Comparative study of the separation and determination of aspartame and its decomposition products in bulk material and diet soft drinks by HPLC and CE

The direct separation of aspartame (alpha-L-aspartyl-L-phenylalanine methyl ester) LL-alpha-APM, and several decomposition products namely LL-beta-aspartame (LL-beta-APM), L-alpha-aspartyl-L-phenylalanine (alpha-AP), L-beta-aspartyl-L-phenylalanine (beta-AP), and diketopiperazine (DKP) was accomplished by high performance liquid chromatography (HPLC) using a Chirobiotic T (Teicoplanin) column, and capillary zone electrophoretic (CZE) methods. The presence of any of these decomposition products in diet soft drinks labeled to contain the sweetener, also in coffee containing the artificial sweetener LL-alpha-APM, were investigated.