Date of Award

2019

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Chemistry (MS)

Administrative Home Department

Department of Chemistry

Advisor 1

Lynn Mazzoleni

Committee Member 1

Marina Tanasova

Committee Member 2

Daisuke Minakata

Abstract

Biomass burning aerosols are highly complex organic mixtures of thousands of components with consequences for global climate. Complex mixture component identification requires accurate mass measurement capability to separate components on a milli-Dalton scale, frequently using ultrahigh resolution mass spectrometry with electrospray ionization. Certain sample preparations and the ionization process may introduce artifacts that obscure the composition of the sample. Two method considerations were explored using isotopically labeled 15NH4OH and MeOH-d3 to track artifact formation in biomass burning samples. Informatics techniques and a custom molecular formula assignment software were used to identify the isotopic atoms in artifact products. Sample preparation with NH4OH was found to significantly alter the detected complex mixture composition, potentially by NH4+ adduction and by reactions between NH3 and carbonyls. Solvation in MeOH likely induced artifact formation by converting carbonyls to esters and acetals/hemiacetals for non-aromatic species. In addition, Hydrogen-Deuterium exchange using MeOH-d1 was studied to infer the presence of amino and hydroxyl groups, and estimate the number of carboxyl functional groups. The results have important implications for ultrahigh resolution mass spectrometry analyses of complex environmental samples and their labile H content.

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