USE OF MICROCOLUMNS FOR SAMPLE PREPARATION PRIOR TO THE ANALYSIS OF ARSENIC SPECIES BY HPLC-ICP-MS.

To understand the biogeochemical cycles of arsenic in the environment, it is necessary to analyse the arsenic species that are transported and mobilized in natural waters, such as rivers, lakes, aquifers, and coastal seawaters. In these types of samples, arsenic speciation is hampered by the extremely low concentrations of these species, and the interferences caused by the potentially high concentrations of group I and II metals and chloride on the chromatographic separation and the subsequent detection by ICP-MS. To overcome these problems, the use of micro-columns prior to analysis to remove the matrix interferences and/or preconcentrate the target analytes has been investigated. Adjustment of the sample pH, and the choice of appropriate eluent solutions have enabled us to separate some arsenic species from chloride in seawater and preconcentrate other species in samples of lake water, thus reducing disturbance of the chromatography due to saturation of the column with chloride, and matrix interferences on the detection, due to the excessive presence of easily ionisable elements in seawater.