Analytical Sciences

Three-dimensional Representation Method Using Pressure, Time, and Number of Theoretical Plates to Analyze Separation Conditions in HPLC Columns

Masahito ITO,*,** Katsutoshi SHIMIZU,** and Kiyoharu NAKATANI*

*Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
**Hitachi High-Tech Science Corporation, 1-24-14 Nishi-Shimbashi, Tokyo 105-0003, Japan

There has been considerable discussion of the speed performance of HPLC separation, especially regarding the relationship between theoretical plates and hold-up time. The fundamental discussion focuses on the optimal velocity, u_0,opt, which gives a minimal height equivalent to a theoretical plate of the van Deemter plot. On the other hand, Desmet’s method, using the kinetic performance limit (KPL), calculates the highest performance with a constant pressure drop, without focusing solely on the optimal velocity. In this paper, a precise method based on the KPL is proposed, to understand how increasing pressure enhances both theoretical plates and hold-up time. A three-dimensional representation method that combines the pressure drop with two axes of time and theoretical plates will be useful for discussing the effect of pressure in pressure-driven chromatography. Using three dimensions, the methods based on u_0,opt and the KPL can be combined, because u_0,opt can be visualized three-dimensionally, including the neighbor of u_0,opt; and the question of whether the KPL is an asymptotic or effective limit can be investigated. Three performances of high resolution, high speed, and low pressure can be understood on different packing supports at a glance.

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