To extend the application of a multichannel electrochemical detector (MED) for immunoassay, a MED system consisting of 8 sets of Pt electrodes in an arrangement fitted with the dimensions of a row of microtiter wells in a microtiter plate and a microcomputer-assisted 16-channel potentiostat was constructed. With this developed MED system, electroactive enzymatic products produced in eight microtiter wells can be analyzed simultaneously with a developed amperometric procedure. To demonstrate the applicability of the MED system for immunoassay, an immunosystem containing rabbit-IgG and alkaline phosphatase-conjugated goat anti rabbit-IgG was studied. From the dynamic range of 10-1000 ng/mL (0.064-6.4pM) and the detection limit of 1.0 ng/mL (6.4pM) obtained, the developed MED shows a tremendous improvement in sensitivity, detection limit, and efficiency compared with that obtained from conventional electrochemical immunoassay.

lic acid spacers at para-position were derived from coplanar 3,3,4,4-tetrachlorobiphenyl and 3,3_,4,4_,5-pentachlorobiphenyl (IUPAC No. 77 (PCB 77) and 126 (PCB 126), respectively). It appeared from the results that the length of the spacer did not affect significantly the sensitivity of the assays established. The direct ELISAs using the antibodies in combination with various hapten–peroxidase tracers showed IC50-values for polychlorinated biphenyl (PCB) 77 and 126 of 1.3–19.2μg l−1. The ELISAs were tested for their cross-reactivity profiles using 20 selected congeners. The assays were highly specific for non-ortho-substituted (coplanar) congeners and did not recognize the more abundant but less toxic non-coplanar PCBcongeners or organochlorine compounds. The superior assaywas found for the antibody againstPCB126-(CH2)3-hapten mimic–bovine serum albumin (BSA) in combination with PCB 77-CH2-hapten mimic-peroxidase tracer. The IC50-values for the assay to PCB 77 and 126 were 2.0 and 5.2μg l−1, respectively; the highest cross-reactivity values (PCB 126=100%) achieved for non-coplanar structures and metabolites were only 1.3 and 1.0% for 2,3,3,4,4,5,5 heptachlorobiphenyl (PCB 189) and PCB 77 ether, respectively. In order to interpret measured data in terms of analytical or toxicological equivalents, a reliable relationship between assay responses and the coplanar congener content of Aroclor-contaminated samples should be verified and validated.