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A 2H nuclear magnetic resonance study of the state of water in neat silica and zwitterionic stationary phases and its influence on the chromatographic retention characteristics in hydrophilic interaction high-performance liquid chromatography
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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2011 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 38, 6630-6638 p.Article in journal (Refereed) Published
Abstract [en]

(2)H NMR has been used as a tool for probing the state of water in hydrophilic stationary phases for liquid chromatography at temperatures between -80 and +4°C. The fraction of water that remained unfrozen in four different neat silicas with nominal pore sizes between 60 and 300Å, and in silicas with polymeric sulfobetaine zwitterionic functionalities prepared in different ways, could be determined by measurements of the line widths and temperature-corrected integrals of the (2)H signals. The phase transitions detected during thawing made it possible to estimate the amount of non-freezable water in each phase. A distinct difference was seen between the neat and modified silicas tested. For the neat silicas, the relationship between the freezing point depression and their pore size followed the expected Gibbs-Thomson relationship. The polymeric stationary phases were found to contain considerably higher amounts of non-freezable water compared to the neat silica, which is attributed to the structural effect that the sulfobetaine polymers have on the water layer close to the stationary phase surface. The sulfobetaine stationary phases were used alongside the 100Å silica to separate a number of polar compounds in hydrophilic interaction (HILIC) mode, and the retention characteristics could be explained in terms of the surface water structure, as well as by the porous properties of the stationary phases. This provides solid evidence supporting a partitioning mechanism, or at least of the existence of an immobilized layer of water into which partitioning could be occurring.

Place, publisher, year, edition, pages
Elsevier , 2011. Vol. 1218, no 38, 6630-6638 p.
Keyword [en]
HPLC, Hydrophilic interaction chromatography, Retention mechanisms
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-46064DOI: 10.1016/j.chroma.2011.04.056PubMedID: 21855078OAI: diva2:436904
Available online 29 April 2011 Available from: 2011-08-25 Created: 2011-08-25 Last updated: 2011-10-20Bibliographically approved
In thesis
1. Zwitterionic Sulfobetaine Polymers as Stationary Phases for Liquid Chromatography
Open this publication in new window or tab >>Zwitterionic Sulfobetaine Polymers as Stationary Phases for Liquid Chromatography
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Liquid chromatography is an important separation technique for a vast number of analytes. This thesis mainly focuses on the development of stationary phases for liquid chromatography based on zwitterionic sulfobetaine polymers.

In the thesis, various ways to prepare zwitterionic polymers in an aqueous environment using reversible addition fragmentation chain transfer (RAFT) polymerization are described. Both telomers, i.e. short soluble polymer chains containing a functional terminal group, as well as graft polymers on various supports have been synthesized. The RAFT polymerization technique provides an increased degree of control of the final polymers, which may aid in the preparation of more specifically tailored separation materials.

Sulfobetaine polymers carry both a positive and a negative charge within a single entity, which results in interesting solution properties as well as highly biocompatible features. These unique features make them especially suited for separation of highly polar and/or charged compounds. An example of the successful separation of short peptides using a stationary phase synthesized with the RAFT technique is given.

The unusual properties of sulfobetaine-type polymers are believed to be associated with the structure of water close to the polymer. A study of water structure in some silica based stationary phase grafted with zwitterionic sulfobetaine polymers was conducted. The impact of water structure on retention characteristics was investigated.

Place, publisher, year, edition, pages
Umeå: Kemi, 2008. 60 p.
sulfobetaine, polymer, RAFT polymerization, zwitterionic, separarion, liquid chromatography, stationary phase
National Category
Analytical Chemistry
urn:nbn:se:umu:diva-1809 (URN)978-91-7264-614-8 (ISBN)
Public defence
2008-09-27, KB3A9, KBC-huset, Umeå, 10:00
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2011-09-12Bibliographically approved

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Wikberg, ErikaSparrman, TobiasIrgum, Knut
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