A STUDY OF THE STRIPPING VOLTAMMETRIC BEHAVIOR OF SELECTED METAL-CHELATES AND ITS APPLICATION TO AUTOMATED-ANALYSIS OF RIVER WATERS

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+ i n 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 partici pation of the adsorbed complexing agent in the overall process. Simila rly, Cd2+ can be determined in the presence of benzimidazole sulfoxide s (II) and (III) by ASV in Britton-Robinson (BR) buffer pH 9, with 120 s 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 pyrro lidine dithiocarbamate (IV) with LODs of 0.70, 0.64 and 0.20 ppb, resp ectively 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 electrol yte of 5 x 10(-3) mol dm(-3) LiCl. Participation of the adsorbed compl exing agent in the ASV process is also observed for Sn4+ and Cu2+ in a n oxalate/ammonium chloride/HCl buffer with lowered LODs of 0.51 ppb a nd 0.76 ppb in the presence of p-methylene blue (V). The chelating age nt 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 bee n combined in the development of an automated method for the determina tion of trace Zn, Cd, Pb and Cu in an artificial river water matrix. T he accuracy and precision of this procedure is discussed. Determinatio n of Ni, Sn and As by this automated method and in such a matrix prove d to be inaccurate.