DETERMINATION OF PARAQUAT IN FRUITS AND VEGETABLES BY A MAGNETIC PARTICLE BASED ENZYME-LINKED-IMMUNOSORBENT-ASSAY

A competitive enzyme-linked immunosorbent assay (ELISA) for the quanti tation of the free paraquat cation was developed using polyclonal rabb it anti-paraquat antibodies bound to a magnetic particle solid phase. A method for the extraction of the paraquat cation from various fruits and vegetables in less than 30 min was developed for use in conjuncti on with the immunoassay. The procedure has an estimated detection limi t of 10 ng/g (ppb) paraquat cation based on the 20 pg/mL estimate in b uffer. Results can be easily converted to the dichloride result by div iding the cation concentration by 0.724. Paraquat cation recoveries av eraged 99% using this extraction method and immunoassay for cabbage, a pples, and potatoes. A collaborative study in which paraquat-fortified zucchini samples were extracted using the traditional 5 h reflux prio r to spectrophotometric and immunoassay measurement yielded a correlat ion of 0.994 with a slope of 1.05.