Electrooxidation and electroreduction of undiluted acetonitrile at platinum microelectrodes. In situ determination of water in acetonitrile

Well-defined and reproducible reduction waves of undiluted acetonitrile hav e been obtained at Pt microelectrodes in the presence of a minimum of 5 x 1 0(-3) M tetraalkilammonium perchlorates (TAAP). At smaller TAAP concentrati ons, traces of alkali metal ions interfered and the wave plateau could not be obtained. Neither was it possible to obtain a total oxidation wave of ac etonitrile in the presence of a small concentration of LiClO4, in this case due to the oxidation of the ClO4- counterions. An addition of water to ace tonitrile led to the formation of a new cathodic wave, the height of which was proportional to concentration of water up to 0.022 mol/L. The detection limit of determination of water in pure acetonitrile was estimated as 0.00 90 mol/L.