SURFACE ELECTROCHEMISTRY OF -DIMETHYLTHIAZOL-2-YL)-2,5-DIPHENYL-2H-TETRAZOLIUM BROMIDE ([MTT]BR) ADSORBED ON A GRAPHITE ELECTRODE

-Dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide ([MTT]Br), which is of importance as a biological redox indicator, irreversibly a dsorbs on a graphite electrode and exhibits two surface elechochemical redox processes. The mechanism of reduction and re-oxidation of this species on the surface is discussed as a function of pH. AM1 calculati ons and redox data are interpreted to show that protonation of the fir st reduced product leads to a ring-opening pathway, eventually generat ing the two-electron reduced formazan species. Cyclic voltammetry, rot ating-disk voltammetry, pH dependence studies and electronic spectrosc opy are used to characterize the system.