Isotherm linearity and sample capacity in liquid chromatography

• Published in: Journal of Chromatography A 1980-01, Vol.193 (2), p.181-195
• Main Authors: De Jong, A.W.J., Kraak, J.C., Poppe, H., Nooitgedacht, F.
• Format: Article
• Language: English
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(00)81486-7

The significance of distribution isotherm measurements for preparative liquid chromatography is discussed. Experimental methods for the determination of isotherms on liquid chromatographic phase systems are compared on the basis of accuracy, precision and speed. In this respect the break-through method constitutes a favourable compromise. Using this method, various normal-phase adsorption systems with dichloromethane as the mobile phase, phenol as the solute and porous silicas from several sources with various particle sizes and surface areas were compared. Significant differences in the linear range of the various silicas were found. Particle size has only a small influence, while larger surface areas, as expected, give longer linear ranges. For adsorption systems using alkyl-modified silicas, phenols as solutes and methanol-water mixtures as the mobile phase, the source of the material was found to be of less importance. Chain length has an adverse effect on the isotherm linearity; the modified silica with the shortest chain length (C-2) has a significantly larger linear range.