Used as a stable isotope-labeled internal standard in mass spectrometry-based assays to accurately quantify enzymatic activity, particularly in studies involving oxidoreductases. Its deuterated structure allows for precise differentiation from non-labeled analogs during analytical detection, improving measurement accuracy in complex biological matrices. Commonly applied in high-throughput screening and pharmacokinetic studies where reliable quantification of metabolic reactions is required. Also employed in fluorescence-based assays due to its strong emission properties, enabling dual-mode detection (fluorescence and MS) for enhanced sensitivity and validation.