Used as an internal standard in analytical chemistry, particularly in mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, for accurate quantification of salicylic acid in various samples. Its deuterated form ensures minimal interference with the analysis, providing reliable and precise results. Commonly applied in pharmaceutical research to study drug metabolism and pharmacokinetics. Also utilized in environmental testing to detect and measure salicylic acid in water, soil, and biological samples. Its stability and isotopic labeling make it a valuable tool for trace analysis in complex matrices.