Advanced chemometrics and fundamental considerations for non-targeted analysis with comprehensive multidimensional gas chromatography coupled with time-of-flight mass spectrometry

Thesis (Ph.D.)--University of Washington, 2020Comprehensive two-dimensional gas chromatography (GCÃ GC) coupled with time-of-flight mass spectrometry (TOFMS) is a powerful analytical technique capable of separating complex mixtures, providing valuable information about the chemical composition of samples. However, the inherent data density associated with three-dimensional data provides a unique challenge to analytical chemists. As a result, significant effort has been invested in utilizing advanced chemometrics to glean meaningful information about samples from large and complex data sets. Herein, this dissertation introduces several investigations conducted on optimizing separation conditions to be amenable to chemometric deconvolution algorithms as well as the development, study, and application of advanced chemometric techniques applied to GCÃ GC-TOFMS data. To begin, the metric trilinear deviation ratio (TDR) is utilized to study the impact of experimental parameters such as column selection and modulation period, PM, on the quantitative accuracy of parallel factor analysis (PARAFAC) deconvolution. TDR scales with increasing change in second dimension retention time, Δ2tR, associated with pseudo-isothermal conditions on the second dimension, 2D, and quantitative accuracy decreases as TDR increases. Two column sets were utilized with varying film thickness on the first column, 1D, and each column set was studied using two PM for a total of 4 experiments. It was reported that using 1D columns with larger film thicknesses allows the analyst to employ a shorter PM, in turn lowering the Δ2tR, leading to higher quantitative accuracy. Many GCÃ GC-TOFMS studies relate to identifying class distinguishing analytes and can be tedious when performed manually. Fortunately, the use of discovery-based chemometric tools such as principal component analysis (PCA) and Fisher ratio (F-ratio) analysis has increased in popularity as less time-intensive and automated techniques for untargeted analyses. To begin, this dissertation will investigate mass channel purity obtained via the tile-based F-ratio algorithm using diesel fuel spiked with non-native analytes using GCÃ GC-TOFMS. The F-ratio algorithm, considered a supervised discovery technique because class membership is known a priori, was first used to “discover” the spiked non-native analytes. Then, using a novel signal ratio (S-ratio) algorithm, the mass channel selectivity information output by the F-ratio method was studied using three statistical metrics: null distribution analysis, p-value, and lack-of-fit (LOF). The result of this investigation revealed that a mass channel has a high likelihood of being pure when its p-value and LOF are sufficiently low. Finally, F-ratio analysis was applied to a dataset including patients with an anterior cruciate ligament (ACL) injury to discover potential biomarkers of post-traumatic osteoarthritis (PTOA) post-injury. Standard F-ratios are calculated by the between class variance divided by the sum of the within-class variance, scaling up as the between class variance increases and the within-class variance remains sufficiently small. However, many biological studies involve significant biological variance (~30%) that may not be associated with disease state or injury severity, etc. Herein, the standard tile-based F-ratio algorithm was modified to use only the within-class variance associated with control samples. It was expected that the control class contained less within-class variance relative to the patient class, due to the expectation that some patient samples would be associated with increased severity of injury or the presence of coexisting conditions. Hit lists (metabolites discovered via F-ratio) from standard F-ratio and control-normalized F-ratio were studied and directly compared to establish a comprehensive metabolome of potential biomarkers for PTOA development post ACL injury. Reported in this dissertation is a discussion on the complementary nature of standard and control-normalized F-ratio, followed by demonstration of class distinguishing metabolites via PCA

Radical ring-opening polymerization of sustainably-derived thionoisochromanone

We present the synthesis, characterization and radical ring-opening polymerization (rROP) capabilities of thionoisochromanone (TIC), a fungi-derivable thionolactone. TIC is the first reported thionolactone to readily homopolymerize under free radical conditions without the presence of a dormant comonomer or repeated initiation. Even more, the resulting polymer is fully degradable under mild, basic conditions. Computations providing molecular-level insights into the mechanistic and energetic details of polymerization identified a unique S,S,O-orthoester intermediate that leads to a sustained chain-end. This sustained chain-end allowed for the synthesis of a block copolymer of TIC and styrene under entirely free radical conditions without explicit radical control methods such as reversible addition-fragmentation chain transfer polymerization (RAFT). We also report the statistical copolymerization of ring-retained TIC and styrene, confirmed by elemental analysis and energy-dispersive X-ray spectroscopy (EDX). Computations into the energetic details of copolymerization indicate kinetic drivers for ring-retaining behavior. This work provides the first example of a sustainable feedstock for rROP and provides the field with the first six-membered monomer susceptible to rROP, expanding the monomer scope to aid our fundamental understanding of thionolactone rROP behavior

Perspectives from the 2022 cohort of the American Chemical Society Summer School on Green Chemistry & Sustainable Energy

The field of chemistry is uniquely equipped to solve many current and impending global challenges; however, minimizing potential negative impacts on the environment, society, and the economy requires a holistic approach to developing new processes and chemicals. For this reason, there is an urgent need to incorporate green chemistry and systems thinking into chemistry-based disciplines so that the most sustainable, least toxic, and least resource-intensive research directions and methods are prioritized. The next generation of researchers and instructors is poised to implement these approaches; however, most graduate curricula do not include coursework on green chemistry and systems thinking. Every year, the American Chemical Society Green Chemistry Institute hosts the Summer School on Green Chemistry & Sustainable Energy for early career researchers to learn about green chemistry and systems thinking approaches for tackling sustainability goals. In this Perspective, 2022 summer school participants highlight sustainability challenges in their own work that can be addressed using the skills and knowledge acquired at the summer school, including in carbon capture, organic pharmaceutical synthesis, nanomaterial synthesis, catalysis, and other areas. In addition, how green chemistry can meet practical needs in industry settings and be infused in education and government policy is discussed.Fil: Saraf, Mohit. Drexel University; Estados UnidosFil: Roy, Monika A.. University Of Massachusetts Lowell; Estados UnidosFil: Yarur Villanueva, Francisco. University of Toronto; CanadáFil: Kundu, Anirban. Université Mcgill; CanadáFil: Tran, Hung-Vu. University Of Houston; Estados UnidosFil: Ghosh, Moumita. Indiana University; Estados UnidosFil: Ezenwa, Sopuruchukwu. Purdue University; Estados UnidosFil: Gastelu, Gabriela. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Prebihalo, Emily A.. University of Minnesota; Estados UnidosFil: Cala Gómez, Luis Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Cleary, Scott R.. Colorado School Of Mines; Estados UnidosFil: Devineni, Geetesh. The George Washington University; Estados UnidosFil: Lee, Gahyun Annie. The Fu Foundation School Of Engineering And Applied Science; Estados UnidosFil: Umenweke, Great C.. University of Kentucky; Estados UnidosFil: Koby, Ross F.. University of Minnesota; Estados UnidosFil: Nixon, Rachel. University of Illinois. Urbana - Champaign; Estados UnidosFil: Voutchkova, Adelina. American Chemical Society. Office of Sustainability; Estados Unidos. The George Washington University; Estados UnidosFil: Moores, Audrey. Université Mcgill; Canad