Calibration-Free Determination of Copper, Zinc, Cadmium and Lead in Tap Water Using Coulometric Stripping Potentiometry

✍ Scribed by Eskil Sahlin; Daniel Jagner

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 103 KB
• Volume: 10
• Category: Article
• ISSN: 1040-0397
• DOI: 10.1002/(sici)1521-4109(199807)10:8<532::aid-elan532>3.0.co;2-j

✦ Synopsis

Coulometric stripping potentiometry has been used to achieve calibration-free determinations of Cu(II), Zn(II), Cd(II) and Pb(II) in tap water samples. With the coulometric approach, interference from the formation of Cu-Zn intermetallic compounds (CuZn x ) on the quantification of Zn(II) was circumvented and the average stoichiometry of CuZn x could be determined. For Zn to Cu concentration ratios below 1, CuZn is quantitatively formed. At higher ratios amalgamated Zn coexists with CuZn, CuZn 2 and CuZn 3 . Both mercury soluble and mercury insoluble CuZn x exist. The former dissociates, with a half time of the order of one second, at potentials between the oxidation potentials for amalgamated Zn and that for CuZn x , while formation of the latter is irreversible. Due to interference from surface active groups on the glassy carbon surface, used as a substrate for the mercury film, determination of Zn(II) was not possible at Zn to Cu concentration ratios below approximately 0.1.