Combination of various analytical techniques for speciation of low molecular weight aluminium complexes in plant sap

Abstract

The possibilities for speciation of low molecular weight aluminium organic acid complexes (LMW-Al) in plant sap were investigated by applying a combination of various chromatographic and spectroscopic techniques. The behavior of different LMW-Al complexes was investigated in synthetic aqueous solutions on anion and cation exchange fast protein liquid chromatography (FPLC) columns with inductively coupled plasma – atomic emission spectrometry (ICP-AES) or electrothermal atomic absorption spectrometry (ETAAS) detection. Plant sap of Sempervivum tectorum with a high concentration of Al (9.3 μg cm–3) and Sansevieria trifasciata with an appreciably lower Al concentration (0.065 μg cm–3) were analyzed. The speciation study in plant sap indicated that the species present in these samples, existed as negatively charged LMW-Al complexes which were eluted at the retention time typical for Al-citrate and Al-aconitate. In order to identify Al binding ligands eluted under the chromatographic peak analysis by electrospray ionization (ESI)-MS technique using Z spray ion source were also applied. The predominant LMW-Al negatively charged complexes in Sempervivum tectorum and Sansevieria trifasciata were found to be Al-citrate and Al-aconitate. It was shown that other LMW organic acids do not form complexes with Al in the samples studied.