Preparation and evaluation of immunosorbents for selective trace enrichment of phenylurea and triazine herbicides in environmental waters

The development of new immunosorbents for the selective solid-phase extraction of phenylurea and triazine herbicides from environmental waters is presented. The production and purification of polyclonal antibodies against isoproturon and atrazine are described. The immunoconjugates were characterized by electrospray mass spectrometry before immunization of rabbits. Silica-based sorbents were shown to be more effective than rigid hydrophilic polymers for the covalent coupling of antibodies because no nonspecific interactions occurred between analytes and the silica matrix. Off-line enrichment using cartridges shows that the immunosorbent can trap several analytes in the same group (9 in a mixture containing 13 phenylurea herbicides, and 6 in a mixture containing 9 triazine herbicides). A stepwise elution with increasing amounts of methanol showed that the analytes had different affinities for the immunosorbents. The elution conditions were found to be similar for the two immunosorbents, and 70% methanol was necessary for the efficient desorption of all the analytes. High selectivity was illustrated by analyzing Seine river samples spiked with mixtures of phenylurea or triazine herbicides. No interfering compounds were detected in the chromatograms, and the base lines were as clean as those corresponding to drinking water samples. Isoproturon was easily detected in surface waters at the 0.1 μg/L level with no cleanup. These results demonstrate the potential of such immunosorbents for the selective preconcentration of herbicides for multiresidue analysis. The identification of herbicides in unknown samples is strongly supported by the selective preconcentration.