Submitted to: Journal of Chromatography A
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2010
Publication Date: 7/1/2010
Citation: Whelan, M., Kinsella, B., Furey, A., Cantwell, H., Lehotay, S.J., Danaher, M. 2010. Determination of anthelmintic drug residues in milk using UPLC-MS/MS with rapid polarity switching. Journal of Chromatography A. 1217(27):4612-4622. Interpretive Summary: The analysis of veterinary drug residues in animal-derived foods, such as milk and beef, is an important function of regulatory bodies worldwide to ensure the proper usage of the chemicals by producers and to help ensure food safety. Currently, inefficient analytical monitoring methods are used by many regulatory agencies, which need updating to more efficient and effective modern approaches. In the case of worm controlling agents, known as anthelmintics, the previous analytical methods required multiple analyses to cover all 38 of them for monitoring purposes. This research combined different analytical methods into the same analysis, thereby saving time, solvent, and effort. The streamlined method was validated thoroughly to demonstrate its satisfactory performance in regulatory applications. In the future, it is already being routinely used by regulatory laboratories in Ireland, and it will be transferred to U.S. monitoring labs in the near future.
Technical Abstract: A new UPLC-MS/MS (ultra-performance liquid chromatography coupled to tandem mass spectrometry) method was developed and validated to detect 38 anthelmintic drug residues, consisting of benzimidazoles, avermectins and flukicides. A modified QuEChERS-type extraction method was developed with an added concentration step to detect most of the analytes at <1 µg kg-1 levels in milk. Anthelmintic residues were extracted into acetonitrile using magnesium sulphate and sodium chloride to induce liquid-liquid partitioning followed by dispersive solid phase extraction for cleanup. The extract was concentrated into dimethyl sulphoxide, which was used as a keeper to ensure analytes remain in solution. Using rapid polarity switching in electrospray ionization, a single injection was capable of detecting both positively and negatively charged ions in a 13 min run time. The method was validated at two levels: the unapproved use level and at the maximum residue level (MRL) according to Commission Decision 2002/657/EC criteria. The decision limit (CCa) of the method was in the range of 0.14 to 1.9 and 11 to 123 µg kg-1 for drugs validated at unapproved and MRL levels, respectively. The performance of the method was successfully verified for benzimidazoles and levamisole by participating in a proficiency study.