ALUMINUM AND SILICON SPECIATION IN HUMAN SERUM BY ION-EXCHANGE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY AND GEL-ELECTROPHORESIS

Speciation of aluminium and silicon in serum was studied by a reliable and sensitive high-performance liquid chromatographic-electrothermal atomic absorption spectrometric (HPLC-ETAAS) hybrid method, based on t he use of a polymeric anion-exchange column (Protein-Pak DEAE-5PW). Th is polymer-based column minimizes the risk of aluminium losses and of silicon contamination from the column during separation. The results o btained were compared with the results of previous studies carried out using different, complementary techniques including ultramicrofiltrat ion, gel filtration and a silica-based column for HPLC. In order to as certain which protein(s) of serum actually bind(s) aluminium, gel elec trophoresis was employed for the further separation of the column frac tions obtained by HPLC and aluminium was determined in separate aliquo ts of the same fractions. From all the experiments, it appears that tr ansferrin (Tf) is the only serum protein that binds aluminium and it c ontains about 90% of total serum aluminium. It was also confirmed that in the presence of desferrioxamine (DFO), aluminium is partly displac ed from its complex with transferrin to a low molecular mass AI-DFO co mplex. Aluminium citrate seems to be the main low molecular mass alumi nium species in serum, amounting to about 12 +/- 5% of the total alumi nium in an aluminium-loaded serum sample. The proposed speciation proc edure permits the simultaneous identification and determination of thr ee aluminium species in metal-spiked serum (AI-Tf, AI-DFO and Al-citra te). The results for silicon suggest that it seems to be unspecificall y adsorbed to several serum proteins and its speciation is not affecte d by the presence of DFO. Moreover, no evidence was found to confirm p ossible interrelations between aluminium and silicon species in serum to justify significant aluminosilicate formation in human serum.