IMMUNOANALYSIS AND SEPARATION OF DISSOLVED FROM PARTICLE-BOUND PESTICIDE-RESIDUES

A small-volume filtration method was developed for use in the analysis of total, bound and dissolved residues of four agrochemicals which di ffered in physico-chemical properties, in turbid water. Low immunoassa y recoveries of molinate, chlorpyrifos and endosulfan (but not diuron) in highly turbid water samples suggested that the antibodies were una ble to recognize particle-bound residues. However, in samples of moder ate or low turbidity, the results indicated that the data obtained by immunoassays may approximate the total residue load in samples, especi ally if the samples are filtered through a non-absorptive membrane. Th e adsorption pattern of each membrane was different for each pesticide , and related to their water solubilities and partition coefficients. A syringe filter with an aluminium oxide membrane was more suitable th an one with cellulose acetate, polyvinylidene difluoride or polytetraf luoroethylene for filtration of small volumes of water for separation of the dissolved residues, and removal of the residue that desorbed du ring filtration, without losses of the pesticide on to the membrane. T his method should facilitate ecotoxicological analysis by enabling the direct analysis of agrochemicals by immunoassay in field water sample s.