engleski

Method recovery and reproducibility for determination of six indicator PCBs in pine needles

Pine needles are covered by wax which has the ability to absorb lipophilic pollutants such as polychlorinated biphenyls (PCBs) from ambient air. This is why pine needles are often used in biomonitoring atmospheric pollution. As PCB levels in pine needles are relatively low (ng/g) the method for their determination, has to be highly selective and sensitive, The aim of this study was to test the recovery and reproducibility of a method introduced for determination of six indicator PCBs (PCB-28, PCB-52, PCB-101, PCB-138, PCB-153, PCB-180 ; IUPAC numbering) in pine needles over a long period. This method was adopted from Franich and co-workers (Fresenius J Anal Chem (1993)347:337-343) and modified in 1998 by Herceg (M.Sc. Thesis, University of Zagreb, 1999).Twenty-four hour wax extracts from dried and ground pine needles were cleaned-up in a multiphase procedure which included precipitation of wax by cooling, saponification with potassium hydroxide, and adsorption chromatography on a multilayer silica column. Qualitative and quantitative analysis was done by using the capillary gas chromatography with electron capture detection. Between 1998 and 2002, thirteen samples were analysed. Recovery and reproducibility were determined by adding known amounts of compounds to samples of dried ground needle extracts at the level similar to levels at which they were present in native samples (range: 1.4-2.1 ng/g dry weight). Mean recoveries of the six PCB congeners ranged between 34 and 54 %, whereas long-term reproducibility expressed as relative standard deviation (RSD) was in the range of 29-43%. The variation of results was in good agreement with the results obtained in an earlier validation (recoveries range: 33-54 % RSD_reproducibility 31-48 %) (Herceg S., M.Sc. Thesis, University of Zagreb, 1999). Although the recoveries are relatively low, probably due to the multiphase clean-up which was absolutely necessary, this analytical method for determination of PCBs in pine needles has been considered acceptable because if its long-term reproducibility.

Polychlorinated biphenyls; indicator PCBs; pine needles

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