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Chemistry

Analytical chemistry

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Displaying 1176 - 1200 of 2094

Electrospray Tandem Quadrupole Fragmentation of Quinolone Drugs and Related Ions. On the Reversibility of Water Loss from Protonated Molecules

November 30, 2010
Author(s)
Pedatsur Neta, Bhaskar Godugu, Yuxue Liang, Yamil Simon, Xiaoyu Yang, Stephen E. Stein
Selected reaction monitoring (SRM) of quinolone drugs showed1 different sensitivities in aqueous solution vs. biological extract. The authors suggested formation of two singly protonated ions with different behavior, one undergoing loss of H 2O and the

Novel Reduced Pressure-Balance Syringe for Chromatographic Analysis

November 19, 2010
Author(s)
Bret Windom, Thomas J. Bruno
When withdrawing a fluid sample from an apparatus at reduced pressures for additional chromatographic analyses, a gas tight plunger syringe proves ineffective as it does not create a substantial pressure differential to pull a fluid from a reduced pressure

A Microwave Study of Hydrogen-Transfer-Triggered Methyl-Group Rotation in 5-Methyltropolone

November 10, 2010
Author(s)
Vadim V. Ilyushin, Emily A. Cloessner, Yung-Ching Chou, Laura B. Picraux, Jon T. Hougen, Richard Lavrich
We present here the first experimental and theoretical study of the microwave spectrum of 5-methyltropolone, which can be visualized as a 7-membered aromatic carbon ring with a five-membered hydrogen-bonded cyclic structure at the top and a methyl group at

Electron ionization and gas-phase ion molecule reactions of methylcyclohexane

November 9, 2010
Author(s)
C. Q. Jiao, Karl Irikura, S, F. Adams, A Garscadden
Absolute cross sections for electron impact ionization of methylcyclohexane (MCH, C 7H 14) are measured as a function of the electron energy in a range of 10 to 200 eV. The reactions between selected hydrocarbon ions with MCH, mainly via hydride transfer

High precision, broadband optical measurements with fiber laser frequency combs

November 2, 2010
Author(s)
Nathan R. Newbury, Ian R. Coddington, Esther Baumann, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot
Optical frequency combs have been used extensively, and with remarkable success, to measure the absolute frequency of cw lasers. The use of frequency combs has also expanded to include applications such as precision ranging, component metrology, and

Fast high-resolution frequency agile spectroscopy of laser sources

October 24, 2010
Author(s)
Fabrizio R. Giorgetta, Ian R. Coddington, Esther Baumann, William C. Swann, Nathan R. Newbury
Time-resolved, high-accuracy and high-resolution spectroscopy of frequency-agile cw lasers is critical to realizing their full potential for sensing, but is not possible with conventional spectroscopy methods. We demonstrate a dual comb-based spectrometer

Detection and Characterization of Selenoproteins by Tandem Mass Spectrometry Assisted by Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Application to Human Plasma Selenoproteins

October 22, 2010
Author(s)
Guillaume Ballihaut, Lisa Kilpatrick, Eric L. Kilpatrick, William Davis
There has been an on-going effort and long term goal to accurately assess selenium status and selenium nutritional requirement in humans through the quantification of human plasma selenoprotein P (SelP) and glutathione peroxidase 3 (GPx3). To achieve this

Organic Compounds in the C3H6O3 Family: Microwave Spectrum of cis-cis-Dimethyl Carbonate

October 18, 2010
Author(s)
Francis J. Lovas, David F. Plusquellic, Susanna L. Widicus Weaver, B. A. McGuire, G. A. Blake
Geometry optimization calculations on 13 members of the C3H6O3 family of organic species have been carried out to determine their relative binding energies. Dimethyl carbonate [(CH3)2CO3] is one of the lower energy species in this family, which includes

Application of Inkjet Printing Technology to Produce Test Materials of 1,3,5-Trinitro-1,3,5 Triazcyclohexane for Trace Explosive Analysis

October 15, 2010
Author(s)
Eric S. Windsor, Marcela N. Najarro, Anna N. Bloom, Bruce A. Benner Jr, Robert A. Fletcher, John G. Gillen, Richard Lareau, Inho Cho, Mike Boldmand
The feasibility of using piezoelectric drop-on-demand inkjet printing to prepare test materials for trace explosive analysis is demonstrated. Both pure high explosives and plastic-bonded putty explosives were formulated into inkjet printable solutions and

Elemental Analysis of a Single-Walled Carbon Nanotube Candidate Reference Material

October 15, 2010
Author(s)
Rolf L. Zeisler, Rick L. Paul, Rabia Oflaz, Lee L. Yu, Jacqueline L. Mann, William R. Kelly, Brian E. Lang, Stefan D. Leigh, Jeffrey A. Fagan
A material containing single-walled carbon nanotubes (SWCNTs) together with other carbon species, cata-lyst residues, and trace element contaminants has been prepared by the National Institute of Standards and Technology for characterization and

Properties for Accurate Gas Flow Measurements

October 15, 2010
Author(s)
John D. Wright
Accurate gas properties are needed to take full advantage of the low uncertainties provided by NIST’s Gas Flow Calibration Services. If a flowmeter user and NIST use different values for these properties (molecular mass, compressibility, density, viscosity

Thermochemistry of Ammonium Nitrate, NH4NO3, in the Gas Phase

October 7, 2010
Author(s)
Karl K. Irikura
Hildenbrand and coworkers have shown recently that the vapor above solid ammonium nitrate includes molecules of NH4NO3, not only NH3 and HNO3 as previously believed. Their measurements led to thermochemical values that imply an enthalpy change of D298 = 98

Unique para-effect in electron ionization mass spectra of bis(perfluoroacyl) derivatives of bifunctional aminobenzenes

September 15, 2010
Author(s)
Kirill V. Tretyakov, Nino G. Todua, Roman S. Borisov, Vladimir G. Zaikin, Stephen Stein, Anzor I. Mikaia
A new kind of "para-effect" under EI conditions has been discovered for a series of bis(perfluoroacyl) derivatives of o-, m- and p- phenylendiamines, hydroxybenzeneamines and mercaptobenzeneamines of a common structure RCOX C 6H 4 NHCOR (X = NH, S, O; R =

Synthesis and Electronic Properties of the Misfit Layered Compound [(PbSe)1.00]1[MoSe2]1

September 1, 2010
Author(s)
Ian M. Anderson, Michael D. Anderson, Andrew A. Herzing, Colby Heideman, Raimar Rostek, David C. Johnson
An ultra-low thermal conductivity compound with the ideal formula [(PbSe)1.00]1[MoSe2]1 has been successfully crystallized across a range of compositions. The lattice parameters varied from 12.41 Å to 12.75 Å and the quality of the observed 00ℓ diffraction
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