Micelle-mediated methodology for speciation of chromium by flame atomic absorption spectrometry

The concept of cloud point phenomenon is used to perform metal speciation a fter the studied metallic forms have reacted with suitable ligands for the formation of hydrophobic complexes, which are subsequently entrapped in the surfactant micelles. As an analytical demonstration, trace concentrations of Cr(III) and Cr(VI) were conveniently detected in samples with a complex matrix, such as sea water, without any laborious and expensive treatment us ing flame atomic absorption spectrometry. The speciation of Cr is performed using Triton X-114 as surfactant and, as chelating agents, ammonium pyrrol idinedithiocarbamate for Cr(VI) and 8-hydroxyquinoline for Cr(III). Analyti cal curves were rectilinear up to concentrations of 130 mu g l(-1) for Cr(I II) and 85 mu g l(-1) for Cr(VI) with detection limits of 1.4 mu g l(-1) an d 0.65 mu g l(-1), respectively. The method affords recoveries in the range 96-104% and a relative standard deviation lower than 2.2%. It is proved th at the method can be successfully employed as an alternative to the commonl y used preconcentration and speciation analytical techniques. By selecting the appropriate complexing agent(s) other metal speciations are feasible pr ovided that some detailed study precedes the application.