TABLE OF CONTENTS Theoretical investigations into this technique have shown that it is capable of achieving the resolving power of gas chromatography (GC). Liquid chromatography (LC) has undergone tremendous developments in recent years. The resolving power in chromatography in general depends on three factors: the number of theoretical plates (N) , the relative selectivity ?K/K and the relationship between the migration rate of the corresponding zone and that of the liquid phase (R):
(K is a thermodynamic member and corresponds to the median distribution coefficient of two neighbouring coefficients). Assuming almost equal selectivities in the gas and liquid phases and a uniform R value of 0.5 with GC and LC which is common in practice, LC approaches the efficiency of GC, as far as comparable N values or heights of equivalent theoretical plates (HETP) which are closely related to this.
The new high-efficiency carrier materials for column chromatography are mainly particles with a solid core and a thin porous envelope with particle diameters in the micro range. Majors [1] tested the commercial carrier materials in an automatic high-performance liquid chromatograph (HPLC) system with antioxidants. He separated a four-component mixture of aromatic amines at HETP values of < 1 mm within 10 minutes and with good reproducibility on Corasil I (glass bead with a single layer of porous silica gel) loaded with ?, ? ?-oxydipropionitrile. He also achieved separations of phenolic antioxidants as well as quantitative determinations in extracts of polyacetals the results of which are much superior...
