1H NMR urine analysis as an effective tool to detect creatine supplementation.

Creatine is one of the main compounds in muscular energetic metabolism leading to phosphocreatine to maintain high ATP levels. Creatine is found in blood and excreted in small amounts in urine. Creatine supplementation and athletic performances are supposed to be correlated, particularly in intensive and intermittent efforts. After oral creatine supplementation, a 1H nuclear magnetic resonance (NMR) spectroscopy method was developed for its direct analysis, without any pretreament of urine samples. This method can be used to detect any supplementation of creatine, a substance prohibited in France. The detection limit is 10 micromol/L (1.31 mg/L) and analysis is performed in 10 min. After a single oral supplementation of 2.1 g to three subjects, a kinetic investigation reveals a maximum concentration of 20 mmol/L (2.62 g/L), observed between 1 and 6 h after ingestion. This procedure was used to test 13 urine specimens obtained from bodybuilders. From the concentrations measured (range: 0.41 to 10.30 mmol/L, 54 to 1350 mg/L), the doping practices of at least nine athletes could be observed. Creatine is not often analyzed in hospital laboratories. This paper documents how easily creatine can be determined and quantitated by 1H NMR spectroscopy.