Current factories producing plant-based fossil-fuel replacements are neither environmentally friendly nor economically viable because their main product, bio-oil, is burned for heat rather than sold for profit. However, bio-oil is rich in potentially valuable aromatic compounds. In order to valorize bio-oil and improve the economic viability of the factories, we need to understand bio-oil’s composition and the effect of processing parameters—such as plant feedstock and pretreatment method. Unfortunately, bio-oil is a complex lignocellulosic mixture that is difficult to analyze. To fully characterize the hundreds of compounds present, analysis typically requires top-end mass spectrometers and lengthy separations. This cost prohibits many laboratories from pursuing bio-oil research. Then time-consuming separations limit recursive analyses to optimize process parameters. The question takes shape: is it possible to analyze complex lignocellulosic mixtures without lengthy separations or top-end mass spectrometers? To assess the feasibility of rapid, affordable analysis, I set out to develop qualitative and quantitative methods using a quadrupole-time-of-flight (QTOF) mass spectrometer. I hypothesized that (a) ionization dopants could mitigate the need for lengthy separations pre-injection and that (b) tandem mass spectrometry could compensate for the midrange resolving power of the QTOF. To test this hypothesis, I started by analyzing another lignocellulosic biomaterial: autohydrolyzate, the product of hydrothermal pretreatment of biomass feedstocks. I observed that two anionic dopants—hydroxide and chloride—worked exceptionally well for selective analysis of the two major components of a lignocellulosic mixture, lignin- and carbohydrate-derivatives. Tandem mass spectrometry confirmed the game-changing selectivity of the dopants. With these favorable results, I applied the ionization dopants to two case studies. Chloride dopant and tandem mass spectrometry were employed to qualitatively analyze the little understood lignin-carbohydrate complexes found in lignocellulosic mixtures. Hydroxide dopant and tandem mass spectrometry were employed to quantitatively analyze the feasibility of valorizing biooil as a performance-enhancing diesel fuel additive. Both projects offered exciting success that redefined the scope of research possible using a QTOF. I demonstrated that by using ionization dopants and tandem mass spectrometry, it is possible for laboratories with limited means to use a cost-effective QTOF for both qualitative and quantitative analysis of complex lignocellulosic mixtures.
|Advisor:||Benitez, Nelson Vinueza|
|Commitee:||Bereman, Michael, Freeman, Harold S., Michielsen, Stephen|
|School:||North Carolina State University|
|Department:||Fiber and Polymer Science|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 79/12(E), Dissertation Abstracts International|
|Subjects:||Analytical chemistry, Organic chemistry|
|Keywords:||bio-oil, electrospray ionization, ionization dopant, lignin, quadrupole-time-of-flight, tandem mass spectrometry|
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