[Rapid determination of multiple prohibited and restricted veterinary drug residues in fish and shrimp by ultra high performance liquid chromatography-tandem mass spectrometry].

A method was established for the rapid determination of 28 prohibited and restricted veterinary drugs of five classes (sulfonamides, quinolones, chloramphenicols, nitrofurans metabolites and triphenylmethane) in fish and shrimp by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) coupled with simultaneous extraction and purification. After optimizing the sample pretreatment methods and chromatographic conditions, the samples were hydrolyzed with hydrochloric acid. The five kinds of residual drugs were simultaneously extracted with acetonitrile after nitrofuran metabolites derivatized with 2-nitrobenzaldehyde. The extraction solutions were dehydrated with sodium chloride and salted out. The acetonitrile layer was purified with n-hexane and concentrated to near dryness. The residues were dissolved in 1.0 mL methanol. Then, the solutions were purified by dispersive solid phase extraction with C18, N-(n-propyl)ethylenediamine (PSA) and amino bonded silica gel (NH2) sorbents. The residues were separated on a ZORBAX C18 chromatographic column (50 mm×2.1 mm, 1.8 µm). The MS data were acquired in positive and negative multiple reaction monitoring (MRM) modes, and quantitated by the isotope internal standard method. With this approach, the linear relationships of the 28 veterinary drugs were good. The linear correlation coefficients were greater than 0.99. The limits of detection and limits of quantification were in the range of 0.1-0.8 µg/kg and 0.3-2.7 µg/kg, respectively. The average recoveries at three spiked levels (1, 5, and 20 fold of the LOQs) were 70.0%-120% with relative standard deviations of 0.9%-10.0%. The method is simple, rapid, accurate and sensitive, and it is suitable for the rapid determination of various prohibited and restricted drugs in fish and shrimp.

[Simultaneous determination of antibiotics and triphenylmethanes veterinary drug residues in fish and shrimp by dispersive solid phase extraction purification-ultra high performance liquid chromatography-tandem mass spectrometry].

A method was established to rapidly determine 20 kinds of veterinary drug residues including three catagories of antibiotics (sulfonamides, quinolones, and chloramphenicols) and two kinds of triphenylmethanes (malachite green (MG) and leucomalachite green (LMG)) in fish and shrimp, based on dispersive solid phase extraction purification-ultra high performance liquid chromatography-tandem mass spectrometry. The samples were first hydrolyzed using a dipotassium hydrogen phosphate solution, and then extracted using acetonitrile. Afterward, the extraction solution was dehydrated and salted out with sodium chloride and condensed to nearly dry using a rotating evaporator. This residue was dissolved in 1.0 mL methanol. The resulting solution was purified by dispersive solid phase extraction method with C18 and PSA sorbents, and filtered through a filter. The target compounds were separated employing a ZORBAX C18 column. The mass spectrometer datas were acquired by multiple reaction monitoring (MRM) of positive and negative modes and quantitated applying the isotope internal standard method. The 20 veterinary drugs showed a good linear relationship in the range of 0.2-300 µg/L. The limits of detection and the limits of quantification were 0.1-0.6 and 0.3-1.8 µg/kg, respectively, while the correlation coefficients were greater than 0.99. The average recoveries at the three spiked levels (1, 5, and 20 times of quantitative limits) ranged between 72.5%-118%, with the relative standard deviations of 1.9%-9.8%. The advantages of method include a simple pretreatment, a high detection efficiency, and a low cost. Moreover, it is suitable for the simultaneous determination of multiple veterinary drug residues in fish and shrimp.

[Determination of six amide herbicide residues in soil by QuEChERS-gas chromatography-mass spectrometry].

A method was developed for the determination of six amide herbicides, such as acetochlor, alachlor, metolachlor, metazachlor, butachlor and pretilachlor, by QuEChERS-gas chromatography-mass spectrometry. The soil samples were extracted by 10 mL acetonitrile, 10 mL deionized water and 4 g sodium chloride, then purified with 50 mg N-propyl ethylenediamine (PSA), 50 mg C18, 10 mg graphitized carbon black (GCB) and 100 mg MgSO4. Low-polar silica capillary column HP-5MS was used. The extracts were detected by electron impact ionization (EI) source in the selected ion monitoring (SIM) mode. The results showed that good linearities were obtained with the mass concentrations of the six amide herbicides in the range of 0.01-1.00 mg/L, and their correlation coefficients ranged from 0.9996 to 1.0000. Under the condition of adding contents of 0.025, 0.10 and 0.50 mg/kg, the average recoveries of the six amide herbicides ranged from 92.0% to 108%, and the relative standard deviations were 1.64%-8.25%. The limits of detection (LODs) were 0.002-0.006 mg/kg and the limits of quantification (LOQs) were 0.005-0.02 mg/kg. Comparing with the gas chromatography-electron capture detection (GC-ECD) which used to detect the amide herbicides, this method can improve the anti-interference ability, and get better separation of the six amide herbicides. The method has the advantages of simplicity, rapidity, and application value.