Used as a stable isotope-labeled internal standard in mass spectrometry and gas chromatography for the accurate quantification of benzyl alcohol and related compounds in pharmaceutical and biological samples. Its deuterated structure allows clear differentiation from non-labeled analytes, improving measurement precision. Commonly applied in metabolic studies, pharmacokinetics, and drug impurity profiling where trace-level detection and high analytical sensitivity are required. Also employed in deuterium labeling studies to track reaction pathways and mechanisms in organic synthesis.