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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Comparison of Artificial Flavors in Commercial Products and Actual Natural Flavor via Gas Chromatography Mass Spectroscopy Data.

Sluss, Randi Jasmine 19 August 2009 (has links)
In this research project, real natural strawberries bought from different local sources were profiled by gas chromatography-mass spectroscopy (GCMS). These profiles were then used as a reference to compare GCMS profiles of commercial artificial strawberry flavor products such as strawberry flavored Cool Splashers™, Gatorade®, and Aquacal® flavored water. The chromatograms obtained were patterned using simple visual observations, scatter plot designs, Mann-Whitney U Test, and correlation coefficients. The artificially flavored commercial products tend to have simpler chromatograms. The Burger King® milkshake, Gatorade®, and Hi-C® are the most similar to that of the natural strawberry flavor. Their correlation coefficients are 0.972, 0.870, and 0.984 respectively. The Mann-Whitney U Test results also support the conclusions from correlation coefficients. However, the natural products tend to have more constituents including the main flavoring compounds. Thus fresh produce have better flavor and are more nutritious for a good reason.
2

The development of a sensitive method to study volatile organic compounds in gaseous emissions of lung cancer cell lines

Maroly, Anupam 29 August 2005 (has links)
The ultimate objective of this research was to develop a low cost, reliable system that would lead to early detection of lung cancer. Tests involved the quantitation of gaseous metabolic emissions from immortalized lung cancer cell lines in order to correlate the chemical markers to be of cancerous origin. The specific aims of the project were the study of gas emissions in selected cancer cell lines and identification of volatile organic compounds (VOCs) in them. Disadvantages of earlier studies were that the measurements were not real time or state specific so that molecular identification was often inconclusive. Furthermore the methods of study used in the past were not quantitative, which limited their practicality for medical applications. We felt the need to prove or disprove these earlier results using a new technique. The method we proposed is different and unique when compared to previous methods because cell lines have not been studied extensively for cancer markers. We have studied cancer cell lines which are adherent, immortalized cultures originating from primary tumors obtained from patients with no prior treatment for lung cancer. We have used an alternative method for the spectrometric analysis and quantitation of the selected chemical markers. The pre-concentration method involved a Purge and Trap unit with a thermal desorber where the vapor concentration was enhanced. The concentrated head space gases were analyzed using a Gas Chromatograph ?? Mass Spectrometer setup. This setup eliminated the bulky apparatus used in earlier studies. It is simpler in design and more comprehensive so that external factors such as patient??s diet, habitat and lifestyle do not contribute to our study of recognition of cancer markers. Based on the results obtained in the above experiments, a more comprehensive, inexpensive study of lung cancer related markers could be made. The first section, after giving an introduction to lung cancer, goes on to explain the background work done by other researchers on cancer. The third section gives a detailed explanation of the experimental setup. This is followed by all the tests conducted with corresponding results. The final section deals with the conclusions drawn from all experiments.
3

Screening and Quantitation of Volatiles from Explosive Initiators and Plastic Bonded Explosives (PBX)

Alexis J Hecker (18405276) 03 June 2024 (has links)
<p dir="ltr">The detection of explosives and explosive devices based upon the volatile compounds they emit is a long-standing tool for law enforcement and physical security. Towards that end, solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) has become a crucial analytical tool for the identification of volatiles emitted by explosives. Previous SPME studies have identified many volatile compounds emitted by common explosive formulations that serve as the main charge in explosive devices. However, limited research has been conducted on initiators like fuses, detonating cords, and boosters. In this study, a variety of SPME fiber coatings (i.e., polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), carboxen/polydimethylsiloxane (CAR/PDMS), and polyacrylate (PA)) were employed for the extraction and analysis of volatiles from Composition C-4 (cyclohexanone, 2-ethyl-1-hexanol, and 2,3-dimethyl-2,3-dinitrobutane (DMNB)) and Red Dot double-base smokeless powder (nitroglycerine, phenylamine). The results revealed that a PDMS/DVB fiber was optimal. Then, an assortment of explosive items (i.e., detonation cord, safety fuse, slip-on booster, and shape charge) were analyzed with a PDMS/DVB fiber. A variety of volatile compounds were identified, including plasticizers (tributyl acetyl citrate, N-butylbenzenesulfonamide), taggants (DMNB), and degradation products (2-ethyl-1-hexanol). </p><p dir="ltr">Taggants, like DMNB, are one of the pivotal components added to explosives. These distinctive chemical markers, deliberately introduced during manufacturing to facilitate the identification of explosives, are commonly detected using SPME GC- MS, but their quantitation remains underexplored. To address this, we investigated total vaporization headspace (TV- HS) GC- MS for quantifying taggants in the headspace of Composition C4. Factors effecting the extraction of DMNB, such as shape and age of the sample, and surface depletion, were also examined. The results revealed that the shape of the sample did not affect the amount of DMNB in the headspace but the older the sample, the more DMNB was detected in the headspace. Surface depletion was also seen in samples that were exposed to air for more than one week. Then calibration curves with calibrants of DMNB in acetone were established for quantitation. The average concentration of DMNB in the headspace was determined to be 125 parts per million (ppm).</p><p><br></p>
4

Strukturelle Merkmale N-modifizierter Braunkohlen unter besonderer Berücksichtigung der Huminstoffe / Structural properties of N-modified brown coals with emphasis on humic substances

Ninnemann, Horst 14 January 2008 (has links) (PDF)
Motiviert durch die Zunahme der weltweiten Nachfrage nach hochwertigen Humusstoffen wurde am Institut für Holz- und Pflanzenchemie ein neuartiger Humusersatzstoff entwickelt. Dieses N-modifizierte Produkt wird auf Basis eines patentierten Normaldruckverfahrens der oxidativen Ammonolyse (OA) aus ligninhaltigen Ausgangssubstanzen, im vorliegenden Fall Lausitzer Braunkohle, hergestellt. Ziel war, die bisher vorliegenden Erkenntnisse der strukturellen Eigenschaften solcher Humusstoffe zu erweitern. Im Fokus standen die Gehalte und Charakteristik der Huminstofffraktionen (Humine, Humin- und Fulvosäuren). Der Stickstoff und die Art seines Einbaus in die organische Substanz spielt hierbei eine besondere Rolle. Für die Huminstoffisolierung kam die hinsichtlich der Ausbeuten und des Zeitaufwandes optimierte IHSS-Methode zum Einsatz. Wesentliche Merkmale N-modifizierter Substanzen sind erhöhte Huminsäurengehalte, zeitlich differenziert wirksame N-Bindungsformen und damit eine Diversifizierung der Funktionalität. Zusätzlich mit dem geringen Aschegehalt unterscheidet dies N-modifizierte Lausitzer Braunkohle von anderen auf Braunkohlebasis erzeugten Bodenverbesserungsmitteln des Marktes. Es konnte gezeigt werden, dass Huminsäuren hinsichtlich der Bereitstellung von Stickstoff und Funktionalität (z.B. Austauscherplätze) eine Schlüsselrolle einnehmen. Die Veränderungen durch die OA basieren stofflich auf der Bildung regenerierter Huminsäuren und chemisch u.a. auf der oxidativen Ringspaltung von Aromaten an nicht veretherten phenolischer OH-Gruppen von Methoxyphenolstrukturen. Dabei ist diese Reaktion entgegen früherer Annahmen nicht an eine Demethoxylierung gebunden und erfordert auch keine verschärften Reaktionsbedingungen (z.B. erhöhter Druck). Diese und weitere Reaktionsmechanismen führen zu ammoniumartig, amidartig und fest organisch gebundenen N-Bindungsformen. 15N-NMR-Spektroskopische Untersuchungen an einem 15N-angereicherten Produkt, Py-GC/MS-Untersuchungen und nasschemische Experimente zeigen, dass in der Vergangenheit die Bedeutung heterocyclischer, insbesondere heteroaromatischer N-Bindungsformen überschätzt wurde. Amidartiger Stickstoff präsentiert sich dabei als außerordentlich heterogen hinsichtlich seiner Hydrolysestabilität bzw. Pflanzenverfügbarkeit. Für die effektive Beurteilung möglicher Ausgangssubstanzen hinsichtlich ihrer Eignung für die Herstellung von Humusdüngestoffen nach dem Prinzip der OA kann der Huminsäurengehalt herangezogen werden. Er wird mit Hilfe eines degradativen Verfahrens ermittelt. Die mit dem Huminsäurengehalt in Verbindung stehenden Stoffeigenschaften von Kohlen korrelieren gut mit dem N-Einbau. Aus Sicht der Verfahrensführung hängt die Intensität des N-Einbaus eng mit dem Oxidationsregime zusammen. Durch Anwendung von reinem Sauerstoff anstelle von Luft als sehr einfach und günstig zu realisierende Maßnahme kann die Reaktionszeit halbiert werden. / The development of a novel artificial humus material at the Institute of Wood- and Plant Chemistry was accounted by the increasing demand for high grade humic matter. This N-modified product base on a patented ambient pressure technology of the oxidative ammonolysis. of lignin containing substances, in particular Lusitian lignite. Objective of the work was to broadening the current knowledge of structural properties with focus on the contents and characteristics of humic substances fractions (humins, humic acids, fulvic acids). Especially attention was given to nitrogen and its way of incorporation into organic matter. For isolating humic substances the IHSS method was used. The procedure was adapted in order to increase the yield of humic acids and decrease time needed. Main characteristics of N-modified substances are higher contents of humic acids and subtly differenciateted effective N-binding forms with leads to higher diversity of the chemical functionality. This and the low ash content makes the differences to other brown coal based soil improving agents available on the marked. It has been shown that humic acids give the main part providing nitrogen and functionality (e.g. cation exchange capacity). The oxidative ammonolysis leads to regenerated humic acids as well as e.g. the clevage of aromatic structures by reactions of free phenolic groups. In contrast to former assumptions the cleavage is not strongly related to demethoxylation or strong reaction conditions like high pressure. This and other reactions lead to short, middle, and long lasting N-binding forms. 15N-NMR-spectroscopic investigations on a 15N-enriched product, Py-GC/MS-investigations and conventional investigations show an overestimation of heterocyclic, in particular heteroaromatic N-binding forms up to now. Consequently amide like nitrogen reveals as extraordinary according to its persistent behaviour to hydrolysis and plant availability respectively. Corresponding the correlation of the N-incorporation and humic acid content of raw materials the latter can be used for evaluating possible raw material for its usage for N-modification. It can be easy obtained in a degratadive way. From the process engineering point of view the success of N-incorporating is strongly correlated to the oxidation conditions during processing. Using pure oxygen instead of air shorts the needed reaction at 50%.
5

Strukturelle Merkmale N-modifizierter Braunkohlen unter besonderer Berücksichtigung der Huminstoffe

Ninnemann, Horst 20 November 2007 (has links)
Motiviert durch die Zunahme der weltweiten Nachfrage nach hochwertigen Humusstoffen wurde am Institut für Holz- und Pflanzenchemie ein neuartiger Humusersatzstoff entwickelt. Dieses N-modifizierte Produkt wird auf Basis eines patentierten Normaldruckverfahrens der oxidativen Ammonolyse (OA) aus ligninhaltigen Ausgangssubstanzen, im vorliegenden Fall Lausitzer Braunkohle, hergestellt. Ziel war, die bisher vorliegenden Erkenntnisse der strukturellen Eigenschaften solcher Humusstoffe zu erweitern. Im Fokus standen die Gehalte und Charakteristik der Huminstofffraktionen (Humine, Humin- und Fulvosäuren). Der Stickstoff und die Art seines Einbaus in die organische Substanz spielt hierbei eine besondere Rolle. Für die Huminstoffisolierung kam die hinsichtlich der Ausbeuten und des Zeitaufwandes optimierte IHSS-Methode zum Einsatz. Wesentliche Merkmale N-modifizierter Substanzen sind erhöhte Huminsäurengehalte, zeitlich differenziert wirksame N-Bindungsformen und damit eine Diversifizierung der Funktionalität. Zusätzlich mit dem geringen Aschegehalt unterscheidet dies N-modifizierte Lausitzer Braunkohle von anderen auf Braunkohlebasis erzeugten Bodenverbesserungsmitteln des Marktes. Es konnte gezeigt werden, dass Huminsäuren hinsichtlich der Bereitstellung von Stickstoff und Funktionalität (z.B. Austauscherplätze) eine Schlüsselrolle einnehmen. Die Veränderungen durch die OA basieren stofflich auf der Bildung regenerierter Huminsäuren und chemisch u.a. auf der oxidativen Ringspaltung von Aromaten an nicht veretherten phenolischer OH-Gruppen von Methoxyphenolstrukturen. Dabei ist diese Reaktion entgegen früherer Annahmen nicht an eine Demethoxylierung gebunden und erfordert auch keine verschärften Reaktionsbedingungen (z.B. erhöhter Druck). Diese und weitere Reaktionsmechanismen führen zu ammoniumartig, amidartig und fest organisch gebundenen N-Bindungsformen. 15N-NMR-Spektroskopische Untersuchungen an einem 15N-angereicherten Produkt, Py-GC/MS-Untersuchungen und nasschemische Experimente zeigen, dass in der Vergangenheit die Bedeutung heterocyclischer, insbesondere heteroaromatischer N-Bindungsformen überschätzt wurde. Amidartiger Stickstoff präsentiert sich dabei als außerordentlich heterogen hinsichtlich seiner Hydrolysestabilität bzw. Pflanzenverfügbarkeit. Für die effektive Beurteilung möglicher Ausgangssubstanzen hinsichtlich ihrer Eignung für die Herstellung von Humusdüngestoffen nach dem Prinzip der OA kann der Huminsäurengehalt herangezogen werden. Er wird mit Hilfe eines degradativen Verfahrens ermittelt. Die mit dem Huminsäurengehalt in Verbindung stehenden Stoffeigenschaften von Kohlen korrelieren gut mit dem N-Einbau. Aus Sicht der Verfahrensführung hängt die Intensität des N-Einbaus eng mit dem Oxidationsregime zusammen. Durch Anwendung von reinem Sauerstoff anstelle von Luft als sehr einfach und günstig zu realisierende Maßnahme kann die Reaktionszeit halbiert werden. / The development of a novel artificial humus material at the Institute of Wood- and Plant Chemistry was accounted by the increasing demand for high grade humic matter. This N-modified product base on a patented ambient pressure technology of the oxidative ammonolysis. of lignin containing substances, in particular Lusitian lignite. Objective of the work was to broadening the current knowledge of structural properties with focus on the contents and characteristics of humic substances fractions (humins, humic acids, fulvic acids). Especially attention was given to nitrogen and its way of incorporation into organic matter. For isolating humic substances the IHSS method was used. The procedure was adapted in order to increase the yield of humic acids and decrease time needed. Main characteristics of N-modified substances are higher contents of humic acids and subtly differenciateted effective N-binding forms with leads to higher diversity of the chemical functionality. This and the low ash content makes the differences to other brown coal based soil improving agents available on the marked. It has been shown that humic acids give the main part providing nitrogen and functionality (e.g. cation exchange capacity). The oxidative ammonolysis leads to regenerated humic acids as well as e.g. the clevage of aromatic structures by reactions of free phenolic groups. In contrast to former assumptions the cleavage is not strongly related to demethoxylation or strong reaction conditions like high pressure. This and other reactions lead to short, middle, and long lasting N-binding forms. 15N-NMR-spectroscopic investigations on a 15N-enriched product, Py-GC/MS-investigations and conventional investigations show an overestimation of heterocyclic, in particular heteroaromatic N-binding forms up to now. Consequently amide like nitrogen reveals as extraordinary according to its persistent behaviour to hydrolysis and plant availability respectively. Corresponding the correlation of the N-incorporation and humic acid content of raw materials the latter can be used for evaluating possible raw material for its usage for N-modification. It can be easy obtained in a degratadive way. From the process engineering point of view the success of N-incorporating is strongly correlated to the oxidation conditions during processing. Using pure oxygen instead of air shorts the needed reaction at 50%.

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