title: Systematic investigations of peak deformations due to co-solvent adsorption in preparative supercritical fluid chromatography.
abstract: Strangely shaped overloaded bands were recently reported using a standard supercritical fluid chromatographic system comprising a diol column as the stationary phase and carbon dioxide with methanol as the mobile phase. Some of these overloaded elution profiles appeared strongly deformed and even had "anti-Langmuirian" shapes although their solute compounds had "Langmuirian" adsorption. To obtain a more complete understanding of the generality of these effects, the investigation was expanded to cover also other common co-solvents, such as ethanol, 2-propanol, and acetonitrile, as well as various stationary phase materials, such as silica, and 2-ethylpyridine. From this expanded study it could be confirmed that the effects of deformed overloaded solute band shapes, due to co-solvent adsorption, is general phenomena in supercritical fluid chromatographic. It could also be concluded that these effects as well as previously observed "solvent effects" or "plug effects" are entirely due to competition between the solute and solvent molecules for the adsorption sites on the stationary phase surface. Finally, guidelines were given for how to evaluate the risk of deformations occurring for a given solvent-column combination, based simply on testing retention times of solutes and co-solvent.
authors.affiliation: Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
authors.forename: Emelie
authors.initials: E
authors.lastname: Glenne
authors.affiliation: Respiratory, Inflammation and Autoimmunity, Innovative Medicines and Early Development, AstraZeneca R&D, 431 83 Molndal, Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Leek
authors.affiliation: Respiratory, Inflammation and Autoimmunity, Innovative Medicines and Early Development, AstraZeneca R&D, 431 83 Molndal, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Klarqvist
authors.affiliation: Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
authors.forename: Jörgen
authors.initials: J
authors.lastname: Samuelsson
authors.affiliation: Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden. Electronic address: Torgny.Fornstedt@kau.se.
authors.forename: Torgny
authors.initials: T
authors.lastname: Fornstedt
mesh_terms: D000327:Adsorption; D002245:Carbon Dioxide / Q000737:chemistry; D025924:Chromatography, Supercritical Fluid / Q000295:instrumentation / Q000379:methods*; D000432:Methanol / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*
chemical_list: D012997:Solvents; D002245:Carbon Dioxide; D000432:Methanol
keywords: Adsorption strength; Anti-Langmuir band shape; Co-solvent adsorption; Langmuir band shape; Supercritical fluid chromatography