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Application of comprehensive two dimensional gas chromatography to wine analysisVestner, Jochen 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This study focused on the potential of comprehensive two-dimensional gas
chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOF-MS) for
the improved analysis of volatile wine constituents. Solid phase microextraction
(SPME) in combination with GC×GC-TOF-MS was successfully used for the detailed
investigation of the impact of three commercial Oenococcus oeni lactic acid bacteria
(LAB) strains on the volatile composition of Pinotage wines subjected to malolactic
fermentation (MLF). Due to increased separation power and enhanced sensitivity
obtained by using two orthogonal separations coupled with the structural information
provided by deconvoluted TOF-MS spectra, GC×GC-TOF-MS allowed for the
identification and semi-quantitative analysis of much larger numbers of compounds
compared to previous studies applying one-dimensional gas chromatography. The
combination of univariate and multivariate statistical assessment was used as a
powerful tool for data interpretation. The obtained results contribute significantly to
the understanding of the impact of MLF on the volatile composition of Pinotage wine
Some compounds have been linked to MLF for the first time.
Moreover, the impact of these commercial starter cultures on the composition of
volatile sulfur and nitrogen compounds in the same wines was studied by
one-dimensional gas chromatographic methods with headspace injection and solid
supported liquid-liquid extraction together with sulfur selective detection and tandem
mass spectrometry. This study demonstrated also for the time, the impact of MLF on
the composition of volatile sulfur and nitrogen compounds in Pinotage wine.
GC×GC-TOF-MS was further used for the evaluation of the suitability of a new phase
for stir bar sorptive extraction (SBSE) analysis of wine volatiles. Despite instrumental
complications, beneficial extraction properties of the new stir bar phase for especially
more polar compounds could be demonstrated. In addition, the extraction ability of
this novel phase was evaluated for the analysis of selected thiazoles in wine using
heart-cutting two dimensional gas chromatography in combination with nitrogen
selective detection. Advantageous extraction performance of the new stir bar phase
compared to a conventional polydimethylsiloxane (PDMS) phase for the determined
thiazoles was demonstrated. / AFRIKAANSE OPSOMMING: Hierdie studie het gefokus daarop om die potensiaal van omvattende tweedimensionele
gaschromatografie gekombineer met vlugtyd massaspektrometrie
(GC×GC-TOF-MS) vir die verbeterde analise van vlugtige wynkomponente te
ondersoek. Soliede fase mikro-ekstraksie (SPME) in kombinasie met GC×GC TOF
MS is met sukses aangewend vir ‘n ondersoek na die impak van drie kommersiële
Oenococcus oeni melksuur bakteria (LAB) rasse op die samestelling van die vlugtige
fraksie van Pinotage wyne wat appelmelksuurgisting (AMG) ondergaan het. As
gevolg van die verbeterde skeidingsvermoë en die verhoogte sensitiwiteit wat verkry
word deur twee ortogonale skeidings te kombineer, tesame met die inligting
aangaande die molekulêre struktuur wat die die gedekonvoleerde TOF massaspektra
verskaf, maak GC×GC-TOF-MS die identifikasie en semi-kwantitatiewe analise van
aansienlik meer komponente, in vergelyking met die gebruik van een-dimensionele
gaschromatografie, moontlik.
Die kombinasie van monoveranderlike asook multiveranderlike statistiese evaluering
is gebruik as ‘n kragtige tegniek vir data interpretasie. Die resultate wat verkry is dra
tot ‘n groot mate by tot die ontrafeling en begrip aangaande die impak wat AMG op
die samestelling van vlugtige komponente in Pinotage wyn het. Daar word ook vir die
eerste keer aangetoon dat somminge komponente verband te hou met AMG.
Aanvullend hiertoe is die impak wat hierdie kommersiële kulture (wat gebruik word
om fermentasie te inisieer) op die voorkoms van swawel en stikstof bevattende
vlugtige komponente het bestudeer deur gebruik te maak van een-dimensionele
gaschromatografiese metodes met ‘headspace’ inspuiting en vloeistof-voeistof
ekstraksie tesame met swawel en stikstof selektiewe deteksie en tandem
massaspektrometrie. Hierdie ondersoek werp lig, ook vir die eerste keer, op die
samestelling van vlugtige swawel en stikstof bevattende komponente in Pinotage
wyn.
GC×GC-TOF-MS is ook gebruik vir die evalueering van die toepaslikheid van ‘n
nuwe stasionêre fase vir gebruik met roerstaaf sorptiewe ekstraksie (SBSE) vir die
analisering van vlugtige komponente in wyn. Ten spyte van instrumentele
komplikasies, is die voordele wat hierdie nuwe fase vir die ekstraksie van vernaamlik
meer polêre komponete aangetoon. Vervolgens is die ekstraksievermoë van hierdie
nuwe fase vir die analise van sekere tiasole in wyn met ‘heart-cutting’ twedimensionaly
gaschromatografie in kombinasie met stikstof-selektiewe deteksie gedemonstreer. Verbeterde ekstraksie van die nuwe roerstaaf fase vir die analise
van tiasole, in vergelyking met ‘n tradisionele polydimethylsiloxane (PDMS) fase is
voorts aangetoon.
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DESIGNING STATIONARY PHASES FOR IMPROVED PROTEIN SEPARATIONSTyrel A Wagner (12469887) 28 April 2022 (has links)
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<p>As monoclonal antibodies (mAbs) become a more important part of the pharmaceutical industry, the need for better quicker analysis of then will also increase. To do this, better stationary phases specifically designed for mAbs need to be developed to analyze the quality of mAbs by their critical control attributes. The three main critical control attributes are size, charge, and glycosylation. This work focuses mainly on the development of stationary phases to analyze critical control attributes in size and charge through using a non-porous silica base and surface confined atom transfer radical polymerization to grow improved stationary phases that minimize undesired interactions and maximize desired interactions.</p>
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The Determination of Lead and Cadmium in Tobacco Using High Performance Liquid Chromatography and Dithiocarbamate Derivitization.Klein, Mark Stephen 07 May 2011 (has links) (PDF)
A reversed phase-high performance liquid chromatography method has been developed that is capable of resolving lead and cadmium diethyldithiocarbamate complexes. The method does not require the presence of hazardous solvents to optimize peak shape and resolution; the mobile phase consists of methanol, water, and a surfactant. Tobacco samples were chemically oxidized and reacted with sodium diethyldithiocarbamate reagent prior to analysis using the HPLC method. The lead diethyldithiocarbamate determination was compromised by the presence of a significant interference in the analysis; lead determinations in 10 foreign and domestic tobacco samples ranged from 27.14 to 134.84 μg/g. The cadmium diethyldithiocarbamate determination was not adversely affected by interferences. Cadmium determinations in 10 foreign and domestic tobacco samples ranged from 0.89 to 6.96 μg/g. The tobacco samples were also analyzed using atomic absorption spectrometry. Foreign tobacco brands that contained clove as a spice showed lower levels of cadmium and lead.
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Expression of wild type and variants of human apolipoprotein A-I in Pichia pastoris / Expression de type sauvage et des variantes de l’Apolipoprotéine A-I humaine chez Pichia pastorisJanakiraman, Vignesh Narasimhan 11 December 2015 (has links)
Les lipoprotéines de haute densité (High Density Lipoprotein, HDL) permet deréduction de risque de maladies cardio-vasculaires principalement en raison de leurcapacité à éliminer le cholestérol accumulé des artères (via transport inverse ducholestérol). Les effets protecteurs des HDL sont médiés par l'apolipoprotéine AI(ApoA1), qui est le La protéine la plus importante quantitativement du HDL. L’ApoA1favorise l'efflux de cholestérol vers le foie pour l'excrétion. Une augmentation desniveaux plasmatiques de l’ApoA1 est généralement acceptée d'êtrecardioprotecteur, ce qui en fait un potentiel thérapeutique. Deux variantes naturelle(mutants) de l’ApoA1, Milano et Paris, sont caractérisées par une mutationponctuelle unique a permis l'introduction d'un résidu cystéine. Populations avecApoA1-Milano ont été rapportés d'avoir un système cardiovasculaire, même avec defaibles niveaux de plasma de ApoA1 et HDL. Il est donc d'intérêt pour générerrecombinante de type sauvage et des variantes de ApoA1 humaine pour desapplications thérapeutiques potentielles. Dans cette étude, de type sauvagerhApoA1 a été produit chez P. pastoris et purifié par chromatographie en modemixte en une seule étape. Par la suite, un processus intégré a été le développementde la production et la récupération rapide de type sauvage rhApoA1 chez P. pastorispar chromatographie par lit expansée. En outre, les variantes de l'ApoA1, Milano &Paris, ont été générées par mutagenèse dirigée et ont été exprimés chez P. pastoris.Les motifs d’adsorption de rhApoA1-Milano et rhApoA1-Paris ont été comparés àcelle de type sauvage ApoA1 et les différences ont été discutées. / The high-density lipoprotein (HDL) complex helps reduce the risk of cardiovasculardisorders mainly due to its ability to remove accumulated cholesterol from arteriesvia reverse cholesterol transport. These protective effects of HDL are known to bemediated by Apolipoprotein A-I (ApoA1), which is the major protein component ofHDL. ApoA1 is a lipid binding protein and promotes cholesterol efflux fromperipheral tissues to the liver for excretion. An increase in the plasma levels ofApoA1 is generally accepted to be cardioprotective, making it a potentialtherapeutic. Two naturally occuring variants of ApoA1, namely the Milano & Parismutants, are characterised by a single point mutation resulting in the introduction ofa Cysteine residue. Populations with ApoA1-Milano have been reported to have ahealthier cardiovascular system even with low plasma levels of ApoA1/HDL. It ishence of interest to generate recombinant wild type and variants of human ApoA1for potential therapeutic applications. In this study, wild type rhApoA1 was producedin P. pastoris and purified by mixed-mode chromatgraphy in a single step.Subsequently, an integrated process has been development for the production andrapid recovery of wild type rhApoA1 in Pichia pastoris. This has paved way to theestablishment of a scalable integrated process that could be further developed toindustrial levels. In addition, the cysteine variants of ApoA1, Milano & Paris, havebeen generated by site directed mutagenesis and have been successfully expressedin P. pastoris. The binding patterns of rhApoA1-Milano and rhApoA1-Paris have beencompared with that of wild-type ApoA1 and the differences have been discussed.
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