High-performance liquid chromatographic column efficiency as a function of particle composition and geometry and capacity factor

Abstract

Reduced plate height ( h) vs. reduced velocity ( v) plots have been measured over a wide range of v for 36 high-performance liquid chromatographic systems. Column type was varied over wide limits and solute capacity factor ( k′) values were changed over the range 0.6–22. Resulting data can be accurately described by the Knox equation h = Av 1/3 + B/v + Cv, where A is roughly constant ( A = 0.5–0.8) for all columns studied, but values of B and C are strongly dependent on column type and solute k′ values. These observations can be rationalized by a quantitative model that recognizes two effects: (a) surface diffusion of solute molecules in the stationary phase (along the pore wall) and (b) restricted diffusion of small solute molecules within particles having narrow pores and long alkyl chains bonded to their surface.