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

This study was inspired by the need of solving main problems of stripping v oltammetry involving a short lifetime of electrodes, the necessity of mecha nical regeneration of their surface and toxicity of mercury. The proposed e lectrodes (sensors) consist of a tungsten wire or a carbon-containing filam ent (thread). The latter was modified using one of the following methods: e lectroplating with mercury "in situ" or beforehand, or deposition of an ins oluble mercury-organic complex on the filament surface beforehand and elect rochemical 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 compositio n and potential waveforms, and to compare the efficiency of the proposed se nsor and earlier sensors. It was shown that long-lived mercury-free tungste n electrodes may serve to determine copper ions over the concentration inte rval from 10 to 1000 mu gl(-1). The carbon-containing filament may be used to determine copper, lead and cadmium concentrations at the level of mu gl( -1). A total of 10 measurements can be made using one and the same section of the electrode. Relative standard deviations of concentrations found rang e from 0.026 to 0.14 for various versions of electrodes and concentration i ntervals. The lifetime of the sensor is determined by the length of the wir e or the thread and the replacement frequency of the working section. The o btained 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 con ditions and for remote unattended environmental monitoring. (C) 2001 Elsevi er Science B.V. All rights reserved.