Automation of pH Optimization Experiments During LC Development

Abstract

The selection of an optimal mobile phase pH under solvent gradient conditions is experimentally challenging. Although quaternary pumps are widely available, they are often used in binary mode to run simple solvent gradients with one pH-adjusted buffer at a time. A more effective use of quaternary pumps is to deliver two different aqueous buffer components (A and B) in a constant proportion to simulate a single, premixed buffer component, while simultaneously producing a solvent gradient by increasing the organic solvent component (S). This approach largely automates the pH optimization experiments. A more detailed investigation of pH effects becomes possible with less time and effort. Once a suitable pH has been identified, the same separation can be reproduced by a simpler binary gradient method which is more suitable for routine work. This study demonstrates the feasibility of this approach both theoretically and through actual examples.