Used as a stable isotope-labeled internal standard in mass spectrometry and metabolic research to trace arginine metabolism in biological systems. Enables accurate quantification of L-arginine and related metabolites in plasma, urine, and tissue samples. Commonly applied in studies of nitric oxide synthesis, urea cycle function, and protein turnover. Its labeled carbon atoms allow researchers to distinguish between endogenous and exogenous arginine, supporting pharmacokinetic and metabolic flux analyses. Also utilized in clinical diagnostics and nutritional studies involving amino acid metabolism.