Used as a stable isotope-labeled internal standard in mass spectrometry for the quantification of muconic acid in biological samples. Its primary application is in biomonitoring studies, especially for assessing exposure to benzene, as muconic acid is a major urinary metabolite of benzene. The deuterated form allows for accurate differentiation from endogenous non-labeled compounds during analytical testing. Commonly employed in environmental and occupational health laboratories to improve measurement precision and reliability in GC-MS or LC-MS workflows.