Speciation of low molecular weight (LMW) Al complexes was performed in human serum from eight healthy volunteers in order to investigate the individual variability in the percentage and composition of LMW-Al species. Spiked samples (100±120 ng cm 23 Al 3z ) were microultra®ltered through a membrane ®lter (cut-off 30 000 Da) to separate Al bound to transferrin from LMW-Al complexes. A 0.5 cm 3 volume of the ®ltrate was injected onto an anion-exchange fast protein liquid chromatography (FPLC) column and aqueous 4 mol dm 23 NH 4 NO 3 linear gradient elution was applied for 10 min to separate LMW-Al complexes. Fractions of 0.2 cm 3 were collected throughout the chromatographic run and Al was determined `off-line' by electrothermal atomic absorption spectrometry (ETAAS). The characterisation of LMW-Al species in spiked serum was performed not only on the basis of the retention time (ETAAS detection), but also by electrospray (ES)-MS-MS analysis. A tandem quadrupole mass spectrometer equipped with a Z spray ion source as LC-MS interface was used for the identi®cation of LMW ligands eluted under the chromatographic peaks. It was found experimentally that the amount of LMW-Al species in spiked serum ranged from 14 to 55%. On the basis of FPLC-ETAAS and ES-MS-MS analysis, it was found that the main LMW-Al species present in serum were Al-citrate, Alphosphate and ternary Al-citrate-phosphate complexes. The distribution of these species varied among particular individuals. In some of them Al-citrate and Al-phosphate were the main LMW-Al species in serum, while in others the ternary Al-citrate-phosphate complex was also present. The serum of some other individuals did not contain Al-phosphate and the main LMW-Al species were either Al-citrate and Al-citrate-phosphate complexes or Al-citrate species alone. The limit of detection for the separated Al species on the FPLC column was 5.0 ng cm 23 , while the RSD was found to be 8%.

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Analytical procedures were developed for the speciation of Zn using fast protein liquid chromatography (FPLC), flame atomic absorption spectrometry (FAAS) and convective interaction media (CIM) fast monolithic chromatography with FAAS and electrospray (ES)-MS-MS detection. The investigation was performed on synthetic solutions (2 microg cm-3 Zn) of hydrated Zn2+ species and Zn complexes with citrate, oxalate and EDTA (ligand-to-Zn molar ratio 100:1) over a pH range from 5.4 to 7.4. It was found that Zn interacts with various buffers and the careful adjustment of the pH with diluted solutions of KOH is, therefore, required. FPLC separations were carried out on a Mono Q HR 5/5 strong anion-exchange column, applying an aqueous 1 mol dm(-3) NH4NO3 linear gradient elution over 15 min, at a flow rate of 1.0 cm3 min(-1). The separated Zn species were determined in 1.0 cm3 eluate fractions "off line" by FAAS. Speciation of Zn was also performed on a weak anion-exchange CIM DEAE fast monolithic disc by applying an aqueous 0.4 mol dm(-3) NH4NO3 linear gradient elution over 7.5 min, at a flow rate of 2.0 cm3 min(-1) and determination of the separated Zn species in 1.0 cm3 eluate fractions "off line" by FAAS. Zn-binding ligands in separated fractions were also characterized by electrospray (ES)-MS-MS analysis. The CIM DEAE disc was found to be more efficient in the separation of negatively charged Zn complexes than the Mono Q FPLC column. On the CIM DEAE disc Zn-citrate was separated from both Zn-oxalate and from Zn-EDTA. All these species were also separated from hydrated Zn2+, which was eluted with the solvent front. This method has an advantage over commonly used analytical techniques for the speciation of Zn which are only able to distinguish between labile and strong Zn complexes. Good repeatability of the measurements (RSD 2-4%), tested for six parallel determinations (2 microg cm(-3) Zn) of Zn-EDTA, Zn-citrate and Zn-oxalate was found at a pH of 6.4 on a CIM DAEA disc. The limit of detection (3s) for the separated Zn species was 10 ng cm(-3). The proposed analytical procedure was applied to the speciation of Zn in aqueous soil extracts and industrial waste water from a lead and zinc mining area.