Determination of Polychlorinated Biphenyls by Exhaustive Chlorination Method

Abstract

Technique to determine residual polychlorinated biphenyls (PCBs) has been complicated by the fact that PCBs are not single compound, but complex mixtures of isomers having various degrees of chlorination.
A method is described for the determination of PCBs through exhaustive chlorination.
The procedure is as follows.
1. Approximately 1μg of the ordinarily cleaned-up sample of PCBs is treated with 0.5ml of antimony pentachloride at 220°C for 2 hours in a sealed glass tube.
No prior separation of PCBs from DDE is required.
2. Decachlorobiphenyl formed is taken up into 20ml of benzene, and the solution is washed successively with 30% hydrochloric acid, 10% tartaric acid solution and water, dried by passing through micro-column packed with 1g of silica gel containing 5% water, and concentrated under stream of dry air.
3. Decachlorobiphenyl is analysed by gas-liquid chromatography with electron capture detector by using liquid phases such as DEGS-PA and OV-1.
At levels higher than 1μg, the described procedure gives almost quantitative yield of decachlorobiphenyl.
By this method total PCBs can be determined unequivocally as decachlorobiphenyl equivalent. Therefore, on assuming that residual PCBs constantly contain 50% chlorine, estimation of the amount of PCBs originally present can also be made with an error of up to 25%, because the chlorine contents of the common commercial PCBs preparations varies exclusivelyb etween 40 and 60%.