Used as a labeled internal standard in analytical chemistry, particularly in mass spectrometry and nuclear magnetic resonance (NMR) studies, to ensure accurate quantification of p-cresol in various samples. It aids in tracing metabolic pathways and studying environmental or biological degradation processes involving p-cresol. Also employed in research to investigate the behavior and distribution of p-cresol in complex matrices, such as urine, blood, or industrial effluents. Its deuterated form provides a stable reference for precise measurements without interference from naturally occurring isotopes.