Determination of coumarin rodenticides in soils by high performance liquid chromatography

A method for the determination of warfarin, coumatetralyl, bromadiolone, flocoumafen and brodifacoum residues in soils with post. column derivatization and fluorescence detection by high performance liquid chromatography (HPLC) was established. The samples were extracted with a mixed solution of acetone, ammonium and methanol (100 : 3 : 100, v/v/v) after adding ratilan as internal standard. The extracts were vacuum. concentrated and dissolved in 5 mL mixed solution of hexane and chloroform (3 : 1, v/v) for solid phase extraction (SPE) clean up on an aminopropyl column. The analytes were eluted from the column using 15 mL of 50 mmol/L tetrabutylammonium dihydrogen phosphate in methanol. The solvent was evaporated and the sample was dissolved in a mixed solution of methanol and 0. 25% (v/v) acetic acid aqueous solution (3 : 2, v/v). The coumarin rodenticides were separated on a C-18 column by HPLC and on. line derivatized with a mixed solution of methanol, ammonium and water (1 : 1 : 8, v/ v/v) and detected with a fluorescence detector. Good linearities of the ana. lytes were achieved over the mass concentration of 0. 02-10. 00 mg/L, with correlation coefficients above 0. 999. The limits of quantification (LOQ, S/N = 10) were 2. 2-18. 5 mu g/L for the five coumarin rodenticides. The recoveries were 94. 6% - 118. 0% at the spiked levels of 0. 1-0. 3 mg/kg in soil with the relative standard deviations of 0. 8% - 10. 2% (n = 3). The results indicated that the method is sensitive and accurate with repeatability.