Simultaneous Determination Of Veterinary Drugs Residues In Incurred Chicken By LC-MS/MS Based On Lyophilization

The classic sample pretreatment techniques usually lead to great deviations and environmental pollution due to excessive homogenization,multi-step extraction,over concentration and using large amounts of organic reagents.In this study,utilizing the principle of lyophilization,a simple vortex extraction combined with selective and sensitive liquid chromatography-tandem mass spectrometry is expected to be an alternative of the classic analytical method of antimicrobials residues.In addition,for evaluating and validating this novel sample pretreatment strategy,three major groups of antimicrobials including fluoroquinolones,sulfonamides and macrolides were taken as example,a LC-MS/MS method based on lyophilization?classic extraction as control?has been firstly developed to determine seven kinds of antimicrobials residues in administered chicken samples.Then the experimental data of different incurred chickens and different instruments were analyzed and compared using statistical software SPSS 19.0.It aims to exploit new ideas for the research of veterinary drugs residues detection,and provide newtechniques,new theories and approach support for determination of other veterinary drug residues.Chickensamples were lyophilized,the residues were rehydrated with water,then extracted with 4 mL of 1%acetic acid in acetonitrile,followed by vortex,centrifugation;the supernatant was diluted with 20%methanol in 0.1%formic acid solution to8mL.Extracts were analyzed by liquid chromatography-tandemmass spectrometry.Deuterated enrofloxacin,ciprofloxacin and sulfamonomethoxine were used as internal standards.Target analytes were separated on Zorbax SB-Aq column?150 mm×2.1 mm i.d.,3.5?m?using acetonitrile and 0.1%formic acid as mobile phases and determined by liquid chromatography-tandem mass spectrometry operating in positive electrospray ionization mode.Analytes were quantified using the matrix-matched calibration curves.The method wasgood linear in the experimental concentration range with correlation coefficients?r²?higher than 0.99.The limit of detectionand limit of quantificationrangedfrom 0.2 to 1.5?g kg^-1 and 0.5 to 4.0?g kg^-1,respectively.In the three spiked concentrations of 50,100 and200?g kg^-1(the spiked concentrations of sarafloxacin were 10,20,and 40?g kg^-1),recoveries of 7 antimicrobials in chicken muscles ranged from 61.0%to 93.9%and the coefficient of variation ranged from 1.1%to 14.1%by external standard method,the average recoveries of the five antimicrobials in chicken muscles ranged from 86.2%to119.6%and the coefficient of variation ranged from 1.1%to 15.0%by the internal standard method.The results of statistical analysis demonstrated thatthe mean values ofse ven a ntimicrobia ls in the incurred positive chickens,exce ptfluoroquinolones in the fourth and sixth c hic kens,sulfamonomethoxine and tylosin in the fifth chicken by lyophilization approache were no statistically significant differences?Pvalue>0.05?with those by classic extraction method;the mean values of all compounds were no statistically significant differences?Pvalue>0.05?bylyophilization method with three different liquid chromatography-tandem mass spectrometers.No matter different incurred levels or different LC-MS/MS instruments,the comparable accuracy and precision were obtained for the lyophilization method and classic extraction method.In addition,the former could more effectively eliminate matrix effects.The novel lyophilization sample pretreatment technique,which is simple,green and practical,should be adopted during the residue analysis of antimicrobials in animal muscle matrices.