Separation and identification of different therapeutic pharmaceutical drugs on humic acid-based HPLC column: Method optimization using central composite design

Multimode chromatographic separations are highly desirable in pharmaceutical and environmental sciences. Current study deals with the application of newly developed mixed-mode end capped-immobilized humic acid onto an aminopropyl silica based chromatographic column for separation and identification of six drugs belonging to different therapeutic groups for its applicability in pharmaceutical industries. For this, central composite design was used to evaluate the separation and resolution by optimization of three most effective parameters (acetonitrile%, flow rate, and pH of mobile phase). Second-order quadratic model was used to evaluate their effect on resolution of peaks; the probability value (<0.05) obtained from analysis of variance suggested the best applicability of the model. Desirability function was applied to calculate optimum conditions (44.8% acetonitrile, 1.75 mL/min of flow rate, and 7.5 pH) required to achieve maximum separation with good resolution within 11 min. The method was validated for linearity, precision accuracy, selectivity, and sensitivity. The results revealed a highly precise (coefficient of variance > 1%), linear (R2 = 0.99), and highly selective method. Moreover, the limit of detection/quantification values revealed acceptable sensitivity of the method. The developed column was compared for its efficiency with a commercially available column and found to be highly applicable for industrial applications.