Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT:
The separation of apple, cocoa and green tea phenolic compounds by comprehensive
2-dimensional liquid chromatography (2-D-LC) has been studied. In the first
dimension, phenolic compounds were separated according to polarity by hydrophilic
interaction chromatography (HILIC) on a diol stationary phase with a mobile phase
containing acetonitrile, methanol, acetic acid and water. Gradient reversed-phase (RP)
LC using a C18 column with fluorescence detection was employed in the second
dimension to separate compounds according to hydrophobicity. Compounds were
identified using negative electrospray ionisation mass spectrometry (ESI-MS) coupled
to both HILIC and RP separations.
The coupling of HILIC and RP separations proved to be especially beneficial
since this provided simultaneous information on both the polarity and hydrophobicity
of phenolics. The low degree of correlation (r2 < 0.21) between the two LC modes
afforded peak capacities in excess of 3000 for the off-line method. An on-line method
was also developed utilizing a short, small particle-packed column to provide fast
separation in the second dimension. A 1 mm i.d. column was used in the first
dimension for the on-line system to reduce injection volumes onto the second
dimension column. A significantly lower practical peak capacity was measured for
the on-line system, due largely to the reduction in second dimension peak capacity.
On the other hand, analysis could be performed in an automated fashion using the online
system reducing the risk of sample alteration and guaranteeing better operation
reliability and reproducibility. Especially the off-line comprehensive HILIC × RP-LC
method developed demonstrated its utility in the analysis of various groups of
phenolic compounds including proanthocyanidins, phenolic acids, flavonols and
flavonol conjugates in a variety of natural products. / AFRIKAANSE OPSOMMING:
Die skeiding van fenoliese komponente in appel, kakao en groen tee is deur middel
van ‘comprehensive’ 2-dimensionele vloeistof chromatografie (2-D-LC) bestudeer.
Hidrofiliese interaksie chromatografie (HILIC) is gebruik om die fenoliese
komponente in die eerste dimensie te skei op grond van polariteit, deur gebruik te
maak van ‘n diol stationêre fase en mobiele fase bestaande uit asetonitriel, metanol,
asynsuur en water. ‘n Gradiënt omgekeerde fase (RP) LC analisie op ‘n C18 kolom
met fluorosensie deteksie is in die tweede dimensie gebruik om fenole volgens
hidrofobisiteit te skei. Negatiewe elektrosproei-ionisasie massa spektometrie (ESIMS)
gekoppel aan HILIC en RP skeidings is gebruik vir identifikasie van fenole.
Die koppeling van HILIC en RP skeidings veral voordelig deurdat dit gelyktydige
informasie verskaf het oor die polariteit sowel as die hidrofobisiteit van die fenoliese
komponente. Die lae graad van korrelasie (r2 < 0.21) tussen die twee LC metodes was
verantwoordelik vir piek kapasiteite bo 3000 vir die af-lyn metode. ‘n Aanlyn metode
was ontwikkel deur gebruik te maak van ‘n kort, klein partikel gepakte kolom om
vinnige skeiding in die tweede dimensie te verseker. 1 mm i.d. kolom was gebruik in
die eerste dimensie vir die aanlyn sisteem om die inspuit volume op die tweede
dimensie kolom te verminder. Aansienlike laer praktiese piek kapasiteit was gemeet
vir die aanlyn sisteem, grootliks toegeskryf aan die reduksie in die tweede dimensie
piek kapasitiet. Aan die ander kant, analise kan geoutomatiseerd uitgevoer word deur
gebruik te maak van die aanlyn sisteem, wat monster alterasie, beter betroubaarheid
en reproduseerbaarhied verseker. Veral die ontwikkelde af-lyn ‘comprehensive’
HILIC × RP-LC metode toon demonstreerbare voordele vir die analiese van verskeie
groepe fenoliese komponente, insluitende proantosianiede, fenoliese sure, flavonole
en gekonjugeerde flavonole in ‘n verskeidenheid natuurlike produkte.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2420 |
| Date | 12 1900 |
| Creators | Kalili, Kathithileni Martha |
| Contributors | De Villiers, A. J., University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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