The effect of wine matrix ingredients and conditions on the headspace (HS) sampling of 3-alkyl-2-methoxypyrazines was investigated with solid-phase microextraction (SPME) and capillary gas chromatography, using a nitrogen phosphorus detector. Changes in the recovery of 3-ethyl-, isopropyl-, sec-butyl-, and isobutyl-2-methoxypyrazines from the static headspace of synthetic wine matrices spiked with 5mg/L of each analyte were investigated and reported as a function of SPME fiber type, extraction time, and temperature. The influence of pH, ethanol, phenolics, and ground oak was studied. DVB/Carboxen?/PDMS SPME fibers at an extraction temperature of 50°C for 30 minutes with 30% (w/v) added sodium chloride resulted in the highest analyte recoveries. Although, PDMS (100 micron) SPME fibers at an extraction temperature of 35°C for 30 minutes with 30% (w/v) added sodium chloride resulted in the lower analyte recoveries, the fiber remained functional after 50 to 75 analyses after other coatings deteriorated. Changing the sample ethanol concentration from 0 to 20% (v/v) resulted in an exponential decrease in the recovered analytes. Below pH 2, there was extensive loss of the analytes in the headspace. No measurable impact on alkylmethoxypyrazine headspace concentrations was observed with exposures to selected phenolics and to ground oak. / Master of Science

Gas Chromatography (GC) is an analytical technique in the chemistry field widely used to separate compounds present in a sample mixture. Conventional GC systems are an extremely versatile and powerful tool to perform complex separations. However, these systems come with the cost of being bulky and requiring a high amount of power for operation. With considerable research for over 40 years, the advent of Micro-Gas Chromatography (µGC) made it possible for miniaturized, compact, low-power, and field portable GC systems. This thesis presents a portable µGC system that enables real-time analysis of complex compound separations, made possible with the use of multiple separation columns and a novel multidimensional compound identification algorithm. The system architecture and the software design with multiple features enabling portability of the µGC system are discussed. A set of microfabricated separation columns (µSCs) and photoionization detectors (PIDs) are integrated to realize a fully functional µGC system that is tested with different types of complex compound mixtures. An in-depth analysis of processing the output chromatograms obtained from the setup for signal filtering and peak detection is described in this thesis. A multidimensional analysis for compound identification in complex mixtures is presented. / Master of Science / Volatile organic compounds (VOCs) are generally chemicals that have high vapor pressure and low boiling points used and produced in the processing of petroleum products, paint, refrigerants, pharmaceuticals, and adhesives. VOCs are emitted as gases from certain solids or liquids, some of which may have short- and long-term adverse health effects even with minute exposure. Gas Chromatography (GC) is a common analytical technique used to detect, identify, and quantify VOCs in the environment, and conventional GC Systems have been utilized for this purpose. The separation of compounds occurs inside an analytical column that has selective interaction between the column and the analytes passing through. However, these systems are expensive, bulky, consume high power, and require expertise to operate. Recently, advancements in the Microelectromechanical systems (MEMS) field has paved the way to create Micro-Gas Chromatography (µGC) systems with improved performance when compared to traditional systems. Active research is ongoing to improve the portability of µGC systems for reliable and quick on-field analysis. In this thesis, we present a µGC system that has a robust and scalable design that allows the development of a portable µGC system. The compound separation of complex mixtures is showcased using the portable µGC system setup. The output chromatograms obtained from the µGC system are pre-processed, which involves noise filtering and peak detection, followed by an analysis using a multidimensional compound identification algorithm.

Micro gas chromatography (μGC) system is a miniaturized and portable version of the conventional GC system, suitable for various applications such as healthcare and environmental analysis. The process of gas chromatography requires precise temperature control for the micro-fabricated preconcentrators and separation columns used since temperature changes directly affect retention time. Proportional Integral and Derivative (PID) controllers provide reliable temperature control and can be tuned to obtain the desired response. The conventional method of tuning the PID control parameters by trial and error is a tedious process and time-consuming process. This thesis aims to develop a PID auto-tuning and control system for auto-tuning microfabricated heaters in modular μGC systems. The developed system is based on the Ziegler Nichols rule-based PID tuning method for closed-loop systems, which uses the relay response of the micro-heater to calculate the PID tuning parameters. The system also includes an analysis system to verify the performance of the PID-tuned values and a tuning system where the PID values can be further tuned to obtain more precise control for the heaters. The aim of developing this system is to reduce the effective tuning time for heaters while satisfying the control requirements. In this thesis, we discuss the tuning methodology and the implementation of the PID tuning and control system, followed by a performance evaluation of the heaters tuned using the proposed system is discussed. / Master of Science / Gas chromatography (GC) is an established technique used for the qualitative and quantitative analysis of compounds present in a mixture. Micro-gas chromatography (μGC) systems are miniaturized versions of conventional GC systems. They are portable, energy-efficient, and facilitate on-site analysis in real-time, which is suitable for applications such as health care, forensics, and environmental analysis, requiring in-field analysis. GC is based on the principle that components of a gaseous mixture, when passed through a heated column coated with a stationary phase, separate out based on their extent of interaction with the stationary phase. The temperature control needs to be precise since it directly affects the process. PID control is the most common and reliable method for temperature control. It can be tuned to obtain the desired response, which can, however, be a tedious process. This thesis aims to develop a PID auto-tuning and control system for μ-fabricated heaters in μGC systems. As a part of this thesis, a system facilitating faster tuning of PID parameters for a given heater using the Ziegler Nichols closed-loop tuning method is developed. It uses the relay response of the micro-heater to determine the tuning value. The obtained PID values can be evaluated using the analysis system developed as a part of the system and can be further fine-tuned using the provided system to obtain the desired response. As a part of this thesis, we first discuss the development of the PID tuning and control system, after which the performance of the tuned values is evaluated for two micro-heaters.

Cannabis sativa L. is a species of flowering plant from the Cannabaceae family which contains over 100 different phytocannabinoids and terpenes. The therapeutic effectiveness of Cannabis sativa L. depends on the cannabinoid content, and the unique aroma in this plant is produced by the terpenes. The two most widely known cannabinoids are Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD). The legalization of hemp (defined as Cannabis sativa L. < 0.3% Δ9-THC by dry mass) has flooded the market with various hemp and hemp-derived consumer products. These studies focus on using Liquid Chromatography and Gas Chromatography to survey the cannabinoid and terpene content observed for commercially popular Cherry Wine hemp cultivars. Twelve samples of Cherry Wine hemp were obtained representing three field grown hemp plants, a hemp plant grown in a controlled indoor environment, and eight cloned hemp plants also grown in a controlled indoor environment. The analyses revealed variability in the cannabinoid and terpenes contents that reflect plant genetics, daylight exposure duration, and hemp processing and storage conditions. Nitrogen was examined as a substitute carrier gas for increasingly expensive helium for the analysis of terpenes. Finally, Liquid Chromatography was also applied to evaluate the cannabinoid content versus label claims of ten Δ8-Tetrahydrocannabinol (Δ8-THC) hemp-derived consumer products. Examples of under and over reporting of cannabinoids were observed indicating potential risks to consumer safety and need for improved product regulation.

This thesis describes the implementation of zero-cost auto-tuning techniques for embedded Proportional Integral and Derivative (PID) controllers, specifically focusing on their application in the control of proportional valves within Micro Gas Chromatography (uGC) systems. uGC systems are miniaturized versions of conventional GC systems, and require precise temperature, flow and pressure control for the micro-fabricated preconcentrators and micro columns. PID controllers are widely used in process control applications due to their simplicity and effectiveness. The Commercial Off The Shelf (COTS) available controllers are expensive, bulky, need system compatibility and have high lead times. The proposed auto-tuner features simple Python-implemented empirical calculations based on Ziegler Nichols relay-based PID tuning method to determine the optimal PID gains. Leveraging Wi-Fi the system enables tuning for any embedded platform while visualizing transient response through the Graphical User Interface (GUI). The embedded-GUI interface provides a customizable auto-tuning experience extending usage across diverse temperature, pressure and flow regulation applications in environmental analysis. Specifically for uGC systems, the GUI integrates with existing hardware stack using minor software enhancements to enable rapid, automated PID tuning for thermal and flow control applications. The performance is analyzed by evaluating response metrics including overshoot, rise time, and steady-state error. / Master of Science / Commercially available flow and thermal regulators are expensive and bulky. In applications like micro gas chromatography (uGC) systems, these commercial tools to regulate actuator control reduce portability and may require different regulators for different control ranges. To overcome these challenges, we developed an open-source, transparent Proportional-Integral-Derivative (PID) auto-tuner for micro-electromechanical systems (MEMS) actuators in uGC systems. The proposed Python-based Graphical User Interface (GUI) approach leverages simple empirically-driven calculations to determine optimal gains. By interfacing with any embedded system through standard connection like Wi-Fi, the auto-tuner enables interactive, vendor-agnostic tuning while visualizing full transient response. This provides accessible, customizable auto-tuning capabilities to enhance closed-loop PID control across instrumentation and device applications at no or minimal additional hardware cost. In uGC systems, we utilize the same setup for thermal, flow, and pressure control, with additional sensor costs offset by the implementation of multiple closed loops on the same system.Precise temperature and flow control is critical in many applications, such as minimizing fluctuations in analyte retention times in uGC systems. PID control offers reliable closed-loop control for such applications, but tedious manual tuning is required for each system. The proposed auto-tuner presented in this work will greatly simplify PID tuning to improve temperature and flow rate precision in these systems. The performance is analyzed by evaluating response metrics including overshoot, rise time, and steady-state error. This thesis discusses the auto-tuning technique, PID implementation, and experimental performance analysis. Overall, this work presents a novel embedded PID automated methodology for rapid and precise thermal and flow control in uGC and other precision regulation applications. The proposed auto-tuning method provides effective tuning across a wide variety of applications such as motors, temperature and pressure control, and flow regulation systems.

The accuracy and utility of using Inverse Gas Chromatography (IGC) to characterize the microphase structure of block copolymers, and the strength of the thermodynamic interactions between the components of polymer blends and the unlike segments of block copolymers was examined. There were three parts to the study. First, the Scott ternary solution model, which is used for the study of thermodynamic interactions in polymer blends, was extended to low molecular weight mixtures. From vapor-liquid equilibrium data in the literature, the Gibbs free energy of mixing of binary mixtures (G_M ) calculated with the model were compared to experimental values. Mixtures containing ketones, aromatics hydrocarbons, chlorinated hydrocarbons, alcohols and water were studied. With the exception of mixtures containing water and low molecular weight alcohols, a fair to good correlation between theoretical and experimental values was observed. Second, the Gibbs free energy of mixing of nitrocellulose, polyvinyl chloride and poly(vinylidene fluoride) containing blends were measured with the Scott model from IGC data. For the nitrocellulose containing blend, the calculated Gibbs free energy of mixing values were large in magnitude (-2.0 to -5.0 calories/gram) and in fair agreement with the experimental heats of mixing determined from microcalorimetry measurements. For the remaining blends, the IGC data could not be distinguished from the results normally obtained for immiscible blends. The calculated G_M values were small in magnitude relative to the experimental error of the quantities. Concerning the block copolymers, the relative incompatibility of the constituent blocks of perfectly alternating block copolymers of polydimethylsiloxane and bis-A-polycarbonate and styrene-isoprene-styrene triblock copolymers was reflected in the measured G_M values. Overall, it was concluded that IGC is a good method for characterizing thermodynamic interaction between blend and copolymer constituents, but a severe limitation of the method is that the interactions are often too weak to measure accurately. Finally, the microphase structure of the above copolymers were studied by IGC from the retention behavior of hydrocarbon probes below the upper glass transition temperature of the copolymers. The degree of microphase separation, the size of the hard phases and the continuity of the soft phases in the copolymers characterized, and the results obtained were consistent with small angle x-ray, electron microscopy and differential scanning calorimetry data on the same materials. / Doctor of Philosophy

A cromatografia é uma técnica de separação cuja classificação se dá por meio do estado físico da fase móvel (líquido, gasoso, supercrítico, entre outros). Dentre as técnicas cromatográficas mais utilizadas e cujo conhecimento é bastante conhecido está a cromatografia gasosa. Embora esta técnica tenha sido bastante estudada existem ainda algumas vertentes que não totalmente estudadas, sendo uma delas a cromatografia gasosa de alta pressão na entrada da coluna (HIPGC). A HIPGC destaca por oferecer vantagens analíticas como alta eficiência, maior velocidade no tempo de análise e também facilita a migração de compostos com alta massa molecular. As desvantagens e dificuldades estão concentradas na instrumentação. O uso de alta pressão requer conexões que suportem tal pressão, sistema de injeção adequado a fim de eliminar vazamentos entre outros. Neste trabalho, sucessivos sistemas instrumentais foram montados visando o desenvolvimento, aprimoramento e avaliação de um sistema instrumental simples e versátil para HIPGC. Na avaliação do sistema foi utilizada coluna capilar empacotada pelo método \"slurry packed\". A escolha da coluna foi realizada a partir de curvas de eficiência de Van deemter. O sistema instrumental desenvolvido para HIPGC é apropriado para pressões de entrada de até 1800 psi. Além disso, este sistema apresentou boa reprodutibilidade nas análises e não apresentou vazamentos. Os resultados mostraram o potencial da técnica HIPGC na redução do tempo de análise. / Chromatography is a separation technique whose classification takes place by means of the physical state of the mobile phase (liquid, gas, supercritical, etc.). Among the most commonly used chromatographic techniques and whose knowledge is well known is gas chromatography. Although this technique has been widely exploited there are some topics which weren\'t fully investigated, one of them being high-pressure chromatography column input (HIPGC). HIPGC shows analytical advantages as high efficiency, faster analysis time and facilitates the migration of compounds with high molecular mass. The main difficulties in HIPGC are found in the instrumentation. The high pressure requires an appropriate connection that works in this range of pressure and one injection system suitable to transport the sample at different pressures. In this work, different instrumental systems were assembled to develop equipment to HIPGC that is simple and versatile. In the system evaluation was used capillary columns packed by methodology\'s \"slurry packed\" were used. The choice of the column was made from van Deemter efficiency curves. The system developed for instrumental HIPGC it is appropriate for inlet pressures up to 1800 psi. Furthermore, this system showed good reproducibility of analysis and didn\'t show leaks. The results showed the potential of HIPGC, such as shorter analysis time.

A cromatografia é uma técnica de separação cuja classificação se dá por meio do estado físico da fase móvel (líquido, gasoso, supercrítico, entre outros). Dentre as técnicas cromatográficas mais utilizadas e cujo conhecimento é bastante conhecido está a cromatografia gasosa. Embora esta técnica tenha sido bastante estudada existem ainda algumas vertentes que não totalmente estudadas, sendo uma delas a cromatografia gasosa de alta pressão na entrada da coluna (HIPGC). A HIPGC destaca por oferecer vantagens analíticas como alta eficiência, maior velocidade no tempo de análise e também facilita a migração de compostos com alta massa molecular. As desvantagens e dificuldades estão concentradas na instrumentação. O uso de alta pressão requer conexões que suportem tal pressão, sistema de injeção adequado a fim de eliminar vazamentos entre outros. Neste trabalho, sucessivos sistemas instrumentais foram montados visando o desenvolvimento, aprimoramento e avaliação de um sistema instrumental simples e versátil para HIPGC. Na avaliação do sistema foi utilizada coluna capilar empacotada pelo método \"slurry packed\". A escolha da coluna foi realizada a partir de curvas de eficiência de Van deemter. O sistema instrumental desenvolvido para HIPGC é apropriado para pressões de entrada de até 1800 psi. Além disso, este sistema apresentou boa reprodutibilidade nas análises e não apresentou vazamentos. Os resultados mostraram o potencial da técnica HIPGC na redução do tempo de análise. / Chromatography is a separation technique whose classification takes place by means of the physical state of the mobile phase (liquid, gas, supercritical, etc.). Among the most commonly used chromatographic techniques and whose knowledge is well known is gas chromatography. Although this technique has been widely exploited there are some topics which weren\'t fully investigated, one of them being high-pressure chromatography column input (HIPGC). HIPGC shows analytical advantages as high efficiency, faster analysis time and facilitates the migration of compounds with high molecular mass. The main difficulties in HIPGC are found in the instrumentation. The high pressure requires an appropriate connection that works in this range of pressure and one injection system suitable to transport the sample at different pressures. In this work, different instrumental systems were assembled to develop equipment to HIPGC that is simple and versatile. In the system evaluation was used capillary columns packed by methodology\'s \"slurry packed\" were used. The choice of the column was made from van Deemter efficiency curves. The system developed for instrumental HIPGC it is appropriate for inlet pressures up to 1800 psi. Furthermore, this system showed good reproducibility of analysis and didn\'t show leaks. The results showed the potential of HIPGC, such as shorter analysis time.

Comprehensive gas chromatography (GC×GC) is a modern and advanced analytical method designed to separate very complex samples, when the separation efficiency of classical gas chromatography is not sufficient. GC×GC allows complete simultaneous analysis of a sample on two different columns, interconnected by special interface called the modulator. Three types of control units were set up and a robust pulse flow modulator (PFM) was developed in this work. PFM working parameters have been always optimized to allow combinations of columns with different sizes. Optimized PFM allows application of columns with 10-60 m length and 0.15-0.25 mm internal diameters for the first dimensions and with 1-10 m length and 0.25-0.32 mm internal diameters for the second dimension. For demonstration reasons, analyses of complex real samples, such as essential oils, oil derivatives and biological samples, were performed. PFM was compared with the commercial cryofocusation modulator Zoex for the selected column set and one sample (a mixture of volatile solvents) on a gas chromatograph equipped with both modulators. The average repeatability of retention times, expressed as a relative standard deviation, was approximately 2.0 % for PFM (cryofocusation about 0.5 %) and of the peak areas was approximately 3.5 %...

Ceratitis fasciventris, Ceratitis anonae and Ceratitis rosa are polyphagous agricultural pests originating from African continent. Their behaviour is heavily altered by pheromones. Insect chemical communication channels are species-specific, represents taxonomic and reproduction barriers. Taxonomy of this group (so-called Ceratitis FAR complex) is unclear. Therefore new chemical approaches along with genetic tests for identification of entities within the cryptic species FAR complex are being developed. To study multi-component mixtures of male volatiles originating from the three mentioned fruit fly species, comprehensive two-dimensional gas chromatography with time- of-flight mass spectrometer (GC×GC-TOFMS) was used. A number of compounds were identified, out of which 23 were found to be distributed and shared among the studied species, 11 out of these were present in all three species. Analyses of male pheromone volatiles, using gas chromatography combined with electroantennographic detector (GC-EAD) revealed 4 common compounds with antennal activity shared among three studied species: methyl (E)-hex-3-enoate, 6-methylhept-5-en-2- one, linalool, and methyl (2E,6E)-farnesoate. The species-specific EAD active compounds in C. fasciventris were esters of isomers of hexenoic acid, whereas isomers of...