Monolithic columns in high-performance liquid chromatography.

Comparisons of columns, column packings and column packing methods are made difficult and sometimes invalidated by differences and inadequacies in the test procedures used and the experimental data recorded. This paper reviews test procedures and recommends standards for a) the experimental and test parameters which must be recorded in order to enable comparisons to be made from laboratory to laboratory, b) the group of chromatographic parameters which best represent column performance for comparative purposes, with methods for their calculation, c) test solutes and eluents for some different types of packing materials. A computer program in BASIC is given which converts the experimental parameters into relevant chromatographic parameters.

Standardization of test conditions for high performance liquid chromatography columns

In Ion-pair reversed-phase chromatography, the retention of ionized analytes on a nonpolar bonded stationary phase is enhanced by the presence of a "hydrophobic" counterlon (hetaeron) in the mobile phase. Either ion-pair formation in the mobile phase with relatively strong retention of the complex or the conversion of the stationary phase into an ion-exchanger may explain the phenomenon. Analysis of the pertinent equilibria shows that the observed hyperbolic or parabolic dependence of the capacity factors on the hetaeron concentration cannot shed light on the mechanism. The experimental data obtained for the retention of catecholamlnes by using C4-C10 alkyl sulfates and other similar hetaerons in a wide concentration range, however, could be mechanistically interpreted from the chain length dependence of the parameters for the relationship between the capacity factors and hetaeron concentration. Although the results clearly demonstrate that in the system investigated, ion-pair formation governs retention, ion-exchange mechanism can be operative under certain conditions. Changes in retention upon addition of salt to the eluent are treated both theoretically and experimentally. The effect of organic solvents on the behavior of the chromatographlc system is discussed in view of the proposed theory.

George R. Laird

Papers

Soap chromatography—a new high-performance liquid chromatographic technique for separation of ionizable materials

Interaction of radial and axial dispersion in liquid chromatography in relation to the “infinite diameter effect”