Quantitative immunoassay for determining polyaromatic hydrocarbons in electrical insulating oils

The development and application of a combined sample extraction and immunoa ssay protocol for the quantification of polyaromatic hydrocarbons (PAHs) in transformer oils is reported. Tests were performed on 12 different used tr ansformer oils from three major manufacturers. The removal of matrix interf erents was achieved by loading oil fractions onto silica solid phase extrac tion cartridges and eluting with non-polar solvent prior to evaporation and reconstitution in a more polar medium. Extracts were immunoassayed using t wo commercially available PAH test kits either having broad specificity tow ards priority PAHs or enhanced binding specificity toward more carcinogenic PAHs. The total and carcinogenic PAH test kits yielded PAH levels in the o il extracts 5.86-fold and 126-fold lower than the industry-standard IP346 m ethod. The latter method, widely used by the industry, since it correlates with biological carcinogenicity tests, grossly over-estimates PAH levels in oils since it is a non-specific gravimetric solvent extraction approach. T he assay was found to be unaffected by the extract sample matrix and was ca pable of determining PAHs at the nanogram per millilitre level. The assay p rotocol was simple, low-cost and rapid (<2 h) and equally amenable to opera tion at remote sites or high-throughput sample screening. The binding speci ficity of the total anti-PAH antibody was examined by preparing and loading an anti-PAH immunosorbent with oil, prior to solvent displacement of antib ody-bound compounds and by gas chromatography (GC)-mass spectrometry (MS) a nalysis. (C) 2001 Elsevier Science B.V. All rights reserved.