Design and development of a modular centrifugal platform with adjustable mixing and automated position-switching for stepwise gradient elution in reversed-phase liquid chromatography†

This study introduces a modular centrifugal platform developed for stepwise gradient elution in reversed-phase liquid chromatography, featuring adjustable mixing and automated position-switching mechanisms. Traditional methods of gradient elution rely on precision syringes and mixers to control eluent composition, but incorporating external pumping systems into centrifugal platforms presents substantial technical and economic challenges. To overcome these limitations, an adjustable eluent mixer was designed to generate concentration gradients by utilizing Coriolis-induced metering and shake-mode mixing processes. The eluent composition was controlled by varying the platform's rotational speed, with the effects of geometric and operational parameters on liquid distribution thoroughly analyzed. An operating curve was established to correlate methanol–water eluent compositions with rotational speed. Furthermore, a switchable fraction collector capable of automated position switching was developed to collect eluates from each elution step. By synchronizing rotational speed with ratchet-driven movements, the outer ring containing multiple fraction collectors rotates relative to the inner disk, enabling efficient replacement of filled collectors. Experimental results demonstrated the successful separation and collection of water-soluble dyes, highlighting the platform's potential as a cost-effective and precise solution for chromatographic applications.