DETERMINATION OF IMIDOCARB IN BOVINE TISSUES AND MILK SAMPLES BY LC-MS/MS

We present a sensitive and selective method for detecting imidocarb in bovine tissues and milk samples using a solid-phase extraction (SPE) with diatomaceous earth column and liquid chromatography with electrospray tandem mass spectrometry (LC-ESI-MS/MS) on positive mode. Chromatographic separation was performed on a TSK-GEL ODS 100 V column using 0.1% formic acid in water/methanol. Limit of detection (LOD) was 0.5 ng/mL for standard solution. Limit of quantitation (LOQ) was ranged from 1.0 to 10 mu g/kg for bovine tissue and milk samples. The linearity of the calibration curve was excellent in matrix matched standards, and yielded the coefficients (r(2) = 0.997-0.999, range from LOQ to 250, 750, or 5000 mu g/kg) of imidocarb. Recoveries were in the range of 73.3-98.6% with associated precision values (within-day: 1.0-6.7%, n = 6, and between-day: 2.0-7.7% for 3 days) for repeatability and reproducibility. This developed method is well adapted for residue analysis of imidocarb in bovine tissues and milk based on maximum tolerated residue levels.