Used primarily as an internal standard in mass spectrometry for the accurate quantification of N′-Nitrosonornicotine (NNN) in biological and environmental samples. Its deuterated structure allows for differentiation from non-labeled NNN during analytical testing, improving measurement precision. Commonly applied in tobacco product analysis, smokeless tobacco, and cigarette smoke to assess carcinogenic nitrosamine levels. Also utilized in metabolic studies to track NNN transformation and exposure biomarkers in urine and blood samples. Supports regulatory compliance and cancer risk assessment related to tobacco use.