Ascorbic acid oxidation in SDS micellar systems

In this contribution the results of atmospheric and electrochemical oxidation of AA in the SDS micellar solutions and in the microemulsions pentanol/water stabilized by SDS are presented. The hydrophilic vitamin C readily dissolves in water and O/W microemulsions as well as undergoes the irreversible two-electron oxidation reaction. It was found that the atmospheric oxidation of AA is accelerated by the SDS up to the CMC and inhibited in the concentrated SDS solutions. We also found that the rate of atmospheric oxidation of ascorbic acid is higher in the water-in-oil (W/O) than in the oil-in-water (O/W) microemulsions and increases with the increasing oil content. The influence of the SDS on the electrochemical behavior of vitamin C was also studied. The general conclusion emerging from this investigation is that the increasing surfactant concentration shifts the ascorbic acid oxidation potential to higher values whereas the corresponding peak current values diminish. In the microemulsions the AA oxidation is slowed down by increasing the pentanol amount in the system.