|
(38-62) Comparison of ASE and soxhlet extraction for organic pollutants in soil. Körner, W.*,1, Waller, U.1, Kaiser, O.1, Lachenmair, I.1, Reifenhäser, W., 1 Bayerisches Landesamt für Umweltschutz, Augsburg, /, Germany ABSTRACT- Solvent extraction is generally the first step in the analysis of solid environmental matrices for persistent organic pollutants such as chlorinated dioxins and furans (PCDD/PCDF) and polychlorinated biphenyls (PCB). The classical methods, e.g. soxhlet extraction, require much time (24h) and high amounts of organic solvents. In this respect the accelerated solvent extraction (ASE) offers a fast and convenient alternative. However, due to the application of high pressure and temperature, ASE is prone to deliver higher extraction yields than soxhlet extraction. We performed ASE (175°C, 14 MPa, 5 cycles á 5 min static extraction time) as well as 24h soxhlet extraction of freeze-dried soil samples (n=10) with toluene and analyzed both extracts after the same clean up procedure for PCDD/PCDF and PCB by GC/MS. As expected, ASE generally yielded higher levels than soxhlet extraction. The concentration ratio ASE/soxhlet was up to 2.0 for PCDD/PCDF (I-TEQ value) and up to 3.6 for PCB (sum of 6 congeners). Surprisingly, for several samples the individual substances of the same class of compounds showed different concentration ratios ranging e.g. from 1.3 for PCB 180 to 3.7 for PCB 52 in one sample. In conclusion, the results demonstrate that it is not possible to define factors for an accurate and precise extrapolation of concentrations obtained with ASE to those achieved after soxhlet extraction or vice versa. That is an obstacle for the introduction of ASE in existing monitoring programs where the highest possible analytical accuracy is necessary to detect possible time trends in the environmental concentrations of organic pollutants. Key words: ASE, Soxhlet, PCDD/PCDF, PCB |
