Analysis of Metribuzin and Associated Metabolites in Soil and Water Samples by Solid Phase Extraction and Reversed Phase Thin Layer Chromatography

Abstract

A method to analyze metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one, and its major metabolites, deaminated metribuzin, DA, 6-(1,1-dimethylethyl)-3-(methylthio) -1,2,4-triazin-5(4H)-one, diketometribuzin, DK, 4-amino-6-(1,1-dimethylethyl)-1,2,4-triazin-3,5(2H,4H) -dione and deaminated diketometribuzin, DADK, 6-(1,1-dimethylethyl)-1,2,4-triazin-3,5(2H,4H)-dione in soil and water samples by reversed-phase thin layer chromatography (RPTLC) is described. Soil samples were extracted with MeOH:0.01 M CaCl₂.2H₂O (4:1) and the extracts filtered to remove the sediment. The extract then was diluted with deionized water and eluted through a C18, solid phase extraction (SPE) cartridge. Water samples (150-mL) were eluted directly through C18, SPE cartridges. Both soil and water extracts were chroma-tographed on pre-coated RPTLC plates. The concentration of metribuzin was determined by UV densitometry at 290 nm. Recoveries of metribuzin from soil samples fortified at 2 mg kg⁻¹ ranged from 73–86%. Recoveries from water samples fortified at 10 and 100 μg L⁻¹ ranged from 85 to 92%. The detection limit of the method for metribuzin is 30 nanograms.