title: Rapid colorimetric assay of trimethoprim and sulfamethoxazole in pharmaceuticals.
abstract: A method is described for the direct colorimetric determination of trimethoprim and sulfamethoxazole in pharmaceutical preparations, without prior separation. Estimation of trimethoprim is based on its ion-pair formation with bromophenol blue and subsequent measurement of absorbance of the ion-pair at 418 nm. Estimation of sulfamethoxazole is possible without removal of trimethoprim by solvent extraction.
mesh_terms: D003124:Colorimetry; D004338:Drug Combinations; D013420:Sulfamethoxazole / Q000032:analysis*; D014295:Trimethoprim / Q000032:analysis*
chemical_list: D004338:Drug Combinations; D014295:Trimethoprim; D013420:Sulfamethoxazole