Development of a High Performance Liquid Chromatography Method for the Analysis of Next-generation Cyanide Antidote, 3-mercaptopyruvate, in Plasma

Although the current FDA approved cyanide antidotes (i.e., sodium nitrite, sodium thiosulfate, and hydoxocoboalamine) are effective for treating cyanide poisoning, each individual antidote has major limitations, including large effective dosage, delayed onset of action, or dependence on enzymes generally confined to specific organs. To overcome these current limitations, next-generation cyanide antidotes are being investigated, including 3-mercaptopyruvate (3-MP). Analytical methods capable of detecting 3-MP from plasma are essential for the development of 3-MP as a nextgeneration cyanide antidote. Although 3-MP has been analyzed by LC-MS-MS, this instrument is not widely available. Therefore, a high performance liquid chromatography (HPLC) method with fluorescence detection (FLD) was developed to analyze 3-MP from swine plasma such that more labs could potentially perform the method. Sample preparation included spiking the plasma with the internal standard (3-mercaptopropionic acid) and reacting the 3-MP and IS with monobromobimane to prevent the characteristic dimerization of 3-MP. The method produced a limit of detection of 0.5 nM, a large dynamic range, and good accuracy and precision. The solid phase mixed-mode anion exchange sample preparation protocol produced excellent selectivity for the method. The wide availability and affordability of the instrumentation and the simple of the implementation method presented should allow more labs to contribute to further investigations of 3-MP as a promising cyanide antidote

Zeolite deactivation during hydrocarbon reactions: characterisation of coke precursors and acidity, product distribution

The catalytic conversion of hydrocarbons over zeolites has been applied in large scale petroleum-refining processes. However, there is always formation and retention of heavy by-products, called coke, which causes catalyst deactivation. This deactivation is due to the poisoning of the acid sites and/or pore blockage. The formation of coke on hydrocarbon processing catalysts is of considerable technological and economic importance and a great deal of work has been carried out to this study. The main aim of this work is to understand the deactivation of zeolite catalysts as a result of coke deposition. The deactivation by coke of USHY zeolite was investigated during catalytic conversion of hydrocarbons – 1-pentene, n-heptane and ethylbenzene – as representatives of olefins, paraffins and aromatics respectively, at different reaction temperatures, time-on-streams and composition. Three novel techniques, coke classification, thermogravimetric method for characterising coke precursors and indirect temperature programmed desorption (TPD) for catalyst acid sites characterisation were developed to further study catalyst deactivation mechanism. Product distribution, coke formation, characterisation of coke precursors, as well as the role of strong acid sites on hydrocarbon reactions are presented and discussed. During catalytic reactions of 1-pentene over USHY zeolite, cracking and hydride transfer were the predominant reactions in initial stage which deactivated rapidly allowing isomerisation to become the main reaction afterwards. Deactivation studies showed that coke formation was very strong initially which is in good correlation with the initial rapid deactivation. The hydrogen freed during this initial time from the formation of high C/H ratio coke components contributed to the formation of hydride transfer products. The amount of coke precursors decrease with increasing reaction temperature due to the higher desorption of coke precursors into gas phase while hard coke amount increased with temperature as expected from an activated process. The coke amount formed was not proportional to the reactant feed composition, because of a strong pseudo-zeroth- order initial coking on strong acidic sites. The thermogravimetric method provides insight into the chemical character of coke precursor components in terms of the mode of their removal and allows further classification of coke precursors into small and large coke precursors. The concentration and strength of acid sites of coked catalysts were studied by the TPD methodology. Besides, characterisation of coke precursors was also revealed. The initial deactivation preferentially on strong acid sites is very fast. The concentration of free acid sites is inversely correlated well with the total concentration of coke rather than individual coke groups. Coke precursors tend to be more stable at higher reaction temperatures. Furthermore, by selectively poisoning strong acid sites of USHY zeolite, it shows conclusively that strong acid sites are responsible for cracking and hydride transfer reactions as well as strong coke formation while weak acid sites can only catalyse double bond isomerisation

Synthesis of Metal, Oxide, Alloy, and intermetallic Nanocrystals for Catalysis

The synthesis of nanocrystals is the core of the nanoscience. The highly controlled nanomaterials are desirable for the studies of catalysis, in order to unambiguously correlate the catalytic properties with the structure and composition of catalysts. In this thesis, highly controlled nanocrystals are synthesized through solution phase synthesis. Shape controlled nanocrystals can be synthesized as cubes, octahedra, icosahedra, truncated cubes, cuboctahedra tetrapods, octapods and spheres. The nanocrystals with these morphologies selectively expose {100} and/or {111} facets as well as high-index facets, thus enabling various investigations of structure sensitive catalysis at the nanoscale. In addition to the shape control, the composition of metal catalysts is also tunable by making alloy or intermetallic nanocrystals. The nanocrystals of Pt-Mn, Pt-Fe, Pt-Co, Pt-Ni, Pt-Cu, Pt-Zn, Pt-Pb, Pt3Mn, Pt3Fe, Pt3Co, Pt3Ni, Pt3Zn, Pt3Pb, FePt, and etc. allow the fundamental exploration of catalysis. Oxides, heterostructures, as well as artificial crystals which have a long range ordered crystalline structure, are also prepared. These highly controlled nanomaterials have been demonstrated as ideal model materials for studies of catalysis. In this thesis, formic acid and methanol electrooxidation, oxygen reduction reaction, oxygen storage, CO oxidation, and enhanced stability are discussed