Electrolytic Reduction of Indigo in Pyridine Application to the Determination of Dissolved Oxygen

The electrochemical reduction of indigo in pyridine as solvent has been investigated in connection with the determination of oxygen dissolved in pyridine, using polarography, cyclic voltammetry, controlled electrode potential electrolysis and coulometry. In the absence of protons, the total current of the first and second reduction waves for an unsaturated solution of indigo (LiClO 4 as background electrolyte) apparently represents a one‐electron transfer. In the presence of an excess of available protons (added as pyridinium nitrate), indigo is reduced in a reversible two‐electron process to indigo white (leucoindigo). The rapid conversion of indigo white to indigo by oxygen in pyridine solution can be used to determine coulometrically the concentration of oxygen in pyridine via measurement of the indigo produced on adding the pyridine‐oxygen sample to a solution of in situ electrolytically generated indigo white. The latter approach indicated a general method for the determination of dissolved oxygen in nonaqueous solvents.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/101790/1/197000109_ftp.pd