Used as an internal standard in analytical chemistry, particularly in mass spectrometry and liquid chromatography-mass spectrometry (LC-MS) methods, to accurately quantify carbendazim residues in environmental, food, and biological samples. Its deuterated structure allows for clear differentiation from non-labeled carbendazim, improving measurement precision and reliability. Commonly applied in pesticide residue testing, metabolism studies, and environmental fate analysis due to its stability and consistent behavior during sample processing.