Dummy Template Research Articles

A Novel Magnetic Molecular Imprinted Polymer for Selective Extraction of Zearalenone from Cereal Flours before Liquid Chromatography-Tandem Mass Spectrometry Determination.

Zearalenone (ZEN) is a nonsteroidal estrogenic mycotoxin produced by various Fusarium species and commonly occurring in corn and other cereals. Even though its acute toxicity is low, still the estrogenic activity of ZEN and metabolites is a matter of concern. In this work, a new magnetic molecularly imprinted polymer (mMIP) for the selective extraction of ZEN from cereal flours is presented. The mMIP was synthesized previously using quercetin as dummy template, and here we wanted to test its applicability to complex food samples. Analyte determination was carried out by high-performance liquid chromatography coupled to tandem mass spectrometry. The selectivity of the mMIP and the main validation method parameters were assessed. In particular, even in samples as complex as cereals, matrix effect was negligible. Although the mMIP showed cross-selectivity towards both ZEN-related and quercetin-related compounds, nonetheless ZEN recovery was > 95% for the two lower spiking levels, and the quantification limit was 0.14 ng g−1, i.e., ca. 500 times lower than the maximum limit fixed for most cereals by European law. Therefore, the material, also in comparison with a commercial sorbent, appears suitable for the application in food analysis, also to isolate ZEN at trace levels.

Superparamagnetic core-shell dummy template molecularly imprinted polymer for magnetic solid-phase extraction of food additives prior to the determination by HPLC

A highly sensitive and selective method for the simultaneous extraction and determination of trace vanillin, ethyl vanillin, maltol and ethyl maltol in beverage samples using magnetic solid-phase extraction coupled with high-performance liquid chromatography (HPLC) was developed. The novel superparamagnetic dummy template molecularly imprinted polymers (Fe3O4@MDMIP) were prepared by adopting a sol-gel approach using 3-hydroxy-2,6-bis(hydroxymethyl) -4-pyrone, whose structure was similar to that of the vanillin and maltol, as the dummy template for selective extraction of vanillin, ethyl vanillin, maltol and ethyl maltol. The obtained Fe3O4@MDMIP exhibits high uniformity and monodispersity. Besides, Fe3O4@MDMIP has an outstanding magnetic susceptibility (56.33 emu g−1) than common obtained samples. The maximal adsorption capacity (Qmax) of the resulting Fe3O4@MDMIP for the four food additives was up to 609.99 mg g−1. The imprinting factors of the Fe3O4@MDMIP ranged from 2.07 to 2.71 for the four food additives, which indicated that the obtained adsorbents have high selectivity. Under the optimum experimental conditions, the Fe3O4@MDMIP was successfully applied to the magnetic solid-phase extraction of vanillin, ethyl vanillin, maltol and ethyl maltol followed by HPLC determination in beverage samples. Validation experiments indicated that the developed method presented good linearity (2.07–463 ng mL−1), satisfactory precision (RSD, 2.68–6.91%), and high recovery (91.2–107.1%). The limits of detection ranged from 44 to 201 ng L−1, and the enrichment factors were in the range of 432–484. The results demonstrated great potential of the optimized method for sample preparation in routine analysis of trace food additives.

The determination of patulin from food samples using dual-dummy molecularly imprinted solid-phase extraction coupled with LC-MS/MS

A molecularly imprinted polymer (MIP) with specific adsorption for patulin was successfully polymerized by precipitation polymerization using 2-oxindole (2-oxin) and 6-hydroxynicotinic acid (6-HNA) as dummy template molecules, methylacrylic acid (MAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a crosslinker, 2,2-azobis-(2-methylpropionitrile) (AIBN) as a initiator, and methanol as a porogen solvent. The molecularly imprinted solid phase extraction (MI-SPE) column was prepared using the polymer as a sorbent and applied for the selective extraction of patulin from real samples. The results showed that the MI-SPE method had high selectivity and specific adsorption towards patulin with mean recoveries ranged between 81.3% and 106.3% and a relative standard deviation (RSD) < 4.5%. Additionally, the developed MI-SPE method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) exhibited good linearity in the range of 1–100 ng mL−1 with correlation coefficients (R2) >0.998. The limits of detection (LODs, S/N = 3) were 0.05–0.2 ng g−1, and the limits of quantification (LOQs, S/N = 10) were 0.2–0.5 ng g−1. The developed method showed a better purification and higher patulin recovery for real samples than the quick, easy, cheap, effective, rugged, safe “QuEChERS” method.

Preparation and Application of Molecularly Imprinted Monolithic Extraction Column for the Selective Microextraction of Multiple Macrolide Antibiotics from Animal Muscles

This study aimed to prepare a molecularly imprinted monolithic extraction column (MIMC) inside a micropipette tip by situ polymerization with roxithromycin as the dummy template. The polymers possessed excellent adsorption capacity and class-specificity to multiple macrolide drugs. MIMC was directly connected to a syringe for template removal and for the optimization of extraction conditions without any other post-treatment of polymers. A liquid chromatography-tandem mass spectrometric method was developed for the selective microextraction and determination of macrolide antibiotics in animal muscles based on MIMC. High recoveries of 76.1–92.8% for six macrolides were obtained with relative standard deviations less than 10.4%. MIMC exhibited better retention ability and durability when compared with the traditional C18 and HLB cartridges. The proposed method shows a great potential for the analysis of macrolide drugs at the trace level in animal foodstuffs.

Attapulgite/hydrophilic molecularly imprinted monolithic resin composite for the selective recognition and sensitive determination of plant growth regulators in cucumbers

In this study, through in-situ polymerization process, a novel composite of attapulgite/hydrophilic molecularly imprinted monolithic resin (AT/HMIMR) were prepared in pipette tips for extraction trace plant growth regulators in cucumbers. In the preparation procedure, fibrillar attapulgite nanoparticles were embedded to increase extraction capacity, polyethyleneglycol-6000 was employed as a dual-function porogen, that acted as both the structure-directing agent of the HMIMR and the attapulgite dispersant. N-(1-naphthyl) ethylenediamine dihydrochloride was used as a dummy template to accurate quantification on extraction procedures. Experimental parameters of AT/HMIMR for extracting plant growth regulators from cucumbers were optimized, and the results showed that the recoveries of ranged from 92.4% to 101.1% with relative standard deviations ≤ 6.5% (n = 3). Considering its microporous monolithic column structure, multiple adsorption mechanism, and specific selectivity, AT/HMIMR shows promise for applications that require specific recognition for the analytes in real complex samples.

Comparative evaluation of aflatoxin and mineral binding activity of molecular imprinted polymer designed for dummy template using in vitro and in vivo models

The amelioration of aflatoxicosis in ducklings was examined by feeding molecular imprinted polymer (MIP) synthesized to target the aflatoxin B1 (AFB1) analog molecule [5, 7-dimethoxycoumarin (DMC)] as a smart and novel toxin binder in comparison to a commercial toxin binder (CTB). MIP was characterized with some techniques, such as scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) that showed morphology and thermal resistance of MIP, respectively. The SEM showed that more pores and big cavities were formed in the network of the MIP. TGA plots of MIP showed dehydration at temperatures of about 31 °C–200 °C and gradual decomposition until 300 °C. The in vitro and in vivo ability of MIP and CTB to adsorb some minerals (Ca, Cu, Mg, P and Zn) was evaluated. The in vivo efficacy of MIP as an aflatoxins (AFs) binder in duckling exposed to aflatoxin-contaminated feed from 4 to 18 d of age was also compared to that of the CTB. A total of 240 4-d-old ducklings were assigned to experimental diets. Each diet was replicated four times with 10 birds in each pen, and the initial body weight classes were considered as blocks. The experimental treatment diets included: 1- Control (basal diet without any additive or AFs), 2- MIP (5 g/kg diet), 3- CTB (5 g/kg diet), 4- AFs (0.2 mg/kg diet), 5- AFs + MIP (0.2 mg/kg + 5 g/kg diet), and 6- AFs + CTB (0.2 mg/kg + 5 g/kg diet). In vitro study may clearly reflect the possibility of adsorbing minerals by CTB as compared to MIP whilst the results were not confirmed by in vivo study and it seems that reduction in plasma levels of minerals is related to the adverse effects of AFs. Livers showed histopathological alterations, with bile-duct proliferation of all aflatoxin fed ducklings. Macroscopic study indicated liver of birds fed diets containing AFs showed abnormal signs including yellowish, friable and rounded shape without protective effect of MIP and CTB. The results obtained from in vivo study indicate the partial alleviation of the adverse effects of AFs in ducklings by dietary supplementation of MIP and CTB (5 g/kg) on plasma albumin, Zn, Mg and Ca.

Preparation of dummy molecularly imprinted polymers for extraction of Zearalenone in grain samples

Surface molecularly imprinted polymers (MIL-101@MIPs) were prepared using MIL-101 as supporting core, imprinted polymers as selective shell synthesized with coumarin-3-carboxylic acid as dummy template of Zearalenone (ZEN), methacrylic acid as functional monomer, and ethylene glycol dimethacrylate hydroxyethyl methacrylate as cross-linker. The polymers were characterized by scanning electron microscopy, transmission electron microscopy, energy–dispersive X-ray spectroscopy, X-ray diffraction, and particle-size distribution analyses. MIL-101@MIPs were used as the sorbent to compose the self-made cartridge. The cartridge was used to purify and enrich ZEN from real samples. Under optimized SPE conditions, a self-made cartridge can be reused for at least seven cycles. Elution was monitored with a high-performance liquid chromatography–fluorescence detection system. The linearity of the method ranged within 6.25–250 ng kg−1. The limits of detection ranged within 2.09 – 4.16 ng kg−1, and the limits of quantification ranged within 6.25 –12.50 ng kg−1, respectively. The matrix effects of four real samples were discussed. The spiking recoveries of ZEN ranged within 81.70%–90.10% with relative standard deviations lower than 5.56%. The performance of the self-made cartridge and immunoaffinity column was compared by chromatography.

Determination of sulfonamides in meat with dummy-template molecularly imprinted polymer-based chemiluminescence sensor.

In this study, a molecularly imprinted polymer capable of recognizing 15 sulfonamides was first synthesized with sulfabenz as the dummy template. The calculation results from computation simulation showed that the specific 3D conformation of the template had an important influence on the polymer's recognition ability. Then, the polymer was used as recognition reagent to prepare a chemiluminescence sensor on a conventional 96-well microplate for the determination of the residues of 15 sulfonamides in meat (chicken and pork). Due to the 4-(imidazol-1-yl)phenol-enhanced luminol-H2O2 system, the limits of detection for the 15 analytes were in the range of 1.0-12pg/mL. The recoveries from the standard fortified blank samples were in the range of 72.7-99%. Furthermore, one assay could be finished within 30min, and the sensor could be reused 4 times. Therefore, this sensor could be used as a very useful tool for routine screening of residues of sulfonamides in meat samples. Graphical abstract Assay procedures of the molecularly imprinted polymer-based chemiluminescence sensor for determination of sulfonamides.

A Novel CdSe/ZnS Quantum Dots Fluorescence Assay Based on Molecularly Imprinted Sensitive Membranes for Determination of Triazophos Residues in Cabbage and Apple.

In the present study we have developed a direct competitive CdSe/ZnS quantum dot (QD) fluorescence assay based on micro-array-imprinted membranes for the determination of triazophos in cabbage and apple. The imprinted membranes were directly synthesized on the surface of a 96-well plate by thermal polymerization using triadimefon as the dummy template. Under optimal conditions, the assay showed an excellent linear response over the concentration ranges of 0.1–10,000 μg L−1 with a good coefficient of determination (R2= 0.982). The sensitivity (IC50) and limit of detection (LOD, expressed as IC15) of the developed assay were 3.63 mg L−1 and 0.31 μg L−1, respectively. The applicability of the developed approach was tested for detecting triazophos in incurred samples. The method showed excellent recoveries (109.6–118.9%) and relative standard deviations (RSDs) between 9.9 and 19.5%. The obtained results correlated well with those obtained by LC-MS/MS (R2= 0.9995). The competitive assay using CdSe/ZnS QDs as fluorescence-labeled probe showed good sensitivity, steady and fast response, and excellent anti-interference ability compared to conventional fluorescence-quenching methods. Finally, the feasibility of the proposed methodology was successfully applied for detection of triazophos in real samples.

Rapid detection of aflatoxin B1 by dummy template molecularly imprinted polymer capped CdTe quantum dots.

A novel and sensitive fluorescent sensor was synthesized for the rapid and specific recognition of aflatoxin B1 (AFB1) by our combining molecular imprinting techniques with quantum dot technology. Molecularly imprinted polymers coated CdTe quantum dots (MIP@CdTe QDs) were prepared through the Stöber method with 5,7-dimethoxycoumarin as a dummy template. 3-Aminopropyltriethoxysilane was selected as the functional monomer, and tetraethyl orthosilicate was used as the cross-linking agent. The best molar ratio of 5,7-dimethoxycoumarin to functional monomer to cross-linker was 4:20:15. The MIP@CdTe QD composites were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and fluorescence spectroscopy. Under the optimum conditions, the relative fluorescence intensity of the MIP@CdTe QDs showed adequate linearity with AFB1 concentration over the range from 80 to 400 ng/g. The detection limit is 4 ng/g, according to 3s/K. Finally, the method was successfully applied to the quantitative determination of AFB1 in real samples. The spike recoveries at different spiking levels ranged from 99.20% to 101.78%, which were consistent with those measured by ultrahigh-performance liquid chromatography-mass spectrometry. The method developed for AFB1 detection lays the foundation for rapid detection of trace amounts of other exogenous harmful substances in a complicated matrix.

Green protocol for the preparation of hydrophilic molecularly imprinted resin in water for the efficient selective extraction and determination of plant hormones from bean sprouts

In this study, a novel and green synthesis of a new hydrophilic molecularly imprinted 3-aminophenol−hexamethylenetetramine (MIAPH) resin for the selective recognition and separation of plant hormones was developed. The MIAPH resin was obtained using 3-aminophenol as multifunctional monomer which introduced hydroxyl, amino, and imino groups simultaneously, and adenine was used as a dummy template for molecular imprinting. Meanwhile, hexamethylenetetramine released formaldehyde slowly through hydrolysis which was used as the cross-linking agent to avoid the direct and excessive use of toxic formaldehyde. The entire procedure was performed under mild conditions, and was facile, environmentally friendly and energy-efficient. The obtained MIAPH resin showed high specific recognition toward plant hormones and higher recoveries in bean sprouts compared to NIAPH, HLB, and C18. Various parameters affecting the extraction efficiency were optimized, and the calibration linearity of the MIAPH‒SPE‒HPLC method was determined from 0.07 to 2.86 mg kg−1 with a correlation coefficient (r) ≥ 0.9994 under the optimal conditions. Recoveries of spiked standards ranged from 90.2 to 99.1% for bean sprout with a relative standard deviation of ≤5.3%. Finally, the established MIAPH‒SPE‒HPLC method was successfully applied for the selective extraction and sensitive detection of plant hormones in a variety of complex vegetable matrices.

Trace analysis of estrogens in milk samples by molecularly imprinted solid phase extraction with genistein as a dummy template molecule and high-performance liquid chromatography–tandem mass spectrometry

Dummy molecularly imprinted polymer microspheres (DMIPMS) towards estrogens were synthesized by Pickering emulsion polymerization employing genistein (GEN) as a dummy template molecule. The FTIR analysis indicated the successful preparation of the imprinted polymers, and the characterization results of scanning electron microscopy and nitrogen adsorption desorption measurement indicated that the obtained DMIPMS are in possess of regular spherical shapes, porous structures and narrow diameter distribution, a BET surface area of 402.74 m2 g−1, a total pore volume of 0.568 cm3 g−1 and a pore diameter of 3.62 nm. The binding capacity and selectivity of DMIPMS were investigated in equilibrium binding experiments and chromatographic evaluation experiments through scatchard analysis and molecular imprinting factor (IF) analysis, respectively. The MIPs showed high binding capacity and excellent selectivity towards seven selected natural and synthetic estrogens, which are Estrone (E1), 17β-estradiol (βE2), estriol (E3), ethinylestradiol (EE2), dienestrol(DS), diethylstilbestrol (DES), and hexestrol (HEX). A method for selective determination of seven estrogens in milk samples via dummy molecularly imprinted solid phase extraction coupled with HPLC-MS/MS was developed, which showed good linearity from 2 to 500 µg L−1 with a correlation coefficient (R2) of more than 0.999. The detection limits were within the range of 0.10–0.35 µg L−1 and the recoveries of the seven estrogens at three spiking levels (10,100,250 µg L−1) ranged from 88.9% to 102.3% with relative standard deviation (RSD, n = 5) for intra-day and inter-day assays varied from 0.8% to 4.5%. The developed method is thus proven to be efficient and reliable for regular monitoring of trace estrogens in complex matrices such as milk samples.

Aflatoxins screening in non-dairy beverages by Mn-doped ZnS quantum dots – Molecularly imprinted polymer fluorescent probe

Synthesized molecularly imprinted polymer (MIP) materials have been anchored on the surface of PEG-Mn-doped ZnS quantum dots (QDs) to develop a fluorescence probe for aflatoxins (AFs) recognition/determination in non-dairy beverages. MIP synthesis used 5,7-dimethoxycoumarin (DMC) as a dummy template molecule, and methacrylic acid (MAA) as a functional monomer. Under optimized conditions (1.25 mL of 5 mg L−1 MIP-PEG-ZnS QDs solution, pH 5.0, and 12 min delay time before scanning), the prepared MIP-QDs composite was found to offer high affinity and selectivity for AFs (AFB1, AFB2, AFG1 and AFG2). A fast fluorimetric screening method (total AFs assessment) was therefore feasible. The limits of detection (LOD) and quantification (LOQ) were 0.016 and 0.053 mg L−1, respectively. Analytical recoveries (inter- and intra-day assays) were from 99 ± 4% to 107 ± 5%, with RSD (intra-day assay) lower than 13, and RSD (inter-day) lower than 7%. The optimized method was applied for total AFs assessment in several non-dairy beverage samples.

Development and application of water-compatible molecularly imprinted polymers for the selective extraction of carbamazepine from environmental waters

A molecularly imprinted polymer (MIP) was designed in order to allow the selective solid-phase extraction of carbamazepine (CBZ), an anticonvulsant and mood-stabilizing drug, at ultra-trace level from aqueous environmental samples. A structural analog of CBZ was selected as a dummy template and different synthesis conditions were screened. The selectivity of the resulting imprinted polymers was evaluated by studying the retention of CBZ in a solvent similar to the one used for the synthesis. The presence of imprinted cavities in the polymers was then demonstrated by comparing the elution profiles (obtained by using MIP and a non-imprinted polymer, NIP, as a control) of the template, of CBZ, and of a structural analog of CBZ. Then, the extraction procedure was further optimized for the treatment of aqueous samples on the two most promising MIPs, with special attention being paid to the volume and composition of the percolation and washing solutions. The best MIP provided a highly selective retention in tap water with 81% extraction recovery for CBZ in the elution fraction of the MIP and only 14% for NIP. The repeatability of the extraction procedure was demonstrated for both tap and river waters (RSD below 4% in river water) for the drugs CBZ, oxcarbamazepine, and one metabolite (carbamazepine 10,11-epoxide). A MIP capacity of 1.15μmolg-1 was determined. Finally, an analytical procedure involving the MIP was developed allowing the detection of CBZ at a concentration level of only a few nanograms per liter in river water. The selectivity provided by the MIP resulted in a 3000-fold increase of the signal-to-noise ratio in LC/MS analysis as compared to the use of conventional sorbent. Graphical abstract.

A dummy molecularly imprinted solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry for selective determination of four pyridine carboxylic acid herbicides in milk

We aim to develop a solid-phase extraction (SPE) based on a dummy molecularly imprinted polymer (MIP) and liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) for selective determination of four pyridine carboxylic acid herbicides (aminopyralid, picloram, fluroxypyr, and clopyralid) in milk samples. Using picloram as the dummy template, MIP nanocomposites with highly selective recognition and adsorption for the target molecule and its structural analogs were successfully synthesized by precipitation polymerization. Adsorption isotherms and kinetics were used to determine the adsorption performance and specific recognition mechanism of both MIPs and non-molecularly imprinted polymers (NIP). The Scatchard plot analysis revealed that two different binding sites were formed in the MIP with maximum binding capacity (Qmax) of 1171.8 μg·g−1 and 3022.5 μg·g−1, respectively. Recovery at three spiking levels of 10, 20, and 50 μg·L−1 ranged between 75.3 and 89.8% with relative standard deviations (RSDs) <14.3%.The limit of detection (LOD) was estimated to be 0.124 μg·L−1. Finally, the feasibility of the proposed methodology was successfully applied to quantify aminopyralid and another three pyridine carboxylic acid herbicides in milk.

A nanocomposite consisting of an amorphous seed and a molecularly imprinted covalent organic framework shell for extraction and HPLC determination of nonsteroidal anti-inflammatory drugs.

A novel nanocomposite consisting of an amorphous seed and a molecularly imprinted covalent organic framework shell was prepared via a heterogeneous nucleation and growth method. By using ibuprofen as the dummy template, a molecularly imprinted covalent organic framework (MICOF) with a large surface area was prepared from 1,3,5-triformylbenzene and 4,4'-diaminobiphenyl. It was placed on the surface of monodisperse amorphous seeds. Owing to strong π-interaction, the MICOF@SiO2 nanocomposite displays fast binding kinetics, large adsorption capacities and selectivity for nonsteroidal anti-inflammatory drugs (NSAIDs). Following desorption from the MICOF@SiO2 with methanol containing 1% ammonium hydroxide, the NSAIDs ketoprofen, ibuprofen, diclofenac, indomethacin, flurbiprofen and naproxen were quantified by HPLC with UV detection. Under optimized conditions, the method exhibits good linearity within the range of 0.002-1.0μgmL-1, low limits of detection (0.38-2.92μgL-1), and acceptable repeatability. The recoveries of NSAIDs at three spiking levels range from 77 to 112%, and the RSDs are <9.4%. The method was successfully applied to the analysis of NSAIDs in spiked environmental water samples. Graphical abstract A molecular imprinted covalent organic framework nanocomposite (MICOF@SiO2) was prepared by heterogeneous nucleation and growth method. It was explored as a sorbent for the solid phase extraction of nonsteroidal anti-inflammatory drugs before determination by HPLC with UV detection.

Detection of chloramphenicol in chicken, pork and fish with a molecularly imprinted polymer-based microtiter chemiluminescence method

ABSTRACTIn this study, 4-nitrotoluene (NT) was used as dummy template to synthesize a molecularly imprinted polymer that was highly specific for chloramphenicol. The polymer was coated in the wells of 96-well microplates as recognition reagent to develop a chemiluminescence method. The analyte solution and an enzyme-labelled hapten were added into the wells to perform competition, and the light signal was induced with a highly efficient luminol-H2O2-4-(imidazol-1-yl)phenol system. Then, the optimized method was used to determine chloramphenicol in meat (chicken, pork and fish), and the limit of detection (LOD) was 5.0 pg g−1. Furthermore, the polymer-coated plate could be reused four times, and one test could be finished within 20 min. The recoveries from the standard fortified blank meat samples were in the range of 71.5–94.4%. Therefore, this method could be used as a useful tool for routine screening the residue of chloramphenicol in meat samples.

Determination of carbonyls in ambient PM2.5 by coupling dummy template imprinting technology and high performance liquid chromatography

The determination of ambient carbonyls by the derivative method inevitably leads to the introduction of extra 2,4-dinitrophenylhydrazine (2,4-DNPH) into the sample solution. Traditional solid phase extraction (SPE) materials cannot remove this interference. To address this issue, a selective molecularly imprinted solid phase extraction (MISPE) column was prepared. With 2,4-dinitroaniline (2,4-DNAN) as the dummy template, MISPE could eliminate the excessive derivative agent (2,4-DNPH) in the air samples. Consequently, the sample could be concentrated effectively while the sensitivity increased greatly. By coupling MISPE and high performance liquid chromatography (HPLC), the developed method was used to study the concentration and source of 14 carbonyls of PM2.5 during spring in Guangzhou Higher Education Mega Center. Results showed that the total concentration of carbonyls increased with the level of air pollution. Particularly, the content of isovaleraldehyde increased sharply to account for 21% of the 14 total carbonyls in the haze days. Moreover, a high positive correlation between isovaleraldehyde and propionaldehyde was found either in normal days or haze days. From the correlation analysis, it was shown that anthropogenic emissions together with photochemical reaction had contributed to the abnormally high levels of carbonyls in ambient PM2.5 in the haze days. This aspect should be further investigated.

Computer-Aided Design of Molecularly Imprinted Polymers for Simultaneous Detection of Clenbuterol and Its Metabolites.

Molecular imprinting technology (MIT) offers an effective technique for efficient separation and enrichment of specific analytes from complicated matrices and has been used for illicit veterinary drug detectionin recent years due to its high selectivity, good chemical stability, and simple preparation. The development of in silico-based approaches has enabled the simulation of molecularly imprinted polymers (MIPs) to facilitate the selection of imprinting conditions such as template, functional monomer, and the best suitable solvent. In this work, using density functional theory (DFT), the molecularly imprinted polymers of clenbuterol and its metabolites were designed by computer-aided at B3LYP/6-31 + G (d, p) level. Screening molecular imprinting components such as functional monomers, cross-linkers, and solvents has been achieved in the computational simulation considerations. The simulation results showed that methacrylic acid (MAA) is the best functional monomer; the optimal imprinting ratio for both clenbuterol (CLB) and its dummy template molecule of phenylephrine (PE) to functional monomer is 1:3, while the optimal imprinting ratio for the two dummy template molecules of CLB’s metabolites is 1:5. Choosin gethyleneglycol dimethacrylate (EDGMA) as a crosslinker and aprotic solvents could increase the selectivity of the molecularly imprinted system. Atoms in Molecules (AIM) topology analysis was applied to investigate the template-monomer complexes bonding situation and helped to explain the nature of the reaction in the imprinting process. These theoretical predictions were also verified by the experimental results and found to be in good agreement with the computational results. The computer-simulated imprinting process compensates for the lack of clarity in the mechanism of the molecular imprinting process, and provides an important reference and direction for developing better recognition pattern towards CLB and its metabolite analytes in swine urine samples at the same time.

Hollow porous dummy molecularly imprinted polymer as a sorbent of solid-phase extraction combined with accelerated solvent extraction for determination of eight bisphenols in plastic products

In this study, a highly selective and binding hollow porous dummy molecularly imprinted polymer (HPDMIP) was prepared for the separation and determination of bisphenols (BPs) in plastic products using bisphenol AF (BPAF) as dummy template, 4-vinylpyridine as the functional monomer, and MCM-48 as sacrificial support. HPDMIP was characterized by FT-IR spectroscopy, scanning electron microscope, nitrogen adsorption experiment and thermo-gravimetric analysis. Adsorption and selectivity experiments revealed that HPDMIP had a superior adsorption capacity and fast binding kinetics for recognizing BPs. Therefore, a perfect method using HPDMIP as a sorbent material for solid-phase extraction (SPE) was developed, which achieved specific adsorption and enrichment of trace BPs in complex samples. In addition, accelerated solvent extraction (ASE) along with SPE were used as pretreatment method for extracting and concentrating the BPs, and the BPs were determined based on UHPLC–MS/MS. The conditions of ASE and SPE were thoroughly investigated and optimized. Meanwhile, in the ASE proceeding, a Box-Behnken design was applied. Under the optimal conditions, each target analyte had a good linearity between 0.1 and 50 μg·L−1 with regression coefficients in the range of 0.9967–0.9995. Limits of detection and quantification varied from 0.02 to 0.6 μg·L−1 and 0.05 to 2 μg·L−1, respectively. The spiking recoveries between 50.8 and 138.31% for samples spiked at different concentration levels were achieved. The developed method eliminated the effect of template leakage on quantitative analysis and could be applied to extraction and analysis of BPs in different samples with satisfactory results, which provided a useful tool for further studying the BPs in complex samples.