Determination of polychlorinated biphenyl compounds in electrical insulating oils by enzyme immunoassay

Abstract

The development and performance of a competitive indirect immunoassay for the quantitation of polychlorinated biphenyl compounds (PCBs) in insulating oils is described. Reagent preparation and the assay characterisation, optimisation and validation steps are described. The dynamic range of the assay for Aroclors 1254 and 1260 in methanol was 30–1000 ng ml −1 with 50% signal inhibition values of 217 and 212 ng ml −1, respectively. Impending legislation in the UK is likely to decree that oils containing >50 μg ml −1 PCBs be considered contaminated. Assay sensitivity increased with the degree of PCB chlorination. The assay of structurally related compounds of environmental concern yielded cross-reactivity values of <0.6%. The immunoassay proved reliable for the analysis of diluted transformer oils containing >35 μg ml −1 PCB (neat) but over-estimated PCB levels in diluted oils containing <10 μg ml −1 of neat analyte. The oils required pre-treatment using either solid-phase extraction or washing with KOH–ethanol/sulphuric acid to remove matrix interferents. The analytical performance of the assay was compared against a commercially available semi-quantitative immunoassay kit for PCBs in soil and water.