RP-HPLC Method for Determination of Salbutamol and Bromhexine in Syrup: Modelling and Optimization by Response Surface Methodology

Abstract

In present work, the RP-HPLC method was established for the determination of bromhexine and salbutamol in syrup by using a design of experiment approach. The Plackett-Burman design was applied to screen the influence of independent variables (ratio of organic solvent and pH in mobile phase, flow rate, column temperature, sample injection volume and detection wavelength) on the output data of chromatographic signals (peak area, tailing factor, theoretical plates, resolution) of bromhexine and salbutamol. The Pareto diagram shows that the selected variables affect mainly target function. A central composite design has been used to optimize the values of main factors and Design expert® software predicts the interaction and quadratic model to evaluate the impact of input parameters on output. The optimal conditions were determined with the support of response surface methodology for flow rate 0.9 mL/min, temperature 25 °C and 60% methanol in water with 0.06% orthophosphoric acid as the mobile phase. Good linearity was observed in the concentration range of 8-48 μg/mL for bromhexine and 4-24 μg/mL for salbutamol with a significantly high correlation coefficient (R > 0.999). The limit of detection and limit of quantitation were 0.32 and 0.96 μg/mL, respectively for bromhexine and 0.08 and 0.25 μg/mL, respectively for salbutamol. This method was validated according to ICH guidelines.