Ultratrace determination of aluminium in seawater and complex samples

Oceanographers use surface aluminium concentrations in open-ocean seawater as a tracer to fingerprint the location and magnitude of atmospheric dust deposition. It has become increasingly important to understand the role that such deposition plays in supplying trace elements to surface waters and consequently the effects such episodic supply has on moderating biological processes. For the purpose of real time analysis, quantification must be carried out by a system capable of being deployed shipboard. The most commonly employed technique for this purpose is flow injection analysis (FIA). This project aimed to develop a method for the onboard quantification of aluminium in seawater, specifically for the analysis of Antarctic surface waters. Initially, the project focussed on the establishment and optimisation of a FIA system incorporating fluorescent detection ¬¨‚àëof the aluminium-lumogallion complex. Significant variables affecting the lumogallion chemistry; including, reaction pH, lumogallion concentration and reaction time were optimised for this specific FIA system. Since aluminium concentrations in Antarctic seawater are expected to be in the minomolar to subnanomolar range, investigation into the addition of an 8-hydroxyquinoline column to the manifold, for preconcentration purposes, was carried out. Although initial work involving quantification of aluminium in seawater samples appeared promising, complications .with the robustness of this technique forced an alternative method to be sought. High performance chelation ion chromatography (HPCIC) was considered a suitable alternative for development as a technique for the purpose of shipboard quantification of aluminium in seawater. The HPCIC system developed, involved the novel use of iminodiacetic acid functionalised silica for the separation of aluminium. Separation conditions, such as eluent composition and column temperature were optimised. Both photometric and fluorometric detection systems were developed, employing post column reaction (PCR) with a variety of reagents. Of those tested for photometric detection, Eriochrome¬¨vÜ Cyanine R, which was used for the first time for PCR determination of aluminium in a flow system, was found to be the most sensitive. A limit of detection of 100 nM for a 100 ˜í¬¿L injection volume was achieved for this particular system. For the HPCIC system with fluorescence detection, lumogallion was the reagent of choice given its reported high sensitivity. Variables such as buffer type and pH, as well as temperature and lumogallion concentration were optimised. A limit of detection of 0.39 nM for a 500 ˜í¬¿L injection volume was obtained, with the performance of the system with a variety of other injection volumes also examined. Finally, this study presents a discussion on the applicability of the newly developed HPCIC system to the quantification of aluminium in real samples. This work involves the analysis of paper mill process water and seawater from the Ross Sea, Antarctica. Particular attention is given to the topic of aluminium speciation with sample acidification. Conclusions and suggested future direction of studies in this area conclude this project.