Decline rates of chlorpyrifos residues in green beans grown in plastic greenhouses

Residue levels and decline rates of chlorpyrifos residues in green beans sprayed with Dursban 48 at single and double dose and grown in a greenhouse were studied. Chlorpyrifos residue levels were determined by applying the ethyl acetate based extraction method and analyzing extracts by GC-NPD. Statistical analysis confirmed that decline of chlorpyrifos residue levels can be described as a pseudo-first-order reaction. Half-life periods determined were 3.26 days and 3.17 days for single and double dose treatments, respectively, whereas the corresponding initial residue values were 2.68 and 11.66 mg/ kg, respectively. Chlorpyrifos residues calculated after 21 days were 0.03 (single dose) and 0.12 (double dose) mg/ kg. The value for the double dose is higher than the maximum residue level (0.05 mg/kg) established by the European Union for chlorpyrifos in green beans.