Used as a stable isotope-labeled internal standard in mass spectrometry and high-performance liquid chromatography (HPLC) for the accurate quantification of acetaminophen and its metabolites in biological samples. Its deuterated structure allows clear differentiation from non-labeled compounds during analytical testing, improving precision in pharmacokinetic and toxicology studies. Commonly applied in clinical research, forensic analysis, and drug metabolism studies where reliable detection and measurement are critical.