Abstract
Permitted food colouring matters and ascorbic acid were determined by differential-pulse polarography to monitor their interaction during light degradation studies at pH 5.5 in acetate buffer containing EDTA. Reductive splitting of azo bonds in the food colours was apparent from the formation of amines such as aniline, sulphanilic acid and naphthionic acid, which were determined spectrophotometrically using diazotisation methods. These amines were shown to be degraded further in the light to yield ammonia, which was determined spectrophotometrically as indophenol.