Used as a deuterated internal standard in analytical chemistry, particularly in gas chromatography-mass spectrometry (GC-MS) for accurate quantification of naphthalene and related compounds. It aids in environmental monitoring to detect and measure naphthalene levels in air, water, and soil samples. Also employed in metabolic studies to trace the pathways and degradation of naphthalene in biological systems. Its isotopic labeling ensures minimal interference, enhancing precision in research and regulatory compliance.