Abstract We report a robust HPLC-UV method for ascorbic acid (AS), paracetamol (PA) and guaifenesin (GU) based on response surface/tolerance analysis approach to meet Six Sigma quality of the performance of a chromatographic method. Our goals were the bringing specifications into the optimizations and achieving robustness during the development phase. The critical method attributes (CMAs) were resolution between the peak pairs (Rs), the analysis time(T), tailing factor (Tf), number of theoretical plates (N), and back pressure(P).The critical method parameters (CMPs) included a percentage of organic modifier, a flow rate of the mobile phase, and a temperature of column oven. The separation was performed on a CN column, using an isocratic mode with a mixture of 50 mM potassium dihydrogen phosphate buffer adjusted with ortho-phosphoric acid to pH 2.2 as the aqueous component of the mobile phase and methanol in the ratio 85.9:14.1 (v/v) at 1 ml/min flow rate, with UV detector at 275 nm and a column temperature of 45 °C. The method was validated using the accuracy profiles. Finally, the method was applied to pharmaceutical dosage form.