Electrochemical studies on sulfonephthaleins IV [1]. Bromopyrogallol red self-assembled monolayers on a mercury electrode

The electrochemical reduction behaviour of bromopyrogallol red in aqueous m edium at pH 2.16 on a hanging mercury drop electrode was studied. The resul ts indicate that in acid medium the reduction process proceeds via an ECEC mechanism. The formation and organization of a self-assembled monolayer of bromopyrogallol red on the hanging mercury drop electrode was studied in 0. 1 M HClO4. Cyclic voltammetry and chronocoulometry have been used to charac terize the modified electrode. The amount of bromopyrogallol red adsorbed o n the HMDE expressed as excess surface coverage (Gamma) for both in situ an d ex situ experiments as well as the surface areas occupied by one molecule (sigma) were calculated. It was found that the values obtained for Gamma a nd sigma utilizing cyclic voltammetric and hronocoulometry are almost ident ical. Values for ex sills experiments are a little lower than those for in sills experiments. The effect of the modification time on the organization process and its influence on the rate of electron transfer of the Cd2+/0 co uple were investigated.