Zhengyu Jin

Characterization of an inclusion complex of ethyl benzoate with hydroxypropyl-β-cyclodextrin

The inclusion complex of ethyl benzoate with hydroxypropyl-β-cyclodextrin (HPCD) was prepared by a freeze-drying method and its characterizations were investigated by different analytical techniques including UV, FT-IR and phase solubility methods. All these approaches indicated that ethyl benzoate was able to form an inclusion complex with HPCD, and the ethyl benzoate/HPCD inclusion compounds exhibited different spectroscopic features and properties from ethyl benzoate. The stoichiometry of the complex was 1:1 and it was the benzene ring part of the ethyl benzoate molecule included into the HPCD cavities from the wider edge. The calculated apparent stability constant of the complex was 9485 M(-1). Moreover, the water solubility of ethyl benzoate was significantly improved by phase solubility studies. The release of ethyl benzoate was also regulated by the form of the inclusion complex. The results showed that HPCD was a proper excipient for increasing the solubility and controlled release of ethyl benzoate.

Influence of cyclodextrins on texture behavior and freeze-thaw stability of kappa-carrageenan gel

The influences of cyclodextrins (CDs) on texture characteristics and freeze-thaw stability of κ-carrageenan gel were investigated using texture profile analysis (TPA) and synthesis test. The TPA results demonstrated that the texture behavior of gelatinized κ-carrageenan was obvious influenced by CDs. Hardness was strengthened at low CD concentrations (1-2%, w/w) and then weakened along with the increase of CD concentrations. Springiness was significantly weakened after the CDs were added. Gumminess showed the similar change as hardness and chewiness dropped along with the concentration increasing of CDs, while cohesiveness had little change after the addition of CDs. Moreover, CDs improved the freeze-thaw stability of gelatinized κ-carrageenan. In both texture behavior and freeze-thaw stability aspects, the influences of modified CDs were superior to that of natural CDs. According to the experimental results, a proposed model was given to illuminate the distribution of CDs in the gelatinized κ-carrageenan.

Comparative Analysis of Medroxyprogesterone Acetate Residue in Animal Tissues by ELISA and GC‐MS

Abstract Medroxyprogesterone acetate is a xenobiotic growth promoter of meat‐producing animals. In this study, the liver, kidney, and muscle of rabbits were obtained after the medroxyprogesterone acetate was administrated successively for 5 days at 0.8 mg/kg and withdrawn for 7 days before slaughter. The medroxyprogesterone acetate residues were determined by ELISA method. The average residue in muscle, liver, and kidney, as 7, 6, and 23 µg/kg, respectively. Residues were confirmed by GC/MS by monitoring four ions, 373, 283, 265, and 145 m/z. A good correlation was observed between the GC/MS and ELISA methods.

Separation and identification of synthetic antigens of hexoestrol residue in animal derived food by HPLC-MS

Abstract Hexoestrol and its derivatives, hexoestrol-mono-ether-butyrate-ethyl (HES-MEBE), hexoestrol-di-ether-butyrate-ethyl (HES-DEBE) were separated and identified using liquid chromatography and spectrometry (ESI). The conditions were as follows: Methyl alcohol and water as mobile phase, 0.3 ml/min of flow rate, elution with linear gradient concentrations from 60–100% of methanol for 25 min on a Lichrospher C-18 column. Synthetic antigen was prepared by coupling hexoestrol-mono-caroxyl-propyl-ethyl (HES-MCPE) with carrier protein by the mixed anhydride method, and the conjugation rate, analysed by UV scanning, is 36.

Simultaneous Determination 9 Anabolic Steroids Residues in Animal Muscle Tissues by Gas Chromatography‐Mass Spectrometry

Abstract A method was developed for determining 9 anabolic steroids (ASs) residues in animal muscle tissues by gas chromatography‐mass spectrometry (GC/MS). After undergoing enzymolysis, being homogenized, and then being picked‐up by ultrasound the sample was extracted with tert‐Butyl methyl ether, cleaned up through solid‐phase extraction (SPE) based on the reverse phase (RP) principle, and after derivatization of the analyst of interest, analyzed by GC/MS under selective ion monitoring (SIM). The limits of the detection (LOD) of the GC/MS method used for testing epitestosterone (ETS), nandrolon (17β‐NT), 17α‐methyl‐testosterone (MTS), testosterone 17‐propionate (PTS), 17β‐estradiol 3‐benzoate (BES), estrone (ESN), 17β‐estradiol (17β‐ES), 17α‐ethynylestradiol (EES), and estriol (EST) in animal muscle ranged from 0.10 to 0.33 µg/kg and the limits of quantification (LOQ) were from 0.24 to 0.82 µg/kg. The experiments using spiked samples, such as pork, beef, chicken, and fish, made it clear that at addition level of 2.0 µg/kg, the average recovery of the ASs ranged from 62.5% to 80.5%, and the coefficient of variation ranged from 12.5% to 26.8%, while at an addition level of 5.0 µg/kg, the average recovery was from 70.8% to 86.4%, and the coefficient of variation was from 8.8% to 18.4%.

Determination of 19-nortestosterone residues in aquaculture tissues by enzyme-linked immunosorbent assay and comparison with liquid chromatography and tandem mass spectrometry

19-Nortestosterone (17β-NT) was oximated by carboxymethoxylamine and then coupled with bovine serum albumin (BSA) in a mixed-anhydride reaction in order to produce an antibody. The conjugate rate of 17β-NT and BSA was estimated to be 24 by ultraviolet spectrophotometry. Polyclonal antibody of 17β-NT was acquired from the animal immunized with the conjugate. Through an indirect enzyme-linked immunosorbent assay (ELISA), which demonstrated that the synthesis of immunogen was successful, the titre of antiserum was found to be 6.4 × 105. Based on the purified antibody, a competitive indirect ELISA was developed. ELISA revealed that the limit of detection (LOD) was 0.07 ng g−1, the recovery (in edible tissues) was 71–89%, and the working range was 0.05–31.25 ng g−1. The preliminary evaluation of assay performance through specificity, sensitivity, precision, and accuracy revealed that this ELISA method could be used in the practical detection of 17β-NT in tissue samples. Moreover, this method was compared with high-performance liquid chromatography tandem mass spectrometry, for which the transition for quantification of 17β-NT was 275.4/109.1.

Colorimetric assay for the simultaneous detection of Hg2+ and Ag+ based on inhibiting the peroxidase-like activity of core–shell Au@Pt nanoparticles

In this study, peroxidase-mimicking core–shell Au@Pt nanoparticles (Au@Pt NPs) were synthesized, and both Hg2+ and Ag+ were found to intensively inhibit the catalytic activity of the Au@Pt NPs. The interactions between the two metal ions and Au@Pt NPs were analyzed through characterization by TEM, DLS, EPR and XPS, etc. Based on the inhibition of both Hg2+ and Ag+ toward the catalytic activity of the Au@Pt NPs and the shielding of sodium dodecyl sulfate (SDS) toward interfering metal ions, a highly sensitive and selective colorimetric assay for Hg2+ and Ag+ was developed. In addition, L-cysteine can be used to mask Hg2+ in the presence of Ag+; therefore, a specific detection of Ag+ ions can be accomplished by this Au@Pt NP-based assay. The limits of detection (LODs) for Hg2+ and Ag+ are 3.5 nM and 2.0 nM, respectively. The linear ranges for detecting Hg2+ and Ag+ are from 10 nM to 200 nM and from 5.0 nM to 100 nM, respectively. Moreover, the colorimetric assay is highly selective toward Hg2+ and Ag+ over other common metal ions. This work demonstrates that the optimization of metal nanoparticle preparation and surface modification play very important roles in developing metal ion sensing based on metal NP enzyme mimics. In addition, the metallic nanozyme based colorimetric method here demonstrates advantages in practical applications as it is low-cost, simple, and highly sensitive and selective, although it needs a two-step reaction.

Synthesis and identification of immunogen medroxyprogesterone acetate residues in edible foods and preparation of the Antisera

Medroxyprogesterone acetate (MPA), relative molecular mass is only 344.5 and it has no immunogenecity. The methods of the carbodiimides and the mixed anhydride were both adopted to couple MPA with bovine serum albumin, the carrier protein. The coupling rates of conjugate using the above methods were estimated to be 14 and 20 by ultraviolet spectrophotometry. The coupling was successful according to the analysis of SDS-PAGE illustration. New Zealand white rabbits were immunized with the conjugate the coupling rate of which was 14, and blood was collected after five periods of immunities. Then the titre of antiserum was tested to be 2.6 × 105 by indirect ELISA, which further identified the success of coupling.