Determination of metamitron residues in sugar beet plants and soil applying solid-supported liquid-liquid extraction followed by gradient RP-HPLC

Metamitron {4-amino-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one} is a triazinone herbicide widely used for weed control in sugar and fodder beet plantations. Its residues were found to be relatively stable not only in plants but also in soil, and have to be determined in these materials. In this paper a rapid, simple and inexpensive method for determination of metamitron residues in sugar beets and soil samples has been proposed. Detection limit of 20 μg kg -1 has been achieved. The method was based on extraction ofmetamitron from either plant or soil material to water using methanol-water mixture (95:5), followed by methanol evaporation and purification of the obtained aqueous phase by solid-supported liquid-liquid extraction (SLE). The final step of the procedure was focused on determination of the target compound applying reverse phase high performance liquid chromatography (RP-HPLC) and UV photodiode array detection (PDA). Recovery of metamitron for the spiked samples at the level 0.1 mg kg -' was 93% and 87% for the soil and sugar beet, respectively while relative standard deviations ranged from 4.0% for the soil to 3.7% in case of the plant material.