Determination of Poly Chlorinated biphenyls in sediment of Trondheim fjord (Norway) and Lake Tana (Ethiopia) using pressurized liquid extraction (PLE) and Gas Chromatography – Mass Spectrometry (GC-MS).

Abstract

The presence of polychlorinated biphenyls (PCBs) in the environment is of great concern, as they are compounds that are hazardous to the environment and human health. Environmental investigations of PCBs can be challenging as they are found in trace amount, thus, it is important to have a reliable method for the determination of PCBs in environmental samples. In this work, an analytical method for the determination of PCBs in marine sediment samples was tested on sediment samples from Trondheim fjord, Norway, and Lake Tana Bahir Dar, Ethiopia. The samples were extracted by accelerated solvent extraction (ASE) and the analyses were carried out by gas chromatography coupled with mass spectroscopy. The method made it possible to quantify the Dutch seven target PCBs (indicator PCBs) in marine sediments.

By the GCMS result, from out of the Dutch seven indicator PCBs six PCBs were found and quantified in samples from Trondheim Bay ranging from 13 - 141 ng/g in dry sediment weight. Similarly, four PCB is found and quantified in samples from Steinkjer ranging from 10.5-28.5 ng/g in dry sediment weight. Only PCB 118 is quantified in samples from Verdal fjord with amount of 14.1 ng/g in dry sediment weight. Samples from Ethiopia have only two quantified PCBs ranging from 10.8 – 14.4 ng/g in dry sediment weight.  In all sediment samples the amount of PCB found is under the Effect Range Medium (ERM). ERM value for PCB is 180ng/g. Also according to the Norwegian climate and pollution agency (Klif), all sediment samples lies in moderately polluted (17-190ng/g) group. This indicates all study areas are environmentally safe relative to PCB contamination.

The analytical method was shown to have an acceptable instrumental precision, LOD ( 3 – 5 ng/g in dry weight), LOQ (10-14 ng/g in dry weight),   and linearity (r²= 0.97), while the method remains to be further developed in order to improve the accuracy and selectivity. Specially, PCB 28 and PCB 31 were overlap and not separated in this study. Therefore, further work is recommended to be done in order to achieve a reliable method for the determination of PCBs in marine sediment samples using ASE and GC-ECD (gas chromatography – electron capture detector, which has high selectivity for PCBs) or tandem mass spectroscopy. May be a column of 60m is likely to improve the selectivity of the analyte, which is therefore recommended to test. 

Key word: PCB, ASE, internal standard method, GC-MS, Pressurized Liquid Extraction (PLE)