Laser activated membrane introduction mass spectrometry (LAMIMS) is a modification of membrane introduction mass spectrometry where a silicone membrane serves as a separator between an analyte stream ...and the vacuum of a quadrupole mass spectrometer. Carbon paper, commonly used as a fuel cell gas diffusion layer, has been overlaid upon the silicone membrane to serve as a support for catalyst array libraries that are heated by a CO
2 laser during evaluation. The LAMIMS reactor is a closed environment permitting steady state exposure of the catalyst library to the reactant stream. In this work, Pt/Al
2O
3 catalysts for the dehydrogenation of methylcyclohexane (MCH) to toluene have been ranked by LAMIMS. Spot-to-spot evaluation times (after preconditioning) are 1
min in this study. The data suggests that by optimization of signal-to-noise and spot-to-spot dwell times, ranking can be conducted at substantially under a minute per array spot candidate.
The goals of this paper are to describe the assembly of a simple Raman spectrometer that uses a nitrogen laser and other commonly available or easily purchasable components and to discuss the ways ...that this instrument can be used to enhance the educational experience in undergraduate physical and analytical chemistry laboratories.
BACKGROUNDHuman papillomavirus (HPV)-mediated oropharyngeal squamous cell carcinoma is a subset of head and neck cancer with a unique mechanism of carcinogenesis. Local disease is treated ...definitively with a multimodal approach. Navigating recurrences can be challenging, as they are sometimes indiscernible from de novo primary malignancies. Identification of dynamic biomarkers that are specific to HPV-mediated disease may assist in disease monitoring. We present a 78-year-old man who developed a squamous cell carcinoma in the lung 7 years after completing definitive chemoradiation for his p16+ head and neck squamous cell carcinoma. METHODSA novel assay for plasma circulating tumor HPV DNA was employed and provided a tool for longitudinal disease monitoring during therapy. CONCLUSIONWe bring attention to a novel assay and highlight its potential for use in the treatment paradigm of HPV-mediated oropharyngeal carcinoma.
The synthesis and analysis of inorganic material combinatorial libraries by a directed-sorting, split−pool bead method was demonstrated. Directed-sorting, split−pool, metal-loaded libraries were ...synthesized by adsorbing metal salts (H2PtCl6, SnCl2, CuCl2, and NiCl2) and metal standards (Pt, Cu, Ni in HCl) onto 2-mg porous γ-alumina beads in 96- or 384-well plates. A matrix algorithm for the synthesis of bead libraries treated each bead as a member of a row or column of a given matrix. Computer simulations and manual tracking of the sorting process were used to assess library diversity. The bead compositions were analyzed by energy-dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, electron probe microanalysis, inductively coupled plasma atomic emission spectroscopy, and inductively coupled plasma mass spectroscopy. The metal-loaded beads were analyzed by laser-activated membrane introduction mass spectroscopy (LAMIMS) for catalytic activity using methylcyclohexane dehydrogenation to toluene as a probe reaction. The catalytic activity of individual beads that showed minimal (∼20% of that of Pt on alumina) to high conversion could be determined semiquantitatively by LAMIMS. This method, therefore, provides an alternative to screening using microreactors for reactors that employ catalysts in the form of beads. The directed-sorting method offers the potential for synthesis of focused libraries of inorganic materials through relatively simple benchtop split−pool chemistry.
Thesis (Ph. D.)--University of Wisconsin--Madison, 1992.
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Nitrobenzene is photolyzed in a molecular beam at wavelengths between 220 and 320 nm. The primary photolysis pathways and their kinetic energy releases are determined using vacuum ultraviolet ...ionization in conjunction with time-of-flight mass spectrometry. Three primary photolysis pathways have been detected in the wavelength region between 220 and 320 nm: (UNFORMATTED TABLE OR EQUATION FOLLOWS)$$\eqalign{\rm C\sb6H\sb5NO\sb2&\to \rm C\sb6H\sb5 + NO\sb2,\cr\rm C\sb6H\sb5NO\sb2&\to \rm C\sb6H\sb5NO + O,\cr \rm C\sb6H\sb5NO\sb2&\to \rm C\sb6H\sb5O + NO\ (or\ C\sb5H\sb5 + CO + NO).\cr}$$(TABLE/EQUATION ENDS)The channel producing phenoxy and NO radicals releases relatively large amounts of kinetic energy, with approximately 19% of the available energy appearing in translation. The fragments in the other two channels, however, have only a small amount of kinetic energy (4-10%). The rotational and vibrational energy content of the NO fragment are measured by laser induced fluorescence studies. The average rotational energy content of the NO fragment is observed to be high, 0.32 $\pm$ 0.03 eV and 0.20 $\pm$ 0.02 eV, for the 226-nm and 280-nm photolysis of nitrobenzene, respectively. For both photolysis wavelengths, however, populations are observed for only v = 0 and not v = 1. An impulsive model and a statistical model are compared to the measured internal and kinetic energy distributions for the channel producing NO radicals. Although both models predict a high degree of rotational excitation and a low degree of vibrational excitation of the NO fragment, neither model describes the entire measured energy distribution adequately. If a mechanism consisting of a rearrangement on a nitrobenzene excited state surface to form phenyl nitrite and an impulsive breaking of the N-O bond along a steeply repulsive surface is considered, a combination of a statistical model to describe the rearrangement and an impulsive model to describe the breaking of N-O bond can be used. Although this model does not agree completely with the observed energy distributions, its predictions are closer to the measured energies.
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