Enhancement of sensitivity of electrochemical heavy metal detection by evaporative concentration using a super-hydrophobic surface
ABSTRACT A novel method to concentrate a droplet of a sample solution on a chip evaporatively and improve the sensitivity for electrochemical heavy metal detection was developed. The chip consisted of a working electrode and a Ag/AgCl reference electrode surrounded by a super-hydrophobic surface. When a droplet of an aqueous solution placed on the area was evaporated, it shrank to the sensitive area making contact with the sensitive area. This effectively concentrated the analyte heavy metal ions. Anodic stripping voltammetry was conducted using the system and the technique. To analyze various heavy metal ions, a bismuth or gold electrode was used as the working electrode. A significant increase in peak height was observed by the evaporative concentration, and the effect was enhanced as the volume of the solution increased and the area of the sensitive area decreased.
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ABSTRACT: New insights into the attractive stripping voltammetric performance, scope, and limitations of bismuth film electrodes are presented. The results confirm that the stripping performance of the bismuth electrode compares favorably with that of its mercury counterparts. Measurements of trace copper are feasible despite of its positive stripping potential (versus bismuth). Thallium and indium display well-defined peaks over the 20–100 g/l range following a 2 min deposition. Most metals, with the exception of copper, (e.g. Pb, Cd, Tl, In), form binary alloys with bismuth, and hence, display well-defined and undistorted peaks. Such sharp peaks result in high resolution (of neighboring signals) and permit convenient multi-elemental measurements down to the low g/l level. The bismuth-coated electrode is shown to be prone to errors caused by the formation of Cu–Zn intermetallic compound, that can be circumvented by the addition of gallium, in a manner analogous to mercury film electrodes. The new insights should facilitate the rationale design and operation of effective 'non-mercury' electrodes.Analytica Chimica Acta. 01/2001; 434:29-34.