Stability studies of carbamate pesticides and analysis by gas chromatography with flame ionization and nitrogen–phosphorus detection

As a result of thermal stability studies of carbamate pesticides, a method has been proposed for their direct determination by gas chromatography in the ranges 1–20 and 0.1–1 mg l−1, using flame ionization and nitrogen–phosphorus detection, respectively. The method allows the determination of propham, propoxur, carbofuran, carbaryl, methiocarb, isopropoxyphenol and naphthol in powdered potato samples. The analytes were previously extracted with a light petroleum–dichloromethane (1:1, v/v) mixture and preconcentred by solid-phase extraction through a C8 cartridge. The recoveries obtained from spiked potato samples (n=4 replicates) at two concentration levels, 10 and 0.5 mg of pesticide per kg of sample, were in the ranges 72–115 and 50–73%, with relative standard deviations of 2–7 and 5–8%, respectively. The detection limits were 50–210 and 41–53 μg kg−1 with flame ionization and nitrogen–phosphorus detection, respectively, and reaching the maximum residue levels, 0.05 mg kg−1 for methiocarb and propoxur, set by the Real Decreto 280/1994 (based on the European directive).