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

The development of an immunosensor for the highly sensitive, rapid and automatic analysis of the herbicide atrazine is presented. The immunosensor used the principles of competitive direct enzyme immunoassays, and protein A/G covalently bound to an azlactone-activated polymeric support as immunocomplex affinity binder. The immunosensor was completely automated, and was able 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 and cross-reactivity, and only slight differences in behavior have been found. The best antiserum for sensitivity (R-11) led to a competitive calibration curve with an I50 value of 0.053 μg l−1 (0.24 nM), a limit of detection (90% of blank signal) of 0.007 μg l−1, and a dynamic range from 0.014 to 0.232 μg l−1. The best antiserum in terms of cross-reactivity (R-10) led to a system that was also very sensitive (I50 0.101 μg l−1 and limit of detection 0.011 μg 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 compared to ELISA and chromatography measurements. The immunosensor based on R-10 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.