Determination of copper in natural waters by batch and oscillating flow injection stripping potentiometry

Copper trace analysis in natural waters rich in chloride ions add organic matter mas performed by means of a copper-selective electrode (Cu-ISE), inductively coupled plasma-atomic emission spectrometry (ICP-AES), anodic stripping voltammetry (ASV), batch potentiometric stripping analysis (PSA) and oscillating flow injection stripping potentiometry (OFISP). The results obtained by the first two analytical methods showed that copper was present mainly in the form of various complexes with inorganic (mainly chloride) ions and organic ligands, The organic constituents impeded the application of ASV in the quantitative determination of labile copper concentration in the water samples mainly due to adsorption of organic matter onto the working electrode. Consistent analytical data concerning the labile fraction of copper were obtained by both batch PSA and OFISP in hydrochloric acid medium when standard addition or direct calibration were used. However, discrepancies between the batch PSA results obtained by the two calibration methods mentioned above in nitric acid medium were observed. Unlike batch PSA, OFISP appears to be versatile with respect to the sample matrix in both standard addition and direct calibration approaches. On the basis of this and the other well-known advantages of OFISP it was concluded that this analytical technique is suitable for fast and inexpensive trace heavy metal analysis in natural waters with unknown matrices.