Reversible immunosensor for the automatic determination of atrazine. Selection and performance of three polyclonal antisera

The development of an immunosensor for the highly sensitive, rapid and auto matic analysis of the herbicide atrazine is presented. The immunosensor use d the principles of competitive direct enzyme immunoassays, and protein A/G covalently bound to an azlactone-activated polymeric support as immunocomp lex affinity binder. The immunosensor was completely automated, and was abl e to carry out a complete analysis, including surface regeneration, in less than 25 min, having a complete autonomy for more than 72 h. Three antisera have been tested and their performance compared in terms of sensitivity an d cross-reactivity, and only slight differences in behavior have been found . The best antiserum for sensitivity (R-11) led to a competitive calibratio n curve with an I-50 value of 0.053 mu g l(-1) (0.24 nM), a limit of detect ion (90% of blank signal) of 0.007 mu g l(-1), and a dynamic range from 0.0 14 to 0.232 mu g l(-1). The best antiserum in terms of cross-reactivity (R- 10) led to a system that was also very sensitive (I-50 0.101 mu g l(-1) and limit of detection 0.011 mu g l(-1)) and free of interferences except from propazine. The immunosensor using all the three antisera has been used to determine atrazine in reference river water samples, and results were compa red to ELISA and chromatography measurements. The immunosensor based on R-1 0 antiserum produced the best results when compared to those obtained with reference methods (101.4% and 104.8% mean recoveries for chromatography and ELISA, respectively), although a good correlation is achieved with all the three antisera. (C) 1999 Elsevier Science B.V. All rights reserved.