Long-lived sensors with replaceable surface for stripping voltammetric analysis: Part I Original Research Article

This study was inspired by the need of solving main problems of stripping voltammetry involving a short lifetime of electrodes, the necessity of mechanical regeneration of their surface and toxicity of mercury. The proposed electrodes (sensors) consist of a tungsten wire or a carbon-containing filament (thread). The latter was modified using one of the following methods: electroplating with mercury “in situ” or beforehand, or deposition of an insoluble mercury-organic complex on the filament surface beforehand and electrochemical reduction of the complex during analysis. Rotating disk tungsten electrodes, impregnated graphite disk electrodes and thick-film graphite electrodes were used to choose the solution composition and potential waveforms, and to compare the efficiency of the proposed sensor and earlier sensors. It was shown that long-lived mercury-free tungsten electrodes may serve to determine copper ions over the concentration interval from 10 to 1000 μg l−1. The carbon-containing filament may be used to determine copper, lead and cadmium concentrations at the level of μg l−1. A total of 10 measurements can be made using one and the same section of the electrode. Relative standard deviations of concentrations found range from 0.026 to 0.14 for various versions of electrodes and concentration intervals. The lifetime of the sensor is determined by the length of the wire or the thread and the replacement frequency of the working section. The obtained data confirm the reliability of the long-lived sensors. All the sensors, except the carbon-containing filament modified “in situ”, do not contaminate the environment with mercury. The long-lived sensors can be installed in flow-through systems designed for use under laboratory conditions and for remote unattended environmental monitoring.