Development and validation of RP-HPLC method for simultaneous estimation of sulfadoxine and pyrimethamine in tablet dosage form using diclofenac as internal standard

Abstract Sulfadoxine and pyrimethamine are often formulated together and used in the treatment of malaria especially in pregnant women serving as a prophylaxis. A new simple, precise and accurate reverse-phase high-performance liquid chromatography (RP-HPLC) method has been developed for simultaneous identification and quantification of sulfadoxine and pyrimethamine in tablet dosage form. The analysis was carried out on Waters uBondapak C18 Column (39 × 300 mm, 3.6 µm) with acetonitrile: phosphate buffer (75:25 v/v) as the mobile phase at pH of 2.5, and a flow rate of 1.0 mL/min and a detection wavelength of 230 nm. Sulfadoxine and pyrimethamine eluted at mean times of 2.86 and 3.60 min, respectively. The method was linear with r2 values of 0.9976 and 0.9841 for sulfadoxine and pyrimethamine, respectively (range 31.25–500 µg/mL). The method was accurate (97.06 ± 2.23% and 99.81 ± 1.93% for sulfadoxine and pyrimethamine, respectively), precise, specific, robust, sensitive and cost effective. The developed and validated method was used to assay two brands of tablets containing sulfadoxine and pyrimethamine. The use of internal standard, diclofenac, permitted accurate quantification of the two active pharmaceutical ingredients (APIs) and also aided in decreasing inherent errors while compensating for small variations in peak areas due to sample size fluctuations and variable detector sensitivity. The validated method can be used in routine quality control analysis of fixed-dose combination tablets containing both sulfadoxine and pyrimethamine.