COMBINATION OF FLOW-INJECTION HYDRIDE GENERATION AND SEQUESTRATION ON A GRAPHITE TUBE FOR THE AUTOMATED-DETERMINATION OF ANTIMONY IN POTABLE AND SURFACE WATERS

A method for the determination of antimony in potable and surface waters has been developed, combining the use of flow injection apparatus for hydride generation with sequestration of antimony on a graphite tube, followed directly by atomization and measurement of atomic absorption. The entire measurement procedure and the acquisition of data were under microcomputer control, permitting fully automatic operation and improving measurement precision. Sample volumes of up to 500-mu-l can be manipulated using a sample loop and injection valve, whereas for larger volumes a continuous flow technique has to be used. A study of recovery demonstrated that more than 90% of the antimony contained in sample volumes of up to 5 ml was retained on the surface of an uncoated electrographite tube. Statistical evaluation of calibration data yielded a limit of determination of 20 pg and a limit of detection of 15 pg. This means that in a sample of 5 ml a limit of determination of 5 ng l-1 was obtained, making the reliable determination of antimony at concentrations found in some surface waters possible. The method was applied to the depth profiling of total and dissolved antimony in lake water. In Lake Constance a maximum particle-bound concentration of 25 ng l-1 was measured.