Analytical method of diketopiperazine (5-Benzyl-3, 6-dioxo 2 piperazineacetic Acid: DKP), a major degradation product of aspartame (AMP), in soft drinks was developed by means of high performance liquid chromatography (HPLC). A sample was purified using Bond Elut SCX connected to Bond Elut C8 with 20% acetonitrile as the eluent. A Nucleosil 5-C18column was employed for the HPLC with 10 mM potassium dihydrogenphosphate and acetonitrile (85+15, v/v) adjusted pH to 4.0 as the mobile phase. The calibration curve was rectilinear in the range of 0.5 to 10.0 μg/ml for DKP. The average recoveries were 99.8% and 96.0% for DKP added to soft drinks at the level of 10 μ g/ml and 2.5 μ g/ml, respectively. The DKP was found in six commercial samples in the range of 9.5 to 26.0 μ g/ml.
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