Determination of Six Resorcylic Acid Lactones in Feed by GC-MS

A method was developed to simultaneously detect six resorcylic acid lactones in feed by GC-MS. Samples were extracted with methanol followed by a two step liquid-liquid extraction and an HLB SPE clean-up. The samples were derivatized with BSTFA + TMCS (99/1; v/v) and determined by GC-MS. For all analytes, the ranges of recoveries were 81.2-98.2%, with RSDs of 3.2-15.2%, and the LODs were 0.2-0.6 mu g kg(-1).