Abstract
A rapid and simple method was developed for screening polychlorinated biphenyls in transformer oil. The method is based on liquid-liquid extraction in methanol and subsequent direct gas chromatography-mass spectrometric determination. The extent of methanol polarity allows to extract the PCBs, co-extracting a minimum amount of the apolar oil components, thus avoiding the time-consuming steps involving in sample preparation. Since the regulation established internationally for wastes containing PCBs is 50 mg kg-1, the method rapidly determines whether the transformer oil is PCBs-contaminated or not. In order to reach the best conditions for extraction a multivariate optimization was carried out considering two significant variables: volume of methanol and extraction time. Under optimum conditions, recoveries of Aroclor 1256 and Aroclor 1260 were between 80 and 100%, and precision, expressed as relative standard deviation, was from 2 to 4%. The method was applied to real samples polluted with PCBs.
Highlights
The polychlorinated biphenyls (PCBs) are 209 isomers which are synthesized through chlorination of the biphenyl rings
The proposed method is based on liquid-liquid extraction of PCBs from transformer oil using methanol as a solvent and on direct analyte determination in the extract by mass spectrometry, utilizing selective ion monitoring (SIM) to determine different Aroclors
A small amount of oil is co-extracted as can be seen in the TIC chromatogram of a blank (PCB free-oil) extract shown in Figures 1A and 1B
Summary
The polychlorinated biphenyls (PCBs) are 209 isomers which are synthesized through chlorination of the biphenyl rings. PCBs are very stable compounds and do not degrade Their chemical and physical stability has been responsible for their continued steady (low-level) persistence in the environment. Due to these features, PCBs. Various analytical methods have been reported for the determination of PCBs in transformer oils.[1,2,3,4,5,6,7,8,9,10] In the SW-486 series of US-EPA there are two screening methods, 40201 and 9079.2 In the first case PCBs concentrations may be rapidly estimated in samples of soil and non-aqueous liquid wastes. For exact determination, US-EPA indicates that method 80823 should be used through gas chromatography
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