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McBrady, Adam Dewey. "Microfabricated chromatographic instrumentation for micro total analysis systems /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8570.
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Akbar, Muhammad. "Chip-Scale Gas Chromatography." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56566.
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Instrument miniaturization is led by the desire to perform rapid diagnosis in remote areas with high throughput and low cost. In addition, miniaturized instruments hold the promise of consuming small sample volumes and are thus less prone to cross-contamination. Gas chromatography (GC) is the leading analytical instrument for the analysis of volatile organic compounds (VOCs). Due to its wide-ranging applications, it has received great attention both from industrial sectors and scientific communities. Recently, numerous research efforts have benefited from the advancements in micro-electromechanical system (MEMS) and nanotechnology based solutions to miniaturize the key components of GC instrument (pre-concentrator/injector, separation column, valves, pumps, and the detector). The purpose of this dissertation is to address the critical need of developing a micro GC system for various field- applications. The uniqueness of this work is to emphasize on the importance of integrating the basic components of μGC (including sampling/injection, separation and detection) on a single platform. This integration leads to overall improved performance as well as reducing the manufacturing cost of this technology. In this regard, the implementation of micro helium discharge photoionization detector (μDPID) in silicon-glass architecture served as a major accomplishment enabling its monolithic integration with the micro separation column (μSC). For the first time, the operation of a monolithic integrated module under temperature and flow programming conditions has been demonstrated to achieve rapid chromatographic analysis of a complex sample. Furthermore, an innovative sample injection mechanism has been incorporated in the integrated module to present the idea of a chip-scale μGC system. The possibility of using μGC technology in practical applications such as breath analysis and water monitoring is also demonstrated. Moreover, a nanotechnology based scheme for enhancing the adsorption capacity of the microfabricated pre-concentrator is also described.<br>Ph. D.
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Bagheri, Habib. "Vapour-phase fluorescence detection in gas chromatography." Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280036.
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Ash, Peter William. "Studies of tin oxide gas sensors for gas chromatographic detection." Thesis, University of Plymouth, 1990. http://hdl.handle.net/10026.1/2066.
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Gas sensitive semiconductors have been known for many years and applied in static gas alarm systems for the monitoring of hazardous gases, however, their application has been limited by a lack of selectivity. In this work a semiconducting gas sensor has been configured for use as a gas chromatographic detector thus combining the sensitivity of semiconductor sensors with the selectivity of gas chromatography. The study has been confined to tin oxide devices, more specifically the Taguchi gas sensor (TGS) . The majority of this work has concentrated on the TGS 813 although the use of other TGS is described. The development of suitable instrumentation is described and rigorous optimisation of the operating parameters e.g. heater voltage and column temperature has been performed using the variable step size simplex technique. Attention was concentrated on the response of the TGS 813 to hydrogen which was used as a test gas. A novel figure of merit, response multiplied by retention time and divided by skew factor was designed so that optimum response was obtained whilst maintaining adequate chromatographic separation. Optimum conditions were verified by univariate searches and the response was observed to be most dependant upon heater voltage. A limit of detection of 20 ppb v/v of hydrogen in a 1 ml sample was obtained at optimal conditions. Illustrative analyses of hydrogen were performed in human breath and laboratory air with results found to be in close agreement with literature values. Calibration was found to be linear over at least three orders of magnitude. The response of the TGS 813 to low molecular weight alkanes has also been investigated. It was observed that different heater voltage optima existed for each of the C1-C5 alkanes and that the sensor was relatively more sensitive to the higher molecular weight compounds. As with hydrogen linear response was obtained over at least three orders of magnitude and an illustrative analysis of natural gas showed excellent agreement with known levels. A compromise optimum heater voltage was used to study the response of the TGS 813 to alcohols, aldehydes, ketones and some Cs hydrocarbons. Capillary columns were used in this investigation and it was noted that they had potentially wider application than packed columns due to the use of an inert carrier with an air make-up flow to the detector. This replaced the air carrier gas used previously which might degrade certain stationary phases. Three different types of TGS: the 813; 822 and 831 were used in a study of the response and skew factor for the detection of halogen-containing compounds. Very high skew factors were often observed, although, for some compounds it appeared that symmetrical peaks could be obtained within narrow heater voltage ranges. Skewed response was observed to be dependant upon sensor type, heater voltage and halogen proportion and type. Analysis of the three sensor types was performed and differences in potential surface area and tin oxide additives observed. The presence of additives was observed to adversely affect sensor recovery.
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Webster, Caroline S. "Applications of coupled gas chromatography-atomic emission detection." Thesis, Sheffield Hallam University, 1995. http://shura.shu.ac.uk/20507/.
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This thesis describes the evaluation and application of the atomic emission detector as a detector for capillary gas chromatography. Chapter 1 is a general introduction to the technique, describing the development of the atomic emission detector, the theory of its operation, and some of its applications. This chapter also includes a detailed description of chromatography theory. Chapter 2 describes the experimental conditions used throughout the course of this work. Chapter 3 concentrates on compound independent calibration, beginning with a general introduction to the area and a discussion of studies already made. Four groups of compounds were used to determine the ability of the atomic emission detector to perform compound independent calibration. Initial studies with a group of similar hydrocarbons showed little or no compound/structure dependence. However, results from the same study with a group of phenols did indicate some structure dependence for carbon and oxygen, but when chloroanisoles were tested, this compound dependence was not apparent. A group of different nitrogen-containing compounds was then studied. Here structure dependence was observed on all channels, ie carbon, oxygen and nitrogen. It was also noted that the responses became non-linear at higher concentrations. This would normally indicate detector overload, but not in this case as non-linearity occurred to different extents for the same element in different compounds. A study was also made on the effect of discharge tube ageing on response. Clean and dirty discharge tubes were used for the phenols and the nitrogen-containing compounds. The phenol, carbon and chlorine results showed a decreased sensitivity with the old tube, but the oxygen responses were not affected. The same drop in sensitivity was seen with the nitrogen-containing compounds, but here oxygen was also affected. Chapter 4 describes the use of the atomic emission detector and mass spectrometry as complementary techniques. Perfume samples were analysed using both instruments. A comparison of 'real' and 'fake' perfumes was also made. Results indicated that the atomic emission data was useful in deciding whether to accept or reject mass spectral library guesses. Chapter 5 describes the application of the atomic emission detector for the analysis of refinery streams. The use of the 'backamount' correction facility was also effectively demonstrated. Chapter 6 is a general discussion of the instrument including operational problems encountered and possible modifications to overcome these problems. The overall objective of the thesis is to place the GC-AED combination in the context of the commonly used chromatographic techniques.
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Sreedharan, Nair Shree Narayanan. "MicroGC: Of Detectors and their Integration." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/47785.
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Gaseous phase is a critical state of matter around us. It mediates between the solid crust on earth and inter-stellar vacuum. Apart from the atmosphere surrounding us where compounds are present, natively, in a gaseous phase, they are also trapped within soil and dissolved in oceanic water. Further, those that are less volatile do enter the gaseous phase at high temperatures. It is this gaseous phase that we inhale every second. It is thus critical that we possess the tools to analyze a mixture of gaseous compounds. One such method is to separate the components in time and then identify, primarily based on the retention times, also known as gas chromatography.
This research focuses on the development of gas detectors and their integration, in different styles, primarily for gas chromatography. Utilizing fabrication techniques used in semiconductor industry and exploiting scaling laws we investigate the ability to improve on conventional gas separation and identification techniques. Specifically, we have provided a new spin to the age-old thermal conductivity detector enabling its monolithic integration with a separation column. A reference-less, two-port integration architecture and a one-of-its-kind released resistor on glass are some of its salient features. The operation of this integrated device with a preconcentrator and in a matrix array was investigated. The more unique contribution of this research lies in the innovative discharge ionization detector. An ultra-low power, sensitive, easy to fabricate detector, it requires more investigation for a thorough understanding and will likely mature to replace the thermal conductivity detector, as the detector of choice for universal detection, in time to come.<br>Ph. D.
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Huang, Degui. "Development of a capacitively coupled plasma as a gas chromatographic detector." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29879.
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This work has two objectives: first, to develop an atmospheric pressure radio frequency capacitively coupled plasma (CCP) as a detector for gas chromatography (GC) and, secondly, to understand the excitation process in the CCP from a fundamental point of view.
In the process of developing the CCP as a gas chromatographic detector, the design of a CCP torch useful as an atomic emission detector for GC has involved several stages of evolution. Initially, two plasma torches, a cylindrical one with concentric electrodes and a rectangular one with two parallel electrodes, were designed and their performance evaluated. It was found that the parallel plate torch which utilized a rectangular-bore quartz tube had more stable emission signals, which was attributed to less gas flow turbulence. Therefore the rectangular torch was chosen for further experiments. Another consideration of using the rectangular torch was that it was easier to interface it with a capillary column from a gas chromatograph. With a flow of make-up gas consisting of the plasma gas, the outlet flow of resolved analytes from the GC column was entrained into the discharge. This configuration rninimized the dead volume so that the high resolution provided by the capillary column would not be degraded by the plasma torch volume.
One problem encountered in the initial work was that arcing occurred occasionally through air between the electrodes which often damaged the plasma torch even though quartz tubes enclosed the electrodes to isolate them from the air. The reason for this is believed to be due to the high voltage from the power supply.
In order to make the torch more amendable to testing, a demountable version was designed such that different quartz tube and electrode dimensions could be evaluated. Also, the operating frequency was shifted from 27.12 to 13.56 MHz. One advantage of using the 13.56 MHz RF power supply was that the electrodes did not have to be enclosed in an insulator and could be exposed to air without external arcing around the outside of the
torch because the power supply provides lower output voltage. The torch performance was evaluated for the determination of organotin compounds.
One difficulty still encountered, however, was heating of the parallel plate electrodes which yielded unstable plasma conditions at times. As a result, a new version of the CCP torch was designed by utilizing water cooled electrodes. With this configuration and the 13.56 MHz power supply, the electrode could contact the discharge tube directly and the plasma was formed without arcing. The efficiency of power transfer to the plasma was increased significantly. Furthermore, the plasma created was extremely stable. Both metal and non-metal elements could be excited sufficiently using the modified configuration and excellent results have since been obtained. The detection limits for F, CI, Br, I, S, and C were determined to be 10 to 78 pg/s.
The fulfillment of the second objective was carried out on the modified water-cooled plasma torch as mentioned above. Spatial distributions associated with the CCP which arise as a result of the transverse power coupling geometry were obtained. Some clues as to possible excitation processes in the CCP have been gleaned from the study of the relative intensities of lines for several non-metals. Basically, electron impact is the major excitation mechanism in the CCP. Excitations by the helium or argon metastables may play very a minor role. Charge transfer excitation reactions were found between He₂⁺ and CO and N₂.<br>Science, Faculty of<br>Chemistry, Department of<br>Graduate
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Ware, Margaret LaVerne. "The Development and Application of a Helium Discharge Detector for Gas Chromatography." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539625431.
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Schofield, Paul Anthony. "An investigation of the response mechanism of the nitrogen phosphorus detector." Thesis, Manchester Metropolitan University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300730.
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The Nitrogen Phosphorus Detector is a sensitive, selective device used in gas chromatography. It responds selectively towards nitrogen and phosphorus containing organic compounds with detection limits in the picogram range. The detector is of great importance for the measurement of trace levels of drugs, pesticides and herbicides in biological matrices and the environment. There is, however, some dispute in the literature regarding the detector's response mechanism. The detector is based on a hydrogen-air diffusion flame. Two electrodes polarise the flame with a potential difference of about 200 V and the current through the flame is measured using an electrometer amplifier. The selectivity of the system relies on the presence of an alkali metal source, usually rubidium. In the presence of nitrogen- and phosphorus-containing organics, C~ and PO· anions are formed, yielding a current which is the measured response. It has been suggested that this selective response arises from a charge transfer reaction between the rubidium excited states and ~ or PO· and P02• radicals. Using an AlGaAs diode laser, the rubidium excited state population can be modulated and the influence on detector current monitored. Rubidium resonance-enhanced ionisation, laser-induced fluorescence and emission spectroscopy have all been used to further probe the response mechanism of the detector. Results have demonstrated that during response the C~ radical concentration increases. In addition the diode laser can modulate the excited state rubidium concentration altering it by a factor of 2. However despite more that doubling the Rubidium excited state concentration no increase in detector response is observed. From these observations it has been concluded that the above mentioned charge transfer reaction plays little if any role in detector response.
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Lin, Zhong-Ping. "Gas-phase luminescence of aromatic carbonyl compounds and the design and use of a gas chromatographic detector." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ36559.pdf.
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Powell, Jodi. "Evaluation of Initial Flavor Fade in Fresh Roasted Peanuts using Gas Chromatography-Flame Ionization Detection, Gas Chromatography-Olfactometry, Sensory Analysis, and Chemosensory Techniques." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29127.
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Preventing flavor fade requires an understanding of the relationship between carbonyl amine and lipid oxidation reactions. The polyunsaturated fatty acid content of lipids in peanuts makes them more susceptible to lipid oxidation. The major by-products of the oxidation reaction are nonanal, hexanal, octanal, and decanal. These chemicals are associated with cardboardy, painty, and oxidized flavors associated with flavor fade. The carbonyl-amine reaction yields a variety of pyrazines with positive flavor attributes.
Initial flavor notes were explored through sensory work, Gas Chromatography-Olfactometry, and chemical analysis. The fresh roasted volatiles produced from roasted peanuts and the aldehydes resulting from oxidation were also evaluated using GC-FID to quantify and identify the pyrazines and hexanal over a 21 day storage period. Electronic Nose was used to determine differences between storage periods.
Gas chromatography-Olfactometry identified potent pyrazines contributing to fresh roasted peanutty aroma in fresh peanuts. Using GC-FID a significant decrease (p<.05) in 2-ethylpyrazine and 2,3-diethylpyrazine concentration was found over a 21-day period. No significant difference (p>0.05) was noted in the other pyrazines evaluated. A significant increase (p<0.05) was noted in the hexanal concentration over a 21-day period. The peroxide values and sensory analysis correlated directly with the GC-FID results with a significant increase (p<0.05) in peroxide value at Day 14 and Day 21, and a significant decrease (p<0.05) in fresh roasted peanuty flavor from days 0-21 and a significant increase (p<.05) in painty, cardboardy and bitter from days 7-21. The electronic nose successfully separated Day 0 and Day 21 samples from Day 7 and 14, which were also separated, but with minimal overlap.<br>Ph. D.
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Ghodsian, Bahram. "Development of micromachined field ionization tips for use as an integrated gas detector in a micromachined gas chromatography system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ37704.pdf.
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Murray, Jacolin Ann. "High Flow Air Sampling for Field Detection Using Gas Chromatography-Mass Spectrometry." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2414.
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The ability to rapidly detect and identify hazardous analytes in the field has become increasingly important. One of the most important analytical detection methods in the field is gas chromatography-mass spectrometry (GC-MS). In this work, a hand-portable GC-MS system is described that contains a miniature toroidal ion trap mass analyzer and a low thermal mass GC. The system is self-contained within the dimensions of 47 x 36 x 18 cm and weighs less than 13 kg. Because the instrument has a small footprint, it was used as the detector for an automated near-real-time permeation testing system. In permeation testing, materials that are used to make individual protective equipment such as gloves, masks, boots, and suits are exposed to hazardous analytes to determine how long the equipment can be worn safely. The system described herein could test five samples simultaneously. A multi-position valve rotated among the various sample streams and delivered time aliquots into the MS for quantitation. Current field air sampling techniques suffer from long desorption times, high pressure drops, artifact formation and water retention. These disadvantages can be avoided by concentrating the analytes in short open tubular traps containing thick films. There are several advantages to using polymer coated capillaries as traps, including fast desorption, inertness and low flow restriction. An air sampling trap was constructed utilizing open tubular traps for the concentration of semi-volatile organic compounds. The system consisted of multiple capillary traps bundled together, providing high sample flow rates. The analytes were desorbed from the multi-capillary bundle and refocused in a secondary trap. The simultaneous focusing and separation effect of a trap subjected to a negative temperature gradient was also explored. In this configuration, analytes were focused because the front of the peak was at a lower temperature than the rear of the peak and, hence, moved slower. In addition to the focusing effect, analytes with different volatilities focused at different temperatures within the gradient, allowing for separation.
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Ruellan, Jérémie. "Conception, fabrication et caractérisation d'un capteur de conductivité thermique à base de nanofils de silicium." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY025/document.
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Les nanofils semiconducteurs sont aujourd’hui le sujet de nombreuses recherches pour leurs propriétés physiques intéressantes. S’appuyant plus spécifiquement sur les propriétés thermiques des nanostructures, l’objectif de cette thèse est de démontrer la faisabilité d’un capteur de conductivité thermique conçu à partir de nanofils de silicium pour des applications en tant que jauge Pirani ou détecteur de gaz. Le travail réalisé aborde les questions posées par la réduction de taille des objets telles que l’augmentation du bruit ou la conduction thermique en régime de raréfaction et élabore des solutions à ces problématiques. Le manuscrit aborde l’ensemble des étapes nécessaires à la réalisation d’un capteur, à savoir la conception des dispositifs, s’appuyant sur une étude détaillée du comportement physique des objets utilisés, la fabrication sur plaque 200mm de ces capteurs par la salle blanche du CEA-Leti en ayant recours aux techniques classiques de la microélectronique et enfin leur caractérisation en tant qu’instrument de mesure de pression (jauge Pirani) ou en tant que capteur de concentration de gaz. Le travail réalisé s’intègre dans un projet plus global de réalisation d’un système de détection de gaz portatif pour l’analyse de l’air ou de l’eau<br>Semiconducting nanowires are nowadays the topic of numerous research for their interesting physical properties. Relying more specifically on the thermal properties of nanostructures, the purpose of this thesis is to demonstrate the feasibility of a thermal conductivity detector based on silicon nanowires for pressure sensing (Pirani gauge) or gas detection. The work presented herein addresses the questions raised by the reduction of the objects size such as the increase of the noise or the thermal conduction in a rarefied gas and tries to bring a solution to those problematics. This work deals with all the steps required for the realization of such devices. That is, the design and simulation of the sensor, based on a detailed study of the physical behavior of the objects, the fabrication of such devices on 200mm wafers by the CEA-Leti cleanroom using standard microelectronics processes and finally their characterization as a pressure sensor and gas detector. The work presented here is part of a wider project that aims at developing of a portable gas detection system for air or water analysis
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Navaei, Milad. "Integration of a micro-gas chromatography system for detection of volatile organic compounds." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53924.
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The focus of this dissertation is on the design and micro-fabrication of an all silicon gas chromatography column with a novel two dimensional resistive heater and on its integration with an ultra-low power Thermal Conductivity Detector (TCD) for fast separation and detection of Volatile Organic Compounds (VOC). The major limitations of the current MEMS-GC column are: direct bonding of silicon to silicon, and peak band broadening due to slow temperature programming. As part of this thesis, a new gold eutectic-fusion bonding technique is developed to improve the sealing of the column. Separation of BETX, alkane mixture and VOCs were demonstrated with the MEMS GC column. The time and power required to ramp and sustain the column’s temperature are very high for the current GC columns. To reduce the time required to separate the compounds, a new temperature gradient programming heating method was developed to generate temperature gradients along the length of the column. This novel heating method refocuses eluding bands and counteracts some of the chromatographic band spreading due to diffusion resulting in an improved separation performance. A low power TCD was packaged and tested in a GC by comparison against FID for the detection of a mixture of VOCs. It demonstrated low power operation of a few milliwatts and a very fast response. The MEMS-GC was also demonstrated for rapid detection of the VOC gases released by pathogenic species of Armillaria fungus.
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Lamoureux, Burton Richard. "Charge injection device array detection for atomic spectroscopy with applications in gas chromatography." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185261.
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Very early in the history of atomic emission spectroscopy (AES) it was understood to be a powerful analytical tool. Until the 1930's the usefulness of atomic spectroscopy was not utilized very extensively even though its fundamental power was understood. The breakthrough that placed it in the standard chemistry laboratory was the discovery and implementation of the photoelectric effect. Since this discovery there has been a revolution in atomic spectroscopy which has brought it from the role of a humble servant used for primary elemental screening to an outstanding leader in applications of elemental analysis. Atomic emission spectroscopy of complex samples has long suffered from matrix effects which result in overlapping of spectral lines, fluctuating backgrounds and changing conditions in the source. Investigations employing an echelle polychromator with a two dimensional solid state array detector show great promise in minimizing the effects of these interferences on multielement analyses of complex samples. The Charge Injection Device (CID) detector used exhibits many characteristics which make it uniquely qualified for simultaneous, multielement detection in AES. With only slight modifications to the optics of a commercial spectrometer and the employment of a CID detector, detection limits for a number of elements are quite favorable. Dynamic ranges of over seven orders of magnitude are obtainable with this experimental system. The reduction of matrix effects by utilizing the huge wealth of information available from over 60,000 individual detector elements are demonstrated through results from several complex matrix standards. This CID-polychromator system was also employed for the element selective detection of gas chromatographic (GC) effluents. A microwave-induced plasma (MIP) based on the Surfatron design was built. A helium plasma from this device has shown to have resilience to organic samples and give good emission response to non-metallic atoms. A number of studies with this GC-AES-polychromator system are presented. This system is capable of monitoring atomic emissions from C, H, F, Cl, Br, I, O, N and S all simultaneously, and the selectivity of this system is unsurpassed. Elemental ratios for separated compounds are also presented as a precursor to empirical formula prediction.
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COSTA, JUNIOR NELSON V. da. "Caracterizacao e otimizacao analitica na determinacao de trialometanos em aguas potaveis por purga e armadilha acoplada a cromatografia a gas." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9521.
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Made available in DSpace on 2014-10-09T12:27:35Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:07:31Z (GMT). No. of bitstreams: 0<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Mwenesongole, Ellen Musili. "Simultaneous detection of drugs of abuse in waste water using gas chromatography-mass spectrometry." Thesis, Anglia Ruskin University, 2015. http://arro.anglia.ac.uk/550378/.
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Sewage epidemiology is increasingly becoming an alternative method of estimating drug usage and consumption patterns for a given population. With the constant emergence of new psychoactive substances such as cathinones and piperazines, versatile, reliable, specific and sensitive analytical methods are needed for their detection in complex matrices such as waste water. This thesis reports the development of an analytical method based on solid phase extraction, derivatization with pentafluoropropionic anhydride and analysis by gas chromatography-mass spectrometry for the simultaneous analysis of 29 illicit and therapeutic drugs of abuse. All 29 drugs could be reliably identified in spiked waste water samples using selected ion monitoring and splitless injection. Recoveries for the majority of the drugs were above 70 %. Linearity varied based on the analyte but was assessed in the range 2.0 x 10-4 to 1.4 μg/mL. Intra-assay and intermediate precision of the instrument was determined at 0.005, 0.1 and 1.0 μg/mL, with the majority of relative standard deviations less than 10 %. Limits of detection and quantification for drugs such as amphetamine and methamphetamine were better than reported values for liquid chromatography-tandem mass spectrometry, a more commonly used technique. Untreated 72 h composite waste water samples from Cambridge, UK, were analysed using a six-point standard addition curve. Eleven drugs of abuse were detected, including amphetamine, methamphetamine, butylone and 4-fluoromethamphetamine. The latter two having been detected for the very first time in waste water. Using the validated method, the consumption of heroin, ketamine, cocaine, methamphetamine and amphetamine, in Cambridge, UK, was estimated to be 399.4 ± 90.8, 2463.5 ± 182.5, 195.5 ± 95.4, 84.3 ± 59.1 and 38.9 ± 24.8 mg/day per 1000 inhabitants. This is the first reported validated method for the detection of both classic drugs of abuse and new psychoactive substances in waste water using gas chromatography-mass spectrometry and derivatization with pentafluoropropionic anhydride.
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Irwin, Crystal Marie. "Novel Derivatizing Agents for the Determination of Methylmercury by Gas Chromatography using Electron Capture Detection." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539626853.
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Janzen, Rasmus [Verfasser], and Uwe [Akademischer Betreuer] Karst. "Development of a new small-sized plasma optical emission detector for gas chromatography / Rasmus Janzen ; Betreuer: Uwe Karst." Münster : Universitäts- und Landesbibliothek Münster, 2013. http://d-nb.info/1141383055/34.
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Njie, Njaw. "Use Of Multi-walled Carbon Nanotubes In Matrix Solid Phase Dispersion Extraction Combined With Gas Chromatography." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609590/index.pdf.
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The use of Multi-Walled Carbon Nanotubes (MWCNT) as solid
sorbent in Matrix Solid-Phase Dispersion (MSPD) extraction and
preconcentration method was presented to determine some
commonly used organophosphorus insecticides/OPIs in honey
samples using a Gas Chromatography Flame Ionization
Detector (GC-FID). OPIs are poisonous compounds used to kill
insects and rodents by affecting their nervous system. The limit
of detections obtained after MSPD extraction were 7.0 ng/g for
Malathion, Malaoxon and Fenitrothion and 33.3 ng/g for
Isomalathion. The recovery of the insecticides from spiked
honey, ranged from 83.6% to 103.3% with % RSD ranged
from 9.8% to 12.3% (n=3). The correlation coefficient (R2) of
the calibration data varied from 0.9945 to 0.9987. Standard
addition method was utilized to examine matrix-induced effects
on analyte peaks, and to demonstrate the efficiency of the
method. The MSPD extraction was successfully applied for the
analysis of four honey samples but no insecticide residues were detected.
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Martin, Danica Paige. "Optimization of a Method for the Extraction of Drugs of Abuse from Wastewater." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1617014087323429.
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Li, Dan. "Identification and Differentiation of Tier 1 Bacterial Agents Using Gas Chromatography-Mass Spectrometry." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4053.
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A simple method was developed for detection and differentiation of five Tier 1 bacterial agents, including Bacillus anthracis, Francisella tularensis, Yersinia pestis, Burkholderia pseudomallei and Burkholderia mallei as well as their closely related near neighbors by gas chromatography-mass spectrometry (GC-MS). Generally, different classes of compounds can be used as biomarkers for biowarfare agent detection, including nucleic acids (i.e., DNA or RNA), proteins (i.e., antibodies), carbohydrates (i.e., sugars), lipopolysaccharides, lipids (i.e., fatty acids) and small molecules. One-step thermochemolysis (TCM) was developed to provide GC-MS detectable biomarker signatures, including sugars, fatty acids and small molecules. Solid phase micro-extraction (SPME) was used for biomarker extraction, concentration and introduction into the GC-MS. Statistical algorithms were constructed using a combination of biomarkers for the five agents, which were robust against different growth conditions (medium and temperature). A general GC-MS temperature program was developed for all five Tier 1 bacteria. The total analysis time, including TCM, SPME extraction and GC-MS, is approximately 40 min. The total-ion chromatograms are very different for the five species. The final goal of this research was to develop an accurate, fast, simple, robust and automated method for field application. Therefore, an automated sample preparation system was designed, constructed and tested. The system automatically controls the movement of sample vials from one position to another, crimping of septum caps onto the vials, precise delivery of reagents and TCM reaction times and temperatures. The specific operations of introduction of sample vials, SPME sampling, injection into the GC-MS system and ejection of used vials from the system were performed manually in this study, although they can be integrated into the automated system. Manual SPME sampling is performed by following visual and audible signal prompts for inserting the fiber into and retracting it from the sampling port. A rotating carousel design allows for simultaneous sample collection, reaction, biomarker extraction and analysis of sequential samples. Bacillus species were used to test this autoreactor, and 96% of the samples were correctly identified using a statistical algorithm. This research applies not only to the rapid identification of Tier 1 agents after a biological attack, but should also benefit clinical diagnosis, which is essential to effective treatment.
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Richardson, Douglas Dennis II. "Modern Advancements in Elemental Speciation: From Sample Introduction to Chemical Warefare Agent Detection." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250178457.
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LOIOLA, ELAINE C. D. "Determinacao de residuos de hexaclorociclohexano 'HCH' no soro sanguineo de trabalhadores expostos no arquivo historico de Joinville na decada de 80." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11756.
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Made available in DSpace on 2014-10-09T12:55:29Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:05:58Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Woodbury, Simon Edward. "Application of gas chromatography combustion-isotope ratio mass spectrometry to the detection of adulteration of vegetable oils." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246268.
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Fan, Wen. "Improved Dynamic Headspace Sampling and Detection using Capillary Microextraction of Volatiles Coupled to Gas Chromatography Mass Spectrometry." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/982.
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Sampling and preconcentration techniques play a critical role in headspace analysis in analytical chemistry. My dissertation presents a novel sampling design, capillary microextraction of volatiles (CMV), that improves the preconcentration of volatiles and semivolatiles in a headspace with high throughput, near quantitative analysis, high recovery and unambiguous identification of compounds when coupled to mass spectrometry. The CMV devices use sol-gel polydimethylsiloxane (PDMS) coated microglass fibers as the sampling/preconcentration sorbent when these fibers are stacked into open-ended capillary tubes. The design allows for dynamic headspace sampling by connecting the device to a hand-held vacuum pump. The inexpensive device can be fitted into a thermal desorption probe for thermal desorption of the extracted volatile compounds into a gas chromatography-mass spectrometer (GC-MS). The performance of the CMV devices was compared with two other existing preconcentration techniques, solid phase microextraction (SPME) and planar solid phase microextraction (PSPME). Compared to SPME fibers, the CMV devices have an improved surface area and phase volume of 5000 times and 80 times, respectively. One (1) minute dynamic CMV air sampling resulted in similar performance as a 30 min static extraction using a SPME fiber. The PSPME devices have been fashioned to easily interface with ion mobility spectrometers (IMS) for explosives or drugs detection. The CMV devices are shown to offer dynamic sampling and can now be coupled to COTS GC-MS instruments. Several compound classes representing explosives have been analyzed with minimum breakthrough even after a 60 min. sampling time. The extracted volatile compounds were retained in the CMV devices when preserved in aluminum foils after sampling. Finally, the CMV sampling device were used for several different headspace profiling applications which involved sampling a shipping facility, six illicit drugs, seven military explosives and eighteen different bacteria strains. Successful detection of the target analytes at ng levels of the target signature volatile compounds in these applications suggests that the CMV devices can provide high throughput qualitative and quantitative analysis with high recovery and unambiguous identification of analytes.
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Alli, Azaam. "Analysis of organomercurials in environmental and biological samples by capillary column gas chromatography with atomic fluorescence detection." FIU Digital Commons, 1994. http://digitalcommons.fiu.edu/etd/1069.
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The general method for determining organomercurials in environmental and biological samples is gas chromatography with electron capture detection (GC-ECD). However, tedious sample work up protocols and poor chromatographic response show the need for the development of new methods. Here, Atomic Fluorescence-based methods are described, free from these deficiencies. The organomercurials in soil, sediment and tissue samples are first released from the matrices with acidic KBr and cupric ions and extracted into dichloromethane. The initial extracts are subjected to thiosulfate clean up and the organomercury species are isolated as their chloride derivatives by cupric chloride and subsequent extraction into a small volume of dichloromethane. In water samples the organomercurials are pre-concentrated using a sulfhydryl cotton fiber adsorbent, followed by elution with acidic KBr and CuSO 4 and extraction into dichloromethane. Analysis of the organomercurials is accomplished by capillary column chromatography with atomic fluorescence detection.
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Zapata, Angela Maria. "Development and performance enhancement of a capillary microwave induced plasma mass spectrometer for gas chromatographic detection /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2000.
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Thesis (Ph.D.)--Tufts University, 2000.<br>Adviser: Albert Robbat, Jr. Submitted to the Dept. of Chemistry. Includes bibliographical references (leaves 71-75). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Danielsson, Conny. "Trace analysis of dioxins and dioxin-like PCBs using comprehensive two-dimensional gas chromatography with electron capture detection." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-963.
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Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), two groups of struc-turally related chlorinated aromatic hydrocarbons, generally referred to as “dioxins” are of great concern due to their extreme toxicity and presence in all compartments of the environment. Since they occur at very low levels, their analysis is complex and challenging, and there is a need for cost-efficient, reliable and rapid analytical alternatives to the expensive methods in-volving use of gas chromatography high-resolution mass spectrometry (GC-HRMS). It is im-portant to routinely monitor food and feed items to detect contaminations at an early stage. For the regulation of dioxins and dioxin-like PCBs in food and feed according to current legis-lation, large numbers of samples have to be analysed. Furthermore, soils at many industrial sites are also contaminated with dioxins and need remediation. In order to optimize the cost-efficiency of reclamation activities it is important to acquire information about the levels and distribution of dioxins in the contaminated areas. The aim of the studies underlying this thesis was to investigate the potential of comprehen-sive two-dimensional gas chromatography with a micro-electron capture detector (GC × GC-µECD) as a cost-effective method for analysing dioxins and dioxin-like PCBs in food, feed, fly ash and contaminated soils. Quantification studies of dioxins and dioxin-like PCBs were con-ducted and results were compared with GC-HRMS reference data. Generally, there was good agreement between both the congener-specific results and data expressed as total toxic equiva-lents (TEQs). The developed GC × GC-µECD method meets the European Community (EC) requirements for screening methods for control of dioxins and dioxin-like PCBs in food and feed. The presented results also indicate that GC × GC-µECD has potential to be used as a routine method for the congener-specific analysis of 2,3,7,8-PCDD/Fs and dioxin-like PCBs in matrices such as food and feed, fly ash and soil. However, to fully exploit the potential of the GC × GC-µECD technique, it should be combined with a fast and cost-efficient sample preparation procedure. Therefore, a number of certified reference materials (CRMs) were extracted using a new shape-selective pressurized liquid extraction technique with integrated carbon fractionation (PLE-C), and the purified extracts were analysed for PCDD/Fs using GC × GC-µECD. The results compared well with the certified values of a fly ash and a sandy soil CRM, but they were much too high for a com-plex clay soil CRM. It was concluded that this combination of techniques was very promising for screening ash and highly permeable soils. Further assessments and method revisions are still required before GC × GC-µECD can be used on a routine basis, and available software packages need to be refined in order to accelerate the data-handling procedures, which currently restrict the sample throughput.
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Danielsson, Conny. "Trace analysis of dioxins and dioxin-like PCBs using comprehensive two-dimensional gas chromatography with electron capture detection /." Umeå : Department of Chemistry, Environmental Chemistry, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-963.
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Manzoor, K. "Detection and analysis of spin trapped radical adducts using thermal desorption gas chromatography mass spectrometry (TD-GC-MS)." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/48345/.
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Certain oxygen free radicals are produced constantly in cells by metabolism and exogenous agents. Some, such as the hydroxyl radical, may react with various biomolecules like DNA, lipids or proteins, and thus be involved in the pathogenesis of various diseases. It is often difficult to detect oxygen free radicals due to their relatively short half-life. This problem may be overcome, however, using the spin trapping technique. In this technique, the spin-trap compound is used to trap free radicals, making them stable enough to be analysed using techniques like Electron Paramagnetic Resonance (EPR) spectroscopy or Mass Spectrometry (MS). In the current study, Fenton chemistry has been used to generate hydroxyl radicals. Since the hydroxyl radical adduct of the spin-trap N-<i>tert</i>-butyl-α-phenylnitrone (PBN) is shortlived at room temperature a secondary trapping technique is employed. The resulting spin-trapped species have been sampled using solvent-free extraction approaches i.e. Headspace Solid Phase Microextraction (HS-SPME) or Thermal desorption (TD), and the extracted products then detected and identified by using gas chromatography-mass spectrometry (GC-MS). GC-MS provides an alternative to other traditional techniques like EPR spectroscopy, as it provides more detailed information about structure of the radical adduct. Aldehydes are some of the most important products of oxidative stress, mostly produced through lipid peroxidation, and potentially may be used as biomarkers for different diseases. Their reactivity, production in low quantities and need of derivatisation are some of the challenges faced by analytical chemists to detect them. In the current research, aldehydes are used as secondary source of radicals in the Fenton reaction to produce aldehyde related free radicals. The developed method is not only a solvent free approach but also there is no need of derivatisation. It has the potential to be used as a biomarker assay of oxidative stress.
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Shinde, Suhas, Shivakumar Devaiah, and Aruna Kilaru. "Profiling Abscisic Acid-Induced Changes in Fatty Acid Composition in Mosses." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/4745.
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In plants, change in lipid composition is a common response to various abiotic stresses. Lipid constituents of bryophytes are of particular interest as they differ from that of flowering plants. Unlike higher plants, mosses have high content of very long-chain polyunsaturated fatty acids. Such lipids are considered to be important for survival of nonvascular plants. Here, using abscisic acid (ABA )-induced changes in lipid composition in Physcomitrella patens as an example, a protocol for total lipid extraction and quantification by gas chromatography (GC) coupled with flame ionization detector (FID) is described.
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Grajciariková, Eva. "Monitoring kontaminace vody a sedimentů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-216732.
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The diploma thesis is focused on the issue of the presence of POPs in the surface water and sediments. Monitored compounds were chosen from the group of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDE). Samples were collected in selected localities in the Slovak and the Czech Republic. Selected analytes were extracted with hexane from the aqueous matrix. Analytes were isolated by the ultrasonic extraction using a solvent mixture of hexane-dichlormethane from the solid matrix and the resulting extract was cleaned up by the column chromatography filled with the florisil and the silica gel. Target compounds were analysed by GC/ECD finally. Obtained results show the level of contamination in selected localities in the Slovak and the Czech Republic.
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Hu, Xiaoyi. "Detection and quantitation of diazinon and chlorpyrifos : a novel GC." Scholarly Commons, 2002. https://scholarlycommons.pacific.edu/uop_etds/573.
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An analytical method was developed for detection and quantitation of diazinon and chlorpyrifos, two widely used pesticides in local water pathway. Solid phase extraction combined with GC/MS detection with selected ion monitoring was employed. In establishing calibration curves for GC/MS analysis, it may be impractical to use isotope-labeled analogs as internal standards for all analytes in a complicated matrix. Compounds may have to be used as internal standards which could cause non-linear effects because of different response of analytes and internal standards. A novel sample introduction method, which could eliminate this negative effect of non-linearity, was proposed. Calibration data were acquired using the traditional constant volume injection method, and a new method: constant mass injection of analytes. Calibration curves by the constant mass injection method show a better linearity and y-intercept. The nonlinear effect observed with data obtained in low concentration ranges using the constant volume injection method was eliminated. The effectiveness of these curves by two methods was also tested. Better accuracy was obtained with the constant mass injection method. This constant mass injection of analytes method could be very useful in
quantitative studies of a complicated sample matrix, such as those encountered in the environmental analysis of pesticides, or in the quality control analysis of medical and industrial product. In solid phase extraction, Varian Bondelute SPE C8 cartridge was selected for extraction. With the standard water sample spiked at 500 ng/L for the two analytes, the recovery for diazinon was about 50% and for chlorpyrifos about 60%. With the standard water sample at 1000 ng/L, the recovery for diazinon was about 60% and for chlorpyrifos about 70%. Among three samples from three different sampling sites, diazinon was detected and confirmed. The quantitation of diazinon was done to water sample from the Calaveras River near the Sanguetti Street crossing Stockton, California, with observed concentration 143.2 ng/L.
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Shan, Guangqing. "Detection of aldehydes in lung cancer cell culture by gas chromatography/mass spectrometry and solid-phase microextraction with on-fiber derivatization." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/5891.
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Aldehydes in lung cancer cell culture have been investigated using gas chromatography/mass spectrometry and solid-phase microextraction with on-fiber derivatization. In this study, the poly(dimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used and o-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA) was first loaded on the fiber. Aldehydes in the headspace of lung cancer cell culture were extracted by solid-phase microextraction (SPME) fiber and subsequently derivatized by PFBHA on the fiber. Finally, the aldehyde oximes formed on the fiber were analyzed by gas chromatography/mass spectrometry (GC/MS). Using this method, acetaldehyde decrease was found in both non-small lung cancer cell cultures studied compared to the medium control study. The results of spiking the cell culture with acetaldehyde solution showed that 5 million SK-MES-1 cell lines could consume up to 4.5 uM acetaldehyde in 15-ml medium, and 5 million NCI-H522 cell lines could consume 5.9 uM acetaldehyde in 15-ml medium. The decrease of acetaldehyde may contribute to the metabolism of lung cancer cells. It was proved that GC/MS and SPME with on-fiber derivatization is a simple, rapid, sensitive and solvent-free method for the detection of aldehydes in lung cancer cell culture.
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Jordaan, Maraliese. "Diagnosis of helicobacter pylori infection with the 13C-urea breath test : analysis by means of gas chromatography with mass selective detection." Diss., University of Pretoria, 2007. http://hdl.handle.net/2263/27035.
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Lajtman, Roman. "Sledování chemických změn v mleté kávě skladované různými způsoby." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-433547.
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This diploma thesis deals with the monitoring of chemical changes in ground coffee stored in various containers and then it deals with the determination of water, moisture and aromatic profile of coffee in individual containers, namely a can, a paper bag, a bag with a polyethylene liner, a bag from low density polyethylene with aluminium liner (LDPE + Al) and a glass container. At the beginning of the experiment it was found that the water content in the coffee was 4.72 ± 0.10 % and the moisture content was 9.47 ± 0.01 %. After the original sample was measured, the coffee was poured into 5 packages. At the end of the experiment, a can was chosen as the most suitable package where the lowest water content was measured. The water content was determined to be 6.51 ± 0.11 % and the moisture content was 9.93 ± 0.01 %. However, the differences between the other packages, apart from the paper bag, were very small, and thus in general it can be said that the can, the LDPE + Al package, the bag with the PE liner and the glass container are suitable for storing ground coffee. A total of 44 aromatics were identified when determining the aromatic profile in coffee by HS-SPME-GC-MS. The most represented groups of substances were furans and pyrazines. During storage, there was some loss of substances due to 2 mechanisms. The first of them is evaporation and the second one is the oxidation reactions themselves. Most aromatic substances have evaporated / degraded in paper packaging, where this large decrease is related to its barrier properties. A glass container was chosen as the most suitable packaging with the least loss of aromatic substances.
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OLIVEIRA, JUSTINE P. R. de. "Estudo dos poluentes orgânicos persistentes (POPS) em regiões industriais da Grande São Paulo - via cromatografia a gás acoplada a espectrometria de massas (GC-MS) e captura de elétrons (GC-ECD)." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10186.
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Made available in DSpace on 2014-10-09T12:35:45Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:03:50Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Wu, Wei-Ting, and 吳韋霆. "Dielectric Barrier Discharge Emission Spectrometer for Micro Gas Chromatograph Detector." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/gh6757.
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碩士<br>國立臺灣師範大學<br>化學系<br>104<br>We successfully developed a micro dielectric barrier discharge (DBD) plasma device, which can be used as a gas chromatographic detector. A stainless steel capillary was employed as the inner electrode of the micro plasma device and the copper wire was wound tightly outside the device as the outer electrode. The stable atmospheric DBD plasma can be generate when we apply a high-voltage alternative current (AC), which is a sine waveform, 8~10 kVp-p and 63 kHz frequency, to the electrodes of the plasma device. The volume of plasma discharge region was about 1100 nL. In this study¸ air was used as carrier gas of the gas chromatography, the air DBD plasma was generated successfully and can be applied at total organic carbons (TOCs) detection. The volatile organic compounds react with plasma and strengthen the air plasma spectrum. The spectrometer will detect the increase at 380±2 nm when organic compounds pass through the plasma region. The study further investigates the correlation of voltage, flow rate, and the background gas in tedlar bags to detector response. The air plasma spectrum will be strengthened when volatile organic compounds, such as alkane, alcohols, ketones, esters, aromatic compounds and halides of various functional groups, pass through the plasma region. And the emission spectrum intensity increase when the length of alkanes carbon chain. The estimated limit of detection (LOD) was 1.57 ng for iso-propanol. This micro plasma device is an extremely small, cheap, no electrode erosion, and can operate under air with high sensitivity.
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Chu, Shih-Chi, and 朱世琦. "Micro Helium Plasma Emission Spectrometry for Gas Chromatograph Detector Application." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/22403567962103159126.
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碩士<br>輔仁大學<br>化學系<br>96<br>Plasma is one of the best energy source for molecule excitation and fragmentation. Both spectrum and electric current of plasma change when molecule become exciting or dissociation inside a plasma zone. Micro-plasma system could reduce helium gas and electric power consumptions; this is suitable for micro gas chromatography detector system. A pair of 50μm diameter tungsten wire were used to make two electrodes at distance less than 50μm under and the plasma was initiated in helium under atmospheric pressure. The micro-plasma device was assembled on glass substrates. The volume of the plasma region was only 0.1nL. Only 0.3mW of electrical power is consumed when using an AC sustain voltage of 950V at 2 kHz.
The detection of Br, Cl and F atoms in organic compounds separated in a chromatogram is possible by monitoring emission lines at 827nm, 837nm, 686nm for their characteristic lines. The detection of oxygen radicals in organic compounds can be by monitoring emission lines at 776nm for best quantification result. The detection limits ranged from 13.4pg for n-butanol to 180pg for bromobenzene. The low detection limit, robust nature and simplicity of this detector make it attractive for future integration with microchip gas chromatograph.
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Hung, Te-Yu, and 洪德裕. "Micro Dielectric Barrier Discharge Nitrogen Plasma Emission Spectrometry for Gas Chromatograph Detector." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/08024602960303949602.
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碩士<br>國立臺灣師範大學<br>化學系<br>101<br>A micro dielectric barrier discharge (DBD) plasma device has been developed for gas chromatograph detector. The micro plasma device electrode employed a pair of platinum wires (100 μm diameter) which were sealed inside a glass tube. The distance between these two electrodes was less than 200 μm. A high-voltage alternating current (AC) sine waveform of 8 kVp-p and frequency of 67 kHz was applied to the electrodes stable plasma was generated under atmospheric pressure. The volume of plasma discharge region was smaller than 80.0 nL. In the study, we tested four background gases of oxygen, hydrogen, air and nitrogen and nitrogen had lowest breakdown voltage to form plasma. The volatile organic compounds react with nitrogen ion to form carbon-nitrogen bonds when they passed through the plasma region. The spectrometer detected carbon-nitrogen bonds emission spectrum at 384 nm. The study further investigates the correlation of flow rate, voltage and different background gas in tedlar bags to detector respones. The spectrometer had similar emission spectrum when volatile organic compounds passed through the plasma region such as alkanes, alcohols, ketones, esters, aromatic halides of various functional groups, and the emission spectrum intensity increase with alkanes carbon chain length to increase. The estimated limit of detection (LOD) was 0.54 ng for 2-heptanone. This μ-plasma device is an extremely small, inexpensive, no electrode erosion, and can operate under lower cost nitrogen with high sensitivity.
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Jian, Rih-Sheng, and 簡日昇. "Integrated Gas Chromatograph Detector Employing Microsensor Array of Monolayer Protected Gold nano-Cluster Chemiresistors." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/69684091779597402459.
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碩士<br>輔仁大學<br>化學系<br>95<br>Monolayer Protected Gold nano-Clusters(MPC) were synthesized by the two phase method and used as organic vapor sensing materials in this research. We have synthesized four different ligand shell protected nano-cluster including 1-Octanethiol, Isooctyl 3-mercapropionate and mixed ligand of 1-Octanethiol: 3-mercaptopropionic acid, 4-pyridinethiol. The four MPC’s materials coated with array of chemiresistor micro- sensors and integrated gas chromatograph detector for 8 organic vapors sensing of various functional groups. We established the model of gas molecules diffuse in to the thin film of MPC. The detector responses are rapid, reversible and highly, selective, due to the unigae shell ligand structure of MPC of different functional group. Limits of detection range from 3 to 100 ng. It is also shown that larger sensor active area resulting higher sensitivity under the same linear flow rate. At different temperature testing, the sensitivities decreased MPC-array sorption of different temperature, and MPC film thickness was between 36 to 72 nm by calculation. According to the diffusion model, we estimated that diffusion coefficients are at the order of ~10-16 m2/sec. The diffusion coefficient value determined the depth of gas diffusion. The correlation coefficient between sensitive and depth are from 0.91 to 0.99. However, the sensitivis vapors are mainly determined by the partition coefficients and the resistance conversion coefficients. The differences among vapor’s diffusion coefficients do not influence the sensitivity trend.
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Jay, Chang-Chy, and 張志杰. "A Study on the Simultaneous Determination of Twelve Food Preservatives by Gas Chromatograph - Flame Ionization Detector." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/74690826112824161663.
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碩士<br>國立屏東科技大學<br>食品科學系所<br>95<br>At present, most methods for determining food preservatives are based on the testing methods of Chinese National Standards （CNS 10949-N6190）. The methods require collecting the distillate by dissolving with pure water or solvent or by steam distillation, to extract the distillate repeatedly with ether at different PH values through multiple complicated processes and then the concentrate must be analyzed by Gas Chromatograph-Flame Ionization Detector （GC-FID）.
The above-mentioned methods could be applied when the sample number is small. However, the quantity of vitrics, consumptive materials, manpower, equipment, and operation time would be multiplied when performing analyses on a great variety of food samples. The greater the number of operation processes, the greater the likelihood that system and human errors will increase. Limited by extracting processes and instrument detection conditions, the following five acids and six esters could only be determined one by one: Sorbic Acid, Dehydroacetic Acid, Benzoic Acid, Salicylic acid, p-Hydroxybenzoic acid, Methyl -p-hydroxybenzoate, Ethyl p-Hydroxybenzoate, Propyl -p-Hydroxybenzoate, Butyl p-Hydroxybenzoate, Isopropyl -p-Hydroxybenzoate and Isobutyl p-Hydroxybenzoate.
To enhance the recovery rate and sensitivity of the test, the Steam Distillation Method was chosen from among the traditional methods to avoid the various potential interferences, such as food’s ingredients, structure, composition, additives, etc. Ether was also chosen for proceeding with the extraction and concentration, due to its higher solubility in relation to the target substances. The new operation processes of test and analytic condition of instrument were established by combining GC-FID and DB-5（J&W）. The system and human errors could be avoided by simplifying and streamlining the pretreatment process of the test.
This method could be applied for determining twelve statutory food additive preservatives under the same conditions （Sorbic Acid, Dehydroacetic Acid, Benzoic Acid, Salicylic acid, p-Hydroxybenzoic acid, Methyl p-hydroxybenzoate, Ethyl p-Hydroxybenzoate, Propyl p-Hydroxybenzoate, Butyl p-Hydroxybenzoate, Isopropyl p-Hydroxybenzoate, Isobutyl p-Hydroxybenzoate and Biphenyl.）
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lu, ming-xiang, and 魯名翔. "Study of improving signal to noise ratio for gas chromatograph detector array employing Monolayer Protected Gold nano-Cluster Chemiresistors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/51956812627872883721.
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碩士<br>輔仁大學<br>化學系<br>97<br>This research investigates the signal/noise ratio of micro chemiresistor sensor tested with five different organic vapors. When vapor molecules absorbed by monolayer protected gold nano-clusters (MPC), the distance between two MPCs increased and so as resistance of sensor. We use both direct current (DC) and alternating current (AC) electric circuit to drive the device. In the DC mode, constant current circuit, DC voltage divider with voltage follow circuit, double low-pass filter circuit and triple low-pass filter circuit were studied for signal deviation and limits of detection (LOD). The double low pass filter electric circuit sensing toluene, that standard deviation and LOD were 0.035mV and 24.7pg respectively. The triple low pass filter electric circuit can adjust baseline to zero automatically. In the AC electric circuit, that electric circuit was AC voltage divider with voltage follow, and use AC voltage of square wave for 20Hz, 100Hz and 200Hz. The circuit of 20Hz AC shows standard deviation of 0.42mV and LOD at 2.71ng for toluene. The electric circuitries were easily interfered by environmental factors such as the temperature and 60Hz power frequency. Band-pass filter can decrease the interference, and noise can be reduced. Fast Fourier Transform (FFT) was also used for processing the signals. The standard deviation reduced from 0.728mV to 0.048mV and peaks became more detectable.
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Gonzalez, Angela M. "Nitrogen-specific gas chromatographic detection by atomic plasma spectral emission. Analytical gas chromatography-mass spectrometry studies of subsurface biomarkers." 1999. https://scholarworks.umass.edu/dissertations/AAI9932315.
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Analysis of nitrogen containing compounds by gas chromatography with atomic emission detection has always been problematic. Nitrogen detection has been customarily done using the 174.53 and 174.27 nm atomic lines, with very limited selectivity and sensitivity. Nitrogen can also be detected using the cyanogen (CN) molecular emission bands at 388 nm. It has been reported that a 100-fold improvement in the selectivity using this line can be reached. Therefore, in the present work, the instrument available in the laboratory was modified to allow the use of the 388 nm line for the nitrogen detection. The modification of the instrument involved the use of a mixture of reagent gases that were optimized to produce the best nitrogen emission using the 388 nm line. Figures of merit of the detection using this line, were evaluated and compared with the commonly used nitrogen line (174 nm) and the carbon detection (193 nm). The dependence of the GC-AED response with the molecular structure of the analyte, and its application in the determination of empirical formula was also evaluated, and its application for analysis of petroleum products. The second part of the present work studied the biomarkers in deep subsurface samples and their relationship with the microbial activity. Little is known of microbial community characteristics at depths larger than 50 m below surface, information that is crucial for the clean up of contaminated underground environments. The use of classical approaches to identify microbiota, often results in the characterization of less than 10% of the biota present when analyzing deep subsurface samples, therefore, the analysis of lipid content in the samples have been proposed. Microorganisms use lipids as constituent of their cell walls or as nutritional sources. Monitoring lipids can be used to develop a picture of how, when, where and under which conditions microbes are active in the subsurface. This research was focussed in the biomarker study of a shale and sandstone from Cerro Negro, New Mexico. Biomarkers were determined to study distribution, concentration and availability of resources that support life and microbial activity and their relationship with geochemical parameters.
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Cheng, Yu-Li, and 鄭宇利. "Quantitative Analysis of Gas Chromatography Using SAW Detectors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/2usr8v.
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碩士<br>中原大學<br>電子工程研究所<br>98<br>Surface acoustic wave (SAW) devices have been used as filters in modern communication systems. In addition, the advantages of SAW devices, such as small size, high stability and high sensitivity, make them suitable for sensor applications. By choosing different piezoelectric substrates, SAW devices can be applied in different fields of sensing.
In this thesis, the SAW devices with ST-cut quartz were used as the vapor sensors. The SAW sensor was realized based on a feedback oscillation circuit for quantitative analysis in gas chromatography (GC). Three topics including “the optimization of the experimental condition”, “quantitative analysis of GC/FID” and “quantitative analysis of GC/SAW” are under investigation in this study.
The experimental results successfully complete the quantitative calibration for five different organic vapors including ethyl alcohol, acetone, butanone, benzene and toluene. The GC/SAW system is verified for quantitative detection in organic vapors.
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Huang, You-Jie, and 黃祐杰. "A Current Type Gas Chromatography Detector Employing Micro Argon Plasma." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/12587966358264757463.
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碩士<br>國立臺灣師範大學<br>化學系<br>104<br>Abstract
A self-assembly miniaturized dielectric barrier discharge plasma has applied for the detection of volatile organic gas molecules in this experiment. This miniaturized plasma detector was made by inserting a stainless steel capillary column into a glass tube and sealed it inside a glass tube, then tangled an electric wire around the glass tube. A high-voltage alternating current was applied on both electrodes, a stable plasma was generated under atmospheric pressure. In this experiment , we use argon as a carrier gas to detect signal. When volatile organic gas molecules passed through the plasma, they would reacted with argon ions in the plasma, caused an obviously change in the background voltage of argon plasma. This research further investigated the correlation of the distance between the electrode and plasma, flow rate and voltage to the response of detector ,to find the optimum condition in each variables. When organic gas molecules with different functional groups, such as: alkanes, alcohols, ketones, esters, aromatics and halide passed through the argon plasma ,they all caused an obviously change in the signal. And the intensity of the signal would gradually increased followed by the increasing of the length of carbon chain of organic compounds. The lowest detection limit of this detector for iso-butanol was 1.61 ng. This detector has the advantages of small volume, low cost, and would showed a significant change in the intensity of the signal when organic gas molecules passed through the plasma, therefore, it can be applied for the detection of volatile organic gas molecules.
Key words：dielectric barrier、atmospheric plasma、gas chromatography
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Tsai, Lin-Jeng, and 蔡林正. "Study of SAW Detectors Sensitivity for Gas Chromatography System." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/775ux2.
Full textAbstract:
碩士<br>中原大學<br>電子工程研究所<br>100<br>The modern gas sensing technology plays an important role in industrial safety, personal health and environmental monitoring. The SAW devices provide superior properties: in terms of sensitivity, stability, compact size, response time, processing simplicity and cost; therefore, these SAW devices are suitable for broad applications.
Two-ports SAW devices are used and designed for 433MHz oscillators, these 433MHz oscillators are applied as SAW sensors in the gas chromatography system. The sensitivity performance of SAW devices are used in the GC system. The experimental result of SAW sensor's sensing performance is also compared with those of the commercial FID.
Three gases including ethyl acetate, alcohol and butanone are used for quantitative concentration analysis. Based on the experimental results, the quantitative calibration curves have been obtained successfully. Their standard deviations of accuracy are within 8%, and their sensitivity ranges from 330 to 450 (Hz/μmole) while the limitation of detection is between 0.75 and 0.91 μmole. Moreover, the SAW devices show better sensitivity and sensing limitation under the lower temperature.
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Jang, Ping, and 張平. "Preparation and Application of Cryptand Piezoelectric Crystal Gas Chromatographic Detector." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/75442202112964721914.
Full textAbstract:
碩士<br>國立臺灣師範大學<br>化學系<br>84<br>A cryptand 22 coated piezoelectric quartz crystal
membranesensor with a home-made computer interface was prepared
andapplied as a GC-detector for variousorganic molecules.The
frequency of quartz crystal oscillator decrease due to
theadsorption of organic molecules on cryptand 22.The computer
interface includes the counting interrupt with Intel-8255 andthe
frequency measured with Intel-8254.A software was written to
control the interface and data acquisition. At first,effects
of functional group,molecule weight,steric hindrance and
polarity of organic molecules in bothstatic and flow cells on
frequency respones of thepiezoelectric crystal had been
investigated.The cryptand piezoelectric crystal gas
chromatographic detector demonstratedhigh sensitivity and good
reproducibility.The frequency shiftof various organic molecules
were in the order:R-COOH >> R--NH2 > R-OHand 10 amine (R-NH2) >
20 amine (R2-NH) > 30 amine (R3-N) and morepolarity molecules
had better response. The home-made cryptand piezoelectric
crystal gas chromatographicdetector with detection limits
2.38x10-6g for polar molecular showedgood competitivity with
respect to commercial TCD.