Determination of chromium in estuarine waters by catalytic cathodic stripping voltammetry using a vibrating silver amalgam microwire electrode

作者：Espada Bellido Estrella; Bi Zhaoshun; van den Berg Constant M G^*

来源：Talanta, 2013, 105: 287-291.

DOI：10.1016/j.talanta.2012.10.031

• Chromium determination
• Silver microwire electrode
• Cathodic stripping voltammetry
• Vibrating electrode

Chromium (Cr-VI) in water can be determined by adsorptive catalytic cathodic stripping voltammetry in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate on the hanging mercury drop electrode (HMDE). Predominately Cr-VI is detected and the water is UV-digested to convert all Cr to Cr-VI prior to analysis. We develop here an alternative to the HMDE by using a silver amalgam electrode based on a vibrating microwire. The microwire electrodes were 12.5 mu m in diameter and electrochemically coated with mercury, and were stable for a week. Conditions were re-optimised, and we used a DTPA concentration of 5 mM, 30 mM acetate pH buffer (pH 5.5 in seawater and pH 5.8 in pure water), and 1.5 M nitrate solution. The microwire was reactivated prior to each scan by applying a negative potential (-3 V) for 2 s which removed all deposited Cr. The detection limit for chromium in pH buffer was found to be 0.2 nM Cr-VI and in seawater 0.3 nM Cr-VI at a deposition time of 30 s. The response increased linearly with the concentration of Cr-VI up to 60 nM Cr-VI in seawater. The limit of detection is less good than using the HMDE, but the linear range is good and the microwire electrode could form the basis of apparatus for flow-analysis. The method was successfully tested on water samples from the estuary of the river Mersey (Liverpool Bay) giving chromium concentrations between 1.48 nM and 2.29 nM.

• 出版日期2013-2-15