Determination of Pb and Cd in water by potentiometric stripping analysis (PSA)

The aim of this work was to determine the content of cadmium(II) and lead(II) in drinking spring and well waters from rural part of south Serbia, as in a tap water. We have examined the Jablanica river water as well, which is passing by close to the wells. The analysis of metal ions were carried out simultaneously in examined samples of water using a computerized potentiometric stripping analyzer (PSA) of domestic design and manufacture (Faculty of Technology, Novi Sad and Electrouniverzal, Leskovac). PSA, an electroanalytical technique with high sensitivity and selectivity, applied using mercury thin film electrode, as a working electrode, by standard addition method in the presence of two supporting electrolytes to adjust pH values of examined samples. In the first case, the pH values of examined samples were adjusted at 2 by hydrochloric acid and in the second, the pH values were adjusted at 5.6 by acetate buffer contained 1.0 M NH4Ac/0.5 M HCI in addition of 1.0 mol/dm(3) chloride ions in form of NH4CI. The deposition potentials from -1.0 to -1.3 V were examined, in order to define the optimal electrolysis potential, and pre-electrolysis time of 15 min were used. The procedure was applied to water samples and the results were compared with Graphite Furnace Atomic Absorption Spectrometry (GF-AAS) as reference method.