Used as a deuterated internal standard in analytical chemistry, particularly in gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Its primary application is in the calibration and quantification of naphthalene and related aromatic compounds in environmental, pharmaceutical, and industrial samples. Due to its stable isotopic labeling, it helps distinguish between endogenous naphthalene and added reference material, improving measurement accuracy. Commonly applied in studies involving polycyclic aromatic hydrocarbon (PAH) metabolism, environmental contamination analysis, and reaction mechanism tracing where isotopic labeling is required.