Identification of Pt and Pd bound to humic acid species in spiked soils and street dusts by size exclusion chromatography and ICP-MS

摘要

The formation of PGE–humic acid (HA) complexes in soil and street dust samples was investigated. In order to assess the distribution of Pt and Pd among molecular weight fractions of humic substances, the HA extracts (extracted by 0.1mol L~(-1)sodium pyrophosphate) were analysed by size exclusion chromatography coupled on-line with UV-Vis detection. Similar chromatograms were obtained for soils and street dust samples (254 nm, 280 nm) and two size fractions were operationally defined as high (1600–5000 Da) and low molecular (＜1600 Da) HA fractions. The concentration of Pt and Pd in the separated extracts was determined by ICP-MS. The results indicate that up to 43%of Pt is in the high molecular and up to 52% in the low molecular HA fraction. In both type of soil samples, Pd is preferentially bound to the low molecular HA fraction. Dependence of Pd–HA and Pt –HA formation on the sample type both in the soils and in the street dust sample as well as on Pt oxidation state was established. Metallic Pt shows a tendency for complexation with the fractions of HA higher than 5 000 Da. In the street dust samples, the distribution of Pt and Pd is similar and is strongly dependent on the sample type, being bound mainly to the fractions: higher than 5 000 Da, 1600–5000 Da and the fraction lower than 1600 Da.