Abstract
A simple carrier phase based ultrafiltration technique that is akin to liquid chromatography and is suitable for medium-to-large volume sample preparation in the laboratory is discussed in this paper. A membrane module was integrated with a liquid chromatography system in a "plug and play" mode for ease of sample handling, and recovery of species retained by the membrane. The sample injector and pump were used for feed injection and for driving ultrafiltration, while the sensors and detectors were used for real-time monitoring of the separation process. The concentration of retained species was enriched by utilizing controlled concentration polarization. The recovery of the retained and enriched species was enhanced by backflow of carrier phase through the membrane using appropriate combination of valves. The backflow of carrier phase also cleaned the membrane and limited the extent of membrane fouling. Proof-of-concept of the proposed technique was provided by conducting different types of protein ultrafiltration experiments. The technique was shown to be suitable for carrying out protein fractionation, desalting, buffer exchange and concentration enrichment. Adoption of this approach is likely to make ultrafiltration easier to use for non-specialized users in biological research laboratories. Other advantages include enhanced product recovery, significant reduction in the number of diavolumes of buffer needed for conducting desalting and buffer exchange, minimal membrane fouling and the potential for repeated use of the same module for multiple separation cycles.