On-line solid-phase extraction coupled liquid chromatography-ESI-ion trap-mass spectrometry for analysis of abamectin and ivermectin residues in milk

Abstract

A solid-phase extraction column was on-line coupled to a liquid chromatography electrospray ionization ion-trap tandem mass spectrometer to perform on-line sample pretreatment and simultaneous analysis of abamectin and ivermectin residues in milk samples. Multiple-reaction monitoring of secondary mass spectrometry in the positive mode was used to detect both abamectin and ivermectin. The matrix-fortified external standard calibration curves of the secondary mass spectrometry in the concentration range of 0–15 ng mL⁻¹ for abamectin and ivermectin shows good linearity. The limit of the detection/quantification (LOD/LOQ) for abamectin and ivermectin was 0.67/2.23 ng mL⁻¹ and 0.63/2.11 ng mL⁻¹, respectively. Quantification of five different brands of milk samples by the standard addition method with the assistance of the statistical t-test indicates that two brands of milk samples do contain trace amounts of abamectin and ivermectin. Abamectin and ivermectin are not detected in the other three brands of milk samples. The accuracy of the two brands of milk samples for abamection and ivermectin was 82–88% and the precision was 4.8–9.7%. The running time for one sample was 10 min.