Immunoanalysis and separation of dissolved from particle‐bound pesticide residues

Abstract

A small‐volume filtration method was developed for use in the analysis of total, bound and dissolved residues of four agrochemicals which differed in physico‐chemical properties, in turbid water. Low immunoassay recoveries of molinate, chlorpyrifos and endosulfan (but not diuron) in highly turbid water samples suggested that the antibodies were unable to recognize particle‐bound residues. However, in samples of moderate or low turbidity, the results indicated that the data obtained by immunoassay s may approximate the total residue load in samples, especially if the samples are filtered through a non‐absorptive membrane. The 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 than one with cellulose acetate, polyvinylidene difluoride or polytetrafluoroethylene for filtration of small volumes of water for separation of the dissolved residues, and removal of the residue that desorbed during filtration, without losses of the pesticide on to the membrane. This method should facililate ecotoxicological analysis by enabling the direct analysis of agrochemicals by immunoassay in field water samples.

Keywords:

• Pesticide
• particles
• adsorption
• water