POLAROGRAPHIC IDENTIFICATION AND DETERMINATION OF SYNTHETIC COLORING MATTER IN CORKS

In the final treatment of corks, a certain amount of coloring matter must be added to restore the natural color that is lost during manufacturing. The coloring matter most widely used is Sunset Yellow FCF. Another food coloring matter, Orange II, which is not permitted for use, is often incorporated. Unfortunately both dyes exhibit similar polarographic behavior, making it almost impossible to differentiate between them. This work describes a polarographic procedure that allows one to distinguish between the two coloring materials. An application of the method to the analysis of corks is described, including the quantitation of the coloring matter identified. Detection limits less than 100 ppb. were obtained, corresponding to an amount of coloring matter of about 2-mu-g per cork.