Abstract:

Conditions for pretreatment and determination of organophosphorus pesticide residues contained in fruits of Citrus unshiu Marc. 'Guoqing 1' were optimized. Furthermore, the dynamical regularity of chlorpyrifos in citrus fruits was studied. The results showed that pretreatment techniques were suitable for citrus sample. The limits of detection for dimethoate, methidathion and chlorpyrifos were 0.244，0.306 and 0.409 μg·mL^-1 respectively，the average recoveries were from 74.76 to 99.16 %，and the relative standard derivation (RSD) were between 1.01 % and 10.08 %，which met the requirements of multiple residues analysis in a single run. More pesticide residues and faster dynamical regularity of chlopyrifos were found in the peel than in the pulp of citrus，and almost no residue was found in fruits after 30 days of spraying. The half-life of the pesticide was significantly different between the citrus fruits treated with different pesticide concentrations. The degeneration of chlorpyrifos residue in citrus peel and pulp were 10.71 ~ 10.88 d and 13.55 ~ 13.85 d respectively.

Key words: citrus, organophosphorus pesticides, pesticide residues, solid phase extraction-high performance liquid chromatography (SPE-HPLC), dynamical regularity