Tylosin A and desmycosin in honey by salting-out assisted liquid-liquid extraction and aqueous normal phase ultraperformance liquid chromatography-tandem mass spectrometry

A simple and rapid method was developed for the determination of tylosin A and desmycosin residues in honey. Aliquots of honey samples were dissolved in a concentrated solution of sodium acetate and the target analytes were subsequently extracted with acetonitrile. The resulting organic extract was chromatographed under aqueous normal phase (ANP) LC conditions using a bare silica stationary phase with acidified solutions of ammonium formate in both water and 5:95 water: acetonitrile as the mobile phases. Tylosin A and desmycosin residues were measured using MS/MS in the multiple reaction monitoring (MRM) mode. Based on the analysis of replicate honey samples fortified at 5, 20, and 100 mu g kg(-1), the method was found to provide high accuracy and precision with average intraday trueness ranging from 90.2 to 111.2% and standard deviations of less than 7%. For spiked replicates fortified at the limit of quantification (1 mu g kg(-1)), the intraday accuracies ranged from 72.0 to 102.7% for tylosin A and from 72.1 to 93.8% for desmycosin, with standard deviations all lower than 12%. Matrix effects were relatively minimal and consistent between honey samples which eliminated the need to perform any additional cleanup of the sample extracts prior to ANP-UPLC-MS/MS analysis.