Multi-class determination of anthelmintics in soil and water by LC-MS/MS

The translocation of antiparasitic drugs from animal excrement through soil and water to crops and forages and their recycling to food-producing animals is a potential concern with respect to the contamination of the food chain. To facilitate the investigation of this problem, an LC-MS/MS method for selected anthelmintics in soil and water was developed. The soil sample preparation involved a simple solvent extraction and dispersive clean-up technique. The method was validated at 10, 20 and 40 µg kg⁻¹ for levamisole, fenbendazole, fenbendazole sulphoxide and fenbendazole sulphone and at 20, 40 and 80 µg kg⁻¹ for eprinomectin. LOQs were 10 µg kg⁻¹ for the first four compounds and 20 µg kg⁻¹ for eprinomectin. The overall mean recoveries ranged from 76.1% to 89% for loamy soils and from 79.9% to 96.9% for sandy soils. Analysis of water samples was performed by extraction/concentration on an Oasis-HLB (Aschaffenburg, Germany) cartridge. Validation was performed at 0.25, 0.5 and 1.0 µg l⁻¹. The LOQ for all compounds was 0.25 µg l⁻¹. Method recovery (and RSD) varied between 35.4% (28) for eprinomectin and 125.1% (16) for fenbendazole sulphone. The validated methods were applied to soil and water samples in a study on the behaviour of anthelmintic drugs in a soil-plant-water system (manuscript on “transport investigation of antiparasitic drugs based on a lysimeter experiment” in preparation).