The purpose of this investigation was to test the effect of sample size and carrier gas flowrate on the efficiency (relative to an analytical column) of an annular preparative-scale column. The chromatographic system for this investigation consisted of η-methyl-butyrate injections with nitrogen carrier gas and a liquid phase of Craig polyester succinate on Chromosorb W. The analytical column had an inside diameter of 0.061 inches. The preparative-scale column had an outside diameter of 2.075 inches and an inside diameter of 1.050 inches. The operating temperature for both columns was 215 degrees Fahrenheit. A sample size range of 0.1 to 3.0 milliliters was studied on the preparative-scale unit; this corresponded to a 0.2 to 3.6 microliter range on the analytical unit. Carrier gas flowrates of 4305, 8610 and 17,220 milliliters per minute were studied on the preparative-scale unit. This corresponded to flowrates of 5, 10 and 20 milliliters per minute on the analytical unit. Preparative-scale efficiencies of 20.43, 41.95 and 45.34 per cent were obtained at a sample size of 0.1 milliliter. The above efficiencies correspond to flowwates of 4305, 8610 and 17,220 milliliters per minute. As the sample size was increased to 3.0 milliliters the corresponding efficiencies dropped to 7.20, 17.71 and 27.11 per cent respectively. / Master of Science

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. / Ph. D.

Optimization of capillary gas chromatography-Fourier Transform Infrared (GC-FTIR) spectrometry has been accomplished by studying various columns, lightpipe designs, FTIR detectors and spectroscopic parameters. For adequate separation of complex samples the efficiency of WCOT (Wall Coated Open Tubular) fused silica capillary columns was found to be unmatched by packed columns or wide bore glass capillaries. A consequence of using more narrow bore columns, however, is lower sample capacity and less IR detectability. Two 6 cm light pipes and a more narrow 40 cm lightpipe were compared with respect to both optical throughput and eluent band broadening. FTIR spectroscopic parameters such as mirror velocity and number of scans coadded were examined in order to achieve an optimum signal to noise ratio. The complexity of a particular sample has been shown to dictate certain spectroscopic parameters. The sensitivity differences of two liquid-nitrogen cooled FTIR detectors used in the GC-FTIR experiments have been determined with reference to using them with either a long or short lightpipe. The capability of optimized capillary GC-FTIR has been demonstrated in the analysis of model compound mixtures and comp lex petroleum products including test aviation jet fuels. Major attention was given to the detection and identification of aliphatic and aromatic components in the highly complex samples. Computerized library search routines have been used to tentatively identify eluting components by infrared spectral matching to quality vapor phase library file spectra. Gas chromatography-mass spectrometry (GC-MS) data are also included for the same jet fuel samples to directly compare extent of information provided and relative spectroscopic sensitivities. / Master of Science

A method using gas chromatography for the analysis of carbon dioxide, carbon monoxide, and nitric oxide in diesel exhaust was developed. A gas chromatograph containing a liquid phase column in series with a molecular sieve column, each of which eluted into thermal conductivity detectors, was utilized. Activation of the molecular sieve column was achieved by heat-treating and purging with nitric oxide. The chromatograph was calibrated by introducing sample mixtures of known concentration and measuring the responses. The exhaust gases of a diesel engine were analyzed while the engine operated at constant speed and load. Engine speed was kept at 1400 rpm while several different loads were applied. The results of these tests indicated that carbon dioxide, carbon monoxide, and nitric oxide concentrations all increased with load in the load range studied. Carbon monoxide exhibited a greater dependence on load than did the other compounds. Additionally, water was injected into the intake air stream to study its effect on nitric oxide concentration. Nitric oxide levels were reduced by 15% when a water/fuel mass ratio of 0.75 lb/lb was used. / Master of Science

1. The sensitivity obtained even with the free compounds (except morphine) make gas chromatography a good technique for trace analysis of drugs in biological samples. 2. For many of the drugs studied the detector response curves are not linear with sample concentration but the calibration curves are reproducible if care is exercised. This makes quantitative analysis feasible down to 50-100 nanogram levels with proper technique. 3. Long column life is needed for routine analyses. Those columns employed in this work were used continuously for over seven months with no appreciable deterioration. / Master of Science

The analysis of nitrate-ester propellants and explosives has been performed extensively by gas chromatography for the past decade. As capillary GC technology has advanced, new opportunities for the improvement of existing methods have developed. This investigation probes several of these possibilities. The effect on quantitation of: the solvent, the analysis time, and the use of splitless injection were investigated. Precision was shown to be improved by: 1. using a non-volatile solvent (toluene) rather than CH₂Cl₂, 2. using the most time-efficient method that will allow adequate resolution of the components, 3. using splitless injection (0.80 min. splitless time). After these potential improvements of method were investigated, the mechanism employed in splitless injection was investigated. This mechanism is known as the SOLVENT EFFECT. The investigation showed that: 1. non-volatile components required less splitless time to achieve 100% sample transfer to the column; 2. using splitless injection improved precision over split injection; 3. injector liner design had no effect on precision; 4. column overload did not hurt precision, as long as all peaks remain baseline-resolved; 5. the initial column temperature must be below the boiling point of the solvent (how far below did not appear to be very significant); 6. quantitation is improved by using a solvent that is as non-volatile as possible; 7. varying the split ratio after the split vent has reopened (within the range of 20:1 to 500:1) has no effect on resolving peaks that occur extremely close to the solvent peak. / Master of Science

The scope of supercritical fluid chromatography continues to enlarge. The use of open tublar and packed columns, nearly universal detectors and the introduction of new mobile phases make it more important. In this work sulfur hexafluoride is evaluated as a mobile phase for supercritical fluid chromatography. The separation of a model aromatic hydrocarbon mixture using different packed columns and operational parameters with UV as a detector is presented. The chromatographic properties of supercritical sulfur hexafluoride and supercritical carbon dioxide are compared under corresponding chromatographic parameters. / Master of Science

A gas chromatographic study was made to quantitatively analyze the effluents produced during the thermal cyclization of several polyimidazopyrrolone (pyrrone) model compounds. The study yielded information on analogous polymeric reactions. The model compounds were programed at 5° C/min from 25° to 400° C and volatile species were purged into a gas chromatograph at 25° intervals. An analysis of the effluents revealed that the cyclization reactions are concerted and generally occur below 250°C. The percent of conversion of the model compounds is readily determined by quantitating those reaction products amenable to gas chromatographic analysis. Only the amide-acid-amine and meta-benzimidazole-acid model compounds exhibited complete conversion to the pyrrone structure. Evidence that decarbo:xylation has occurred in the other compounds is presented. / Master of Science

Separation of complex gaseous mixtures using gas chromatography (GC) is an important step in analytical systems for environmental monitoring, medical diagnosis, and forensic science. Due to its high resolving power, analysis speed, and small sample size, GC, has become the premier technique for separation and analysis of volatile and semi-volatile organic compounds. Miniaturization of analytical systems has become a major trend which is mainly driven by advancements in microfabrication techniques and a need for portable lab-on-a-chip systems for onsite monitoring. Microfabricated columns have been explored for applications in analytical processes like GC in several research studies. These microGC columns typically have open rectangular or open circular cross sections which is a result of the etching process utilized in the fabrication. This work reports the fabrication and performance of a new generation of silicon-on-glass micro-electro-mechanical systems (MEMS) based GC columns with microposts namely "semi-packed." These columns can be fabricated on a 2 cm2-die for a 1 m-long channel or a 1 cm2-die for a 25 cm-long channel. The semi-packed columns have a higher sample capacity as the overall surface area is larger than that of open rectangular columns of the same dimensions. The separation efficiency of these columns is also superior to that of open columns due to the presence of the microposts. As compared to conventional packed columns, the semi-packed columns show lower pressure drops and a more uniform flow profile, both of which contribute to, performance in terms of separation efficiency. / Master of Science

Advances in micro-electro-mechanical-systems (MEMS) along with nanotechnology based methods have enabled the miniaturization of analytical chemistry instrumentation. The broader aim is to provide a portable, low-cost, and low-power platform for the real-time detection and identification of organic compounds in a wide variety of applications. A benchtop gas chromatography (GC) system is considered a gold standard for chemical analysis by analytical chemists. Similarly, miniaturization of key GC components (preconcentrator, separation column, detector, and pumps) using micro- and nanotechnology based techniques is an on-going research field. This dissertation specifically deals with the design, fabrication, coating, and chromatographic testing of microfabricated separation columns for GC. This work can be broadly categorized into three research areas: design and development of new column designs, introduction of new stationary phases and the development of novel fabrication methodologies for integrating functionalized thin-film into microchannels for chromatographic separations. As a part of this research, two high performance new micro column designs namely width-modulated and high-density semi-packed columns are introduced for the first time. Similarly, two new types of functionalized stationary phases are also demonstrated i.e. a highly stable and homogenous silica nanoparticles coating deposited using a layer-by-layer self-assembly scheme and a highly conformal functionalized thin aluminum oxide film deposited using atomic layer deposition. Moreover, novel thin-film patterning methods using different microfabrication technologies are also demonstrated for high-aspect ratio multicapillary and semi-packed columns. / Ph. D.