Ambient Ionization Mass Spectrometry for Metabolomics and Reaction Acceleration

Caitlin E Falcone, Purdue University

Abstract

This dissertation discusses two interlocking topics: metabolomics by ambient ionization mass spectrometry and reaction acceleration. Ambient ionization mass spectrometry, a fast technique with minimal sample preparation, was used for rapid screening of metabolites. Leaf spray mass spectrometry was proven as a rapid molecular diagnostic tool for emerald ash borer infestation. Leaf spray mass spectrometry was performed on 23 different ash trees to determine that the mass spectra profiles of healthy and infested ash tree leaflets. The discriminator ions of healthy and EAB-infested ash trees were based on principal component analysis and the chemical identities of the discriminator ions were determined by tandem mass spectrometry and confirmed with standards. Healthy ash trees showed increased levels of ursolic acid and oleanolic acid and trees and EAB-infested ash trees showed increased levels of six-carbon sugar alcohols. This study suggests that leaf spray mass spectrometry of ash tree leaflets provides a potential tool for the early detection of ash tree infestation by the emerald ash borer. Preliminary studies were conducted on the chemical profiling of cerebrospinal fluid for the diagnosis of Parkinson’s disease. Traditional metabolomics utilizes sample preparation and chromatography which allows for the detection of low concentration metabolites and prevents the excess salt content in cerebrospinal fluid from disrupting analysis. To overcome these limitations, reactive paper spray was used to increase the ionization efficiency of low concentration metabolites and inductive nanoelectrospray was used to the mediate the high salt content. Accelerated chemical reactions occur in charged microdroplets. The reduced reaction times making this technique ideal for a screening methodology for reaction conditions and pathway discovery. Reaction acceleration was exploited in preparative ES to discover new pathways and refine conditions to the formation of atropine. Preparative ES gives a binary response as to whether a synthetic route does or does not yield product and a successful reaction in spray guided the choice of possible reactions to pursue in microfluidics. This technique yielded a two-step pathway to the synthesis of atropine that had not previously been published. Reactive extractive electrospray was developed to address the difficulties in continuously accelerating multistep reactions, accelerating reactions in immiscible solvents and reagents, and further accelerating reactions by manipulating the voltages and polarities on individual reagents. Reactive extractive electrospray was used to continuously synthesize atropine by a multistep reaction with similar percent conversions as the two-step process in preparative ES. Reactive extractive electrospray was also used to study how voltage and polarity effects the formation of the Claisen-Schmidt based catalyzed condensation product. In the Hantzsch pyridine synthesis, the reagents used are not immiscible in the traditional bulk solvent, therefore an inferior solvent was necessary to accelerate the reaction in electrospray. Utilizing the dual emitter technique, the traditional bulk solvent was used without issue and the reaction was further accelerated. This reaction was accelerated online removing the distance and high flow rates necessary in previous publications. Herein is a discussion on metabolomics by ambient ionization mass spectrometry and reaction acceleration.

Degree

Ph.D.

Advisors

Cooks, Purdue University.

Subject Area

Chemistry|Analytical chemistry|Organic chemistry

COinS