NICKEL CHLORIDE INTERFERENCES ON ZINC AND COBALT IN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY USING A DUAL CAVITY PLATFORM

The interference mechanisms of nickel chloride in the determination of cobalt and zinc by graphite furnace atomic absorption spectrometry we re investigated using a dual cavity platform. This platform, which has two separate cavities instead of one, allows interferences in the gas phase and in the condensed phase to be differentiated by pipetting th e analyte and the interferent onto the separate Locations as necessary . The interference mechanism of nickel chloride is found to depend upo n the pyrolysis temperature. In the presence of excess nickel chloride , analyte chlorides are formed both in the condensed phase and by reac tion between analyte species and HCL(g) generated by the hydrolysis of nickel chloride. The analyte chlorides are then lost during pyrolysis or at the very beginning of the atomization step. At low pyrolysis te mperatures, where nickel chloride is not significantly hydrolysed, the drop in sensitivity can be attributed to the expulsion of the analyte species together with rapidly expanding decomposition products of nic kel chloride, and/or to gas-phase reaction between analyte atoms and c hlorine in the atomization step.