Single-sample cloud point determination of iron, cobalt and nickel by flowinjection analysis flame atomic absorption spectrometry - application to real samples and certified reference materials

A preconcentration methodology utilizing the cloud point phenomenon is desc ribed for the determination of iron, cobalt and nickel by flame atomic abso rption spectrometry (FAAS). The method employs the formation of complexes o f the metallic species with ammonium pyrrolidinedithiocarbamate (APDC), whi ch are subsequently entrapped in the micelles of the surfactant TX-114, upo n increase of the solution temperature to 70 degreesC. The surfactant micel les, after their dilution to an acidified methanolic solution, are delivere d to the nebulizer of the FAAS by a flow injection analysis (FIA) manifold, allowing for the reproducible injection of a small volume of the sample. T he ability to handle the final texture of the injected solution allows for the single-step determination of these metal ions, in a single sample, with out interferences. Analytical curves were rectilinear up to concentrations of 350 mug l(-1) for Fe, 200 mug l(-1) for Co and 250 mug l(-1) for Ni with detection limits of 19, 5 and 11 mug l(-1), respectively. The method was a pplied to the analysis of several real and spiked samples yielding satisfac tory results. The recoveries obtained were in the range of 97-103% for spik ed samples and 98-99.5% for a Certified Reference Material (CRM).