Development of a highly sensitive enzyme-linked immunosorbent assay for atrazine Performance evaluation by flow injection immunoassay

Specific polyclonal antibodies to the herbicide atrazine (6-chloro-N-ethyl-N′-isopropyl-1,3,5-triazine-2,4-diamine) have been raised by immunizing three New Zealand rabbits. With the antisera (As) a highly sensitive enzyme-linked immunosorbent assays (ELISA) has been developed to determine atrazine in water samples. Several usable competitive immunoassays have been obtained by screening a battery of nine enzyme tracers (ETs) and three antisera. The optimized ELISA presents an IC50 of 0.28 nM (60 ng l−1) and a detection limit of 0.043 nM (9 ng l−1). Cross-reactivity studies have proved that the immunoassay is specific for atrazine while other triazine compounds are only detected on a minor extent. The flow injection immunoanalysis (FIIA) method has an IC50 of 2 nM (0.47 μg l−1) reaching a detection limit of 0.35 nM (75 ng l−1). The performance of both methods has been evaluated by analyzing water samples containing mixtures of atrazine and other pesticides at the ppb level. For this purpose two candidate reference materials have been used (A and B) and a spiked sample stored on Empore disks (sample C). A close correspondence was found between the results obtained with both immunochemical techniques.