Collaborative Research: Fabrication and Optimization of Continuous Stationary Phase Gradients for Liquid Chromatography

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This project is funded by the Chemical Measurement and Imaging Program of the Division of Chemistry at the National Science Foundation. The goal of a chemical separation is to separate a complex mixture into its individual components by taking advantage of differences in the degree of interaction a species exhibits between a stationary phase and a mobile phase. In this project, Professors Maryanne Collinson and Sarah Rutan at Virginia Commonwealth University (VCU) are exploring an alternate approach in the field of chemical separations. Instead of manipulating the composition of the mobile phase during the course of a separation, the stationary phase composition is instead changed. Gradual changes in stationary phases have many advantages including the ability to improve selectivity, separation times, and the ability to detect species in the mixture. The synergy between the collaborating research groups enhances the training of a diverse body of undergraduate and graduate students in state-of-the-art materials synthesis, chromatography, and the predictive power provided by simulations. In addition, by developing a peer-coaching relationship with new faculty, undergraduate instruction in analytical chemistry at VCU is being enhanced.This project focuses on the following three specific aims: (1) design, construction, and characterization of liquid chromatography columns with a continuous gradient in chemical functionality along their length, (2) development and implementation of tools to predict the chromatographic responses for various sets of analytes on a continuous gradient stationary phase, and (3) coupling simulations with experiments to determine what gradient lengths and compositions are needed to obtain optimum separations, thus avoiding the trial and error approach usually used in method development. For proof-of-principle, silica monolithic columns and columns packed with superficially porous particles are strategically modified to incorporate a continuous gradient in C8, C18, amine, and/or phenyl groups using silane chemistry and controlled rate infusion (CRI), a method recently developed in the Collinson group. The integration of the Collinson group's expertise in sol-gel chemistry and surface chemical gradients with the Rutan group's expertise in modeling of separations and liquid chromatography is leading to the development of new methodologies for problems of societal relevance, ranging from biomarker discovery to detection of low levels of environmental contaminants.