Distribution profiles of sulphur in caramel colours on a gel-filtration column studied by HPLC/ICP.

The distribution profiles of sulphur in commercial caramel colours I, III and IV on a gel-filtration column were studied with a high performance liquid chromatograph (HPLC) connected directly to a vacuum-ultraviolet inductively coupled plasma-atomic emission spectrometer (ICP). A small sulphur peak of sulphate was detected in most products of caramel III, whereas caramel I products did not exhibit a sulphur peak, as predicted from the total sulphur concentration. In caramel IV products, sulphur was detected continuously in the fractions of the colouring ingredients with high molecular weights. The molar ratio of sulphur was bound to every 2-4 molecules of original hexose. However, sulphur was also contained in lower molecular weight fractions which were not the colouring constituents, the content being over twice that of the colouring ingredients.