The multi-residue determination of coumarin-based anticoagulant rodenticides in animal materials by high-performance liquid chromatography.

The rodenticides brodifacoum, difenacoum, coumatetralyl and warfarin are determined in animal relicta by high-performance exclusion chromatography on porous silica. The first three compounds are not separated, but are subsequently differentiated by adsorption or reversed-phase high-performance liquid chromatography of the appropriate eluate fraction collected from the exclusion column. The method is rapid, and clean-up (on Sep-Pak silica cartridges) is simple. Mean recoveries from spiked substrates were generally above 80% at levels of 0.1-1.0 mg/kg. Routine limits of determination are about 0.05-0.1 mg/kg for warfarin and about 0.02 mg/kg for the other compounds. If analysis for warfarin is not required, the latter limit can be lowered to about 1 microgram/kg by a slight modification to the clean-up step.