Theoretical Analysis of the Change in Ion Exchange Selectivity in the Complex Displacement Chromatography Systems

• Published in: Russian Journal of Physical Chemistry A 2019-03, Vol.93 (3), p.561-566
• Main Authors: Kharitonov, O. V., Firsova, L. A., Kozlitin, E. A.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chromatography; Displacement; Elution; Hydrogen ions; Ion exchange; Isotherms; Physical Chemistry; Physical Chemistry of Separation Processes. Chromatography; Selectivity; Separation
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024419030099

The ion exchange selectivity of complex displacement chromatography (CDC) is analyzed. It is found that the separation factors determined by other means of complex chromatography, frontal and elution, are not always interchangeable with CDC. A way of determining the separation factors applied to CDC is proposed. A technique for constructing isotherms for the ion exchange of components to be separated with the simultaneous presence of displacer ions, hydrogen ions, and a sorbed complexone in the system is proposed as well. The change in the selectivity towards different valence elements is considered. For protonated complexes, the complete inversion of selectivity corresponds to the transition of the S -shaped separation isotherm from convex to concave. When protonated and binuclear М 2 А complexes are simultaneously present in a system, the inversion of selectivity is accompanied by mixed isotherms of variable type with two intersection points with a diagonal. The spreading of the displacement fronts is determined using the McCabe–Thiele approach. The lower part of the displacement front of the second component is spread in the case of a convex isotherm with an S -shaped pattern. For complex isotherms with two maxima, the center of the front is spread, while the lower and upper parts of the front are quite sharp.