Flow injection spectrophotometry: A new approach for dapsone analysis in pharmaceutical products by coupling reaction with salbutamol sulfate

This research developed and evaluated both batch and flow injection (FIA) spectrophotometric methods for the determination of dapsone (DAP) in pure substances and Pharmaceutical dosage forms. The proposed techniques were based on a reacting of salbutamol sulphate (SAL) with diazotized dapsone in an alkaline medium. This reaction, which occurs at 5 °C, forms a yellow dye with a maximum absorbance at 462 nm. The chemical and physical parameters of both the batch and flow injection (FIA) methods were optimized at 5 °C to maximize sensitivity and repeatability. Under these optimal conditions, Beer's law showed linearity across dapsone (DAP) concentration ranges of 3–50 μg/mL and 1–150 μg/mL. The corresponding correlation coefficients were 0.999 and 0.997, and detection limits were 0.23 μg/mL and 0.05 μg/mL for batch and flow injection FIA methods, respectively. Flow injection method (FIA) provides an economical, rapid, simple, accurate, and high-throughput approach, It is characterized by reduced consumption of samples and reagents, which minimizes waste generation. The diazotization coupling reaction with salbutamol sulfate (SAL) was selected as a safe and effective reagent for this process. This study aimed to develop a rapid and straightforward spectrophotometric method for the efficient quantitative determination of dapsone (DAP) in pharmaceutical formulations.