Biomedical subjects

Richard R Willis

Publications and source records attributed to Richard R Willis.

3 recordsLinked to original sources

PubMed2002

Laser-activated membrane introduction mass spectrometry for high-throughput evaluation of bulk heterogeneous catalysts.

Laser-activated membrane introduction mass spectrometry (LAMIMS), a high-throughput screening method, evaluates heterogeneous catalysts under realistic reactor conditions. It is a precise, versatile system requiring no moving parts. The catalyst array is supported on carbon paper overlaid upon a silicone rubber membrane configured in a variation of membrane introduction mass spectrometry as introduced by Cooks. The carbon paper serves as a heat-dissipating gas diffusion layer that permits laser heating of catalyst samples far above the decomposition temperature of the polymer membrane that separates the array from the mass spectrometer vacuum chamber. A computer-controlled CO2 bar code writing laser is used for fine-tune heating of the catalyst spots above the base temperature of the LAMIMS reactor. The detailed design and performance of LAMIMS is demonstrated on arrays of "real world" bulk water-gas shift catalysts using natural and isotopically labeled reactor feed streams. A bulk catalyst array spot can be evaluated for activity and selectivity in as little as 1.5 min. All array screening results were confirmed by industrial microreactor evaluations.

Journal Article↗

PubMedDate not supplied

Split-pool method for synthesis of solid-state material combinatorial libraries.

The synthesis and analysis of inorganic material combinatorial libraries by the split-pool bead method were demonstrated at the proof-of-concept level. Millimeter-size spherical beads of porous gamma-alumina, a commonly used support material for heterogeneous catalysts, were modified with Al(13)O(4)(OH)(24)(H(2)O)(12)(7+) cations in order to promote irreversible adsorption of the anionic fluorescent dyes Cascade Blue, Lucifer Yellow, and Sulforhodamine 101. The compositions of individual beads were easily determined through three split-pool cycles using a conventional fluorescence plate reader. Small split-pool material libraries were made by adsorbing noble metal salts (H(2)PtCl(6), H(2)IrCl(6), and RhCl(3)) into the beads. Analysis of these beads by micro-X-ray fluorescence showed that quantitative adsorption of metal salts without cross-contamination of beads could be achieved at levels (0.3 wt % metal loading) relevant to heterogeneous catalysis. The method offers the potential for synthesis of rather large libraries of inorganic materials through relatively simple benchtop split-pool chemistry.

Journal Article↗

PubMedDate not supplied

Directed-sorting method for synthesis of bead-based combinatorial libraries of heterogeneous catalysts.

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 gamma-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 (approximately 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.

Catalysis↗