Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Adsorption Studies with Liquid Chromatography: Experimental Preparations for Thorough Determination of Adsorption Data
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Analytical chemistry is a field with a vast variety of applications. A robust companion in the field is liquid chromatography, the method used in this thesis, which is an established workhorse and a versatile tool in many different disciplines. It can be used for identification and quantification of interesting compounds generally present in low concentrations, called analytical scale chromatography. It can also be used for isolation and purification of high value compounds, called preparative chromatography. The latter is usually conducted in large scale with high concentrations. With high concentrations it is also possible to determine something called adsorption isotherms.

Determination of adsorption isotherms is a useful tool for quite a wide variety of reasons. It can be used for characterisation of chromatographic separation systems, and then gives information on the retention mechanism as well as provides the possibility to study column-column and batch-batch reproducibility. If a protein is immobilised on a solid support, adsorption isotherms can be used for pharmacological characterisation of drug-protein interactions. Moreover, they can be used for the study of unexpected chromatographic phenomena.

If the adsorption isotherm is known it is also possible to simulate chromatograms, and subsequently optimise the separation process numerically. The gain of a numerically optimised separation process is higher purity or yield of valuable compounds such as pharmaceuticals or antioxidants, as well as reducing the solvent usage. Taken all together, it saves time, money and the environment.

However, the process of the adsorption isotherm determination requires a number of careful experimental considerations and preparations, and these are the main focus of the thesis. Important steps along the way include the choice of separation system and of suitable analytes, preparation of mobile phases and sample solutions, calibration, determination of injection profiles and column void, and of course the adsorption isotherm determination method itself. It is also important to keep track of parameters such as temperature and pH. These issues are discussed in this thesis.

At the end, a description of useful methods for processing of the raw adsorption isotherm data is presented, as well as a brief passage on methods for numerical optimisation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1118
Keyword [en]
Liquid chromatography, HPLC, UHPLC, Reversed phase, Preparative chromatography, Adsorption isotherm, Injection profile, Sample pH, pH stable conditions, Peak deformation, Band distortion, Overloaded band, Chiral preparative chromatography
National Category
Chemical Sciences Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-216235ISBN: 978-91-554-8858-1 (print)OAI: oai:DiVA.org:uu-216235DiVA: diva2:689784
Public defence
2014-03-14, B22, BMC, Husargatan 3, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2014-02-14 Created: 2014-01-20 Last updated: 2014-04-29
List of papers
1. Injection profiles in liquid chromatography: I. A fundamental investigation
Open this publication in new window or tab >>Injection profiles in liquid chromatography: I. A fundamental investigation
2010 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1217, 4306-4312 p.Article in journal (Refereed) Published
Abstract [en]

This is a fundamental experimental and theoretical investigation on how the injection profile depends on important experimental parameters. The experiments revealed that the injection profile becomes more eroded with increased (i) flow rate, (ii) viscosity of the eluent, (iii) size of the solute, (iv) injection volume and (v) inner diameter of the injection loop capillary. These observations cannot be explained by a 1D-convection-diffusion equation, since it does not account for the effect of the parabolic flow and the radial diffusion on the elution profile. Therefore, the 1D model was expanded into a 2D-convection-diffusion equation with cylindrical coordinates, a model that showed a good agreement with the experimental injection profiles dependence on the experimental parameters. For a deeper understanding of the appearance of the injection profile the 2D model is excellent, but to account for injection profiles of various injection volumes and flow rates in preparative and process-chromatography using computer-optimizations, a more pragmatic approach must be developed. The result will give guidelines about how to reduce the extra-column variance caused by the injection profile. This is important both for preparative and analytical chromatography; in particular for modern analytical systems using short and narrow columns.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-151696 (URN)10.1016/j.chroma.2010.04.045 (DOI)000278920900009 ()
Available from: 2011-04-15 Created: 2011-04-15 Last updated: 2017-12-11Bibliographically approved
2. Injection profiles in liquid chromatography II: predicting accurate injection-profiles for computer-assisted preparative optimizations.
Open this publication in new window or tab >>Injection profiles in liquid chromatography II: predicting accurate injection-profiles for computer-assisted preparative optimizations.
2011 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 34, 5794-5800 p.Article in journal (Refereed) Published
Abstract [en]

In computer assisted optimization of liquid chromatography it has been known for some years that it is important to use experimental injection profiles, instead of rectangular ones, in order to calculate accurate elution bands. However, the incorrectly assumed rectangular profiles are still mostly used especially in numerical optimizations. The reason is that the acquisition of injection profiles, for each injection volume and each flow rate considered in a computer-assisted optimization requires a too large number of experiments. In this article a new function is proposed, which enables highly accurate predictions of the injection profiles and thus more accurate computer optimizations, with a minimum experimental effort. To model the injection profiles for any injection volume at a constant flow rate, as few as two experimental injection profiles are required. If it is desirable to also take the effect of flow rate on the injection profiles into account, then just two additional experiments are required. The overlap between fitted and experimental injection profiles at different flow rates and different injection volumes were excellent, more than 90%, using experimental injection profiles from just four different injection volumes at two different flow rates. Moreover, it was demonstrated that the flow rate has a minor influence on the injection profiles and that the injection volume is the main parameter that needs to be accounted for.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-159084 (URN)10.1016/j.chroma.2011.06.063 (DOI)21782187 (PubMedID)
Available from: 2011-09-26 Created: 2011-09-21 Last updated: 2017-12-08Bibliographically approved
3. Deformations of overloaded bands under pH-stable conditions in reversed phase chromatography
Open this publication in new window or tab >>Deformations of overloaded bands under pH-stable conditions in reversed phase chromatography
2011 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 15, 1966-1973 p.Article in journal (Refereed) Published
Abstract [en]

It has recently been demonstrated, using mathematical models, how peculiar overloaded band profiles of basic compounds are due to the local pH in the column when using low capacity buffers. In this study, overloaded peak shapes resulting after injection of carefully pH matched samples close to the pK(a) of the chosen solute are investigated primarily on two columns; one hybrid silica C18 column (Kromasil Eternity) and one purely polymeric column (PLRP-S), the latter lacking C18 ligands. It was found that distorted peaks of the basic test compound appear even though there is no difference in pH between the injected sample solution and the eluent; the previous explanation to why these effects occur is based on a pH mismatch. Thus, the unusual band shapes are not due to an initial pH difference. Furthermore, it was observed that the effect does not appear on polymeric columns without C18 ligands, but only on columns with C18 ligands, independently of the base matrix (silica, hybrid silica, polymeric).

National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-151463 (URN)10.1016/j.chroma.2010.09.002 (DOI)000289331200006 ()20888565 (PubMedID)
Available from: 2011-04-15 Created: 2011-04-12 Last updated: 2017-12-11Bibliographically approved
4. Why ultra high performance liquid chromatography produces more tailing peaks than high performance liquid chromatography, why it does not matter and how it can be addressed.
Open this publication in new window or tab >>Why ultra high performance liquid chromatography produces more tailing peaks than high performance liquid chromatography, why it does not matter and how it can be addressed.
Show others...
2011 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 39, 6914-21 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (T(f)<2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2μm porous and 2.7μm superficially porous particles (UHPLC) produce significantly higher T(f)-values than the corresponding separation based on 3μm porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the T(f)-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the T(f)-value when translating a HPLC separation to the corresponding UHPLC separation. An aspect that has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that T(f)-values should be complemented by a peak width measure to provide a more objective quality measure.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-159085 (URN)10.1016/j.chroma.2011.08.018 (DOI)21872875 (PubMedID)
Available from: 2011-09-26 Created: 2011-09-21 Last updated: 2017-12-08Bibliographically approved
5. Optimization strategies accounting for the additive in preparative chiral liquid chromatography
Open this publication in new window or tab >>Optimization strategies accounting for the additive in preparative chiral liquid chromatography
Show others...
2012 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1269, no SI, 279-286 p.Article in journal (Refereed) Published
Abstract [en]

This study is an in-depth investigation on how numerical optimization strategies that also account for the additive type and concentration, in preparative batch chromatography, should be performed. As a model system, the separation of Z-(R,S)-2-aminobutyric acid enantiomers on a quinidine carbamate-based chiral stationary phase in polar organic mode was used, with different additive strengths of acetic acid or hexanoic acid in methanol. The inverse method was used to determine the competitive adsorption isotherm parameters for the enantiomers and the additives. Three different optimization strategies were examined: (1) injection volume optimization, (2) optimization of injection volume and additive concentration, and (3) full optimization including injection volume, additive concentration, sample concentration and flow rate. It was concluded that (i) it is important to incorporate the additive concentration in the optimization procedure to achieve the highest production rates, (ii) the full optimization strategy had the overall best results, and (iii) the selection of additive is very important (here acetic acid additive was superior to the hexanoic acid additive). By including the additive in the adsorption model and in the numerical optimization it is not only possible to achieve higher production rates but also to properly select the additive that is most advantageous for the specific separation problem.

Keyword
Additive, Chiral preparative Chromatography, Enantiomers, Inverse method, Optimization, Acid additives, Additive concentrations, Adsorption model, Aminobutyric acids, Batch chromatography, Chiral liquid chromatography, Chiral stationary phase, Competitive adsorption isotherms, Full optimization, Hexanoic acids, In-depth investigation, Injection volume, Inverse methods, Model system, Numerical optimizations, Optimization procedures, Optimization strategy, Production rates, Sample concentration, Separation problems, Acetic acid, Adsorption, Amino acids, Chirality, Inverse problems, Liquid chromatography, Methanol, pH, Saturated fatty acids, Separation, Additives, 2 aminobutyric acid, carbamic acid, hexanoic acid, quinidine, adsorption kinetics, article, chemical composition, chiral chromatography, concentration (parameters), elution, enantiomer, flow rate, ion exchange, priority journal, process optimization, reaction time, separation technique
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-192063 (URN)10.1016/j.chroma.2012.05.052 (DOI)000312475300023 ()
Available from: 2013-01-17 Created: 2013-01-15 Last updated: 2017-12-06Bibliographically approved

Open Access in DiVA

fulltext(1226 kB)652 downloads
File information
File name FULLTEXT01.pdfFile size 1226 kBChecksum SHA-512
1ebef0a76ce040e411cff9ec25d6214293ee47de25f4a7e6a011cf4f106909ba74d420f9c585094ef7102c484b6e60434e47d0d62e86af377e11c4f1a9c556a4
Type fulltextMimetype application/pdf
Buy this publication >>

Search in DiVA

By author/editor
Edström, Lena
By organisation
Analytical Chemistry
Chemical SciencesAnalytical Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 652 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1087 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf