and pepper extracts spiked at three concentration levels each (50, 100, 200μgmL−1). The results indicated that GAs and standardized Ginkgo biloba leaves extracts could be obtained simultaneously through the DMIP-SPE.

Highly class-selective solid-phase extraction of bisphenols in milk, sediment and human urine samples using well-designed dummy molecularly imprinted polymers

Dummy molecularly imprinted polymers (DMIPs) towards bisphenols (BPs) were prepared employing 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) and phenolphthalein (PP) as dummy templates. The selectivity of the resulting DMIPs was evaluated by high-performance liquid chromatography (HPLC). Both PP-DMIP and THPE-DMIP showed excellent class selectivity towards bisphenols. THPE-DMIP prepared using the template molecule with three hydroxyphenyl functionalities achieved higher imprinting factors (IF) for the bisphenols over a range of 7.9–19.8. An efficient approach based on dummy molecularly imprinted solid phase extraction (DMISPE) coupled with HPLC-DAD was developed for selective extraction of eight bisphenols in sediment, milk and human urine samples using THPE-DMIP as sorbents. The method showed good recoveries (82–102%) and precision (RSD 0.2–4%, n=3) for these samples spiked at two concentration levels (25 and 250ngg−1 or ngmL−1). The detection limits ranged between 0.6 and 1.1ngg−1 or ngmL−1. Efficient removal of sample matrix and interferences was also achieved for these samples after DMISPE process. The results demonstrated great potential of the optimized methods for sample preparation in the routine analysis of trace BPs in complex samples.