Competitive inhibition ELISA for the s-triazine herbicides: assay optimization and antibody characterization

Abstract

The present work describes screening and selection of rabbit antisera raised against the s-triazine herbicides, characterization of antibody cross-reactivity and specificity, and improvements in ELISA sensitivity. These results stem from a comprehensive synthetic approach described previously for the production of s-triazine haptens. Both homologous and heterologous ELISA systems were examined by using heterology based on hapten conjugation position, spacer length, and/or alkyl substitution. Sensitivity to the target analyte and to nonspecific effects was least for homologous systems. Except for extreme differences in spacer length, heterology based on conjugation position provided the largest improvement in sensitivity to the target analyte. Matrix and solvent effects depended on the ELISA system used. Specificity studies using several antibodies in competitive inhibition ELISA with over 30 inhibitors showed that conjugation position and alkyl substitutions were important determinants of antibody specificity and that the antibodies recognized the immunizing hapten better than all other inhibitors tested. The resulting assays were capable of detecting the parent and related s-triazines a t low ppb to sub-ppb levels.