SIMULTANEOUS-OPTIMIZATION OF PH AND ORGANIC MODIFIER CONTENT OF THE MOBILE PHASE FOR THE SEPARATION OF CHLOROPHENOLS USING A DOEHLERT DESIGN

By optimizing the pH and volume fraction of organic modifier, the complete resolution of an isocratic separation of a mixture of phenol and thirteen of the nineteen chlorophenol isomers and of a mixture of the three tetrachlorophenols and pentachlorophenol was achieved. The effectiveness of the Doehlert design in optimizing both experimental parameters was investigated. A quadratic model was applied. For mixtures of a small number of compounds, a retention boundary map is proposed to determine limits of the concentration of organic modifier so as to elute compounds within a reasonable analysis time. The resulting three-dimensional graph of the minimum resolution as a function of the experimental parameters allows the direct visual evaluation of the ruggedness of the optimum conditions that are attainable in the selected parameter space and with a given stationary phase.