Contemporary mass spectrometry (MS) instrumentation featuring electrospray ionisation (ESI) or matrix-assisted laser desorption/ionisation (MALDI) ion sources were used to characterise the polymer distributions generated in various free radical polymerisations, allowing insights to be gained into the reaction mechanisms operating in these systems. In studying atom transfer radical polymerisation (ATRP) mediated star polymerisations of methyl acrylate (MA), ESI was found to be more effective in obtaining a comprehensive list of the distinct products present in the samples under investigation when compared to the employed MALDI technique. Furthermore, these studies showed that terminal Br losses observed at relatively high monomer to polymer conversions could be accounted for via mechanisms involving the acetone derived radicals (CH3)2??OH, ??H3 and ??H2COCH3. Through the use of ESI, it was found that for bulk polymerisations of MA and aqueous media polymerisations of N-isopropylacrylamide (NIPAAm) initiated using 60Co ??-irradiation and mediated via reversible addition-fragmentation chain transfer (RAFT), hydrogen radicals formed via the radiolysis of RAFT agent and/or monomer, and in the case of the NIPAAm system, water, are capable of initiating the polymerisations. In the NIPAAm polymerisations under scrutiny, it was also observed that hydroxyl radicals generated via the radiolysis of water may contribute towards the initiation process, and that propagating chains can potentially become terminated via trithiocarbonate cleavage reactions. By using ESI instruments to characterise oligomer samples produced via the free radical polymerisations of vinyl phosphonates, it was observed that chain propagations are initiated via activated monomer radicals, which likely form as a result of transfer reactions involving initiator fragments and vinyl phosphonate monomer units. Transfer to monomer reactions were suggested to limit chain growth in these systems, and evidence was also found for scission reactions involving alkoxy moieties which are formed via intramolecular methine carbon abstraction reactions. Characterisation of the polymer distributions generated in R-group approach RAFT MA star polymerisations using an ESI instrument allowed formation processes operating in acrylate star living/controlled radical polymerisations (CRPs) to be ascertained. Initiator fragment derived linear chains, ideal stars, star-star couples, and terminated star products formed as a result of disproportionation and combination reactions were detected. Evidence for mid-chain radical (MCR) derived reaction pathways was also observed; specifically, for termination reactions involving intermolecularly formed MCRs on both star arms and linear chains, and for re-propagation of intermolecularly formed MCRs on star arms.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Jennifer S. Brodbelt. Vita. Includes bibliographical references. Also available from UMI.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 144-158).

The electrospray survivability of B. subtilis spores and E. coli was tested in atmospheric mobility experiments. E. coli did not survive electrospray charging and desolvation, but B. subtilis did. Experimental conditions ensured that any surviving bacteria were charged, desolvated, and de-agglomerated. B. subtilis was also found to survive both positive and negative electrospray and subsequent introduction into vacuum conditions. Attempts were made to measure the charge distribution of viable B. subtilis spores using electrostatic deflection. From those experiments, it was found that either the spores do not become highly charged under the electrospray conditions used or only spores in a low positive or negative charge state survive.

The billion dollar pharmaceutical research and development pipeline suffers greatly from high attrition rates of novel therapeutic compounds within pre-clinical and clinical trials. Poor bioavailability in many new drugs, originating in the various methodologies of high throughput screening, may explain part of these growing failure rates. One interpretation of this phenomenon relies on bioavailability's correlation with aqueous solubility; much modern processing allows chemicals to fully develop without touching water, yielding upwards of 90% of new chemical entities practically insoluble in aqueous media. Thus, one approach to alleviating bioavailability and potentially clinical attrition rates necessitates augmented aqueous solubility. The amorphous nanoparticle presents the largest boost in aqueous solubility of a chemical through processing alone. In this contribution, we propose electrospray as a novel, competitive candidate to produce pharmaceutical amorphous nanoparticles with the intent of augmenting solubility. Electrospray represents an idyllic nominee for three reasons: repeatability, flexibility, and scalability. Electrospray offers low batch to batch variation with less than 30% relative standard deviation between various droplets. This triumphs over the several orders of magnitude in variation in pneumatic sprays. Electrospray's flexibility draws from its ability to attain diameters over several orders of magnitude, ranging from hundreds of microns to several nanometers; in this contribution droplets are produced between 500 nm and 1[micro]m. Finally, electrospray displays scalability to any industrial requirement; though a single nozzle operates at mere microliters per hour, a single multiplexed array of emitters may increase this throughput by several orders of magnitude. This exploration, utilizing Indomethacin as a model low solubility chemical, verifies electrospray as a compatible processing tool for the pharmaceutical industry. Scanning electron microscopy coupled with the image analysis software ImageJ gleans the size and shape of emitted (and dried) particles. Amorphicity verification of particles employs grazing angle x-ray diffraction. Finally, ultraviolet and visual spectrum spectroscopy evaluates the solubility advantage of particles.

No / Competition experiments in which 1,2-phenylenediamine, C6H4(NH2)2, condenses with equimolar quantities of benzil, (C6H5CO)2, and a 3,3'- or 4,4'-disubstituted benzil (XC6H4CO)2 (X = F, Cl, Br, CH3 or CH3O) to form a mixture of 2,3-diphenylquinoxaline and the corresponding 2,3-diarylquinoxaline (Ar = XC6H4) in the microdroplets produced in a nebuliser allow a Hammett relationship with a ρ value of 1.85 to be developed for this accelerated condensation in the nebuliser. This structure reactivity relationship reveals that an appreciable amount of negative charge builds up on the carbon of the carbonyl group of the benzil during the rate-limiting step of the reaction, thus confirming that this process involves nucleophilic addition of the 1,2-phenylenediamine to the benzil. In general, the presence of an electron donating substituent, particularly in the 4 and 4' positions, in the benzil retards the reaction, whereas an electron attracting substituent, especially in the 3 and 3' position, accelerates it. / 2019 British Mass Spectrometry Summer Studentship for NWF.

Perovskite solar cells have attracted much attention both in research and industrial domains. An unprecedented progress in development of hybrid perovskite solar cells (HPSCs) has been seen in past few years. The power conversion efficiencies of HPSCs has been improved from 3.8% to 24.2% in less than a decade, rivaling that of silicon solar cells which currently dominate the solar cell market. Hybrid perovskite materials have exceptional opto-electrical properties and can be processed using cost-effective solution-based methods. In contrast, fabrication of silicon solar cells requires high-vacuum, high-temperature, and energy intensive processes. The combination of excellent opto-electrical properties and cost-effective manufacturing makes hybrid perovskite a winning candidate for solar cells. As power conversion efficiencies of HPSCs improves beyond that of the established solar cell technology and their long-term stability increases, one of the crucial hurdles in the path to commercialization remaining to be adequately addressed is the cost-effective scalable fabrication. Spin-coating is the prevailing method for fabrication of HPSCs in laboratories. However, this technique is limited to small areas and results in excessive material waste. Two types of scalable manufacturing methods have been successfully demonstrated to fabricate HPSCs: (i) meniscus-assisted coating such as doctor-blade coating and slot-die coating; and (ii) dispersed deposition based on the coalescence of individual droplets, such as inkjet printing and spray coating. Electrospray printing belongs to the second category with advantages of high material utilization rate and patterning capability along with the scalability and roll-to-roll compatibility. In Chapter 3 of this dissertation, electrospray printing process is described for manufacturing of HPSCs in ambient conditions below 150 C. All three functional layers were printed using electrospray printing including perovskite layer, electron transport layer, and hole transport layer. Strategies for successful electrospray printing of HPSCs include formulation of the precursor inks with solvents of low vapor pressures, judicial choice of droplet flight time, and tailoring the wetting property of the substrate to suppress coffee ring effects. Implementation of these strategies leads to pin-hole free, low surface roughness, and uniform perovskite layer, hole transport layer and electron transport layer. The power conversion efficiency of the all electrospray printed device reached up to 15.0%, which is among the highest to date for fully printed HPSCs. The most efficient HPSCs rely on gold and organic hole-transport materials (HTMs) for achieving high performance. Gold is also chosen for its high stability. Unfortunately, the high price of gold and high-vacuum along with high-temperature processing requirements for gold film is not suitable for the large-scale fabrication of HPSCs. Carbon is a cheap alternative electrode material which is inert to hybrid perovskite layer. Due to the ambipolar transport property of hybrid perovskite, perovskite itself can act as a hole conductor, and the extra hole transport layer can be left out. Carbon films prepared by doctor-blade coating method have been reported as the top electrode in HPSCs. The efficiencies of these devices suffer from the poor interface between the doctor-blade coated carbon and the underlying perovskite layer. In Chapter 4, electrospray printing was applied for the fabrication of carbon films and by optimizing the working distance during electrospray printing, the interface between carbon and the underlying perovskite layer was greatly improved compared to the doctor-blade coated carbon film. The resulting HPSCs based on the electrospray printed carbon electrode achieved higher efficiency than that based on doctor-blade method and remarkably, this performance is close to that of gold based devices. In Chapter 5, preliminary results are provided on the laser annealing of hybrid perovskite films to further advance their scalable manufacturing. All layers of HPSCs require thermal annealing at temperature over 150 C for about half an hour or longer. The time-consuming conventional thermal annealing complicates the fabrication process and is not suitable for continuous production. High temperature over150 C is also not compatible with flexible substrates such as PET. Laser annealing is a promising method for overcoming these issues. It has several other advantages including compatibility with continuous roll-to-roll printing, minimal influence on non-radiated surrounding area, and rapid processing. Laser annealing can be integrated with the electrospray process to realize the continuous fabrication of hybrid perovskite film. Rapid laser annealing process with optimized power density and scanning pattern is demonstrated here for annealing perovskite films. The resulting hybrid perovskite film is highly-crystalline and pin-hole free, similar to that obtained from conventional thermal annealing. / Doctor of Philosophy / Hybrid perovskite solar cell (HPSC) is a promising low-cost and high efficiency photovoltaic technology. One of the big challenges for it to be commercially competitive is scalable fabrication method. This dissertation focuses on developing electrospray printing technology for HPSCs. This is a scalable method with high material usage rate that naturally lead to large scale fabrication of HPSCs. Electrospray printing parameter space was systematically studied and optimized to synthesize high-quality perovskite films and other functional layers including hole transport layer and electron transport layer. All electrospray printed high-efficiency perovskite solar cell devices were successfully demonstrated under the ambient condition and low temperature. Another achievement of this thesis is the electrospray printing of carbon film to replace the costly gold electrode in perovskite solar cells. Laser annealing technique is demonstrated for HPSCs, which is compatible with continuous fabrication and integrates easily with electrospray printing.

Brevetoxins are natural neurotoxins that are produced by “red tide” algae. In this study, brevetoxin-1 and brevetoxin-2 were incubated with rat liver hepatocytes and rat liver microsomes, respectively. After clean-up steps, samples were analyzed by liquid chromatography-electrospray mass spectrometry (LC-ES-MS). Two metabolites were found for brevetoxin-1: brevetoxin-1-M1 (MW 900 Da), formed by converting one double bond in the E or F ring into a diol; and brevetoxin-1-M2 (MW 884 Da), a hydrolysis product of brevetoxin-1 involving opening of the lactone ring. The incubation study of brevetoxin-2 found two metabolites. Brevetoxin-2-M1 (MW 912 Da) was elucidated by negative mode LC-MS/MS to be the hydrolysis product of brevetoxin-2. The second metabolite (brevetoxin-2-M2, MW 896 Da) was deduced to be brevetoxin-3. All brevetoxins have high affinities for sodium ions. Attempts to obtain informative product ions from the collision induced decomposition (CID) of [M + Na]+ brevetoxin precursor ions only resulted in uninformative sodium ion signals. In our nano-electrospray experiments, the addition of ammonium fluoride resulted in the formation of the ammonium adduct or protonated brevetoxin with a concomitant decrease of the sodium adduct peak. Product ion spectra of [M + NH4]+ and [M + H]+ were similar and provided useful structural information. The optimal values for ammonium fluoride concentration and the cone voltage were experimentally determined. In negative mode electrospray, without additives, deprotonated molecules of brevetoxins do not appear in high abundances, and thus are not well-suited for CID experiments. Several anions were tested for their abilities to form brevetoxin-anion adducts by mixing ammonium salts of these anions with brevetoxin-2 and brevetoxin-3. Under CID, [M + Cl]-, [M + Br]-, [M + OAc]-, [M + HCOO]-, [M + NO3]- adducts all produced only the respective anions in CID experiments, and thus, gave no structural information. In contrast, upon CID, both [M + F]- and [M + HCO3]- precursor adducts gave structurally-informative fragment peaks that exhibited similarities to those of [M - H]- ions; the detailed fragmentation mechanisms are discussed. In comparison, fluoride is a better choice to study brevetoxins in negative ES-MS by the anionic adduct approach.

A crescente demanda por água doce de boa qualidade, associada ao aumento na frequência de florações tóxicas de cianobactérias em reservatórios utilizados para consumo humano, levou à publicação da Portaria nº. 518/04 pelo Ministério da Saúde. Entre outros parâmetros de potabilidade, as empresas fornecedoras de água tratada devem realizar o monitoramento de cianotoxinas. Para tanto, métodos analíticos rápidos e precisos para a determinação destes compostos são imprescindíveis. Neste contexto, o presente trabalho teve como objetivo empregar a cromatografia líquida acoplada à espectrometria de massas para o estudo das principais cianotoxinas em território nacional: microcistinas, anatoxina-a(s), cilindrospermopsina e saxitoxinas. Os resultados obtidos estão distribuídos em capítulos específicos dedicados a cada grupo de toxinas. Dessa forma, o primeiro capítulo apresenta um estudo de fragmentação na fase gasosa de ânions de microcistinas em um equipamento do tipo orbitrap. É demonstrado que o modo negativo de ionização por electrospray fornece informações estruturais importantes e complementares ao modo positivo de ionização. Uma abertura seletiva do peptídeo cíclico é proposta e mecanismos discutidos, o que facilita a interpretação de resultados durante a caracterização de variantes desconhecidas. O modelo de fragmentação desenvolvido foi utilizado para identificar a variante [Leu1]MC-LR em um extrato de Microcystis spp. O segundo capítulo descreve metodologias qualitativas de LC/MS para o monitoramento e identificação do organofosforado natural anatoxina-a(s), cuja análise é prejudicada pela ausência de padrões comerciais. A cromatografia de interação hidrofílica foi empregada e mecanismos de fragmentação na fase gasosa propostos, discutindo-se os íons característicos desta estrutura química. Tal modelo permitiu a identificação desta toxina nas cepas de Anabaena oumiana ITEP-25 e ITEP-26 pela primeira vez. O terceiro capítulo disserta sobre os mecanismos de fragmentação na fase gasosa da toxina cilindrospermopsina quando ionizada por electrospray na forma de aduto com metais alcalinos. Diferenças nas vias de fragmentação são demonstradas de acordo com o raio atômico do metal formador do aduto, com implicações práticas na sua determinação cromatográfica. Já o quarto capítulo discute os mecanismos de fragmentação de variantes sulfatadas de saxitoxinas (GTX1e4, GTX2e3, dcGTX2e3, GTX5) após ionização por electrospray no modo positivo e negativo. É demonstrado pela primeira vez que uma conformação estrutural específica do grupamento sulfato explica a intensa eliminação de SO3 observada para as variantes GTX1, GTX2 e dcGTX2 no modo positivo de ionização. Por outro lado, o modo negativo de ionização apresenta vantagens uma vez que a dissociação na fonte é insignificante se comparada à dissociação observada no modo positivo. Como resultado, métodos quantitativos no modo negativo podem apresentar maior sensibilidade, permitindo a detecção destas toxinas em amostras ambientais em quantidades mais baixas. De maneira geral, conclui-se que a cromatografia líquida acoplada à espectrometria de massas é ferramenta poderosa para a análise quali e quantitativa das principais cianotoxinas, podendo ser amplamente empregada para o monitoramento de água para consumo humano. / The increasing occurrence of toxic cyanobacterial blooms in reservoirs used to supply drinking water for human consumption has prompted the publication of resolution 518/04 by the Brazilian Ministry of Health. Among other quality requirements, the monitoring of cyanotoxins in treated water is mandatory for companies responsible for potable water distribution. Therefore, precise and rapid analytical methods are essential. In this context, the aim of this work is to employ liquid chromatography coupled to mass spectrometry to study the most important cyanotoxins in our country: microcystins, anatoxin-a(s), cylindrospermopsis and saxitoxins. The obtained results are distributed in four chapters, each one dedicated to a single group of toxins. In this way, chapter one presents the gas-phase fragmentation behavior of deprotonated microcystins in an Orbitrap instrument. It is demonstrated that electrospray negative ionization can provide significant structural information about microcystins. These results are complementary to the positive ionization mode. A selective ring opening process is proposed and possible mechanisms are discussed, which may facilitate data interpretation when unknown variants are considered. The general fragmentation model was further applied to the characterization of [Leu1]MC-LR in a Microcystis spp. cell extract. The second chapter describes qualitative analytical methods for the identification of anatoxin-a(s), a natural organophosphate whose determination is hampered by the lack of commercial standards. Hydrophilic interaction liquid chromatography was employed and fragmentation mechanisms proposed, identifying the characteristic product ions of this toxin. The developed methods were further used to identify anatoxin-a(s) for the first time in Anabaena oumiana strains ITEP-25 and ITEP-26. The third chapter presents data related to the gas-phase fragmentation behavior of cylindrospermospin when this toxin is ionized as metal adducts. Different fragmentation pathways are accessed depending on the atomic radius of the metal cation involved. Practical implications for the chromatographic analysis of this toxin are presented. The last chapter describes the fragmentation behavior of sulphate-containing saxitoxin variants (GTX1&4, GTX2&3, dcGTX2&3, GTX5) after electrospray ionization in both the positive and negative modes. A mechanism for the intense SO3 elimination from [M+H]+ ions from GTX1, GTX2 and dcGTX2 is proposed for the first time and relies on a specific structure conformation. On the other hand, the negative ionization mode shows much less in-source dissociation when compared to the positive mode. As a consequence, methods based on negative ionization might be more sensitive for sulfate-containing variants, allowing the detection of lower amounts of these toxins in environmental samples. At the end, it can be concluded that liquid chromatography is a well-suited and powerful technique for the qualitative and quantitative analysis of cyanotoxins, being an invaluable contribution to water safety evaluation.