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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.
261

Microwave extraction of essential oils (from black pepper and coriander) at 2.46 GHz

Ramanadhan, Balasundaram 27 October 2005
Essential oils are composed of a wide range of bioactive chemical compounds. They traditionally found application as flavour, fragrances and medicinal aroma. Today, the essential oils are sought-after for innumerable applications starting from markers for plant identifications to base for semi-synthesis of highly complex molecules. The extraction of highly delicate essential oils from plants remains a crucial step in all these applications. By using microwaves to mediate the extraction, it is possible to maintain mild conditions and effect superior extraction. However, apart from laboratory trials, essential oil extraction using microwave energy is largely an unexplored area. In the current work, an integrated procedure for microwave extraction followed by volatiles sampling and analysis from selected botanical raw materials (viz. black pepper, Piper nigrum and coriander Coriandrum sativum) was developed. There are two problems to overcome in the extraction from solid plant materials: that of releasing the essential oil from solid matrix and letting it diffuse out successfully in a manner that can be scaled-up to industrial volumes. Towards this end, an innovative volatiles extraction unit was conceived, designed and developed that used thin layer, for microwave exposure and rotational mixing, to mitigate the effects of thermal gradient and non-uniform exposure of bulk matter. The effect of varying the microwave field on the essential oils extracted was studied. The microwave field that coupled in the region of extraction was estimated from temperature rise measurement using the microwave power equation (with water as reference dielectric). The essential oil extracted under different microwave fields were compared using gas chromatography-mass spectrometry (GC-MS) and data analysis with SAS statistical software. The microwave field at the site of extraction was sensed by symmetrical placement of biomaterial sample and a reference, in a rotational extractor, such that they both couple the same field during tumbling motion. By measuring the temperature rise in the reference accurately, it is possible to estimate the microwave field present at that position. The rotational extractor has a second degree of freedom, in that it can slide along the axel taking discrete positions. Each position leads to a different microwave exposure of the sample. It is possible to measure the relative variation of microwave field using temperature rise data at each position. It was found that, at position labeled R4, located at 65.6 mm from the right extreme of the microwave cavity had the highest effective microwave field strength of value 92.7 V/m. The volatiles released from the biomaterials, black pepper and coriander, were sampled using solid phase micro extraction and analyzed using gas chromatography-mass spectrometry. The highest peaks representing beta-caryophyllene in black pepper and linalool in coriander were identified using mass spectrometric peak matching using NIST library.The extract (in terms of ion count) for each microwave parameter (such as field, water content level and solvent type) was plotted as a trend graph. The current experiment successfully tested the procedure for following the microwave process in the extraction of sensitive spice volatiles (from black pepper and coriander). With the microwave field measured at the region of extraction, it was possible to plot pepper extraction versus the microwave field to which the pepper sample was exposed. The extraction was represented in terms of cumulative value of ion counts obtained in GC-MS analysis. This unique procedure developed in the current research allows for the graphical comparison of the microwave extractions. It was found that black pepper has a better response to microwave extraction than coriander. The pepper extraction was found to increase proportionately with increase in microwave field strength. The extraction was also enhanced proportionately by the incremental addition of water content at constant microwave field.
262

Application Of Active Sampling And Sptd/gc-ms Analysis Methodologies For Terpenes At Uludag Mountain

Aktas, Yusuf 01 September 2003 (has links) (PDF)
Measurement of monoterpenes including / alpha-pinene, camphene, beta-pinene, d-limonene, gamma-terpinene, linalool, 1-isopulegol, 1-borneol, dl-menthol, alpha-terpineol, dihydrocarveol, citronellol, pulegone, geraniol / and gas phase inorganic pollutants (O3 and NOx) were investigated on Uludag Mountain, which is the highest point in North-west Turkey. The sampling site (1645 m altitude) is surrounded by mainly Uludag fir, which is characteristic to Uludag, while altitudes lower than 1000 m were composed of mixed deciduous trees. Sampling apparatus and sampling strategy for collection of the studied terpenes on Uludag Mountain were developed. Breakthrough Volume experiments were performed for accurate sampling. Samples were collected in a field campaign performed during October 2002 by means of active sampling onto glass coated stainless steel tubes containing Tenax&amp / #61666 / TA (55 mg) and Carbopack&amp / #61652 / B (65 mg). The mass flow rate and duration of sampling were 30 mL/min and 4 hours. Short-Path-Thermal-Desorption/Gas Chromatography-Mass Spectrometer (SPTD/GC-MS) was used for the analysis of monoterpenes during 12-14 October 2002. The cryogenic preconcentration (-40oC) was maintained by liquid CO2. HP-1-MS capillary column provided good resolution of peaks, except for pulegone and citronellol at standard operation procedure. Internal standard calibration was applied by adding carefully measured spikes of fenchone to the samples and standards. The detection limits for each terpene were found to be at sub-ppbv level. Daily intermediate standard measurements and auto-tune provided checking the instrumental capabilities. Selected Ion Monitoring mode was used for analysis of the terpenes. For quantitation of the spectra at least one qualifier ion was expected to be within 80% correlation with target ion. Alpha-pinene, camphene, beta-pinene, and d-limonene were determined. The average concentrations of monoterpenes were found to be 0.385, 0.168, 0.111, and 0.204 ppbv respectively. Simultaneous measurements of O3, NOx, SO2, and meteorological parameters were also performed. The data resolution was 15 min for each pollutant. Ozone displayed strong diurnal variation (around 5-30 ppb), while NOx concentrations were almost constant around 15 ppb. During the sampling campaign terpenes showed similar behaviours with O3, but not with NOx. Terpenes had a direct relation with temperature and relative humidity.
263

SIMPLE AND RAPID ASSAY METHOD FOR SIMULTANEOUS QUANTIFICATION OF URINARY NICOTINE AND COTININE USING MICRO-EXTRACTION BY PACKED SORBENT AND GAS CHROMATOGRAPHY-MASS SPECTROMETRY

Seno, Hiroshi, Suzuki, Osamu, Ishii, Akira, Zaitsu, Kei, Hattori, Hideki, Ogawa, Tadashi, Iwai, Masae 08 1900 (has links)
No description available.
264

Microwave extraction of essential oils (from black pepper and coriander) at 2.46 GHz

Ramanadhan, Balasundaram 27 October 2005 (has links)
Essential oils are composed of a wide range of bioactive chemical compounds. They traditionally found application as flavour, fragrances and medicinal aroma. Today, the essential oils are sought-after for innumerable applications starting from markers for plant identifications to base for semi-synthesis of highly complex molecules. The extraction of highly delicate essential oils from plants remains a crucial step in all these applications. By using microwaves to mediate the extraction, it is possible to maintain mild conditions and effect superior extraction. However, apart from laboratory trials, essential oil extraction using microwave energy is largely an unexplored area. In the current work, an integrated procedure for microwave extraction followed by volatiles sampling and analysis from selected botanical raw materials (viz. black pepper, Piper nigrum and coriander Coriandrum sativum) was developed. There are two problems to overcome in the extraction from solid plant materials: that of releasing the essential oil from solid matrix and letting it diffuse out successfully in a manner that can be scaled-up to industrial volumes. Towards this end, an innovative volatiles extraction unit was conceived, designed and developed that used thin layer, for microwave exposure and rotational mixing, to mitigate the effects of thermal gradient and non-uniform exposure of bulk matter. The effect of varying the microwave field on the essential oils extracted was studied. The microwave field that coupled in the region of extraction was estimated from temperature rise measurement using the microwave power equation (with water as reference dielectric). The essential oil extracted under different microwave fields were compared using gas chromatography-mass spectrometry (GC-MS) and data analysis with SAS statistical software. The microwave field at the site of extraction was sensed by symmetrical placement of biomaterial sample and a reference, in a rotational extractor, such that they both couple the same field during tumbling motion. By measuring the temperature rise in the reference accurately, it is possible to estimate the microwave field present at that position. The rotational extractor has a second degree of freedom, in that it can slide along the axel taking discrete positions. Each position leads to a different microwave exposure of the sample. It is possible to measure the relative variation of microwave field using temperature rise data at each position. It was found that, at position labeled R4, located at 65.6 mm from the right extreme of the microwave cavity had the highest effective microwave field strength of value 92.7 V/m. The volatiles released from the biomaterials, black pepper and coriander, were sampled using solid phase micro extraction and analyzed using gas chromatography-mass spectrometry. The highest peaks representing beta-caryophyllene in black pepper and linalool in coriander were identified using mass spectrometric peak matching using NIST library.The extract (in terms of ion count) for each microwave parameter (such as field, water content level and solvent type) was plotted as a trend graph. The current experiment successfully tested the procedure for following the microwave process in the extraction of sensitive spice volatiles (from black pepper and coriander). With the microwave field measured at the region of extraction, it was possible to plot pepper extraction versus the microwave field to which the pepper sample was exposed. The extraction was represented in terms of cumulative value of ion counts obtained in GC-MS analysis. This unique procedure developed in the current research allows for the graphical comparison of the microwave extractions. It was found that black pepper has a better response to microwave extraction than coriander. The pepper extraction was found to increase proportionately with increase in microwave field strength. The extraction was also enhanced proportionately by the incremental addition of water content at constant microwave field.
265

Identifiering av lakbara potentiellt farliga ämnen i gummiasfalt / Identification of leachable potential harmful substances in rubber asphalt

Gustavsson, Jakob January 2010 (has links)
The main purpose of the project was to identify potential environmentally harmful substances which can be leached from rubber asphalt. A method for analysing asphalt was developed and three rubber asphalt materials were analysed after being cryogrinded. One of the materials was also tested in a road machine made for testing of asphalt paving. The particles created in the machine were analysed in the same manner as the cryogrinded asphalt materials. The asphalt materials were leached by water during 24 hours. The leachates were extracted with dichloromethane, dried with sodium sulphate and concentrated to a small volume. The extracts were analysed with gas chromatography-mass spectrometry (GC-MS). Due to low concentrations of substances the GC-MS was operated in SIM-mode (Selected Ion Monitoring). Thirteen substances were chosen for the analysis. The substances were aniline, benzothiazole, butyl benzyl phthalate, bisphenol-A, decanoic acid, dibutyl phthalate, diethylhexyl phthalat, phenanthrene, chrysene, naphthalene, 4-n-nonyl phenol and 4-tert-octyl phenol. Benzothiazole and 4-tert-octyl phenol were detected and quantified in the leachates. In addition to the analysis of organic substances, pH was measured too. The leachates produced in this project were also sent to an analysis company for several analyses, for example analysis of metals and sulphur. Toxicity tests were performed on the same leachates within an exam work made by Gro Runeman at Lund University. The results of the metal analysis, sulphur analysis, and toxicity tests are not covered within the scope of this report. For the results of these tests and analyses, see Gro Runeman’s report: Evaluating toxicity of asphalt leachates. / Detta examensarbete är utfört vid Statens Geotekniska Institut (SGI). Huvudsyftet med arbetet är att identifiera potentiellt miljöfarliga ämnen som kan laka ut från gummiasfalt. En metod för analys av asfalt har tagits fram och tre olika gummiasfalter har analyserats efter att ha kryomalts. En av dessa asfalter har också använts i en provvägmaskin där det damm som bildades har samlats upp och analyserats. Inom ramen för examensarbetet har också en litteraturstudie gjorts för att bland annat ta reda på vad som är gjort inom området sedan tidigare. För att ta reda på vad asfalten innehåller för föreningar gjordes först en fastfasextraktion av krossad (ej kryomald) asfalt där diklormetan användes som lösningsmedel. Från början var tanken att en GC/MS-screening skulle göras för att på så sätt få en överblick av samtliga organiska ämnen som finns i asfalten men på grund av de väldigt låga halterna av i gaskromatografen analyserbara föreningar var det nödvändigt att begränsa analysen till några få föreningar. De föreningar som analysen inriktade sig mot var anilin, bensotiazol, bensylbutylftalat, bisfenol-A, dekansyra, dibutylftalat, di(etylhexyl)ftalat, fenantren, krysen, naftalen, 4-n-nonylfenol, pentaklortiofenol och 4-tert-oktylfenol. Laktester utfördes genom att de kryomalda asfaltmaterialen lakades med vatten under 24 timmar. Efter extraktion, torkning och koncentrering analyserades lakextrakten med avseende på de föreningar som hittats vid fastfasextraktionen. I lakvattnen hittades bensotiazol samt 4-tert-oktylfenol. Dessa föreningar kvantifierades genom att en enpunktskalibrering gjordes. Utöver analyserna ovan mättes även pH på lakvattnen. Lakvattnen skickades också på metall- och svavelanalys samt turbiditets- och fenolindexmätning till ett större analysföretag. Toxicitetstester har utförts på samma lakvatten av Gro Runeman inom ramen för ett examensarbete vid Lunds Universitet. För resultaten från toxicitetstester, metallanalyser samt turbiditets- och fenolindexmätningar hänvisas till Gro Runemans rapport: Evaluating toxicity of asphalt leachates. Delar av denna rapport är skrivna i samarbete med Gro Runeman.
266

Determination Of The Postexplosion Residues Of Nitro Group Containing Explosives In Soil With Gc-ms And Gc-tea

Dursun, Hayrettin 01 December 2007 (has links) (PDF)
There is an increase in bombing assaults in recent years in our country. Determining the explosive material used in these cases by the quick and correct analysis of the evidence obtained after the explosions, is an important starting point for the investigations which are done to reach the perpetrators. The forensic chemistry investigations have to be correct, exact and rapid in order to reach the right criminal. In this study, the Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Thermal Energy Analyser (GC-TEA) methods which are being used for the determination of the explosive materials&rsquo / residues used in bombing attacks are optimized with the standard solutions of 2,4,6-Trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazocyclohexane (RDX) and standard mixture solution. The two methods were compared by analysing the postexplosion soil samples. Also an efficient and applicable sample preparation procedure was developed. The results showed that both methods are efficient and sensitive for the postexplosion investigations. It is seen that GC-TEA has lower detection limit and simple chromatograms due to its selectivity against only nitro group containing explosives. However it is concluded that there is a need for a reliable and sensitive method like GC-MS which provides identification and library search, for the determination of the organic components which can not be identified with GC-TEA
267

Treatability And Toxicity Of Nonylphenol Compounds In Anaerobic Batch Reactors

Bozkurt, Hande 01 December 2011 (has links) (PDF)
Nonylphenol (NP) and its ethoxylates are used in formulation of pesticides and detergents, production of personal care products and many industrial sectors such as textile, metal plating, plastic, paper and energy. They are also used in the formulation of household cleaning agents. Industrial uses in the production line make up 55% of the total use / whereas industrial and domestic cleaning processes constitute 30 and 15%, respectively. Since they are widely used in industry and households, NP compounds enter the environment mainly by industrial and municipal wastewater treatment plant effluents. NP is considered strongly toxic and has adverse effects even with short term exposures. Moreover, with its similarities to natural hormones, NP and its ethoxylates are considered as endocrine disrupter compounds. In studies conducted with human cells, chicken embryo, trout and mice eostrogen receptors, positive responses were observed. Due to their lipophilic and hydrophobic characteristics they accumulate in cells, tissues and organic materials such as sludge. For these reasons, fate of NP and its v ethoxylates in wastewater treatment plants and in sludge treatment processes gained importance. Nonylphenol polyethoxylates (NPnEO) are degraded in microbial media and lose their ethoxylates to nonylphenol diethoxylate (NP2EO), nonylphenol monoethoxylate (NP1EO) and NP. Moreover, nonyl phenoxycarboxylic acids (NPnEC) can be formed during some of these reactions. Because the first degradation reactions are fast, concerns and studies are focused mainly on NP2EO, NP1EO, NP, NP1EC and NP2EC. Even though these general degradation information is available, studies on sludge are very rare. In this study, treatability and toxicity of NP2EO in anaerobic batch reactors is investigated. First, with the use of Anaerobic Toxicity Assay (ATA) test, toxic doses of NP2EO which was added to the reactor as the parent component, were determined. Moreover, the degradation of these chemicals were studied in larger scale batch anaerobic digesters. The aim of this part was to observe the degradation patterns and products. Throughout the study the fate of NP and its ethoxylates was followed in aqueous and solid phases by the use of Gas Chromatography / Mass Spectrometry system (GC/MS). ATA tests showed that NP2EO was not toxic to anaerobic microorganisms at the doses investigated in this study. It was rather stimulating and caused an increase in methane production in the reactors. On the other hand the spiked NP2EO&rsquo / s at 0.5 and 2.5 mg/L concentration were completely degraded in the larger scale batch reactors. At the same time, an increase in the concentrations of NP and NP1EO was observed which supported the fact that NP2EO was degraded into NP1EO and NP under anaerobic conditions. Abiotic degradation was not observed.
268

Analytical techniques for quality assessment of separated and commingled recycled polymer fractions

Camacho, Walker January 2002 (has links)
<p>Different methods for quality assessment of separated andcommingled plastics from household and electronic waste havebeen developed. Especial attention has been given tospectroscopic methods since they are non-destructive andrequire little or no sample preparation at all.</p><p>A wide variety of low molecular weight compounds have beenidentified in recycled polyethylene (HDPE) and polypropylenefrom hard packaging waste by gas chromatography- massspectroscopy (GC-MS) after microwave assisted extraction (MAE).Low molecular weight substances such as alcohols, esters,ketones and fragrance and flavour compounds were detected inthe recycled resins. The major category of compounds identifiedin the virgin resins is conformed by aliphatic hydrocarbonssuch as alkanes and alkenes. It was found that theconcentration of aromatic hydrocarbons without functionalgroups, e.g. ethylbenzene and xylenes in recycled HDPE wasapprox. 5 times higher and equal to 120 and 35 ppb,respectively.</p><p>The potential of near infrared (NIR) and Fourier transformRaman (FT-Raman) spectroscopy in combination with multivariateanalysis as a rapid, non-destructive and accurate analyticalmethod has been studied and the feasibility of these methodsfor at/in line characterisation of several properties ofrecyclates has also been explored.</p><p>NIR in diffuse reflectance mode has been successfully usedfor quantification of antioxidants in polyethylene, thestandard error of prediction is almost comparable to the errorof wet methods, i.e., extraction plus liquid chromatography.The error of prediction of this method is 35 ppm for Irganox1010 and 68 ppm for Irgafos 168. The inaccuracy in thequantification of Irgafos 168 is due to the fact that thisantioxidant degrades during polymer processing.</p><p>NIR and Mid-infrared (Mid-IR) worked well for fastdetermination of molecular weight and crystallinity of therecycled HDPE and acceptable errors of prediction, comparableto that of the reference methods, i.e. size exclusionchromatography (SEC) and differential scanning calorimetry(DSC) have been obtained.</p><p>The present thesis also shows that NIR and Raman are goodcandidates for in/on line compositional analysis of mixedpolymer fractions from recycled plastic waste. Diffusereflectance NIR allows a rapid and reliable measurement ofpellets and requires no previous sample preparation. Thecomposition of binary blends can be determined with highaccuracy. The PP content in the PP/HDPE blends was predictedwith a RMSEP equal to 0.46 %w in the 0-15 %wt region and theRMSEP for PP in the PP/ABS blends was 0.3 %wt.</p><p>The thermal and thermoxidative stability of recycled PP,HDPE and a 20/80 PP/HDPE blend subjected to multiple extrusionhave been studied by DSC, thermal analysis (TGA) andchemiluminiscence (CL). A decrease in T<sub>ox</sub>and OIT was observed after each extrusion step.The drop in OIT was sharper after the first two extrusions. TheOIT values produced by DSC and CL were in good agreement.However, CL provided more information about the oxidationprocess taking place in the blends.</p><p>The moisture content in recycled polyamide 6,6 was readilydetermined by NIR in transmission mode and it could bepredicted with a RMSEP = 0.05 %wt. The accuracy of the methodappeared to be as good as that of the more time consumingthermal methods such as TGA, DSC and loss on dry (LOD), whichwere used as reference methods. The influence of differentamounts of water on the viscoelastic properties of nylon hasbeen investigated.</p><p><b>Keywords:</b>Recycling, HDPE, PP, blends, nylon 6,6, ABS,water content, MAE, GC-MS, NIR, FT-Raman, chemiluminiscence,low molecular weight compounds, antioxidant content,crystallinity, molecular weight, thermal stability,characterisation methods, analysis of polymers, blends.</p>
269

Les hydrocarbures aromatiques polycycliques dans le café : mise au point de méthodes analytiques et étude de l'étape de torréfaction

Houessou, Justin Koffi 01 February 2007 (has links) (PDF)
No description available.
270

Charakterisierung des CVD-Beschichtungsprozesses von C-Fasern mit pyro-Kohlenstoff

Meyer, Norbert 29 January 1997 (has links)
In der Arbeit werden Moeglichkeiten der Charakterisierung des Beschichtungsprozesses von C-Fasern mit pyro-Kohlenstoff vorgestellt. Dabei liegt der Schwerpunkt der Untersuchungen auf der ramanspektroskopischen Charakterisierung der Ober- flaechenstruktur von modifizierten Fasern. Die Unter- suchungen zeigen den Einfluss verschiedener Prozessparameter (Reaktortemperatur, Gasphasenkonzentration, Auswahl des jeweiligen Precursors etc.) auf die Oberflaechenstruktur der abgeschiedenen Schichten. Der Nachweis einer Vorzugsorientierung der Graphitmikro- kristallite auf der Faseroberflaeche wird mit verschiedenen Analysenmethoden durchgefuehrt. Dabei werden die ramanspektroskopischen Messergebnisse mit Ergebnissen anderer Methoden (wie Elektronenbeugung und Elektronenmikroskopie) verglichen. Waehrend des Beschichtungsprozesses wird die Gasphasen- zusammensetzung im Reaktor analysiert. Das Zersetzungs- verhalten von unterschiedlichen Precursoren bei verschiedenen Temperaturen wird untersucht. Korrelationen zwischen den einzelnen Precursoren aufgezeigt.

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