[Determination of fipronil and its metabolites in livestock and poultry liver by high performance liquid chromatography-tandem mass spectrometry with dispersive solid phase extraction].

The residues of fipronil and its metabolites, namely fipronil-desulfinyl, fipronil-sulfone, and fipronil-sulfide, have attracted increasing attention since the European egg contamination incident. In this study, by optimizing the pretreatment method and chromatographic conditions, a simple extraction method coupled with high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of fipronil and its metabolites, including fipronil-desulfinyl, fipronil-sulfone, and fipronil-sulfide, in livestock and poultry liver. The optimal pretreatment method for fipronil and its metabolites was determined by comparing the recoveries obtained with different extraction solvents (methanol, acetonitrile, acetone, and ethyl acetate), and by purification with N-propyl ethylenediamine (PSA) and octadecylsilane (C18). The samples were extracted with 10 mL acetonitrile, then purified with 150 mg PSA and 100 mg C18, following which the extracted solutions were directly injected for analysis. Separation was performed on an Agilent ZORBAX SB-C18 column (150 mm×2.1 mm, 3.5 µm) with gradient elution using acetonitrile and water as the mobile phases. The target compounds were detected by electrospray ionization (ESI) in the negative mode under multiple reaction monitoring, and quantified by the external standard method with matrix-matched standard correction curves. The results indicated that the linear ranges for the four compounds ranged from 0.1 µg/L to 10.0 µg/L with correlation coefficients (r2) higher than 0.995. The limit of detection was 0.2 µg/kg and limit of quantitation was 0.5 µg/kg. The average recoveries were between 81.1% and 99.8% at three spiked levels of 0.5, 1.0, and 10 µg/kg, with relative standard deviations (RSDs) of 6.1%-11.7%. The matrix effect experiment showed that fipronil and its metabolites had matrix inhibition effects. Matrix-matched standard curve correction was performed to eliminate matrix inhibition effects. The proposed method was used for the analysis of 99 liver samples, where fipronil-sulfone was detected in four samples with values of 1.25-2.82 µg/kg. The method is simple, sensitive, and accurate, and is suitable for the determination of fipronil and its metabolites in livestock and poultry liver.

Nε -carboxymethyllysine and Nε -carboxyethyllysine kinetics and water loss analysis during chicken braising.

BACKGROUND: Braised chicken is one of the well-known traditional processed meat products in China. However, reports are scarce with respect to the formation of Nɛ -carboxymethyllysine (CML) and Nɛ -carboxyethyllysine (CEL) during chicken braising. Furthermore, braising for a long time and using high-temperature process will result in water loss. However, the relationship between water loss and advanced glycation end products (AGEs) kinetics is limited. The present study aimed to investigate the relationship between water loss and kinetics of free and protein-bound CML and CEL in braised chicken under different braising conditions (60-100 °C for 5-60 min). RESULTS: Levels of free and protein-bound CML and CEL were found to increase with heating time and temperature. The correlation coefficient (r2 ) was largest at zero-order reaction (free CML: r2 = 0.908-0.954, protein-bound CML: r2 = 0.901-0.958, free CEL: r2 = 0.952-0.973, protein-bound CEL: r2 = 0.959-0.965). The activation energy was 44.158 ± 3.638 kJ mol-1 for free CML, 40.041 ± 3.438 kJ mol-1 for protein-bound CML, 40.971 ± 0.334 kJ mol-1 for free CEL and 40.247 ± 0.553 kJ mol-1 for protein-bound CEL. Furthermore, with the increase of braising time and temperature, the drip loss and cooking loss also became aggravated. A significant positive correlation between water loss and AGEs levels during braising was observed by Pearson's correlation analysis (P < 0.05). CONCLUSION: We conclude that the levels of free and protein-bound CML and CEL during braising were different, although they all met zero-order reaction kinetics. Water loss was probably one of the main reasons for the formation of AGEs during chicken braising. © 2020 Society of Chemical Industry.

[Simultaneous determination of 11 mycotoxins in feeds by high performance liquid chromatography-tandem mass spectrometry].

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the simultaneous determination of 11 mycotoxins in feeds. The samples were extracted with acetonitrile, then cleaned up by multifunctional purification column filler and PRIME HLB solid phase extraction column. The 11 mycotoxins were separated on an Agilent Zorbax SB-C18 column (150 mm×2.1 mm, 3.5 µ m) with gradient elution program, and methanol-5 mmol/L ammonium acetate solution containing 0.1%(v/v) formic acid were used as mobile phases. The target compounds were detected under electrospray ionization (ESI) both in positive and negative modes with multiple reaction monitoring mode, and quantified by internal standard method. The results indicated that the 11 mycotoxins showed good linear relationships in their respective linear ranges, and the correlation coefficients were greater than 0.99. The limits of quantification (LOQs) were between 2.0 and 50.0 µ g/kg. The average recoveries were between 79.3% and 101.6% at three spiked levels (1, 2 and 5 times LOQs) with relative standard deviations (RSDs) of 5.9%-13.2% (n=5). The method is simple, rapid, sensitive, and can be used for the analysis of the 11 mycotoxins in feeds.

Preparation and Application of Novel Magnetic Molecularly Imprinted Composites for Recognition of Sulfadimethoxine in Feed Samples.

Novel magnetic molecularly imprinted composites were prepared through a facile method using sulfadimethoxine (SDM) as template. The inorganic magnetic nanoparticles were linked with the organic molecularly imprinted polymer (MIP) through irreversibly covalent bond. So, the resulted composites showed excellent stability and reusability under acidic elution conditions. The magnetic MIP composites showed good selectivity, high binding capacity and excellent kinetics toward SDM. Adopting the magnetic MIP composites as extraction material, an off-line magnetic solid-phase extraction (SPE)/high performance liquid chromatography (HPLC) method was established. The calibration curve was linear in the range of 0.05 - 15 mg kg(-1) (r(2) = 0.9976). The LOD and LOQ were 0.016 and 0.052 mg kg(-1), respectively, while the recoveries were in the range of 89.3 - 107.0%. These novel magnetic MIP composites may become a powerful tool for the extraction of template from complex samples with good efficiency.