Simultaneous determination of penicillin and their major enzymatic metabolites in milk and milk powder by high performance liquid chromatography-tandem mass spectrometry

Abstract

A high performance liquid chromatographytandem mass spectrometry (HPLCMS/MS) method has been developed for the determination of eight compounds in milk and milk powder. They are four penicillins (penicillin G penicillin V amoxicillin and ampicillin) and four major βlactamase enzymatic metabolites of them (penilloic acid G penilloic acid V amoxiilloic acid and ampilloic acid). The compounds were extracted from the samples with acetonitrile and water cleaned up by HLB solid phase extraction cartridges and then detected by HPLC-MS/MS and quantified by external standard method. The linearities were satisfactory with the correlation coefficients >0.99 at the mass concentrations ranging from 4 μg /L to 200 μg/L for penicillins and from 10 μg / L to 500 μg / L for enzymatic metabolites. The limits of detection and the limits of quantification were 5 -50 μg / kg (S/N≥3) and 8-100 μg / kg (S/N≥10) respectively. The average recoveries of the eight compounds were 83.48% -96.97% in milk and 82.70% - 95.14% in milk powder. The relative standard deviations (RSDs) in milk and milk powder were 3.86% - 10.87% and 3.02% - 9.81% respectively. In conclusion the established method is convenient accurate and sensitive so that it can be applied to the determination of penicillin residues and enzymatic metabolites in milk and milk powder.