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Experimental Proof of a Chromatographic Paradox: Are the injected molecules in the peak?
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
2004 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, 953-958 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2004. Vol. 76, 953-958 p.
National Category
Analytical Chemistry Computational Mathematics
Identifiers
URN: urn:nbn:se:uu:diva-96953DOI: 10.1021/ac030268jOAI: oai:DiVA.org:uu-96953DiVA: diva2:171701
Available from: 2008-04-04 Created: 2008-04-04 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Adsorption Isotherm Parameter Estimation in Nonlinear Liquid Chromatography
Open this publication in new window or tab >>Adsorption Isotherm Parameter Estimation in Nonlinear Liquid Chromatography
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the development and validation of methods for the industrially important area of adsorption isotherm parameter estimation in preparative, nonlinear high performance liquid chromatography (HPLC). Preparative chromatography is a powerful separation method to get pure compounds from more or less complex liquid mixtures, e.g., mixtures of mirror-image molecules. Computer simulations can be used to optimize preparative chromatography, but then competitive adsorption isotherm parameters are usually required. Here two methods to estimate adsorption isotherm parameters are treated: (i) the perturbation peak (PP) method and (ii) the inverse method (IM).

A new theory for the PP method was derived and led to a new injection technique which was validated experimentally. This injection technique solved the severe problem with vanishing peaks and enabled us to use the PP method to estimate binary competitive adsorption isotherms valid over a broad concentration range. Also, the injection technique made it possible to estimate competitive adsorption isotherms for a quaternary mixture for the first time. Finally, an interesting perturbation peak phenomenon, known as the “Helfferich Paradox”, was experimentally verified for the first time.

The IM is a relatively new method to determine adsorption isotherm parameters. It has the advantage of requiring very small samples, but also requires an advanced computer algorithm. An improved implementation of this computer algorithm was developed and tested experimentally. Also, a variant of the IM called “the inverse method on plateaus” was tested experimentally and the estimated adsorption isotherm parameters were shown to be valid over a broader concentration range than those estimated with the standard IM.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 24 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 96
Keyword
High performance liquid chromatography (HPLC), Preparative chromatography, Competitive adsorption isotherm parameters, Perturbation peak (PP) method, Inverse method (IM), Computer simulation, Parameter estimation, Numerical method
National Category
Computational Mathematics Analytical Chemistry
Research subject
Scientific Computing
Identifiers
urn:nbn:se:uu:diva-5971 (URN)91-554-6355-X (ISBN)
Public defence
2005-10-19, Room B21, Uppsala Biomedical Centre, Husargatan 3, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2005-09-27 Created: 2005-09-27 Last updated: 2011-10-27Bibliographically approved
2. Development of Methods for Phase System Characterization in Liquid Chromatography
Open this publication in new window or tab >>Development of Methods for Phase System Characterization in Liquid Chromatography
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis is first and foremost to improve the fundamental knowledge of nonlinear and preparative separation theory by focusing on some of the remaining “white spots” on the theoretical chromatographic map. Secondly, the acquired knowledge is used to develop, validate and execute new methods for phase characterization in liquid chromatography. The methodology used in this thesis is a combination of experiments, fundamental nonlinear theory and systematic computer simulations.

A fundamental knowledge of the molecular interactions between the compounds to be separated and the separation media requires the determination of adsorption isotherms over a broad concentration range to give a complete picture of all interactions in the separation system - weak as well as strong. In addition, such adsorption data is essential for optimization in preparative chromatography.

For the first time, it has been experimentally shown that the injected molecules are not present in the detected peak when a small excess of molecules are injected into a chromatographic system equilibrated with a constant stream of identical molecules. Several experimental procedures for this method were developed such as (i) the optimal injection strategy and (ii) different labeling methods for visualizing the injected molecules. Remarkable phenomena in the single-component case, such as invisible peak deformation and deformed (invisible) frontal chromatograms, are reported, investigated, and explained. This phenomenon has asides from its future practical implementation, also a large didactic value.

The accuracy of the ECP method is experimentally improved, and used to characterize the separation of protolytic compounds at different pH on modern commercially available silica and hybrid silica column packing materials. That investigation enables us to answer why basic compounds give a much more compact preparative peak profile at pH 11 than they yields at lower pH.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 69 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 416
Keyword
Analytical chemistry, Liquid chromatography, Adsorption isotherms, Adsorption energy distribution, Tracer pulse method, Elution by characteristic points, Peak deformation, Validation, Hybrid column material, Alkaline separation, Injection-profiles, Analytisk kemi
Identifiers
urn:nbn:se:uu:diva-8597 (URN)978-91-554-7145-3 (ISBN)
Public defence
2008-04-25, B41, BMC, Husargatan 3, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2008-04-04 Created: 2008-04-04 Last updated: 2009-03-20Bibliographically approved

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Samuelsson, JörgenFornstedt, Torgny

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