Evaluating the measurement uncertainty in determination of sulfamethoxazole in compound sulfamethoxazole tablets by dual-wavelength spectrophotometry

Abstract

An evaluation of measurement uncertainty in the determination of sulfamethoxazole (SMZ) in compound sulfamethoxazole tablets using dual-wavelength spectrophotometry is presented. The average SMZ content determined was 0.3570 g/tablet, with an average tablet mass of 0.5671 g. The method leverages the ability to minimize interference from overlapping spectral bands by measuring absorbance differences at two distinct wavelengths (257 nm and 306 nm). Sources of uncertainty, including the average mass of tablets, sample mass, and absorbance values, were systematically analyzed. Findings reveal a combined standard uncertainty for a single determination of 0.0154 g/tablet. Absorbance measurement uncertainty, particularly for the standard at 306 nm (A_C306) and the sample at 306 nm (A_s306), were identified as significant contributors to the overall uncertainties. Triplicate analysis provided a limited reduction in the impact of repeatability uncertainty, with the overall combined standard uncertainty improving minimally to 0.0154 g/tablet. These results suggest that method optimization, such as adjusting concentrations to ensure absorbance readings are in a more optimal range, or consideration of alternative techniques may be needed to enhance the precision of SMZ quantification, contributing to robust quality control in pharmaceutical analysis.