Matrix solid-phase dispersion microextraction and determination of pesticide residues in medicinal herbs by gas chromatography with a nitrogen-phosphorus detector

A gas chromatography method for the determination of residues of 6 pesticides in Isatis indigotica Fort and Paeonia lactiflora Pall is described. Optimizations of different parameters were performed. The method used 0.5 g herb sample, silica gel as the matrix solid-phase dispersion sorbent, and acetone as the eluting solvent. Recoveries at spiked concentrations between 0.1 and 5 mg/kg were between 80.63 and 110.12%, with relative standard deviations ranging from 0.43 to 17.67%. The limits of quantitation were 0.01 mg/kg for metalaxyl, triadimefon, and paclobutrazol and 0.05 mg/kg for vinclozolin, tebuconazole, and fenarimol. The method may be useful as a screening protocol for the determination of these pesticides in medicinal herb samples.