Presenter: Erick Partida (Moss Landing Marine Laboratories)

Description:
Unravelling the complex cycling of trace metals in coastal and open ocean settings requires a step change in our ability to make measurements at high spatial and temporal resolution. While shipboard Flow Injection Analysis (FIA) methods have been instrumental in generating high-resolution data as part of the CLIVAR and GEOTRACES program, the need for highly trained analysts, high maintenance requirements and limited automation potential of FIA manifolds inhibits a more widespread use and unattended operation. In this contribution, a novel analyzer for the fluorescent determination of aluminium in seawater based on programmable Flow Injection (pFI) will be presented. pFI offers several advantages relative to traditional FIA manifolds, most notably the ability to precisely control the mixing of reagent(s) and sample, thereby ensuring high reproducibility and low reagent consumption in a microfluidic manifold with minimal maintenance requirements. We have successfully adapted the classic aluminium lumogallion fluorescent assay to pFI to achieve a detection limit on the order of 8 nmol/L without preconcentration and a reagent consumption < 300 microliters per sample, which is well within the range for measurements within estuarine environments. We will also discuss the application of this new method to investigate the seasonal cycling of dissolved Al, and the biogeochemical link between Al and silica within the Elkhorn Slough, a seasonally hypersaline estuary in Monterey Bay. Our ongoing efforts to incorporate a preconcentration step to lower the limit of detection within the range appropriate for open ocean measurements (~0.1 nmol/L) will also be discussed. This work will showcase the suitability of pFI manifolds for trace metal analysis, and the potential of the technique for autonomous operation in coastal settings.