Development and validation of methodology for the determination of residues of organophosphorus pesticides in tomatoes

the organophosphorus pesticides are frequently applied in tomato cultivation in brazil. in the present work an analytical methodology for quantification of the organophosphorus pesticides: acephate, chlorpyrifos, malathion, methamidophos and parathion-methyl residues in tomatoes was developed and validated using gas chromatography with a nitrogen-phosphorus detector (gc-npd). the possibility of a matrix effect was studied. analytical curves prepared in an extract of the matrix were linear from 0.006 to 0.80 mg l-1. the precision studies supplied results with rsd <15%. the recoveries of the pesticides calculated from the curve prepared in the matrix extract were between 88 and 118%. with the proposed procedure quantification limits between 0.0132 and 0.135 mg kg-1 were obtained.