Abstract:

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 C₁₈ 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 analytes 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 μg/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.

Key words: coumarin rodenticides, fluorescence detection, high performance liquid chromatography (HPLC), post-column derivatization, residues, soils