Abstract

A method capable of simultaneously detecting residues of three sulfonylurea herbicides at μg/I and μg/kg level in water and alkaline soils has been described. The method is based on solid phase extraction and HPLC with UV detection. In alkaline soils especially those containing low organic carbon it was possible to extract the herbicides with de‐ionised water and no clean up step was needed. Soil samples spiked with technical grade triasulfiiron, metsulfuron‐methyl and chlorsulfuron were extracted twice by shaking with de‐ionised water for one hour and centrifuging at 10000 rpm for 15 minutes. Supernatants filtered through glass micro‐fibre filters were passed through C₁₈ cartridges previously pre‐conditioned with methanol and de‐ionised water at a flow rate of < 20 ml/min. Residues of the herbicides retained on the cartridge were eluted with acidified methanol. The eluate was analysed by HPLC. A C₁₈ column was used with a mobile phase of methanol /water (40 + 60, V/V for for the herbicide residues were 1.0 μg/l and 3 μg/kg in water and soil, respectively. The average recoveries for water samples ranged from 73 ‐ 94%, while for soil samples recoveries were 77 ‐ 97% for the three compounds studied.