Analysis of creatine and creatinine in urine by capillary electrophoresis

Creatine is found in the urine of subjects ingesting creatine monohydrate a s an ergogenic aid. Creatinine, the catabolic breakdown product of creatine , is a major constituent of normal urine. It is of interest to follow the e xcretion of creatine and creatinine in urine as a function of time after cr eatine ingestion. In this study, creatine and creatinine were analyzed in u rine by capillary electrophoresis. The optimization of the method was discu ssed, with the best results being obtained using a 30 mM phosphate-150 mM s odium dodecyl sulfate buffer at pH 6, with the detector set at 214 nm and a n applied voltage of 15 kV across a 45 cm capillary. Verification of the me thod was provided by HPLC analysis and spiking. The application of the meth od was demonstrated by analysis of creatine and creatinine in urine samples collected in a 24-h period following creatine ingestion. (C) 1999 Elsevier Science B.V. All rights reserved.