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A closer study of peak distortions in supercritical fluid chromatography as generated by the injection
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.ORCID iD: 0000-0001-8561-6872
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
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2015 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1400, 131-139 p.Article in journal (Refereed) Published
Abstract [en]

Abstract In SFC the sample cannot be dissolved in the mobile phase, so it is often dissolved in pure modifier, or another liquid, sometimes resulting in serious distortions of the eluted peak profiles already at moderately high injection volumes. It is suspected the reasons for these effects are solvent strength mismatch and/or viscosity mismatch. This study presents a systematic and fundamental investigation of the origin of these peak deformations due to the injection solvent effects in SFC, using both systematic experiments and numerical modeling. The first set of experiments proved that the injection volume and the elution strength of the sample solution had a major impact of the shapes of the eluted peaks. Secondly, the sample band elution profile was numerically modeled on a theoretical basis assuming both un-retained and retained co-solvent injection plugs, respectively. These calculations quantitatively confirmed our first set of experiments but also pointed out that there is also an additional significant effect. Third, viscous fingering experiments were performed using viscosity contrast conditions imitating those encountered in SFC. These experiments clearly proved that viscous fingering effects play a significant role. A new method for determination of adsorption isotherms of solvents was also developed, called the “Retention Time Peak Method” (RTPM). The RTPM was used for fast estimation of the adsorption isotherms of the modifier and required using only two experiments.

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 1400, 131-139 p.
Keyword [en]
Supercritical fluid chromatography, Viscous fingering, Peak distortion, Solvent strength, Modeling, Tracer peak
National Category
Analytical Chemistry
Identifiers
URN: urn:nbn:se:kau:diva-37860DOI: 10.1016/j.chroma.2015.04.059ISI: 000356742500016PubMedID: 26002105OAI: oai:DiVA.org:kau-37860DiVA: diva2:851618
Available from: 2015-09-07 Created: 2015-09-07 Last updated: 2016-02-25Bibliographically approved
In thesis
1. Fundamental Investigations of Supercritical Fluid Chromatography
Open this publication in new window or tab >>Fundamental Investigations of Supercritical Fluid Chromatography
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis aims at a deeper understanding of Supercritical Fluid

Chromatography (SFC). Although preparative SFC has started to replace Liquid Chromatography (LC) in the pharmaceutical industry - because of its advantages in speed and its less environmental impact - fundamental understanding is still lacking. Therefore there is no rigid framework to characterize adsorption or to understand the impact of changes in operational conditions.

 

In Paper I we demonstrated, after careful system verification, that most methods applied to determine adsorption isotherms in LC could not be applied directly in SFC. This was mainly due to operational differences and to the fact that the fluid is compressible which means that everything considered constant in LC varies in SFC.

 

In Paper II we showed that the most accurate methods for adsorption isotherm determination in LC, the so called plateau methods, do not work properly for SFC. Instead, methods based on overloaded profiles should be preferred.

 

In Paper III a Design of Experiments approach was successfully used to quantitatively describe the retention behavior of several solutes and the productivity of a two component separation system. This approach can be used to optimize SFC separations or to provide information about the separation system.

 

In Paper IV severe peak distortion effects, suspected to arise from injection solvent and mobile phase fluid mismatches, were carefully investigated using experiments and simulations. By this approach it was possible to examine the underlying reasons for the distortions, which is vital for method development.

 

Finally, in Paper V, the acquired knowledge from Paper I-IV was used to perform reliable scale-up in an industrial setting for the first time. This was done by carefully matching the conditions inside the analytical and preparative column with each other. The results could therefore provide the industry with key knowledge for further implementation of SFC.

Abstract [en]

This thesis aims at a deeper understanding of Supercritical Fluid

Chromatography (SFC). Although preparative SFC has started to replace Liquid Chromatography (LC) in the pharmaceutical industry - because of its advantages in speed and its less environmental impact - fundamental understanding is still lacking. Therefore there is no rigid framework to characterize adsorption or to understand the impact of changes in operational conditions.

 

In Paper I-II it was demonstrated why most methods applied to determine adsorption isotherms in LC could not be applied directly for SFC. Methods based on extracting data from overloaded profiles should be preferred.

 

In Paper III a Design of Experiments approach was successfully used to quantitatively describe the behavior of several solutes in a

separation system. This approach can be used to optimize SFC separations or to provide information about the separation system.

 

In Paper IV severe peak distortion effects often observed in SFC were carefully investigated and explained using experiments and simulations.

 

Finally, in Paper V, the prerequisites for performing reliable and predictable scale-up of SFC were investigated by small and large scale experiments.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2015. 63 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2015:45
Keyword
Supercritical Fluid Chromatography, SFC, Modeling, Adsorption Isotherms, Scale-up, Peak Distortion, Injection, Design of Experiments, Perturbation Peak Method, Elution by Characteristic Points Method, Method transfer
National Category
Analytical Chemistry Chemical Engineering
Research subject
Chemistry
Identifiers
urn:nbn:se:kau:diva-37913 (URN)978-91-7063-663-9 (ISBN)
Public defence
2015-10-16, Nyquistsalen 9C 203, Karlstads universitet, Karlstad, 10:15 (English)
Opponent
Supervisors
Note

Paper 4 ("Evaluation of scale-up from analytical to preparative...") ingick som manuskript med samma titel i avhandlingen. Nu publicerad. 

Available from: 2015-09-25 Created: 2015-09-11 Last updated: 2016-03-08Bibliographically approved

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Åsberg, DennisSamuelsson, JörgenFornstedt, Torgny
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