Chlorobiphenyls in sewage sludge; comparison of extraction methods |
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Authors: | M S Rahman M Parreño R Bossi A B Payá-Pérez B Larsen |
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Institution: | (1) Institute of Food and Radiation Biology Bangladesh Atomic Energy Commission, P.O. BOX 3787, Ganakbari, Savar, Dhaka, Bangladesh At the EC Joint Research Center under a training grant from the International Atomic Energy Agency, Vienna, Austria, AT;(2) National Polytechnical School, P.O. Box 2759, Quito, Ecuador At the EC Joint Research Center under a training grant from the International Atomic Energy Agency, Vienna, Austria, AT;(3) National Environmental Research Institute, P. O. Box 358, Roskilde, Denmark At the EC Joint Research Center for SEA Marconi Technologies, Torin, Italy, DK;(4) Environment Institute, EC Joint Research Center, I-21020 Ispra (VA), Italy, IT |
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Abstract: | Six extraction methods for the analysis of PCBs (CB-28, CB-52, CB-101, CB-118, CB-138, CB-153 and CB-180) in sewage sludge
were tested. A certified reference material (CRM 392) was used for the evaluation of the performance of the methods. Soxhlet-Dean-Starch
with toluene as solvent, Soxhlet with hexane:acetone (2:3), cold digestion/saponification with 2 mol/L KOH in methanol followed
by partition with hexane, and sonicated liquid-solid extraction with hexane:acetone (1:1) produced accurate results (97%,
93%, 104%, and 88%, respectively) with acceptable precisions (6.2%, 6.8%, 15% and 12%, respectively). Results in close agreement
with the certified value for all congeners were obtained by treatment with BF3-methanol prior to partition with dichloromethane. However, this is a tedious procedure and involves the use of hazardous
compounds. Cyclic steam distillation produced results with an accuracy of around 80% and a good precision (5.2%). The very
low consumption of solvents and other expensive chemicals by this technique and the possibility of analyzing the extract directly
without clean-up make it an interesting alternative to the more sophisticated methods. Column elution with dichloromethane
was found to be less efficient (61%), but it is a rapid, direct method with a low consumption of solvents and it may therefore
serve as screening method.
Received: 29 April 1997 / Revised: 30 July 1997 / Accepted: 6 August 1997 |
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