Used as an internal standard in analytical chemistry, particularly in mass spectrometry and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. It aids in the accurate quantification of nitrazepam and related benzodiazepines in biological samples such as blood, urine, and plasma. Its deuterated structure provides a distinct mass difference from non-labeled compounds, minimizing interference from matrix components and ensuring precise measurement in forensic toxicology, clinical testing, and drug metabolism studies.