[Gas chromatography determination of metalaxyl in plant material]

The control of mycosis on potatoes, tomatoes and cucumbers with metalaxyl demands toxicological evaluation of its residues. It was necessary to elaborate a gaschromatographic method for the determination of the active compound. The plant materials are extracted by homogenization with methanole. The clean up is carried out by precipitate of coextractives, liquid-liquid-partition and column chromatography with aluminia. The quantitative determination is performed on 3% OV 225/Varaport 30, 1.95% OV 210 and 1.5% OV 17 on Chromosorb W HP packed columns and a phenylmethylsilicon fused silica capillary column using a N/P-detector. The minimum detectable quantity is in the range of 0.02 to 0.08 ng. Recoveries from 84 to 92% were obtained after fortification with 0.05 to 1.0 mg/kg. Limits of determination are in the range from 0.05 to 0.5 mg/kg.