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Essentially Lipids: Analytical methods for the characterization of lipid materials
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes analytical methods for chromatographic characterizations of lipids in biological and technical systems.

Lipids are a group of compounds with a central role in all known forms of life. In addition to the biological roles, lipids are also components in many products of our daily usage. The application areas include food, pharma, cosmetics, biofuels, etc.

Analytical characterization of lipids is challenging since a typical lipid extract often contains several hundred unique compounds which also could vary significantly in chemical properties. Separation is in many cases crucial for identification and quantification of individual lipids and here high performance liquid chromatography (HPLC) is regarded as the technique of first choice today.

In the present work, methodologies for both normal phase (NP) and reversed phase (RP) HPLC are presented. The focus has been to develop methods that are fast, have low analytical complexity and are compatible with several detection systems. Cyanopropyl coated silica was evaluated as stationary phase for NP-HPLC with the aim to separate all the lipid classes in common lipid extracts. The analytes were eluted with a binary mobile phase system based on hexane, toluene and methanol which yielded in a total runtime of 30 minutes. In a subsequent study, additional stationary phases for NP-HPLC were evaluated for online sample cleanup of polycyclic aromatic hydrocarbons (PAHs) in lipid matrixes. In the demonstrated methodology for RP-HPLC, a binary system consisting of methanol/water was utilized with phenylpropyl coated silica to elute all tested lipid classes in 30 minutes.

The methodologies were compatible with various detection techniques including evaporative light scattering detection (ELSD), charged aerosol detection (CAD) as well as electrospray mass spectrometry (ESI-MS) and were applied to characterize lipid materials of both biological and technical nature. 

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm Univeristy , 2015. , 49 p.
Keyword [en]
Lipids, Chromatography, HPLC, Charged Aerosol Detection, Evaporative light scattering detection, mass spectrometry
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-113052ISBN: 978-91-7649-077-8 (print)OAI: oai:DiVA.org:su-113052DiVA: diva2:782699
Public defence
2015-02-27, Magnélisalen, Kemiska Övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2015-02-05 Created: 2015-01-22 Last updated: 2015-01-28Bibliographically approved
List of papers
1. Separation of Lipid Classes by HPLC on a Cyanopropyl Column
Open this publication in new window or tab >>Separation of Lipid Classes by HPLC on a Cyanopropyl Column
2012 (English)In: Lipids, ISSN 0024-4201, E-ISSN 1558-9307, Vol. 47, no 1, 93-99 p.Article in journal (Refereed) Published
Abstract [en]

A new method for the separation and identification of lipid classes by normal-phase HPLC on a cyanopropyl column is described. The use of a simple binary gradient, with toluene as a component, provided a rapid separation of non-polar as well as phospholipid classes. The inherent small differences in performances between possible non-polar eluent components of the gradient, such as hexane, heptane, and iso-octane, had a pronounced impact on retention times for individual phospholipid classes. Separation of molecular species within a lipid class could also be observed.

Keyword
Cyanopropyl column, Normal-phase HPLC, Lipid classes, Phospholipids, Toluene, Hexane, Heptane, Iso-octane
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-76743 (URN)10.1007/s11745-011-3627-0 (DOI)000299532400010 ()
Available from: 2012-05-18 Created: 2012-05-16 Last updated: 2017-12-07Bibliographically approved
2. Separation And Identification Of Lipid Classes By Normal Phase Lc-Esi/Ms/Ms On A Cyanopropyl Column
Open this publication in new window or tab >>Separation And Identification Of Lipid Classes By Normal Phase Lc-Esi/Ms/Ms On A Cyanopropyl Column
2014 (English)In: European Journal of Lipid Science and Technology, ISSN 1438-7697, E-ISSN 1438-9312, Vol. 116, no 5, 653-658 p.Article in journal (Refereed) Published
Abstract [en]

In order to establish a versatile and convenient method for the analysis of lipids, electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to a HPLC separation on a cyanopropyl-bonded stationary phase. A binary gradient mobile phase system consisting of hexane, toluene, methanol and a stable electrospray yielding sodium adduct ions could be used to generate specific product ions in MS/MS mode. By applying the LC/ESI-MS/MS method on an egg yolk sample, 29 different molecular species of phosphatidylethanolamines, phosphatidylcholines, and lysophosphatidylcholines could be detected within 25 min.

Keyword
Alkali metal ion adducts, Cyanopropyl, ESI-MS, Lipid classes, Normal phase HPLC
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-104504 (URN)10.1002/ejlt.201300291 (DOI)000335751100016 ()
Note

AuthorCount:4;

Available from: 2014-03-21 Created: 2014-06-11 Last updated: 2017-12-05Bibliographically approved
3. Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography - A prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates
Open this publication in new window or tab >>Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography - A prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates
2014 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1360, 39-46 p.Article in journal (Refereed) Published
Abstract [en]

The retention characteristics of the major lipid components in biodiesels and edible oils as well as representative polycyclic aromatic compounds (PAHs) have been investigated on five different normal phase HPLC stationary phases, in order to optimize class separation for an automatized online HPLC cleanup of PAHs prior GC-MS analysis. By stepwise comparison of different hexane/MTBE compositions as mobile phases on cyano-, phenyl-, pentabromobenzyl-, nitrophenyl- and amino- modified silica columns, the capacity and selectivity factors for each analyte and column could be calculated. It was concluded that the most suitable column for backflush isolation of PAHs in biodiesel and edible oil matrices was the pentabromobenzyl-modified silica (PBB). A previously described online HPLC-GC-MS system using the PBB column was then evaluated by qualitative and quantitative analysis of a biodiesel exhaust particulate extract and a vegetable oil reference material. The GC-MS full scan analysis of the biodiesel particulate extract showed that the lipids had been removed from the sample and a fraction containing PAHs and oxygenated derivatives thereof had been isolated. Quantified mass fractions of PAHs of the reference material BCR-458 agreed well for most of the certified PAH mass fractions in the spiked coconut oil reference material.

Keyword
Biodiesel particulates, Edible oils, Fatty acid methyl esters, Sample cleanup, High performance liquid chromatography
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-106272 (URN)10.1016/j.chroma.2014.07.064 (DOI)000341469400005 ()
Available from: 2014-07-29 Created: 2014-07-29 Last updated: 2017-12-05Bibliographically approved
4. A single step reversed-phase high performance liquid chromatography separation of polar and non-polar lipids
Open this publication in new window or tab >>A single step reversed-phase high performance liquid chromatography separation of polar and non-polar lipids
2014 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1369, 105-115 p.Article in journal (Refereed) Published
Abstract [en]

This paper reports a simple chromatographic system to separate lipids classes as well as their molecular species. By the use of phenyl coated silica as stationary phase in combination with a simple mobile phase consisting of methanol and water, all tested lipid classes elute within 30min. Furthermore, a method to accurately predict retention times of specific lipid components for this type of chromatography is presented. Common detection systems were used, namely evaporative light scattering detection (ELSD), charged aerosol detection (CAD), electrospray mass spectrometry (ESI-MS), and UV detection.

Keyword
Reversed phase liquid chromatography, Glycerolipids, Phospholipids, Evaporative light scattering detector, Charged aerosol detector, Mass spectrometry
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-111915 (URN)10.1016/j.chroma.2014.10.010 (DOI)000345489000013 ()
Note

AuthorCount:3;

Available from: 2015-01-12 Created: 2015-01-08 Last updated: 2017-12-05Bibliographically approved

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