Used as a reference standard in pharmaceutical analysis for the detection and quantification of sulfamethoxazole metabolites in biological samples. Commonly employed in research settings to study drug metabolism, particularly in assessing the metabolic pathways of sulfonamide antibiotics. Plays a role in toxicological studies to understand the formation of reactive metabolites linked to adverse drug reactions. Also utilized in the development and validation of analytical methods such as HPLC and mass spectrometry for monitoring drug impurities and degradation products.