Browsing by Author "Thurbide, Kevin B."
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Item Open Access Active Control of Selectivity in Organic Acid Analysis by Gas Chromatography(2020-03-04) Darko, Ernest; Thurbide, Kevin B.A new method that allows organic acid selectivity to be dynamically controlled during gas chromatography (GC) is presented. It employs dual in-series stainless steel columns, each coated with a pH-adjusted water stationary phase. The first is a 2 m column coated with a pH 11.4 phase that is connected to a second 11 m column coated with a pH 2.2 phase. In this arrangement, organic acids within sample mixtures are trapped on the first column, while the remaining non-ionizable components continue to separate and elute in the system. Later, by injecting a volatile formic acid solution, the trapped acids are released in-situ to the second column for separation and analysis as desired. The method provides good reproducibility with analyte retention times in consecutive trials yielding an average RSD of 1.9 %. Further, depending on column temperature, analytes can be readily retained for periods investigated up to about 30 minutes without significant deterioration in peak shape. This feature provides considerable control over analyte selectivity and resolution compared to conventional separations. Further, by adding a third conventional GC column in-series, both typical hydrocarbon and enhanced organic acid separations are made possible. The method is applied to the analysis of complex mixtures and matrix interference is found to be significantly minimized. Results indicate that this approach offers beneficial advantages for the selective GC analysis of such acidic analytes.Item Open Access Broadband Cavity-enhanced Absorption Spectroscopy Measurement of Atmospheric Trace Gases and Rayleigh Scattering Cross Sections in the Visible and Ultraviolet(2019-04-26) Jordan, Nick; Osthoff, Hans D.; Thurbide, Kevin B.; Shi, Yujun; Loock, Hans-Peter; Roesler, RolandThis thesis reports on two incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instruments constructed in the cyan (470-540 nm) and the near-UV (350-400 nm) regions of the electromagnetic spectrum. Both devices realized enhancements in their absorption path of several kilometres from a 1 metre-long cavity while being of a compact design, light weight and of small power consumption. The cyan IBBCEAS was used to quantify NO2 and I2 in laboratory air. The instrument operated along a continuous wave cavity ring-down spectroscopy (cw-CRDS) device during a month-long field deployment on Vancouver Island, BC. The cyan IBBCEAS correlated well with the CRDS NO2 measurements (r2 = 0.70). Mixing ratios of I2 were below the limit of detection. The Rayleigh scattering cross-sections of air, N2, O2, Ar, CH4, and CO2 were measured and agreed with literature within measurement uncertainty. The absorption cross-sections of the weakly-bound O2-O2 and the CH4-CH4 collision complexes were also derived. The near-UV IBBCEAS instrument (nicknamed HODOR) measured NO2, HONO and O4 in the laboratory. NO2 and HONO measurements were compared against a TD-CRDS instrument. The results were highly correlated with respect to both species, r2 = 0.973 for NO2 and r2 = 0.978 for HONO, while O4 was measured in cylinder air only. HODOR's LOD (79 pptv in 60 s) with respect to HONO was comparable to state-of-the-art IBBCEAS instruments. HODOR was deployed during two short measurement intensives at the University of Calgary in Apr and Aug 2018 and quantified HONO for the first time in the urban atmospheric boundary layer of Calgary. HONO varied between 10 pptv and 1.43 ppbv during the intensives. Photolysis of HONO was a larger source of hydroxyl radicals than the reaction of O1D with H2O. Rayleigh scattering cross-sections of several gases were measured in the near-UV and agreed with literature. The absorption cross-section of O2-O2 between 350 and 400 nm was also reported. The near-UV IBBCEAS instrument was applied to the characterization of HONO interference in a photolytic NO2 converter. Overall, this work delivered two IBBCEAS instruments which were well-characterized, validated and tested in the laboratory and during field deployments.Item Open Access Characteristics of a novel on-line micro pressurized liquid extraction method(2020-10-05) Taylor, Bradley M.; Thurbide, Kevin B.A novel on-line micro pressurized liquid extraction (μPLE) method is introduced, which directly interfaces miniaturized solid sample preparation with HPLC for fast analysis. The technique employs rapid heating to remove analytes from 5-10 mg samples in typically 20-40 seconds using only about 300 μL of solvent. The resulting extract is then internally transferred to an HPLC injector for chromatographic analysis. Results show that good analyte recoveries can be achieved, similar to conventional PLE and off-line μPLE approaches, without manual sample handling. For example, 103 ± 3% (n= 4) of the acetylsalicylic acid present in pharmaceutical tablets was extracted into methanol after 20 seconds at 180 oC. Further, 105 ± 9% (n= 4) of the caffeine present in a green tea sample was extracted into methanol after 40 seconds at 275 oC. Typical time to analysis was about 95 seconds total for most samples and solvents could also be easily alternated during trials to increase extract selectivity. The on-line μPLE system was applied to the extraction of model PAHs from a biochar matrix and was found to extract 97 ± 5% (n= 4) of anthracene present in the sample after a 30 second static and 60 second dynamic extraction at 220 oC. This yield is much better than results obtained by previous approaches and is attributed to the small size, high temperature, low thermal mass, and dynamic flow of the system. Findings indicate that the on-line μPLE system can greatly assist in such extractions and provide a useful method for rapidly preparing solid samples for analysis using little solvent.Item Open Access Chiral Separations Using a Modified Water Stationary Phase in Supercritical fluid Chromatography(Springer, 2018-07-03) Frantz, Jackson J.; Thurbide, Kevin B.A novel means of achieving chiral separations in supercritical fluid chromatography (SFC) using a water stationary phase is presented. By adding various chiral selectors to the phase, different chiral analytes can be readily separated using neat CO2 as a mobile phase. For example, by adding β-cyclodextrin, it is found that certain flavanone enantiomers can be separated, while using the antibiotic vancomycin as a selector provides separation of some chiral phenoxypropionic acids. Other additives such as sodium chloride and triethylamine are also explored and found to enhance certain separations when also present in the water phase. While column pressure has a moderate impact on chiral analyte retention and separation in this SFC method, column temperature has a comparatively larger influence. In particular, relatively cooler temperatures below about 5 °C are found to markedly increase resolution and selectivity. For instance, notably large resolution of 4.7 is achieved for a phenoxypropionic acid pair at 0 °C and 150 atm CO2. Since the method does not require modifier to elute such polar species, it is also readily compatible with FID detection and does not generate organic waste. Therefore, results indicate that this approach could be a potentially simple and flexible means of achieving chiral separations in SFC.Item Embargo Confirmation and Quantification of Nanobubbles in Water Produced from a Batch Generator Driven by Electric Fields(2023-08) Andrews, Jeas Grejoy; Kimura-Hara, Susana Y.; Kusalik, Peter G.; Marriott, Robert A.; Thurbide, Kevin B.Nanobubbles, also known as ultrafine bubbles, are spherical gas pockets suspended in a liquid or attached to a solid substrate. The former is referred to as bulk nanobubbles, and the latter is termed as surface nanobubbles. Bulk nanobubbles are the focus of this study. Due to their smaller size, and large surface-to-volume ratio, they are remarkable in maintaining neutral buoyancy, and high mass transfer efficiencies. In this study, oxygen nanobubbles are created in water using a self-developed batch generator with the application of an electric field. Preliminary investigations of critical factors with this generator influencing nanobubble generation, such as wire arrangements, low-pressure headspace gas provision, and electric field intensities, are studied. Another focus of this study is to confirm the nanobubble existence using a sensitive speed of sound measurement, vibrating tube density (VTD) meter, and other sizing and counting techniques such as dynamic light scattering (DLS), nanoparticle tracking analyzer (NTA), and cryogenic scanning electron microscopy (Cryo-SEM).Item Open Access Conversion of Petroleum Coke into Valuable Products using Catalytic and Non-Catalytic Oxy-Cracking Reaction(2018-04-20) Manasrah, Abdallah Darweesh; Nassar, Nashaat N.; Chen, Shengnan; Kopyscinski, Jan; Pereira Almao, Pedro; Thurbide, Kevin B.Every year millions of tons petroleum coke (petcoke) is generated as a by-product from bitumen and heavy oil upgrading due to the increasing demand in energy. Petcoke is a carbonaceous solid consisting of polycyclic aromatic hydrocarbons with low hydrogen content, derived from the processing of oil sands and oil refineries. The upgrading and treating of petcoke typically include thermal techniques such as gasification and combustion. However, several challenges limit the effectiveness of these conventional processes such as sulfur and CO2 emissions as well as high energy and costs associated with low efficiency. Therefore, finding an alternative, efficient, environmentally-friendly and cost-effective technology to treat these massive amounts of petcoke is needed. In this study, an oxy-cracking technique, which is a combination of oxidation and cracking reactions, is introduced as an alternative approach for petcoke utilization. This oxy-cracking takes place in basic aqueous media, at mild operation temperatures (170-230 oC) and pressures (500-600 psi). The oxy-cracking reaction mechanism was investigated using Quinolin-65 (Q-65) as a model molecule mimicking the residual feedstocks. Theoretical calaculations along with experimental reaction were carried out on Q-65 to explore the reaction pathways. Consequently, several operating conditions on petcoke oxy-cracking were investigated, such as temperature, oxygen pressure, reaction time, particle size and mixing rate to optimize the solubility and selectivity of oxy-cracked products. To enhance the oxy-cracking reaction conversion, an in-house prepared copper-silicate catalyst was introduced and characterized using BET, SEM, FTIR and XRD techniques. The oxy-cracking technique successfully converted the petcoke into valuable products, particularly humic acids analogs with other functional groups such as carboxylic, carbonyl, and sulfonic acids, as confirmed by FTIR, XPS and NMR analyses, in addition to minimal emission of CO2. Interestingly, based on the experimental findings, the metal contents in the obtained oxy-cracked products are significantly lower than that in the virgin petcoke. Consequently, the heating value and oxidation behaviour of the oxy-cracked products was investigated using TGA. These results showed that the oxy-cracked petcoke is easier and faster to oxidize compared to the virgin petcoke, suggesting that the oxy-cracked petcoke could be an alternative-clean fuel for power generation.Item Open Access Decomposition of Hexamethyldisilazane on Hot Metal Filaments and its Gas-phase Chemistry in a Hot-wire Chemical Vapor Deposition Reactor(2019-09-04) Ampong, Eric; Shi, Yujun; Marriott, Robert A.; Heyne, Belinda; Thurbide, Kevin B.Hot-wire chemical vapor deposition (HWCVD) has been used to produce silicon-containing thin films, nanomaterials, and functional polymer coatings for applications in microelectronic and photovoltaic devices. Silicon carbonitride (SiCyNz) thin films, deposited by HWCVD, have found a wide range of applications due to their nonstoichiometric component that exhibits unique properties from a combination of SiC and Si3N4 binary compounds. Most CVD growth of SiCyNz proceeds through the use of separate Si-containing (SiH4), C-bearing (CH4) and NH3 precursors. Handling of pyrophoric silane is difficult, and the process optimization with multiple source gases is extremely complex. This has urged interest in exploring alternative single-source precursors for SiCyNz deposition. 1,1,1,3,3,3-Hexamethyldisilazane (HMDSZ), a non-pyrophoric and non-corrosive molecule, is one of the single-source precursors for use in HWCVD of SiCyNz thin films. In this work, single-photon ionization using vacuum ultraviolet wavelength at 118 nm coupled with time-of-flight mass spectrometry is employed to examine the products from primary decomposition on tungsten and tantalum filaments under collision-free conditions and from secondary gas-phase reactions in a HWCVD reactor. It has been shown that HMDSZ decomposes on the heated metal filaments to produce methyl radicals via Si-CH3 bond cleavage. The methyl radical formation is controlled by surface reactions at filament temperatures ranging from 1600 to 2400 oC. The activation energy for the formation of methyl radicals on the W and Ta filament has been determined to be 71.2 ± 9.1 to 76.7 ± 8.1 kJ/mol, respectively. A comparison with the theoretical energy (363 kJ/mol) required for the homolytic cleavage of Si-CH3 bond in the gas phase indicates that the dissociation of HMDSZ on the W and Ta surfaces to produce methyl radicals is a catalytic cracking process. Aside from the homolytic cleavages, other decomposition routes of HMDSZ, both concerted and stepwise ones, have been systematically explored in this work. The concerted formation of trimethylsilylamine and 1,1-dimethylsilene was found to be the most kinetically favorable route of all, with an activation barrier of 278 kJ/mol. It is also interesting to find that both the elimination of CH3 radical from a methylated silylamino radical and elimination of H atom from the C atom attached to a Si atom in a silyl radical site proceed without an activation barrier. In the secondary gas-phase reactions, radical-radical and radical-molecule reactions are dominant. Formation of 1,1-dimethylsilanimine ((CH3)2Si=NH) was detected from the HWCVD reactor when HMDSZ was introduced. 1,1-dimethylsilanimine undergoes head-to-tail cycloaddition and nucleophilic addition reaction with the abundant HMDSZ molecules to form 1,1,3,3-tetramethylcyclodisilazane and octamethyltrisilazane that were both detected in this work. The secondary gas-phase reactions are also characterized by a free radical short-chain reaction initiated by the primary decomposition of HMDSZ on the metal filaments to produce methyl radicals. Hydrogen abstraction by methyl radical is the main propagation step in the reactor, and biradical recombination reactions terminate the chain reaction to form various stable products with high molecular masses that were also detected in this work.Item Open Access Dehydration of a Water Stationary Phase as a Novel Separation Gradient in Capillary Supercritical Fluid Chromatography(Elsevier, 2019-06-27) Thurbide, Kevin B.; Saowapon, Matthew T.A novel alternative to gradient elution in capillary supercritical fluid chromatography (SFC) based upon the systematic removal of a water stationary phase from the column, using a pure CO 2 mobile phase, is introduced. By adjusting the flow of water used to humidify the system, the stationary phase can be removed at different rates and this results in proportionately faster analyte elution. As well, the phase can be readily restored within a few minutes. The method demonstrates good reproducibility with analyte retention times yielding an RSD of 1.2% in consecutive trials. Further, it provides results that compare well to a conventional pressure program in capillary SFC, but without the problematic convolution of system pressure and flow rate. The technique also demonstrated the ability to refocus analytes into sharper peaks, resulting in a 30-fold increase in their peak height. This effect can improve detection limits and also allow ionizable analytes like amines and dicarboxylic acids to be eluted with improved peak shape. Results indicate that systematic removal of a water stationary phase from the column is an interesting and potentially effective alternate means of controlling and improving analyte elution in capillary SFC.Item Open Access Dynamic Control of Gas Chromatographic Selectivity during the Analysis of Organic Bases(Scopus, 2019-05-06) Darko, Ernest; Thurbide, Kevin B.A novel method for controlling selectivity during the gas chromatographic (GC) analysis of organic bases is presented. The technique employs tandem stainless steel capillary columns, each coated with a pH adjusted water stationary phase. The first is a 0.5 m trap column coated with a pH 2.2 phase, while the second is an 11 m analytical column coated with a pH 11.4 phase. The first column traps basic analytes from injected samples, while the remaining components continue to elute and separate. Then, upon injection of a volatile aqueous ammonia solution, the basic analytes are released as desired to the analytical column where they are separated and analyzed. Separations are quite reproducible and demonstrate an average RSD of 1.2% for analyte retention times in consecutive trials. Using this approach, the retention of such analytes can be readily controlled and they can be held in the system for periods of up to 1 h without significant erosion of peak shape. As such, it can provide considerable control over analyte selectivity and resolution compared to conventional separations. Further, by employing a third conventional GC column to the series, both traditional hydrocarbon and enhanced organic base separations can be performed. The method is applied to the analysis of complex mixtures, such as gasoline, and much less matrix interference is observed as a result. The findings indicate that this approach could be a useful alternative for analyzing such samplesItem Open Access Elucidating the chemistry of particulate and chlorinated nitrates in the troposphere through method development, and chamber and field studies(2020-09-22) Garner, Natasha Michelle; Osthoff, Hans D.; Gailer, Jürgen G.; Thurbide, Kevin B.; Wieser, Michael E.; Bertram, Timothy H.This thesis explores the chemistry of chlorinated and particulate nitrogen oxides in the troposphere which can impact the budgets of atmospheric oxidants and aerosol. Mixing ratios of nitryl chloride (ClNO2) were measured by chemical ionization mass spectrometry (CIMS) during the ORCA campaign in July 2015 on the west coast of Vancouver Island. Mean ClNO2 mixing ratios were small (< 10 pptv) with a maximum of 46 pptv, in part due to low precursor concentrations, i.e., of nitrogen dioxide (NO2) and ozone, and large nitrate radical sinks, e.g., titration by monoterpenes. Concentrations of ClNO2 were enhanced in air masses with elevated NO2 concentrations that had resided over the ocean, demonstrating the potential of ClNO2 to affect radical budgets in remote environments. The potential loss of ClNO2 by uptake on inorganic and secondary organic aerosol (SOA) was investigated in a newly constructed smog chamber. Uptake probabilities (γ) were determined by box modeling constrained to measured ClNO2 mixing ratios and SMPS derived aerosol surface area. An upper limit of γ< 4x10-4 was determined for (NH4)2SO4 and NH4HSO4 aerosol, but larger values were needed for monoterpene derived SOA, i.e., γ=(8+/-2)x10-4. Uptake of ClNO2 on SOA reduces its lifetime and impact on nitrogen oxide and chlorine budgets downwind of coastal areas where marine and continental air masses combine. A method to quantify NH4NO3 and NaNO3 aerosol by thermal dissociation cavity ring-down spectroscopy (TD-CRDS) was developed. At inlet temperatures of 540 °C and 620 °C, respectively, scatter plots of SMPS volume distribution data and TD-CRDS mixing ratios correlated (r2>0.9) with unity slopes in laboratory experiments. Sample ambient air measurements in Calgary, AB in August 2018 showed the presence of particulate organic nitrates at inlet temperatures < 350 °C (consistent with smog chamber experiments with limonene SOA) and of inorganic nitrate aerosol, demonstrating the potential of TD-CRDS for ambient particulate measurements.Item Open Access Employing a Metallomics Tool to Probe Bioinorganic Processes in the Bloodstream(2020-04-27) Sarpong-Kumankomah, Sophia; Gailer, Jürgen G.; Thurbide, Kevin B.; Jalilehvand, Farideh; Ling, Changchun; Niyogi, SomIn this thesis, I have applied a metallomics method that is based on size exclusion chromatography coupled on-line to an inductively coupled plasma atomic emission spectrometer (SEC-ICP-AES) to analyze biological fluids to gain insight into the bioinorganic chemistry of metals and their possible link to disease processes. The first study involved the qualitative identification of an iron-containing protein in blood plasma. One of the two major iron-containing proteins in human plasma was identified as a haptoglobin-hemoglobin (Hp-Hb) complex that is formed in plasma after red blood cells rupture. Previously identified plasma metalloproteins - transferrin, ceruloplasmin and α2-macroglobulin were also unequivocally confirmed. Since the employed metallomics method can measure the concentration of these metalloproteins in plasma, the results are important as the quantification of the Hp-Hb complex in plasma gave better insight into the lysis of red blood cells, which is of immediate health relevance. In the second study, the metallomics method was applied to investigate the potential of using plasma metalloproteins as disease biomarkers. Blood serum samples from multiple sclerosis patients (21), stroke patients (17) and healthy controls (21) were analyzed for copper, iron and zinc metalloproteins. The results revealed that the concentration of the Hp-Hb complex in serum was statistically significantly higher in stroke patients compared to the other groups, which can be rationalized by the rupturing of red blood cells during a stroke event. Since 330,000 people in Canada live with long term disability effects of stroke, my results demonstrate the usefulness of the developed analytical method to diagnose diseases. The third study involved the application of the metallomics method to gain insight into the plasma transport of an arsenic-selenium compound, [(GS)2AsSe]-, that is formed in red blood cells and is excreted in bile. The analysis of [(GS)2AsSe]- added to human plasma demonstrated that [(GS)2AsSe]- mobilized Zn from plasma proteins in a dose-dependent manner. The formation of [(GS)2AsSe]- in red blood cells and its release into plasma may perturb the metabolism of zinc therein and result in systemic toxic effects. These results are relevant because the mobilization of zinc is potentially implicated in the chronic exposure of human to AsIII, which currently affects >100 million people. Lastly, the metallomics method was employed to gain insight into the stability of a bimetallic complex that has anti-cancer activity in human blood plasma. The fact that ~70 % of Titanocref remains intact in plasma after 60 min implies that this anti-cancer drug is likely to reach cancer cells in vivo. These results exemplify that conceptually-straightforward in vitro studies can provide important insight into the degradation of a bimetallic anti-cancer drug in plasma. Metallomics studies are therefore destined to play an important role in the context of advancing more metal-based drugs to preclinical studies.Item Open Access Exploring Novel Strategies for Universal Detection in Chromatography(2016) Scott, Andrea Ferelyth; Thurbide, Kevin B.; Hinman, Allen Scott; Langford, Cooper Harold; Norman, Ann-Lise; Murch, Susan JeanThis thesis presents novel strategies for the universal detection of polar analytes in chromatography. This included the further development of a universal detector that is compatible with organic solvents, as well as exploring separation techniques that are compatible with the universal Flame Ionization Detector (FID). For instance, the universal response of the Acoustic Flame Detector (AFD) was comprehensively compared to the FID, where a very close linear correlation (r2 of 0.9103) was found between them. A few minor exceptions were also observed, where the most notable differences occurred for organometallic compounds. Overall, results indicate that the AFD provides a uniform response toward most hydrocarbons that is qualitatively very similar to that of an FID. Interestingly, a novel response mode for alkali metals was also observed in a Subcritical Water Chromatography operating regime. Optimal hydrogen flame gas flow rates were found near 40 mL/min for hydrocarbon response and 80 mL/min for alkali response. KCl, NaCl, LiCl and ethanol each displayed a linear FID response with respective sensitivities of 7500, 980, 130 and 1 mV/µg of analyte. This was subsequently demonstrated to greatly alter the FID response of organic salts. Accordingly, their presence in analytical samples or mobile phases must therefore be accounted for when using this detector. Finally, a novel method of separating polar analytes in Supercritical Fluid Chromatography through dynamically controlling analyte retention by tuning the pH of a water stationary phase is presented. The method utilizes a change in mobile phase from N2 to CO2 to effectively reduce stationary phase pH and control the elution of organic acids from the column. This effect is also observed to be reasonably independent of column length and time. For example in the latter case, at 80oC, a hexanoic acid standard analyte can be readily eluted on demand from a 10 m column by switching to CO2 at any point over a run time of about 1 hour. The N2/CO2 switching system is used to analyze organic acids present in a variety of different samples and it is found that they can be eluted on demand with high selectivity over other matrix components.Item Open Access Exploring the stability of polyethylene glycol functionalized nanoparticles in angiogenic blood vessels(2018-09-06) Sagoe, Veritas Aba Ntsifua; Cramb, David Thomas; Anikovskiy, Max; Thurbide, Kevin B.; Thangadurai, V.Research into the stability of liposomes as nanocarriers or nanoparticles (NPs) is well justified during an era where there is emerging research on drug delivery especially with respect to cancer. Nanoparticles face different barriers to reach their targets within a living organism which can potentially affect their stability. In this thesis, we used a systematic approach to introduce a series of liposomes (whose surfaces are partially coated with poly-ethylene glycol (PEG)) into a chicken embryo chorioallantoic membrane (CAM). The CAM was the model of choice as it is mimetic of the angiogenic vasculature present in cancerous tumors. There are fenestrations in these blood vessel walls through which NPs can pass to the tumor mass. Fluorescent liposomes were synthesized by lacing with a dye and using different proportions (2.5, 5 and 10% of the total lipid content) of PEGylated lipids (1, 2 dioleyl-sn-glcero-3phophoethanolamine-N-[Methoxy (Polyethylene glycol)-“1000, 2000 & 5000”] with molecular weights of 1000, 2000 and 5000 dalton (Da). After injection into the CAM, the time dependent behaviour is monitored using fluorescence correlation spectroscopy. The NPs were observed to agglomerate in the blood vessels. Thus, the NPs were subsequently characterized in chicken blood serum and phosphate buffered saline to ascertain the possibility of there being ionic and protein effects on the particle stability.Item Open Access Extraction, Analysis and the Role of Co-contaminants on Sulfolane Biodegradation(2019-04-18) Hassanvand-Gandaei, Nahid; Achari, Gopal; Thurbide, Kevin B.; Gailer, Jürgen G.; Ponnurangam, SathishSulfolane’s extensive use in various oil and gas industries has led to its increased environmental contamination throughout Alberta. The impact of co-contaminants and complex matrices in sulfolane polluted areas can produce challenges in analytical and remediation efforts and generate vastly different results from those obtained in a laboratory setting. Particularly, the low regulatory guidelines of 0.18 mg/kg in soils and 0.09 mg/L in groundwater has created challenges for commercial testing laboratories as these levels are often too close to their instrument detection limits. Potential interferences and false positives have become a cause for concern especially in complex matrices with high organic content. Similarly, groundwater bioremediation efforts can be positively or negatively impacted depending on the type of co-contaminant present alongside sulpholane. A spiking study was conducted to investigate sulfolane analytical challenges faced by various testing labs when analysing sulfolane in peat and clay soils, as well as groundwater samples. It was observed that soil spiked with high sulfolane concentrations (>0.5mg/kg) resulted in more reliable data compared to low concentrations (<0.5mg/kg), with mineral soils providing more reproducible data than the highly-organic peat soil. Similarly, groundwater analysis also provided less variable results in higher concentrations (0.5 mg/L) than lower levels (0.1 mg/L). Soil water extraction efficiency of sulfolane improved with an increase in soil to water ratio, however, clay soils will require additional aliquots to achieve maximum recovery. GC-MS analysis demonstrated that organic soils can produce false positives. Therefore, at low concentrations, interferences, loss of sulfolane due to biodegradation and sample heterogeneity will significantly impact results. Impact of co-pollutants (As (III), fulvic acid, and diisopropanolamine) on sulfolane biodegradation in groundwater was also investigated in this research. Three concentrations of As (III) (low, medium and high) were observed to have negligible impact on sulfolane degradation. Similarly, at environmentally relevant concentrations, fulvic acid did not significantly effect sulfolane removal. Diisopropanolamine, however, was observed to positively and negatively impact sulfolane removal depending on the biological, chemical and physical characteristics of the water matrix used.Item Open Access Functions of natural multicomponent organic mixtures as emergent properties influenced by environmental contaminants(2019-03-20) Vialykh, Elena; Achari, Gopal; Salahub, Dennis R.; Thurbide, Kevin B.; Cook, Robert L.; Ponnurangam, Sathish; Rosario-Ortiz, Fernando L.The primary focus of this study concerns the functions of natural multicomponent organic mixtures as emergent properties influenced by environmental contaminants. Two types of natural multicomponent organic systems were studied: biosolids and humic substances. The investigation of the mixtures interactions of the mixtures with environmental pollutants was performed both by experimental means and computational modelling. The current concern of possible soil pollution via application of municipal biosolids as fertilizers on agricultural land led us to investigate biosolids’ interaction with one of the most widely-spread nanoparticle contaminants present in wastewaters – ZnO NPs. Metal complexation by typical biosolids was explored using methods from the humics literature. Uptake of Zn from NPs in the biosolids was evaluated. Finally, the kinetics of release of Zn species are reported as a function of (i) pH and (ii) the presence of strongly binding ligands (e.g., ion-exchange resin promoting release). The investigation revealed that (i) metal binding sites of biosolids are analogs of humic substances, (ii) ZnO NPs do not survive in the digestion environment, and (iii) any ZnO NPs dissolve to aqueous Zn2+ in < 10 d. Kinetics of Zn in biosolids revealed that Zn release is a function of biosolid protonation. At pH 8, Zn is retained in the biosolids, whereas at pH 4.5, 10% of Zn is released from the biosolids. Adding a chelating resin to the system at pH 5.0 led to Zn release from the biosolids as per Noyes–Whitney kinetics, releasing 85% of the bound Zn in 360 h. Fifteen percent of Zn appeared to be irreversibly bound. These results encouraged us to investigate processes occurring at the molecular level. For this purpose, an approach that perceived natural multicomponent organic mixtures as labile aggregates with emergent functions, was used. The first step in this direction was the generation of computational models for two fractions of the well-studied and characterized natural multicomponent organic mixture, HS, Suwanee River Fulvic and Humic acids. Computational modeling was used to help understand processes and mechanisms on the molecular scale that occur in different fractions of HS, fulvic acids and humic acids, as they interact with organic pollutants. The importance of non-covalent interactions in the emergent functions of HS is highlighted. H-bonding, hydrophilic/hydrophobic surface areas and π-stacking interactions play a significant role in aggregation processes as well as in the sorption of environmental pollutants. In a highly hydrophilic system with small molecules (the SRFA-22 model) H-bonding is the main force that drives the aggregation process. On the other hand, in a highly aromatic and hydrophobic model with larger molecular fragments (SRHA-6) hydrophobic and π-stacking interactions dominate in the aggregation process. The chemical properties of contaminants significantly affect their mechanism of sorption by HS. The interaction of a polar pollutant, phenol, with HS occurs via H-bonding, whereas non-polar benzene interacts via hydrophobic and π-stacking interactions, resulting in much stronger sorption by HS and causing an additional structural rearrangement of the aggregates, making them more stable in the environment. The formation of inner/outer sphere metal-ligand complexes, metal binding sites, complex configurations, binding energies and aggregation/dissolution as emergent properties of HS were determined under various conditions in Chapter IV of the work. The results of computational modeling revealed that (i) the highest Cu2+ binding (55.6%) was by the SRFA-22 organic model, which represents low molecular weight fulvic acids. On the contrary, the highest amount of inner-sphere Mg-organic matter complexes (63.4%) was formed in SRHA-6 which has higher molecular weight constituents. Therefore, a correlation between the type of cation, system aromaticity and the extent of metal complexation is proposed. (ii) The increase of metal-ion concentration and/or decrease of water content resulted in an increase in the number of hydrogen bonds and more compact and stable aggregates with lower hydrophilic and higher hydrophobic surface areas in SRFA-22. However, in SRHA-6 the results varied due to the competition between metal binding, H-bonding and non-polar interactions in the structural arrangement of the aggregates. In general, the aggregation process, driven by metal complexation and water removal, resulted in the formation of more stable conformers, with lower potential energy, with the sole exception of SRHA-6-Cu. Finally, based on the obtained results, future research on expanding the modeling of emergent functions of HS influenced by environmental contaminants to the biosolids mixtures was proposed.Item Open Access Incorporation of Chiral Selectors into a Water Stationary Phase for use in Supercritical Fluid Chromatography(2018-06-14) Frantz, Jackson Joseph; Thurbide, Kevin B.; Shi, Yujun J.; Gailer, Jürgen G.; Schriemer, David C.The direct separation of enantiomers in column chromatography is an important field that has seen considerable maturation and explosive growth in the last three decades. This development has been spurred by needs for fast and cost-effective analysis in application areas such as pharmaceuticals, agrochemicals, and environmental toxicology. Despite this progress, method development in chiral analysis is often difficult and prohibitively costly due to expensive columns and lack of universally applicable selectors. This thesis presents a new method for chiral separations using a modified aqueous stationary phase. By incorporating chiral selectors in a liquid phase on stainless steel capillary tubing, chiral separations may be achieved conveniently and at extremely low cost. Further, the application of unmodified carbon dioxide as a mobile phase for these separations eliminates the need for costly and potentially harmful organic solvents in routine operation, and also allows the use of the universal flame ionization detector. Toward this end, efforts to effect separations using native and derivatized beta cyclodextrin selectors were undertaken, with some promising results for the separation of some flavanone enantiomers. Especially notable was the extremely potent selectivity obtained at novel operating conditions such as subambient temperatures. The thermodynamic and kinetic performance of the system was evaluated revealing some highly novel characteristics. To enable separation of a greater diversity of chiral analytes, the macrocyclic antibiotic selector vancomycin was also investigated. Excellent performance was obtained using this selector for the separation of some phenoxypropionic acid enantiomers. The addition of additives was highly relevant to these separations. Most notably the improvement with ternary agents such as triethylamine revealed the utility of the water stationary phase as a unique molecular scaffolding for promoting chiral discrimination. Finally, applications demonstrating the separation of both a flavanone and phenoxypropionic acid in complex sample matrices, as well as mixed selector phases utilizing both beta cyclodextrin and vancomycin for the simultaneous separation of multiple chiral pairs highlighted the versatility of the novel separation system.Item Open Access Indirect Detection of Explosive Vapours by Thermal Dissociation Cavity Ring-Down Spectroscopy(2018-04-12) Taha, Youssef Mohamad; Osthoff, Hans D.; Shi, Yujun; Thurbide, Kevin B.; Kim, Seonghwan; Hastie, Donald R.This thesis describes two explosive detection methods capable of detecting explosives indirectly in ambient air. The first of the explosive detection methods utilizes a platinum catalyst heated to 350 °C to catalyze the thermal dissociation of nitroaromatic explosives, such as 2,4,6 trinitrotolune (TNT), to NO2 prior to detection. The catalytic thermal dissociation (cTD) CRDS was found to have a (1s, 3σ) limit of detection (LOD) of 0.5 ppbv. The LOD was sufficient for the detection of TNT in ambient air but lacked the sensitivity to detect less volatile nitro aromatic explosives such as 2,4,6 trinitrophenylmethylnitramine (Tetryl). Efforts to improve the sensitivity of the instrument via a trap and purge pre-concentration scheme were of limited success largely due to poor sample recoveries from the Tenax traps used. The second explosive detection technique exploited radicals generated during the thermal decomposition of triacetone triperoxide (TATP), a peroxide explosive, for detection. These radicals were amplified via a peroxide radical chemical amplification scheme (PERCA) that required the addition of NO and a radical chain carrier, commonly CO, to generate NO2. A modelling study was conducted to assess alternative radical chain carriers as well as the effect of TD on amplification chemistry. Dimethyl ether and ethane were found to be appropriate chain carriers. Additionally, the modelling study suggested that elevated TD temperatures slow down radical chemistry and reduce chemical amplification (CL) while reducing the dependence of CL on relative humidity and radical sinks. A TD-PERCA-CRDS instrument was constructed and its temperature dependent chain length calibrated using peroxyacyl nitrates and peroxy nitric acid. The TD-PERCA-CRDS was found to have a CL up to 69±5 at 250 °C and an LOD (1s, 1σ) of 1.3 pptv. The instrument’s relative humidity dependence was reduced compared to that of room temperature PERCA but the instrument was found to suffer from an ozone interference at temperatures greater than 150 °C. A sample of TATP was synthesized in the lab and its identity and purity established using FTIR. TATP decomposition resulted in an NO2 signal that was 22±3 times larger than that expected from TATP saturation vapour pressure, and the LOD was 5 pptv.Item Open Access Mass Spectrometry-based Integrative Structural Modeling of the Doublecortin-Microtubule Interaction(2021-01-21) Rafiei, Atefeh; Schriemer, David C.; Fraser, Marie Elizabeth; Thurbide, Kevin B.; Politis, Argyris; Muench, Douglas G.A comprehensive understanding of protein function requires the structural elucidation of physical contacts with other proteins, known as protein-protein interactions (PPIs). Many PPIs evade classical structural determination techniques for many reasons. One class of PPIs that is challenging to canonical techniques involves large multi-subunit protein complexes comprised of proteins with intrinsically disordered regions. The interaction between doublecortin (DCX) and microtubules (MTs) is a particularly intriguing example of such PPIs. Doublecortin is a critically important protein involved in neuronal development, which appears to function by engaging MTs in a complex interaction pattern involving both ordered and disordered domains. In this work, I developed and used a mass spectrometry-based integrative structural modeling (ISM) approach to generate a unifying structural model of DCX-MT interaction. A crosslinking-mass spectrometry (XL-MS) workflow was developed for the analysis of interactions involving MTs in general. Different crosslinker reagents targeting different amino acid classes were tested and the integrity of the MTs in response to the crosslinking reactions were monitored. Then, a DCX-MT construct was reconstituted in-vitro and XL-MS performed using different reagents. Doublecortin self-association was investigated using isotopically-labeled DCX, to differentiate between inter- and intra- DCX crosslink peptides. It was found that DCX self-associates only in the presence of MTs. The majority of the inter-DCX crosslinks were observed in the C-terminus regions of the DCX sequence. Finally, the structural elucidation of DCX-MT interaction was carried out in a step-wise approach. The residue-based distance restraints from XL-MS along with the cryo-EM map of DCX-MT and the X-ray structures of protein subunits were combined in the Integrative Modeling Platform to identify the MT-binding domain. It was found that the N-terminus doublecortin-like domain is the primary MT binding domain, while the C-terminus doublecortin-like domain and C-tail are MT-dependent oligomerization domains. My modeling results support a DCX-MT interaction model in which DCX can self-associate between all immediate neighbors. Finally, it is shown that fast crosslinking chemistries (i.e. diazirine based photo-crosslinkers) were required to generate a converging model, as the more conventional long-lived crosslinkers are prone to conformational “kinetic trapping”. This has implications for ISM of similar systems, and modeling in general.Item Open Access MICRO-FLAME PHOTOMETRIC DETECTION IN MINIATURE GAS CHROMATOGRAPHY ON A TITANIUM TILE(2019-06-12) McKelvie, Kaylan H.; Thurbide, Kevin B.A novel miniaturized gas chromatography - flame photometric detection device built within a titanium platform (Ti µGC-FPD) is presented. The 7.5 cm x 15 cm monolithic Ti device contains both an OV-101 coated separation column (5 m x 100 µm i.d.) and a shielded cavity to house the hydrogen-rich detector flame. The FPD employs a micro counter-current flame (about 250 µm in diameter) that is stabilized by opposing relatively low flows of oxygen and hydrogen (7-10 mL/min O2 and 40 mL/min H2). Under optimal conditions, the minimum detectable limits are about 70 pg S/s for sulfur and 8 pg P/s for phosphorous. The natural (i.e. unfiltered) selectivity for these responses over carbon is near 104.3 for S/C and 105 for P/C. Even greater selectivity over hydrocarbons can further still be obtained by employing conventional interference filters. Overall, good separations with stable and sensitive detector performance are obtained with the device, and its sturdy Ti structure supports robust operation. Results indicate that this Ti µGC-FPD device may be a useful alternative approach for incorporating selective FPD sensing in µGC analyses.Item Open Access Novel Analytical Method for Trace Level Quantification of Disinfection By-Products in Recycled Wastewaters(2020-12-08) Ortega, Alejandro Rene; Kimura, Susana Y.; Thurbide, Kevin B.; Achari, Gopal; van Humbeck, Jeffrey F.The work of this thesis quantifies and characterizes unregulated priority disinfection by-products (DBPs) in a full-scale potable wastewater reuse treatment plant. DBPs are small organic molecules formed from the reaction between natural organic matter (NOM) and disinfectants. Unregulated DBPs display genotoxic, cytotoxic and potentially carcinogenic properties to humans. Wastewater reuse is an area of growing interest as freshwater sources are being depleted due to increasing human population and climate change. Secondary effluent treated with microfiltration (UF), ozone, and reverse osmosis waters were disinfected to observe the change in DBP composition throughout various stages of the treatment train process. First, a novel multiple reaction monitoring (MRM) method was developed on a gas chromatography – triple quadrupole mass spectrometer (GC-MS/MS) that quantifies 25 DBPs formed from chlorinated and chloraminated wastewater effluents. The order of optimization of each DBP class involved the determination of chemical transitions, collision energies, dwell times, time segments and determination of method detection limits. The optimization of these parameters led to a highly sensitive quantification method for the DBPs found in this method. Method detection limits ranged from 2.0 - 68.9 ng/L. Next, a liquid – liquid extraction (LLE) method for sample analysis was modified to account for the large increase in sensitivity that comes with a triple quadrupole. MS/MS instruments are highly advantageous because of the selection of specific chemical transitions for quantification. This specificity results in precise quantification due to the large signal to noise ratio of each chemical fragment at trace levels. The LLE method was reduced 10 fold in terms of time, reagents, and sample volume compared to published methods. The last part of this work looked at the DBP composition of each water matrix across three seasons of the year. Specifically, waters were sampled in fall, winter, and summer to observe how the change in precursors affected DBP formation.