Test of the water adsorption model of organic electrocatalysis in the carbon monoxide_silver system in alkaline medium

The optimization and characterization of a microsensor for trace zinc based on stripping voltammetry at a single carbon-fiber microelectrode are reported. Despite the absence of a mercury coverage, the carbon-fiber stripping sensor displays a significant hydrogen overvoltage in the physiological pH and a well-defined zinc stripping peak (at ca. -1.17 V). 5 s deposition periods allow convenient quantitation of zinc over the 100¯1000 ng/ml (ppb) range. Detection limits of 0.8 ng/ml (1.2×10-8 M) and 20 ng/ml (3.0×10-7 M) zinc were estimated in connection to 60 and 1 s deposition, respectively. The response is reversible with the stripping/measurement step completely removing the accumulated zinc. Measurement frequencies as high as 30 runs per min can thus be realized (in connection to 1 s deposition and measurement steps). The influence of relevant variables of the deposition and stripping steps is examined. The attractive behavior of the stripping-voltammetric microsensor offers great promise for in vivo monitoring of trace levels of zinc.