Aspartame degradation in solutions at various pH conditions

This study of aspartame degradation in phosphate-citrate buffer solutions of pH 2, 4, 6,7, 8, 10, and 12 using reverse-phase high-performance liquid chromatography (HPLC) showed different major degradation products for different pH ranges. The major degradation product found at pi 12 to 6 was L-phenylalanine methyl ester (PME). The major degradation product found at pH 7 to 10 was 3,6-dioxo-5-phenylmethylpiperazine acetic acid (diketopiperazine, DKP). L-aspartyl-phenylalanine (Asp-Phe) was the major product detected at pH 12.