Development of voltammetric sensors for the determination of sodium dithionite and indanthrene/indigo dyes in alkaline solutions

Linear sweep and cyclic voltammetric studies of indigo, indanthrene dyes an d sodium dithionite in alkaline solutions are reported. The results were ap plied to develop amperometric determination methods for these vat dyes and reducing agent, On different electrode materials (Au, glassy carbon, Pd, Pt ) the reduced dyes give an anodic voltammetric signal, This reaction referr ing to the oxidation of dyestuff is concentration, rotation and potential s can rate dependent. Adsorption of oxidized dyestuff on the electrode surfac e was found to impede the chronoamperometric determination. By introducing potential steps, in situ cleaning of the electrode surface leads to a repet itive renewal and activation of the electrode surface. The use of multipuls e amperometry allowed to measure in a continuous way a voltammetric signal that is proportional to the dye concentration. The sodium dithionite concen tration can also be monitored continuously using chronoamperometry but only in the absence of dyestuff due to the mentioned adsorption. (C) 1999 Elsev ier Science B.V. All rights reserved.