Abstract
A simple, rapid, accurate and sensitive spectrophotometric method has been developed for the quantitative determination of sulphamethoxazole (SMX) in both pure form and its pharmaceutical preparations. The proposed method is based on the diazotization of SMX with sodium nitrite in hydrochloric acid medium to form a diazonium salt, which is coupled with γ-resorsolic acid (2,6-dihydroxybenzoic acid) in alkaline medium of sodium hydroxide to form a stable and water-soluble azo dye exhibited maximum absorption at 432 nm against reagent blank. Beer’s law is obeyed over the concentration range of 5 to 300 μg of SMX /20 mL (0.25-15 ppm) with a good determination coefficient (R2=0.9984) and apparent molar absorptivity 3.34×104 l.mol-1.cm-1. The limit of detection (LOD) and limit of quantification (LOQ) are 0.0584 and 0.1752 μg mL−1, respectively. The recoveries and relative standard deviations in tablets and oral suspension formulations are found as 96.6 to 99.04% and 1.6 to 3.0%, respectively, depending on the concentration level. The method is suitable for the determination of SMX in the presence of other excipients that are usually present in dosage forms. The composition of the resulting product has also been worked out and it is found to be (1:2)SMX: γ-resorsolic acid. This procedure is applied successfully to the analysis of SMX in pharmaceutical preparations (tablets and oral suspension) without prior separation but with acceptable errors.
Highlights
A simple, rapid, accurate and sensitive spectrophotometric method has been developed for the quantitative determination of sulphamethoxazole (SMX) in both pure form and its pharmaceutical preparations
In order to overcome the above limitations, it was thought worthwhile to develop a simple, sensitive and accurate spectrophotometric method for the determination of SMX based on the coupling of diazotized SMX with a new coupling agent, γ-resorsolic acid (2,6-dihydroxybenzoic acid), to form orange colored product in alkaline medium that has been proved successfully for the determination of SMX in both pure form and its pharmaceutical preparations
The solution is filtered into 250 mL volumetric flask, the residue is washed with 5 mL of ethanol and the volume is diluted to the mark with distilled water to obtain a solution containing 100 μg.mL-1 of SMX
Summary
All absorption spectra and absorbance measurements are carried out on a Shimadzu UV-160 double beam UV-visible spectrophotometer (Japan) with 1.0-cm silica cells. The pH measurements are made with a professional Benchtop pH meter BP3001. Sulphamethoxazole solution (100 μg / mL), is prepared by dissolving 0.0100 g of SMX in 5mL of ethanol and the volume is completed to 100 mL with distilled water in a volumetric flask. Working solution of SMX is prepared by an appropriate dilution of the stock solution with distilled water. Γ-Resorsolic acid (Fluka) (0.1%, w/v) solution, is prepared by dissolving 0.1000 g of γresorsolic acid reagent in 100 mL distilled water using a volumetric flask. (1%, w/v) solution is prepared by dissolving 1.000 g of sodium nitrite in 100 mL distilled water. Sulfamic acid (Fluka)(3%, w/v) solution is prepared
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