Combinatorial screening of heterogeneous catalysis in selective oxidation of naphthalene by laser-induced fluorescence imaging

Heterogeneous catalysis is one of the most important processes in the petroleum and the chemical industries. To be able to screen catalysts at high throughput will dramatically improve performance and reduce costs. Here we used laser-induced fluorescence imaging as a high-throughput screening technique in the combinatorial discovery of active catalysts for naphthalene oxidation. Binary catalysts of V-Mo-O, V-Sn-O, V-Ti-O, and V-W-O in various 15-member libraries were screened. Laser ablation ICPMS was employed to confirm the composition of the individual catalysts in the combinatorial library. The addition of MoO3, WO3, SnO2, and TiO2 to V2O5 did not improve the catalytic activity in the conversion of naphthalene to naphthoquinone, but the overall activity was found to increase for certain binary samples. The screening of ternary catalysts of V-Sn-Mo-O revealed that the combination of V (45%)-Sn (45%)-Mo (10%) gave 70% higher catalytic activity than pure V2O5 in converting naphthalene to naphthoquinone. Reaction temperature and sample preparation effects on the activity and selectivity of catalysts are also studied in a combinatorial manner.

Measurement of trace elements in proteins extracted from liver by size exclusion chromatography-inductively coupled plasma-mass spectrometry with a magnetic sector mass spectrometer

Proteins are extracted from liver into aqueous buffer at pH 7 and separated by size exclusion chromatography (SEC). Inductively coupled plasma mass spectrometry (ICP-MS) with a magnetic sector mass spectrometer is used to identify those protein fractions that contain Cu, Zn, Mn, Fe, Cd, S, P, Mo, Co, Ca, or Mg. The experimental setup provides very high sensitivity. Measurements at medium spectral resolution remove polyatomic interferences for some difficult elements like Fe, S, and P. Some elements are found in different molecular weight proteins; for example, cadmium binds to four different protein fractions (>400 kDa, 70 kDa, and metallothionein). Other elements like Mo, Ca, and Mg are present only in low-molecular-weight proteins or other small molecules.

Mass resolution of 11,000 to 22,000 with a multiple pass quadrupole mass analyzer

CO+ and N+2 are separated with resolution of 11,000 [full width half maximum (FWHM)] using a conventional quadrupole mass spectrometer by applying square wave voltages to the entrance and exit lenses to trap or reflect the ions for multiple passes. A resolution of 22,000 (FWHM) with 63% of the total signal remaining is attained using multiple passes when ions are stored between injection pulses. Gated ion extraction also reduces the mass shift and number and intensity of artifact peaks and permits better resolution compared to the performance obtained when the ions are injected continuously.

Speciation of trace elements in proteins in human and bovine serum by size exclusion chromatography and inductively coupled plasma-mass spectrometry with a magnetic sector mass spectrometer

Proteins are separated by size exclusion chromatography while atomic ions from the inorganic elements are detected on-line by inductively coupled plasma-mass spectrometry. A double focusing mass analyzer provides very high sensitivity, low background, and sufficient spectral resolution to separate the atomic ions of interest from most polyatomic ions at the same nominal m/z value. The chromatograms show the distribution of the elements of interest between protein-bound and free fractions and provide the approximate molecular weights of those protein fractions that contain the elements monitored. The distribution of various elements, including V, Mo, Fe, Co, Mn, and lanthanides, in human or bovine serum samples are shown. Alkali metals and Tl are present primarily as free metal ions and are not bound to proteins. Inorganic elements spiked into the serum samples can be followed into various proteins. EDTA does not remove Fe, Pb, Sn, or Th from the proteins but does extract Mn from some proteins. Procedures for determining the effects of breaking disulfide linkages on the metal binding characteristics of proteins are also described.

Base Hydrolysis of Methyltrioxorhenium. The Mechanism Revised and Extended: A Novel Application of Electrospray Mass Spectrometry

The full kinetic pH profile for the base-promoted decomposition of MTO to CH(4) and ReO(4)(-) was examined with the inclusion of new data at pH 7-10. Spectroscopic and kinetic data gave evidence for mono- and dihydroxo complexes: MTO(OH(-)) and MTO(OH(-))(2). Parallel unimolecular eliminations of methane from these species account for the rate-pH profile; the respective rate constants are MTO(OH(-)), k = 4.56 x 10(-)(5) s(-)(1) and MTO(OH(-))(2), k = 2.29 x 10(-)(4) s(-)(1) at 25 degrees C. Some kinetic data were acquired with electrospray mass spectrometry to monitor the buildup in the concentration of perrhenate ions. Reliable signals for each of the isotopomers of ReO(4)(-) were obtained by this method with initial MTO concentrations of 160 &mgr;M.