Analytical QbD: Designing Space for HPLC Method Operable Region for Estimation of Preservatives in Herbal Formulation

Background: Quantification of preservatives in herbal formulation, simultaneously by high performance liquid chromatography analysis is very complex and involves series of steps including sample preparation, selection of suitable mobile phase and its validation for routine applications. Introduction: Application of Quality by Design (QbD) in the development of novel, simple, accurate and precise RP-HPLC method for concurrent quantification of quaternary preservatives in herbal formulation, focusses on development of robust method. Methods: Isocratic analysis was carried out using C-18 column at 231 nm. Risk assessment studies were executed to determine the critical method parameters which were defined as acetonitrile volume in the mobile phase, volume of injection and orthophosphoric acid concentration in the mobile phase. The effect of the critical method parameters on critical method attributes, i.e. retention time, resolution and chromatographic optimization function was further evaluated by means of central composite design and the optimal conditions were determined through derringer's desirability approach of multi-criteria decision making technique. Results: The method was statistically validated according to ICH guidelines having good resolution using optimized mobile phase, acetonitrile: 0.11% orthophosphoric acid in water (12.30: 87.70 % v/v) giving acceptable retention time i.e. 3.7128 +/- 0.0138 of bronopol, 4.5106 +/- 0.00542 of sodium propyl paraben, 10.7228 +/- 0.029 of sodium benzoate and 12.252 +/- 0.027 of sodium methyl paraben. Conclusion: Hence, the QbD based method development assisted in generating a design space with knowledge of all method performance characteristics leading to a better understanding of the method, and achieving desirable method quality.