Enzyme-linked immunosorbent assays based on rabbit polyclonal and rat monoclonal antibodies against isoproturon

This work describes the production and characterization of rabbit polyclonal antisera (pAb) and rat monoclonal antibodies (mAb) against isoproturon. Coating antigen and enzyme-tracer formats were developed. Standard curves for isoproturon were conducted either in 40 mM phosphate buffered saline (PBS) or in Milli-Q water. PAb 352 together with the best enzyme tracer revealed in the optimized ELISA (enzyme tracer format) a test midpoint of 1.06 +/- 0.34 microg/L (n = 19, standard set up in Milli-Q water) with a detection limit of about 0.1 microg/L. The comparable ELISA with mAb IOC 7E1 had test midpoints of 0.07 +/- 0.04 microg/L (n = 7, standards in Milli-Q water) and 0.11 +/- 0.08 microg/L (n = 33; standards in 40 mM PBS). The limits of detection were about 0.003 and 0.01 microg/L in Milli-Q water and PBS, respectively. Noticeable cross reactivities (CRs) were seen with the major metabolites, namely 4-isopropylaniline, 4-isopropylphenylurea, and 1-(4-isopropylphenyl)-3-methylurea. With pAb 352, these CRs were 5%, 7%, and 31%, respectively, and with mAb IOC 7E1, they were 3%, 5%, and ca. 19%, respectively. All arylurea herbicides had only minor CRs, which ranged from no CR (e.g., chlorosulfuron) to a maximum of 3.3% (chlortoluron). Influences of organic solvents (methanol, ethanol, acetonitrile, and acetone) were evaluated. Both pAb- and mAb-based immunoassays showed the highest tolerance for methanol, up to 5%. Ethanol and acetonitrile could not be used above 2% without an influence on the assays. The same was true for acetone, although tested only in the mAb-based assay. Water samples of different origins and matrices were spiked and analyzed with these pAb and mAb ELISAs. The results demonstrated that these immunoassays are useful screening tools.