Development of a Fluorescence-Based in-situ Barium Sensor

摘要

Biogeochemical characteristics render barium a useful tracer of riverine inputs on 10-100 kms spatial scales. Ultimately we seek to determine of barium in seawaters by an in-situ technique. An intermediate step toward achieving that goal is the development of a ship-board technique that allows near real time sampling decisions in the field. To this end an automated on-line chromatographic technique for separating Ba at seawater concentrations from the more abundant cations of seawater was developed. Separation is accomplished via a methanesulphonic acid gradient elution from a CS12 cation column using our seagoing Dionex chromatographic system. Our analytical detection strategy is to use 'designer' chelating agents (made by Molecular Probes) with high binding constants for Ba that fluoresce in the UV-Vis wavelength range upon complexation. Fluorescence-based measurements can be expected be robust to sea-going conditions and be both sufficiently sensitive (a few to 100's nM) and accurate (<= 3%) for in-situ deployment. An ongoing systematic study to optimally handle temperature, pH, salinity and chemical composition affects upon fluorescent signals of the chelated Ba constitute a master's thesis project in our lab slated for completion in fall 2000.