title: Local equilibrium theory analysis of chromatographic peak shapes in the presence of adsorbing modifiers.
abstract: The nature and shapes of solute and modifier peaks for a situation when the modifier and solute adsorb competitively through the Langmuir isotherm is studied using the local-equilibrium theory. The analysis yields 10 different cases depending on the relative adsorption strengths and the concentrations of the modifier and the solute. The origin of positive and negative Langmuirian/anti-Langmuirian-type peaks, even when the adsorption isotherms are strictly Langmuirian, and explicit conditions under which each combination is observed are derived. A fundamental explanation to the origin and propagation of rounded peaks reported in liquid and supercritical fluid chromatography [1-3] is offered. A rigorous theoretical basis for the rule of thumb proposed by Fornstedt and Guiochon [1,2] about the nature of peak shapes when an adsorbing modifier is present, is established.
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta, Donadeo Innovation Centre for Engineering, 9211-116 Street NW, Edmonton, Alberta, Canada T6G 1H9. Electronic address: arvind.rajendran@ualberta.ca.
authors.forename: Arvind
authors.initials: A
authors.lastname: Rajendran
mesh_terms: D000327:Adsorption; D002853:Chromatography, Liquid / Q000379:methods*; D025924:Chromatography, Supercritical Fluid / Q000379:methods; D012996:Solutions; D013816:Thermodynamics
chemical_list: D012996:Solutions
keywords: Adsorbed modifier; Langmuir isotherm; Local equilibrium theory; Peak shapes; Perturbation peaks; System peaks