Nonextractable Pesticide Residues in Humic Substances: Immunochemical Analysis

Immunochemical methods are suited for determining non-extractable pesticide residues in humic substances. Soil samples may be assayed by a non-competitive, direct enzyme immunoassay (EIA). In this case, a signal directly proportional to the amount of non-extractable residues is obtained. 2-Chloro-4-arylamino-6-alkyl-1,3,5-triazines were applied as model compounds for non-extractable triazine residues in dissolved humic material and assayed by a competitive EIA. Cross-reactivities were determined as a measure of the affinity of antibodies toward the model compounds. 2-Chloro-6-isopropyl derivatives were recognized almost equally well as free atrazine. Investigations with a recombinant antibody showed comparable recognition of atrazine and arylamino-s-triazines, although higher concentrations of the analytes were necessary. Samples from photolytic degradation experiments with arylamino-s-triazines were assayed in parallel by EIA and HPLC and yielded comparable results.