Is. Kim et al., Quantitative immunoassay for determining polyaromatic hydrocarbons in electrical insulating oils, ANALYT CHIM, 450(1-2), 2001, pp. 13-25
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.