Comparative Studies on Chemical Modification by Diethyldithiocarbamate for ETV-ICP-OES and ETAAS Determination of Chromium and Nickel

Abstract.

The chemical modification of diethyldithiocarbamate (DDTC) in electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) and in electrothermal atomic absorption spectrometry (ETAAS) was comparatively investigated. The experimental results indicated that the formation of Cr- and Ni-DDTC chelates enhanced significantly the emission signals of Cr and Ni in ETV-ICP-OES, but decreased the absorption signal of Cr and Ni in ETAAS. The different role of DDTC in ETV-ICP-OES and ETAAS was attributed to the different functions of the graphite furnace in the two techniques. The graphite furnace was used as both a vaporizer and an atom-vessel for analytes in ETAAS, but only used as a vaporizer for the sample in ETV-ICP-OES. Thermal gravimetric analysis of Cr- and Ni-DDTC chelates and UV-Vis analysis of the sample vapor collected in CHCl₃ after vaporization of their chelates from the graphite furnace indicated that the analytes were vaporized and transported into ICP as their chelates. In addition, the vaporization mechanism of Cr and Ni was also briefly discussed.