SCIENTIFIC WORK

 

B. Mitrović, R. Milačič and B. Pihlar:

A novel approach to speciation of aluminium by employing fast protein cation-exchange liquid chromatography - inductively coupled plasma-atomic emission spectrometry, Analyst, 121, 627-634 (1996).

 

Abstract:

A fast protein liquid chromatography (FPLC) - ICP-AES procedure was developed for speciation of Al over a wide pH range, from acidic to alkaline region. Positively charged monomeric Al species in synthetic aqueous solutions were separated from polymeric, neutral and negatively charged species on an FPLC cation-exchange column. Aqueous-NaNO3 (8 mol dm-3) linear gradient elution was employed for separation in 10 min at a flow rate of 1.0 cm3 min-1. Separated Al species were determined "off line" by ICP-AES in 0.5 cm3 fractions which were diluted prior to analysis, using internal standard addition of yttrium. Retention times were found to be 1.5 min for Al(OH)2(H2O)4+ [ Al(OH)2+] , 4.0 min for Al(OH)(H2O)52+ [ Al(OH)2+] and 4.5 min for Al(H2O)63+ [ Al3+] . Good reproducibility of measurement (RSD 1.5%) was obtained in the optimal concentration range. LOD (3 s ) for separated Al species was found to be 120 ng cm-3 (1.0 cm3 of sample).

The distribution of Al species over a wide pH range is matched with the reported calculated data, and in general agreed also with the 8-hydroxyquinoline spectrophotometric method. Investigation of the effect of inorganic and organic complexing ligands on speciation of Al indicated that positively charged Al species (Al(SO)4+, AlF2+) and negatively charged (oxalate and citrate) coeluted with Al(OH)2+ and were separated from Al(OH)2+ and Al3+ species, while AlF2+ coeluted with Al(OH)2+ species. At lower pH's (e.g. 4.0) Al-citrate was partially coeluted with Al3+ and Al(OH)2+ species. The same observations were found when soil extracts were analyzed.