Creatine and Creatinine

Method Description

Creatine (methylguanidinoacetic acid) is a naturally occurring compound widely used in dietary supplements for its role in cellular energy metabolism, particularly in muscle tissue. Under conditions of elevated temperature or prolonged storage, creatine undergoes spontaneous cyclization to form creatinine, its primary degradation product. Because this conversion directly reduces the active creatine content of a product, the presence of creatinine serves as a quantitative marker of ingredient degradation — a signal that neither identity testing nor creatine-only purity assays can provide on their own. The method uses reverse-phase UPLC with diode array detection to simultaneously quantify both creatine and creatinine in a single analytical run, delivering the specificity and sensitivity needed to accurately characterize complex finished-goods matrices such as gummies and multi-ingredient blends.