SORPTION AND BOUND RESIDUE FORMATION OF LINURON, METHYLPARATHION, ANDMETOLACHLOR BY CARROT TISSUES - KINETICS BY ONLINE HPLC MICROEXTRACTION

The feasibility of determining the identities and kinetics behavior of three pesticides in carrot tissue slurries using a novel on-line HPLC microextraction was investigated. Linuron, methylparathion, and metol achlor were added to aqueous slurries of carrot tissue particles small er than 150 mu m. For each pesticide, the solution phase and the total pesticide recoverable from the whole slurry concentrations were separ ately monitored over a 10 day period. Kinetics curves for three catego ries of chemical species including solution phase pesticides, labile s orbed fractions, and unrecovered fractions were obtained. The linuron and metolachlor data are consistent with the commonly reported two-ste p sorption mechanism consisting of labile sorption followed by intrapa rticle diffusion, but the methylparathion data resemble a combination of labile surface sorption and solution phase and/or surface chemical decomposition. It is concluded that laboratory test methods of this ty pe could be developed for assessing the risk of bound residue formatio n in vegetables.