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(25-10) FT-IR characterization of metal-bonding organic groups in SFE extracts of soils and sediments. Heltai, György1, Fehér, Balázs*,1, Horváth, Erzsébet2, Kristóf, János3, 1 Department of Chemistry and Biochemistry, Szent István University, Gödöllö, Hungary2 Research Group for Analytical Chemistry of Hungarian Academy of Sciences, Veszprém, Hungary3 Department of Analytical Chemistry, University of Veszprém, Veszprém, Hungary ABSTRACT- The bonding forms of metallic elements in soils and sediments significantly ifluence their bioavailability and environmental mobility. Sequential extraction procedures applied for fractionation of heavy metal content of soils and sediments are not able to distinguish the different metal-organic bonding forms. To overcome this problem a new sequential extraction procedure was proposed using CO2, methanol and H2O solvents in supercritical fluid extractor. The method was applied to soil and sediment samples taken at the Tisza river area. Their total organic matter content was varied from 1 to 7 % w/w. The nature of the organic functional groups in the extracts was investigated by diffuse reflectance Fourier-transform infrared spectroscopy. On the basis of the following findings it was stated that the nature of functional groups plays a significant role in the formation of important metal-organic compounds: 1.) The FT-IR spectra of the soil and sediment samples of different origin show differences in the band ratios in the 2200-1630 cm-1 range. The spectra were compared to those of fulvic and hymatomelanic acids obtained from fossiliferous carriers (leonardite). It was concluded that in the FT-IR spectra of soils and sediments the bands appearing in the 2100 to 1630 cm-1 range can be assigned to quinoidal- and keton-type carbonyl, as well as to COOH and amide groups of humic matter. 2.) Attempts were made to find correlations between the organic matter and metal contents of samples having absorption bands in the 1830-1800 cm-1 range (lactone-type C=O groups). 3.) A correlation was made between the C=O, COOH and amide band patterns and the elemental analysis results to confirm the possible metal-carbonyl nature of the bands in the 2100-2000 cm-1 range. Key words: metal-organic bounds, supercritical fluid extraction, FT-IR, sediment polution |
