Confirmation of Methylphenidate and Its Major Metabolite in Human Urine by Liquid Chromatography-Tandem Mass Spectrometry

A solid phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) for simultaneous determination of methylphenidate and its major metabolite, ritalinic acid in human urine was developed and validated. The analytes were extracted by passing through C₁₈-revised phase extraction cartridge. The elution was evaporated by nitrogen blow， and dissolved by mobile phase, and then assayed by liquid chromatography-electrospray ionization tandem mass spectrometry. The limit of detection (LOD) is 5 μg•L^-1 for two analytes. Recoveries of methylphenidate and ritalinic acid are 80.6% and 68.4%, and inter-relative standard deviation (n=6) are less than 6.0%. The method can answer the requirements of the minimum required performance limit (MRPL) that doping control laboratories need to accomplish for stimulants at the concentration of 500 μg•L^-1 as established by WADA.