Utility of three types of mass spectrometers for determining elemental compositions of ions formed from chromatographically separated compounds

Concentration factors of 1000 and more reveal dozens of compounds in extracts of water supplies. Library mass spectra for most of these compounds are not available, and alternative means of identification are needed. Determination of the elemental compositions of the ions in mass spectra makes feasible searches of commercial and chemical literature that often lead to compound identification. Instrumental capabilities that constrain the utility of a mass spectrometer for determining ion compositions for compounds that elute from a chromatographic column are scan speed, mass accuracy, linear dynamic range, and resolving power. Mass peak profiling from selected ion recording data (MPPSIRD) performed with a double-focusing mass spectrometer provides the best combination of these capabilities. This technique provides unique ion compositions for ions of higher mass from compounds eluting from a gas chromatograph than can be obtained by orthogonal acceleration time-of-flight (oa-TOF) or Fourier transform ion cyclotron resonance mass spectrometry. Multiple compositions are usually possible for an ion with a mass exceeding 150 Da within the error limits of the mass measurement. The correct composition is selected based on measured exact masses of the mass peak profiles resulting from isotopic ions higher in mass by 1 and 2 Da and accurate measurement of the summed abundances of these isotopic ions relative to the monoisotopic ion. A profile generation model (PGM) automatically determines which compositions are consistent with measured exact masses and relative abundances. The utility of oa-TOF and double-focusing mass spectrometry using ion composition elucidation (MPPSIRD plus the PGM) are considered for determining ion compositions of two compounds found in drinking water extracts and a third compound from a monitoring well at a landfill. Published in 2002 by John Wiley & Sons, Ltd.     

Gadolinium‐Decorated Silica Microspheres as Redox‐Responsive MRI Probes for Applications in Cell Therapy Follow‐Up

The redox microenvironment within a cell graft can be considered as an indicator to assess whether the graft is metabolically active or hypoxic. We present a redox‐responsive MRI probe based on porous silica microparticles whose surface has been decorated with a Gd‐chelate through a disulphide bridge. Such microparticles are designed to be interspersed with therapeutic cells within a biocompatible hydrogel. The onset of reducing conditions within the hydrogel is paralleled by an increased clearance of Gd, that can be detected by MRI.     

Semiconductor saturable absorber mirror structures with low saturation fluence

We present two novel semiconductor saturable absorber mirror (SESAM) designs which can exhibit more than ten times lower saturation fluence than classical SESAM devices. Design considerations and characterization data are presented. These devices are particularly suited for passively mode-locked lasers with ultra-high repetition rates.     

Preparation and characterization of manganese- and samarium-manganese-alumina pillared montmorillonites

A Na-montmorillonite was intercalated with manganese- and samarium-manganese-aluminium solutions. The pillared montmorillonites were characterized by X-ray diffraction and nitrogen adsorption. The presence of manganese and samarium-manganese citrates in the intercalation process modify the distance between the clay sheets and the microporous structure of the pillared montmorillonites.     

Event excess in the MiniBooNE search for ¯νμ→¯νe oscillations

The MiniBooNE experiment at Fermilab reports results from a search for ˉν_{μ}→ˉν_{e} oscillations, using a data sample corresponding to 5.66×102? protons on target. An excess of 20.9±14.0 events is observed in the energy range 475相似文献   

Nucleation of the titanium α and β phases. in situ study of the dislocation role by synchrotron X-ray topography

This “in situ” and real time study is an approach to the role of matrix dislocations in the nucleation of the α or β phases in titanium single crystals. When the dislocations interact, forming tangles, subboundaries…, the residual stresses, present at the transformation temperature, trigger the new phase. If the dislocations are isolated at the transformation temperature they are destabilized by the large crystalline anisotropy resulting from the vibrational entropy dependence with the temperature. These dislocations disappear and do no act as preferential nucleation sites.     

Selenofonsartan analogues: novel selenium-containing antihypertensive compounds

2-Butyl-4-(methylseleno)-1-[[2′-(1H-tetrazol-5-yl)-1,1′-biphenyl-4-yl]methyl]-1H-imidazole-5-carboxylic acid (4) and 2-butyl-4-(phenylseleno)-1-[[2′-(1H-tetrazol-5-yl)-1,1′-biphenyl-4-yl]methyl]-1H-imidazole-5-carboxylic acid (5) have been prepared and tested for AT₁ receptor antagonist properties. Both compounds proved to be potent AT₁ receptor antagonists, with pK_b estimates indicating that these selenides are very effective at blocking AT₁ receptor mediated responses.