Theoretical study of the efficiency of liquid chromatography columns with particle size gradient

Modern analytical applications of liquid chromatography require more and more efficient columns. In this work, the possibility of utilizing particle size gradient in the chromatographic column was studied by a theoretical approach. In the course of our work three different scenarios of particle size gradients were considered with different shapes (linear, convex and concave). The evolution of bandwidth inside the column was plotted for each scenario. As a reference point, the bandwidth of the uniform column was used, which had the same pressure drop as the non-uniform column. According to our calculations, in isocratic elution mode, the non-uniform column does not offer any advantage compared to the uniform column, regardless the type of the particle size gradient. In gradient elution mode, however, extra band compression occurs was found. For negative particle size gradients, the final physical bandwidth was found to be approximately 1–4 % smaller than for uniform columns. This slight gain in efficiency in terms of bandwidth compression can be expanded to 5–8 % by the optimization of the limiting particle sizes. These optimized results are obtained when the final particle size is approximately 40% of the initial particle diameter.