The ASV and AdSV behavior of Zn2+, Cd2+, Pb2+, Cu2+, Ni2+ and Sn4+ in the presence of selected complexing/chelating agents has been studied. The presence of 2,5-dimercapto-1,3,4-thiadiazole (I) lowers the limit of detection (LOD) for the ASV determination of Zn2+, Cd2+ and Pb2+ in 5 x 10(-3) mol dm(-3) LiCl supporting electrolyte with a deposition time of 120 s to 0.82, 0.17 and 0.34 ppb, respectively, due to participation of the adsorbed complexing agent in the overall process. Similarly, Cd2+ can be determined in the presence of benzimidazole sulfoxides (II) and (III) by ASV in Britton-Robinson (BR) buffer pH 9, with 120s deposition with lower LODs of 0.12 and 0.06 ppb, respectively. AdSV can also be used to determine Cd2+ with (II), (III) and ammonium pyrrolidine dithiocarbamate (IV) with LODs of 0.70, 0.64 and 0.20 ppb, respectively and with Zn2+ having an AdSV LOD of 1.09 ppb using adsorption of its chelate with (IV) at -900 mV for 60 s in a supporting electrolyte of 5 x 10(-3) mol dm(-3) LiCl. Participation of the adsorbed complexing agent in the ASV process is also observed for Sn4+ and Cu2+ in an oxalate/ammonium chloride/HCl buffer with lowered LODs of 0.51 ppb and 0.76 ppb in the presence of p-methylene blue (V). The chelating agent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (VII) can be used to determine Cd2+, Zn2+ and Pb2+ using the AdSV technique down to LODs of 9.3, 2.7 and 6.3 ppb, respectively. Several of these methods have been combined in the development of an automated method for the determination of trace Zn, Cd, Pb and Cu in an artificial river water matrix. The accuracy and precision of this procedure is discussed. Determination of Ni, Sn and As by this automated method and in such a matrix proved to be inaccurate.
|Publication status||Published - Aug 1996|