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Accumlations of ammonium acetate on polar materials under HILIC condition and its relation to retention of analytes
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Knut Irgum)
Merck SeQuant AB, S-90719 Umeå, Sweden.
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Knut Irgum)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Ammonium acetate is a buffer salt commonly added to mobile phase in HILIC to improve the reproducibility of the retention of analytes. Adding buffer salt would then result to the change in retention and selectivity. In this study, we have developed methods for determine ammonium acetate in form of its hydrolyzed products (ammonium ion and acetate ion) adsorption on twelve different HILIC stationary phases under various mobile phase condition. The effect of functional group and mobile phase compositions on salt adsorption was then discussed. We also tried to develop a method for characterization important retention mechanism of HILIC systems and interpreted them under the relationship with salt adsorption. Adsorption of salt was based on both portioning and electrostatic interaction. Ammonium was found to preferentially adsorb on HILIC stationary phases except Purospher Star NH2 phase. It is worth noting that adding salt to mobile phase can promote partitioning retention mechanism, possibly as a result of phase separation due to salt out effect.

Keyword [en]
HILIC, salt adsorption, retention mechanism
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-68070OAI: oai:DiVA.org:umu-68070DiVA: diva2:615726
Available from: 2013-04-11 Created: 2013-04-11 Last updated: 2013-04-12Bibliographically approved
In thesis
1. Investigations of the retention mechanisms in hydrophilic interaction chromatography
Open this publication in new window or tab >>Investigations of the retention mechanisms in hydrophilic interaction chromatography
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hydrophilic interaction chromatography is well known as a powerful technique separation of polar and ionizable compound nowadays. However the retention mechanism of the technique is still under debate. Understanding retention mechanism would facilitate the method development using the technique and its future improvement. This was inspiring and became the goal of this thesis.

This work involves the characterization of the water enriched layer regarding to water and buffer salt accumulation. Twelve HILIC stationary phase with a diverse surface chemistry regarding to function groups and modification type were studied. Effect of water and salt on regarding to the retention mechanism was investigated by correlating the adsorption data to the retention of selected solutes

This also involved the characterization of interactions involve in the separation of 21 HILIC columns. Interactions was probe by retention ratio of pair solutes which are characteristic for each specific interaction. The data was evaluate using principle component analysis – a multivariable data analysis method. The model was comprehensive and its outcomes were confirmed by the studies on adsorptions of water and salts.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2013. 42 p.
Keyword
HILIC, hydrophilic interaction chromatography, adsorption isotherm, water enriched layer, multivariate data analysis, retention mechanism, separation
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-68071 (URN)978-91-7459-630-4 (ISBN)
Public defence
2013-05-03, KBC Building, Room KB3A3, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2013-04-12 Created: 2013-04-11 Last updated: 2013-05-14Bibliographically approved

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Citation style
  • apa
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  • Other style
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  • Other locale
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Output format
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  • text
  • asciidoc
  • rtf