DIMINUTION OF CHLORPYRIFOS AND CHLORPYRIFOS OXON IN TOMATOES AND GREEN BEANS GROWN IN GREENHOUSES

A simple method based on dichloromethane extraction, gas chromatograph ic pulse flame photometric detection (GC/PFPD) and GC/MS confirmation has been applied to the analysis of chlorpyrifos and chlorpyrifos oxon residues in both tomatoes and green beans grown in two different type s of greenhouses. To establish the influence of environmental conditio ns on the decrease of chlorpyrifos, several field trials have been car ried out in which crops were sprayed at two different doses and in two seasons (spring and winter). Analysis of variance (ANOVA) has been ap plied to the results obtained, showing that the type of crop and the s eason are the most relevant factors in the degradation of chlorpyrifos . The oxon was detected the first 5 days after application, but a corr elation with the diminution of the parent compound has not been found. The half-life of chlorpyrifos ranged between 4 and 5 days depending o n the crop and season.