Multifactor simultaneous statistical optimization of the mobile phase composition for the separation of inorganic anions in reversed-phase ion-interaction chromatography

Abstract

The optimization of the analysis of a mixture of five anions with reversed-phase ion interaction chromatography has been investigated. The criteria selected were the resolution of the most critical peak pair, R s1 (NO − 2-Br −), the total analysis time which corresponds to a certain range of R s2 (NO − 3-SO 2− 4) and the peak height of Cl −, NO − 3 and SO 2− 4. The factors selected to realize the optimization were the mobile phase concentrations of tetrabutylammonium iodide and phthalate buffer, and the pH. Only a limited number of experimental data points, ordered in a central composite design, were required for the computation of the response function with a non-linear regression model. Application of this computer-aided multifactor simultaneous statistical approach resulted in a rapid optimization of the selected criteria. The computed global optimum is close to the best experimentally obtained result.