Simultaneous determination of avermectins in bovine tissues by LC-MS/MS.

Analytical method for the simultaneous quantification of avermectins (AVMs), abamectin B1a, abamectin 8,9-Z isomer B1a, emamectine benzoate B1a, emamectine benzoate 8,9-Z isomer B1a, ivermectin, eprinomectin B1a, doramectin and moxidectin in bovine tissues (muscle, liver and fat) was developed by LC-MS/MS in electrospray positive ion mode. The separation was achieved on a short TSK-GEL ODS 100V column with the mobile phase consisting of acetonitrile and aquatic 0.1 mM ammonium formate containing 0.1% formic acid v/v at a flow rate of 0.2 mL/min with gradient elution. Liquid-liquid extraction with isooctane was used for the sample extraction/preparation of analytes in bovine samples. The linearity of the calibration curves was excellent in matrix-matched standards, and yielded the coefficients (r(2)=0.997-0.999, range from LOQ to 500, 1000 or 5000 ng/g) of determination of the target analytes. Recoveries were in the range of 87.9-99.8% with associated precision values (within-day: 1.5-7.4%, n=6, and between-day: 1.5-8.4% for 3 days) for repeatability and reproducibility. LC-MS/MS method has been proven to be highly efficient and suitable for the simultaneous determinations of eight AVMs in bovine tissue samples.