We describe a novel instrument and electrical circuit for sensitive electrochemical measurements at simultaneous direct electrode heating. The new measuring principle can be applied to working electrodes of various designs featuring two end contacts. In our experiments, the contacts were connected to a 100 kHz AC heating power supply and the potentiostat via the new inductor bridge circuit. A compact heating-generator housing contains all components necessary for sine wave generation as well as amplification and transformation of the heating power. The new arrangement yields high temperature cyclovoltammetric signals for the [Fe(CN) 6 ] 3À/4À redox system with a noise level superior to the earlier symmetrically branched wire electrode designs. Noise and disturbances are dramatically suppressed especially for high resistance electrodes such as glassy carbon electrodes. Without a center contact, the working electrode design is greatly simplified. This opens new opportunities for the design of a great variety of heated electrodes that may be arranged in arrays or consist of materials with relatively high resistivity such as carbon and conducting polymers.

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As a nontoxic substitute for mercury electrodes, bismuth electrodes attained a lot of attention during the last years. In this report we describe for the first time the preparation of two different directly heatable bismuth-modified microwire electrodes. We characterized the electrochemical behaviour using cyclic voltammetry in acetate buffer and alkaline tartrate solution. The bismuth electrodes show a significantly wider potential window compared with bare gold wires. In the presence of picric acid as one example for the detection of explosives, the bismuth electrodes deliver higher signals. By applying heat during the measurements, the signals can be enhanced further. We used the temperature pulse amperometry (TPA) technique to improve the electrochemical response at the different types of electrodes. In this preliminary study, we were able to detect 3 ppm traces of picric acid.

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