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Abstract
Two QuEChERS kits originally designed for the extraction of pesticides in foods and foods of plant origin have been compared for the extraction efficiency of different analytes other than pesticides. Six veterinary drugs that have been prohibited for use in foods of animal origin were studied using milk as a matrix and LC-MS as a separation and detection mode. The Association of Official Analytical Chemists (AOAC) and the European Standard EN QuEChERS kits were compared after optimization of key parameters for extraction of chloramphenicol, metronidazole, chlorpromazine, dimetridazole, ronidazole, and dapsone. The EN QuEChERS kit was superior over the AOAC kit in terms of recoveries: (in brackets are % recoveries) chloramphenicol (79), metronidazole (55), chlorpromazine (93), dimetridazole (97), ronidazole (65), and dapsone (69). Using the AOAC kit gave the following values: (in brackets are % recoveries) chloramphenicol (71), metronidazole (66), chlorpromazine (60), dimetridazole (49), ronidazole (37), and dapsone (33). Additionally, three mass spectrometry scan modes, that is, full scan, SIM, and MS/MS were compared. Results showed that SIM was superior over full scan and MS/MS as in the case of chloramphenicol whose method detection limit (MDL) value was 16.3 µg/kg in the SIM mode and 28.2 µg/kg in the full scan mode.
ACKNOWLEDGMENT
The authors would like to thank the University of Botswana for material and financial support. Rose Kibechu would like to thank DAAD for the fellowship to enable her to pursue her M.Sc. study at the University of Botswana.