Improvement of an enzyme immunoassay for the determination of mercury (II)

Three systems were tested for the optimization of a heterogenous non-competitive enzyme immunoassay (EIA) for the determination of Hg (II). The sensitivity of the non optimized Hg-EIA with a detection limit of 2.1 μg/L Hg (II) was improved by an avidin-biotin-complex (ABC) amplification system to a 2-fold lower detection limit (1.1 μg/L Hg (II)). A conventional competitive EIA with the competition reaction between bound and free Hg (II) for antibody (ab) binding sites yielded a detection limit of 1.0 μg/L Hg (II). Further improvement of sensitivity could be achieved by a competitive displacement EIA. In this case ab molecules bound to immobilized haptens are displaced in the next step by free Hg (II). The detection limit of the displacement approach is 0.4 μg/L Hg (II).