Theory of Liquid Chromatography

This section will describe briefly the parameters that can be adjusted in the laboratory in order to optimise the technique. For a more elaborate description of the separation theory of chromatography, the reader is referred to the appropriate chapter in this book the following references are also suggested [2-4]. 

To a certain extent, HPLC remains an empirical science. Therefore, the ability and experience of the operator are quite certainly the most useful guidelines to decide on the chromatographic conditions to be used, as will be exemplified further. 

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The purpose of studytng the theory of liquid chromatography columns is not merely to understand the function of the column and how a separation can be achieved, but to provtde sufficient knowledge to be able to design a column that will provide a given separation, and consequently an analysis, in the minimum time. 

As described earlier, the revolution in high pressure liquid chromatography arose from a number of factors a better understanding of the theory of liquid chromatography, development of new supports and the development of new instrumentation specifically designed for use in the high pressure environment. 

Early in the development of the theory of liquid chromatography, it was recog-... 

In the 90 yr since the discovery of chromatography, tremendous advances have been realized. It is not the scope of this chapter to review the history or theory of liquid chromatography. The reference section lists a number of good books to that effect (1-6). The goal of this chapter is to illustrate the technique of liquid chromatography as it applies to the isolation of natural products. A brief review of the theoretical basis for the various applicable separation mechanisms and column packings will be presented, followed by practical recommendations and examples of natural products isolations. 

The physical and chemical aspects of liquid chromatography, in addition to mechanical aspects, are briefly described in this chapter. Theoretical approaches are explained in detail in later chapters. The effect of stationary phase materials on the chemical selectivity is described in Chapter 3, and the influence of the eluent components is covered in Chapter 4. The plate number theory is discussed in Chapter 5. Quantitative optimization is explained in Chapter 6. 

The review is organized in the following sections. The chromatographic theory relevant to EFLC and HT-HPLC is first described. Next a detailed description of the physicochemical properties of EEL mixtures is included. This is followed by a survey of the scope of liquid chromatography (LC) techniques that are presently using the attributes of EELs. Finally, a discussion of future applications of EF-HPLC is included. 

The term plate height comes from distillation theory. Some high-performance distillation columns contain discrete units called plates, in which liquid and vapor equilibrate with each other. As a teenager, A. J. R Martin, coinventor of partition chromatography, built distillation columns in discrete sections from coffee cans. (We don t know what he was distilling ) When he formulated the theory of partition chromatography, he adopted terms from distillation theory. 

D. E. Martire, Unified theory of absorption chromatography gas, liquid and supercritical fluid mobile phases , J. Liq. Chromatogr. 10 1569-1588 (1987). 

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