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Chemistry

Analytical chemistry

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Displaying 501 - 525 of 2094

Qualitative characterization of SRM 1597a Coal Tar for polycyclic aromatic hydrocarbons and methyl-substituted derivatives via normal-phase liquid chromatography and gas chromatography/mass spectrometry

June 29, 2017
Author(s)
Walter Wilson, Hugh Hayes, Lane Sander, Andres Campiglia, Stephen Wise
A normal-phase liquid chromatography (NPLC) fractionation procedure was developed for the characterization of a complex mixture of polycyclic aromatic hydrocarbons (PAHs) from a coal tar sample (Standard Reference Material (SRM) 1597a). Using a semi

Revisiting Shape Selectivity in Liquid Chromatography for Polycyclic Aromatic Hydrocarbons (PAHs) - Six-Ring and Seven-Ring Cata-condensed PAH Isomers of Molecular Mass 328 Da and 378 Da

June 28, 2017
Author(s)
Jorge O. Ona Ruales, Lane C. Sander, Walter Brent Wilson, Stephen Wise
The relationship of reversed-phase liquid chromatography retention on a polymeric C18 stationary phase and the shape of polycyclic aromatic hydrocarbons (PAHs) was investigated for three-ring to seven-ring cata-condensed isomers. We report the first

Associations between perfluorinated alkyl acids measured in blood and ovarian follicular fluid and ovarian function in women undergoing assisted reproductive treatment

June 26, 2017
Author(s)
Jessica A. Cloy-McCoy, Jacqueline T. Bangma, Jessica L. Reiner, John Bowden, John Schnorr, Michael Slowey, Tom O'Leary, Louis J. Guillette, Benjamin B. Parrott
Endocrine disrupting contaminants, in combination with other environmental variables, are associated with altered reproductive health. Assisted reproductive technology (ART) procedures offer valuable opportunities to explore the connections between

SI traceable determination of arsenic species in kelp (Thallus laminariae)

June 26, 2017
Author(s)
Lee L. Yu, Rolf L. Zeisler, Rachel C. Stanoyevitch
Kelp is a dietary supplement that contains significant amount of arsenic. Accurate assessment of dietary safety of kelp requires the determination of the arsenic species therein. A procedure was developed to extract the hydrophilic fraction of arsenicals

Normal-phase liquid chromatography retention behavior of polycyclic aromatic hydrocarbon and their methyl-substituted derivatives on an aminopropyl stationary phase

June 16, 2017
Author(s)
Walter Wilson, Hugh Hayes, Lane Sander, Andres D. Campiglia, Stephen Wise
Retention indices for 124 polycyclic aromatic hydrocarbons (PAHs) and 62 methyl-substituted (Me-) PAHs were determined using normal-phase liquid chromatography (NPLC) on a aminopropyl (NH2) stationary phase. PAH retention behavior on the NH2 phase is

Metabolomics Analysis of Effects of Commercial Soy-based Protein Products in Red Drum (Sciaenops ocellatus)

June 14, 2017
Author(s)
Fabio Casu, Aaron Watson, Justin Yost, John Leffler, Gibson Gaylord, Frederic Barrows, Paul A. Sandifer, Dan Bearden, Michael R. Denson
In this study we investigated the metabolic effects of four different commercial soy-based protein products on red drum (Sciaenops ocellatus) using NMR-based metabolomics along with unsupervised principal component analysis (PCA) to evaluate metabolic

Partial Ionization Cross Sections of Organic Molecules

June 13, 2017
Author(s)
Karl K. Irikura
Partial ionization cross sections are the absolute yields of specific ions from an electron- molecule collision. They are necessary for modeling plasmas and for determining the sensitivity of mass spectrometers, among other applications. One mass

Determination of the molar mass of argon from a high precision acoustic comparison

May 18, 2017
Author(s)
XiaoJuan Feng, Jintao Zhang, Michael R. Moldover, Inseok Yang, Mark Plimmer, H. Lin
This article describes the accurate determination of the molar mass of a sample of argon gas used for a determination of the Boltzmann constant. The method due to one of the authors [Moldover et al., J. Res. Natl. Bur. Stand. 93, 85-144 (1988)] uses the

Conformational Changes in Active and Inactive States of Human PP2C? characterized by Hydrogen/Deuterium Exchange-Mass Spectrometry

May 8, 2017
Author(s)
Sharlyn Mazur, Elyssia S. Gallagher, Subrata Debnath, Stewart R. Durell, Kyle Anderson, Lisa M. Jenkins, Ettore Appella, Jeffrey W. Hudgens
PPM serine/threonine protein phosphatases function in signaling pathways and require millimolar concentrations of Mn2+ or Mg2+ ions for activity. Whereas the crystal structure of human PP2Cα displayed two tightly bound Mn2+ ions in the active site, recent

DART-MS analysis of inorganic explosives using high temperature thermal desorption

May 4, 2017
Author(s)
Thomas P. Forbes, Edward R. Sisco, Matthew E. Staymates, John G. Gillen
An ambient mass spectrometry (AMS) platform coupling Joule heating thermal desorption (JHTD) and direct analysis in real time (DART) was developed, generating discretely pulsed rapid heating ramps and elevated temperatures for the detection of inorganic

CH3NH3PbI3 perovskites: Ferroelasticity revealed

April 14, 2017
Author(s)
Evgheni Strelcov, Qingfeng Dong, Tao Li, Jungseok Chae, Yuchuan Shao, Yehao Deng, Alexei Gruveman, Jinsong Huang, Andrea Centrone
Ferrolectricity has been proposed as a plausible meachanism to explain the high photovoltaic conversion efficiency in organic-inorganic perovskites; however, convincing experimental evidence in support to this hypothesis is still missing. Identifying and

The Hybrid Search: A Mass Spectral Library Search Method for Discovery of Modifications in Proteomics

April 3, 2017
Author(s)
Meghan C. Burke, Yuri A. Mirokhin, Dmitrii V. Tchekhovskoi, Sanford P. Markey, Stephen E. Stein, Jenny Heidbrink Thompson, Christopher Larkin
We present a mass spectral library based method to identify tandem mass spectra of peptides that contain unanticipated modifications and amino acid variants. We describe this as a ‘hybrid’ method since it combines matching both ion m/z and mass losses. The

Mass Spectral Library Quality Assurance by Inter-Library Comparison

April 2, 2017
Author(s)
William E. Wallace, Weihua Ji, Dmitrii V. Tchekhovskoi, Karen W. Phinney, Stephen E. Stein
A method to discover and correct errors in mass spectral libraries is described. Comparing across a set of highly curated reference libraries compounds that have the same chemical structure quickly identifies entries that are outliers. In cases where three

Quantifying Stability of Trace Explosives under Different Environmental Conditions

April 1, 2017
Author(s)
Edward R. Sisco, Marcela N. Najarro, Daniel V. Samarov, Jeffrey A. Lawrence
This work investigates the stability of trace deposits of six explosives (ETN, PETN, RDX, HMX, TNT, and Tetryl) to determine environmental stabilities and lifetimes. Explosives were inkjet printed directly onto PTFE coated fiberglass substrates and exposed
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