Used as a stable isotope-labeled internal standard in mass spectrometry and gas chromatography for accurate quantification and metabolic studies of guaiacol and related compounds. Its deuterated structure allows clear differentiation from non-labeled analogs in analytical assays. Commonly applied in environmental analysis, flavor and fragrance research, and pharmaceutical metabolism studies where precise tracking of compound behavior is required. The labeled methoxy group enhances detection sensitivity and improves data reliability in complex matrices.