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Home > Archives > Volume 20, No 8 (2022) > Article

DOI: 10.14704/nq.2022.20.8.NQ44780

Development Spectrophotometric Method for determination of Sulfamethoxazole in Pure Form and Pharmaceuticals via Diazotization and Coupling Reaction

Abdulla M. Sulaiman, Khalida M. Omar


The current article describes simple, rapid, accurate, and highly sensitive spectrophotometric assays for sulfamethoxazole determination (SMX). The proposed method is based on diazotizing SMX in an acidic medium of hydrochloric acid (HCl) with an equimolar of sodium nitrite (NaNO2), followed by coupling with 4-chloro resorcinol in an alkaline medium. The resulting orange azo dye is water-soluble, stable, and exhibits maximum absorption at 498 nm versus reagent blank.Under the proposed optimum conditions. Beer's law is obeyed over the concentration range (1-27.5)µg.mL-1 with correlation coefficient of (0.9989). The molar absorptivity of 2.1478×10 4 L. mol-1 cm -1 and sandell'sindex of 0.0118 µg. cm-2 , while the detection limit (LOD) 0.0686 µg. mL -1 , and quantitation limit (LOQ) 0.2287 µg. mL -1 . The stoichiometry of azo dye is found to be 1:1 SMX : 4-chloro resorcinol. The suggested method has been applied successfully to determination of SMX in available dosage form (tablets and syrup) with good recoveries.


Sulfamethoxazole, Diazotization reaction, Coupling reaction, 4-chloro resorcinol, Spectrophotometric determination

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