Solid Phase Gradients in Preparative Chromatography

The technique of solvent gradients has been widely applied in analytical and preparative chromatography to enhance selectivity and improve productivity. Recently, an alternative concept using solid phase gradients was introduced in analytical chromatography [1]. This concept is based on connecting columns filled with different stationary phases and using a constant mobile phase composition (isocratic conditions). With the availability of suitable column connecting devices [2], it is possible to extend this concept to preparative separations. The application of sequentially connected columns introduces new degrees of freedom like relative lengths and positions of individual segments. In this study, an attempt is made to see if the potential of such stationary phase gradients could be exploited favorably in preparative chromatography for separating multi-component mixtures. A theoretical study was carried out based on numerical solution of the equilibrium dispersive model incorporating specific adsorption isotherm parameters for each segment. The influence of the relative lengths and positions of the stationary phase segments on certain performance criteria is illustrated along with first experimental results. References: [1] S. Nyiredy, Z. Szucs, and L. Szepesy. Stationary phase optimized selectivity liquid chromatography: Basic possibilities of serially connected columns using the "prisma" principle. Journal of Chromatography A, 1157 (1-2): 122-130, July 2007 [2] Bischoff GmbH, K. Bischoff, S. Nyiredy, and Z. Szucs. Elements for separating substances by distributing between a stationary and a mobile phase, and method for the production of a separating device, 2005. Patent application 10 2005 024 154.9, German Patent and Trademark Offic