Used as a stable isotope-labeled internal standard in mass spectrometry and analytical chemistry for quantifying morpholine and its derivatives in pharmaceutical and environmental samples. Its deuterated structure allows for clear differentiation from non-labeled compounds during detection, improving accuracy and sensitivity in quantitative analysis. Commonly applied in drug metabolism studies, pharmacokinetics, and impurity profiling where precise tracking of morpholine-containing compounds is required. Also utilized in research settings to study reaction mechanisms and isotopic effects in organic synthesis.