An improved flow-injection analysis method for the determination of dissolved aluminum in seawater

An improved, highly sensitive, flow-injection analysis method for the determination of dissolved aluminum in seawater, based on the work of Resing and Measures (1994), is presented. The most significant modification to this earlier work is the use of in-line preconcentration of seawater onto a commercially available resin, eliminating the resin-synthesis step. Other modifications include the addition of a column-conditioning step prior to sample loading that increases the quantitative retention and sensitivity, in-line buffering of samples prior to column loading to achieve optimal sample pH, an increased acid-eluent concentration to efficiently remove Al from the resin column, and an increased reaction buffer concentration. The method has a detection limit of 0.1 nM Al when preconcentrating 10 mL sample and a precision of 2.5% based on replicate analyses of a 5 nM Al sample when preconcentrating 2.5 mL sample. The method was applied to surface and deepwater samples collected in the North Pacific (2004 Sampling and Analysis for Fe [SAFe] cruise) and from surface water samples collected across the Columbia River plume. Results suggest that the SAFe samples could potentially serve as seawater reference materials for dissolved Al following further investigation by other researchers using different methods. The use of low-density polyethylene bottles with low-density polyethylene caps as standard protocol for storage of acidified seawater samples for Al analysis is also discussed.