CHEMICALLY-MODIFIED CARBON-PASTE ELECTRODE FOR THE VOLTAMMETRIC DETERMINATION OF BISMUTH

The paper deals with the preparation and analytical characterisation o f a Bismuthiol II-carboxylate -3-(p-carboxyphenyl)-1,3,4-thiadiazoline -2-thione) Modified Carbon Paste Electrode (BMCPE) to be used in the v oltammetric analysis of bismuth. The influence of different experiment al parameters (composition procedure, scan rate, etc.) on the electrod e behaviour is evaluated. Bismuth can be determined by a stripping pro cedure in which it is non-electrochemically preconcentrated at the ele ctrode (at open circuit) thank to the formation of a complex with the modifier present in the electrode surface. It is then reduced (strippe d) by linearly scanning the potential (200 mV s(-1)) from -100 to -800 mV. Under suitable experimental conditions, bismuth can be determined from 1.5x10(-8) mol l(-1) (5 min of preconcentration time) to 6x10(-6 ) mol l(-1) (1 min of preconcentration) with a precision never worse t han +/-7%. The electrode has also been tested on actual samples.