Chun Chang

Dummy-template molecularly imprinted solid phase extraction for selective analysis of ractopamine in pork

Molecularly imprinted polymers (MIPs) for selective adsorption of ractopamine hydrochloride (RAC) were synthesised by an in situ method, in which salbutamol (SAL) was used as the dummy-template to avoid the template leakage. Scanning electron microscopy (SEM), mercury porosimerty and Fourier transform infrared spectroscopy (FTIR) were used to investigate the physical and morphological characteristics of the dummy-template MIPs. The test of adsorption selectivity indicated that the dummy-template MIPs exhibited high selectivity to RAC. The saturated adsorption capacity for RAC on dummy-template MIPs was 90.9 μg g(-1). Based on the dummy-template polymers, a liquid chromatography-mass spectrometry (LC-MS) method was developed for the selective analysis of RAC in real pork samples. The averages of intra- and inter-day accuracy ranged from 78.9% to 92.2% and from 90.7% to 93.1%, respectively. The RSD% of repeatability ranged from 1.9% to 6.3%, and the RSD% of intermediate precision ranged from 3.5% to 9.2%, while the limit of detection (LOD) was 0.02 μg kg(-1).

Determination of clenbuterol from pork samples using surface molecularly imprinted polymers as the selective sorbents for microextraction in packed syringe

In this study, a selective sample pretreatment procedure combing surface molecularly imprinted polymers and microextraction in packed syringe (SMIPs-MEPS) was developed for the analysis of clenbuterol (CLB) from pork samples. SMIPs for CLB were synthesized on silica gel particles through a sol-gel process. A series of characterization and adsorption experiments revealed that the SMIPs exhibited porous structures, good thermal stability, high adsorption capacity and a fast mass transfer rate. The obtained SMIPs were employed as selective sorbents of SMIPs-MEPS for extraction of CLB from pork samples. Several parameters affecting the extraction efficiency were investigated, including the pH of sample solution, number of draw-eject cycles, volume of sample, type and volume of washing solution, and the type and volume of elution solution. Under the optimized conditions, a simple and rapid method for the determination of CLB from pork samples was established by coupling with high performance liquid chromatography (HPLC). The whole pretreatment process was rapid and it can be accomplished with 2min. The limit of quantitation and the limit of detection for CLB were 0.02 and 0.009μgkg(-1), respectively. The average recoveries of CLB at three spiked levels ranged from 86.5% to 91.2% with the relative standard deviations (RSD) ≤6.3%.

Combined microextraction by packed sorbent and high-performance liquid chromatography–ultraviolet detection for rapid analysis of ractopamine in porcine muscle and urine samples

A method for rapid analysis of ractopamine in porcine muscle and urine was developed and validated. The method was based on combined of microextraction by packed sorbent (MEPS) and high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Parameters of the MEPS procedure affecting extraction efficiency were optimised. Optimum extraction conditions were 100 μL of sample in five extraction cycles and sampling time of <3 min. Compared with solid-phase extraction, the MEPS procedure required less extraction time, sample volume and consumption of organic solvents. The method demonstrated high linearity within 0.01-2 μg/mL for porcine muscle and urine samples (R²>0.9985). Accuracies of muscle and urine analyses were 93.9-109.2% and 93.4-105.1%, respectively. Intra-day and inter-day precisions (RSD%) were lower than 11.8% for both analyses. The method was applied for rapid analysis of ractopamine in biological samples. The method was simpler and could be used to screen other β₂-agonists in other extraction media.

Combined solid-phase microextraction and high-performance liquid chromatography with ultroviolet detection for simultaneous analysis of clenbuterol, salbutamol and ractopamine in pig samples

A simple and sensitive method based on the combination of solid-phase microextraction (SPME) and high-performance liquid chromatography with ultroviolet detection was developed for the simultaneous determination of clenbuterol, salbutamol and ractopamine in pig samples. Parameters of the SPME procedure affecting extraction efficiency, such as the type of fiber, extraction time, extraction temperature, ion strength, pH of sample and stirring rate, were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.5-50 µg/L for clenbuterol and ractopamine, and 0.2-20 µg/L for salbutamol. The limits of detection were 0.1 µg/L for clenbuterol, 0.05 µg/L for salbutamol and 0.1 μg/L for ractopamine, respectively. The averages of intra- and inter-day accuracy ranged from 79.8 to 92.4%. The intra-day and inter-day precision were below 9.6% for the three analytes. This method exhibited the advantages of simplicity, rapidity and low solvent consumption, and was suitable for the monitoring of β2 -agonists residue in pig samples.

Monolithic cryogels made of agarose–chitosan composite and loaded with agarose beads for purification of immunoglobulin G

In order to obtain a novel absorbent with high adsorption capacity for the purification of immunoglobulin G (IgG), continuous supermacroporous agarose beads embedded agarose-chitosan composite monolithic cryogels (agarose-chitosan cryogels) were prepared by cryo-copolymerization of agarose-chitosan blend solutions with glutaraldehyde as the crosslinker in the presence of agarose beads. After coupling 2-mercaptopyridine onto divinylsulfone-activated matrix, the obtained cryogels were used for the purification of IgG. The microstructure morphologies of the cryogels were analyzed by scanning electron microscopy. The results showed that the obtained cryogels possess interconnected pores of 10-100 μm size. The specific surface area was 350 m(2)/g with maximum adsorption capacity of IgG 71.4 mg/g. The cryogels showed workable stability, and can be reused at least 15 times without significant loss in adsorption capacity. IgG purity after one-step purification from human plasma was monitored by electrophoresis and the average recovery was estimated to be 90%.

Matrine-imprinted monolithic stationary phase for extraction and purification of matrine from Sophorae flavescentis Ait

A matrine-imprinted monolithic stationary phase (MIP monolith) was prepared by in situ polymerization for extraction and purification of matrine from Sophorae flavescentis Ait. Matrine was used as the template molecule, methacrylic acid as the function monomer, ethylene glycol dimethacrylate as the cross-linking agent, and toluene and dodecanol as the porogenic solvents. Scanning electron microscope study revealed that a monolithic structure with mesopores and 36 μm diameter nodules was obtained. The molecular recognition process and the effect of varying chromatographic conditions on separation were examined by high-performance liquid chromatography (HPLC). Hydrogen bonding, electrostatic, hydrophobic interactions and the molecular shape matching in MIP monolith cavities were proposed to be responsible for the recognition mechanism. The use of MIP monolith as a solid-phase extraction (SPE) sorbent for extraction and purification of matrine from S. flavescentis Ait was investigated. The extraction yield was 89.2% (for 3.0 mmol l(-1) matrine) with enrichment factor 29.

Development of molecularly imprinted column-on line-two dimensional liquid chromatography for rapidly and selectively monitoring estradiol in cosmetics.

Nowadays, the illegal use of estradiol in cosmetics has caused a series of events which endangering public health seriously. Therefore, it is imperative to establish a simple, fast and specific method for monitoring the illegal use of estradiol in cosmetics. In current study, we developed a molecular imprinted monolithic column two dimensional liquid chromatography method (MIMC-2D-LC) for rapid and selective determination of estradiol in various cosmetic samples. The best polymerization, morphology, structure property, surface groups, and the adsorption performance of the prepared material were investigated. The MIMC-2D-LC was validated and successfully used for detecting estradiol in cosmetic samples with good selectivity, sensitivity, efficiency and reproducibility. The linear range of the MIMC-2D-LC for estradiol was 0.5-50μgg-1 with the limit of detection of 0.08μgg-1. Finally, six batches of cosmetic samples obtained from local markets were tested by the proposed method. The test results showed that the illegal use of estradiol still existed in the commercially available samples.

Preparation and evaluation of monolithic molecularly imprinted stationary phase for S-naproxen

An S-naproxen (S-NAP) molecularly imprinted monolithic stationary phase (MIMSP) with specific recognition for S-NAP and naproxen (NAP) was prepared by in situ technique, utilizing 4-vinylpridine (4-VP) as a function monomer, ethylene glycol dimethacrylate (EDMA) as a cross-linking agent, and low-polar solvents (toluene and dodecanol) as porogenic solvents. The selectivity of the polymers for S-NAP and NAP was evaluated by high performance liquid chromatography (HPLC). The binding characteristics were tested by Scatchard analysis. Racemic NAP could be specifically separated to some extent. At the same time, NAP could be separated from ibuprofen under optimized conditions. Scatchard analysis showed that two classes of binding sites existed in the S-NAP-imprinted polymers, with their dissociation constants estimated to be 1.045 and 5.496 μM, respectively. The results demonstrate that S-NAP and NAP can be recognized specifically on the obtained MIMSP.

A novel surface molecularly imprinted polymer as the solid-phase extraction adsorbent for the selective determination of ampicillin sodium in milk and blood samples☆

Surface molecularly imprinted polymers (SMIPs) for selective adsorption of ampicillin sodium were synthesized using surface molecular imprinting technique with silica gel as a support. The physical and morphological characteristics of the polymers were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), elemental analysis and nitrogen adsorption–desorption test. The obtained results showed that the SMIPs displayed great adsorption capacity (13.5 μg/mg), high recognition ability (the imprinted factor is 3.2) and good binding kinetics for ampicillin sodium. Finally, as solid phase extraction adsorbents, the SMIPs coupled with HPLC method were validated and applied for the enrichment, purification and determination of ampicillin sodium in real milk and blood samples. The averages of spiked accuracy ranged from 92.1% to 107.6%. The relative standard deviations of intra- and inter-day precisions were less than 4.6%. This study provides a new and promising method for enriching, extracting and determining ampicillin sodium in complex biological samples.

β-Cyclodextrin anchoring onto pericarpium granati-derived magnetic mesoporous carbon for selective capture of lopid in human serum and pharmaceutical wastewater samples.

Functionalized magnetic carbonaceous nanomaterials, which are important materials with many practical and research applications in biomedical, pharmaceutical and biological fields, have recently attracted much attention. In this study, a magnetic mesoporous carbon coated with β-cyclodextrin (MMC@β-CD) was synthesized for the first time from natural pericarpium granati (PG). The as-obtained MMC@β-CD has high surface areas (203 m(2)g(-1)), large pore volumes (0.16 cm(3)g(-1)), relatively broad mesoporous sizes (6.8 nm) and a high saturation magnetization of 26.2 emu g(-1), which is sufficient for magnetic separation by an external magnetic field. The MMC@β-CD was used as an innovative adsorbent for magnetic solid-phase extraction of lopid via host-guest interaction prior to spectrofluorometric analysis. The proposed method was successfully applied to analyze lopid in human serum and pharmaceutical wastewater samples with recoveries in the range of 85.0-103.5% for the spiked samples. Overall, this work not only provides an inexpensive and eco-friendly method to fabricate MMC@β-CD (or MMC) from PG, but also develops a highly selective approach for capture of lopid in biological samples and environmental substances.