Development and validation of LC-MS/MS method to determine the residue of veterinary drugs ivermectin, doramectin and moxidectin in milk

A comparatively simple, sensitive and rapid analytical method has been developed and validated to determine the residues of avermectins, such as ivermectin, doramectin and moxidectin in milk using LC-MS/MS in positive ionization mode. The MRM transitions 892.71 >569.6, 892.71 >551.5 for ivermectin, 916.88 >593.83, 916.88 >331.40 for doramectin and 640.85 >199.03, 640.85 >498.61 for moxidectin have been used for the purpose of quantification and evaluation of other parameters of the method. The limits of detection of the method have been determined as 0.1 µg/kg, 0.1 µg/kg and 0.2 µg/kg for ivermectin, doramectin and moxidexin, respectively. The limits of quantitation have been calculated as 0.2 µg/kg, 0.2 µg/kg and 0.5 µg/kg for ivermectin, doramectin and moxidectin, respectively. The developed method allows the detection, quantitation and confirmation of macrolide endectosides in raw milk present at trace levels with high precision, accuracy and sensitivity by using simple extraction procedure. In spite of using a simplified extraction procedure, no interferences have been observed from the matrix components during the determination of drug residues. The method can be used for the routine analysis of macrolide endectocides in milk with added advantages of speed and economy. The method can also be tried for other animal products like meat and poultry. All the three avermectins can be determined in a single run. The response observed in positive ionization mode has been found to be better as compared to negative ionization mode. The use of positive ionization mode enables detection of all the three ivermectin, doramectin and moxidectin to very low levels.