Creatine, creatinine, and histidine are all important amino acids in the human body. All of these can be separated by liquid chromatography. The mobile phase contains acetonitrile (MeCN), water, and phosphoric acid. Smaller 3 µm particle columns are available for fast UPLC applications. This liquid chromatography method is scalable and can be used for isolation of impurities in preparative separation. It also suitable for pharmacokinetics.