Antimony speciation at ultra trace levels using hydride generation atomic fluorescence spectrometry and 8-hydroxyquinoline as an efficient masking agent

Abstract

Depending on the pH of the matrix and the concentration of Sb(V), we observed that the atomic fluorescence emission due to Sb(V) could contribute up to 40% of the emission signal during the determination of Sb(III). This can cause significant errors in Sb speciation analyses. Besides, interferences from heavy metals such as Mn(II), Cu(II), Fe(III), Co(II) and Ni(II) can cause severe depression of the signals as compared to the insignificant effects caused by Zn(II), Fe(II), Sn(II) and Pb(II). The compound 8-hydroxyquinoline was found to be an efficient agent to eliminate interference of transition metals in the determination of Sb by hydride generation-atomic fluorescence spectroscopy (HG-AFS). In addition, 8-hydroxyquinoline can effectively mask undesired fluorescence emission from Sb(V) during the determination of Sb(III) and make Sb speciation more accurate. The presence of 8-hydroxyquinoline does not modify the oxidation state of Sb in the sample and the possible metal complexes formed with 8-hydroxyquinoline were stable for more than 8 h. When l-cysteine was introduced as a pre-reductant, a high background signal was observed and it proved to be inefficient as a reductant when the concentrations of Sb(III) were low. A sensitive and interference-free procedure was then developed for the speciation of lake water samples and for the determination of Sb in sediments.