Used as a reference standard in analytical testing for the detection and quantification of sulfamethoxazole and its metabolites in biological samples such as urine and plasma. Commonly employed in pharmaceutical research and forensic toxicology to study drug metabolism and bioavailability. Also utilized in environmental monitoring to assess the presence of sulfonamide antibiotics in water systems. Its acetylated form aids in understanding phase II metabolic pathways of sulfonamides in humans and animals.