Used primarily as an isotopically labeled internal standard in analytical chemistry, especially in mass spectrometry and high-performance liquid chromatography (HPLC) for the detection and quantification of benzidine and its metabolites in biological and environmental samples. Its deuterated structure allows for accurate differentiation from non-labeled compounds, improving measurement precision. Commonly applied in toxicological studies and occupational exposure monitoring where reliable detection of aromatic amines is required. Also utilized in research settings to trace metabolic pathways and assess the stability of dye degradation products.