Levels of metamidophos in air and vegetables after greenhouse applications by gas chromatography.

The diminution of metamidophos residue levels with time in vegetables an greenhouse air was investigated after treatment of tomatoes and green beans. A gas chromatographic method using dichloromethane as an extraction solvent has been developed to analyse metamidophos in vegetables, with obtained recoveries higher than 89%. The reliability of several sorbents for air sampling was tested using standard atmospheres resulting in recoveries higher than 90% from PUF, XAD-2, XAD-4 and Supelpak using Soxhlet extraction with acetone. The dissipation of metamidophos in greenhouse air was studied 52 h after application. Finally the effect of crop, type of greenhouse, season and dose applied on the dissipation kinetic of metamidophos in vegetables, was statisTically studied by analysis of variance resulting in crop and season being the most significant factors.