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Chemistry

Analytical chemistry

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Displaying 526 - 550 of 2094

Liquid Chromatography Column Theory and Technology

March 8, 2017
Author(s)
Lane C. Sander
Column selection is probably the single most important aspect of method development that will directly affect measurement accuracy and precision of liquid chromatographic (LC) measurements. An understanding of physical and chemical properties of LC columns

Liquid Chromatography: Introduction to Method Development

March 8, 2017
Author(s)
Lane C. Sander
The development of fit-for-purpose analytical methods is an essential component of chemical metrology. This presentation will provide guidance on approaches for establishing robust analytical methods, particularly with applications to liquid chromatography

Solid Phase Extraction

March 8, 2017
Author(s)
Lane C. Sander
Solid Phase Extraction [video, running time 29 minutes 2 seconds] \\europa\839.02\training\Solid Phase Extraction (29.02 minutes).mp4 Lane C. Sander Chemical Sciences Division Material Measurement Laboratory National Institute of Standards and Technology

Expanding lipidome coverage using LC-MS/MS data-dependent acquisition with automated exclusion list generation

March 6, 2017
Author(s)
John Bowden, Jeremy P. Koelmel, Nicholas M. Kroeger, Emily L. Gill, Candice Z. Ulmer, Rainey E. Patterson, Richard A. Yost, Timothy J. Garrett
Untargeted omics analyses aim to comprehensively characterize biomolecules within a biological system. Changes in the presence or quantity of these biomolecules can indicate important biological perturbations, such as those caused by disease. With current

Characterization of a PXIe based low-field digital NMR spectrometer

February 25, 2017
Author(s)
Joshua R. Biller, Karl F. Stupic, Anthony B. Kos, Timothy Weilert, George Rinard, Yoshi Nakashima, John M. Moreland
A low-field nuclear magnetic resonance (NMR) instrument is an important tool for investigating a wide variety of samples under different conditions. In this paper, we describe a system constructed primarily with commercially available hardware and control

Measurements of translation initiation from all 64 codons in E. coli

February 21, 2017
Author(s)
Ariel H. Hecht, Jeff E. Glasgow, Paul Jaschke, Lukmaan Bawazer, Matthew S. Munson, Jennifer R. Cochran, Drew Endy, Marc L. Salit
Our understanding of translation represents a cornerstone of molecular biology and underpins our capacity to engineer living matter. For decades, the codon AUG and a few near-cognates (GUG, UUG) have been exclusively considered as “start codons” for

Cytochrome P450 27A1 Deficiency and Regional Differences in Brain Sterol Metabolism Cause Preferential Cholestanol Accumulation in the Cerebellum

February 11, 2017
Author(s)
Natalia Mast, Kyle Anderson, Joseph Lin, Yong Li, Illarion Turko, Curtis Tatsuoka, Ingemar Bjorkhem, Irina A. Pikuleva
Cytochrome P450 27A1 (CYP27A1 or sterol 27-hydroxylase) is a ubiquitous, multifunctional enzyme catalyzing regio- and stereo-specific hydroxylation of different sterols. In humans, complete CYP27A1 deficiency leads to cerebrotendinous xanthomatosis or

Believable Statements of Uncertainty

February 8, 2017
Author(s)
Richard M. Lindstrom
Nearly fifty years ago, two landmark papers appeared that should have cured the problem of ambiguous uncertainty statements in published data. Eisenhart’s paper in Science called for statistically meaningful numbers, and Currie’s Analytical Chemistry paper

Fabrication of Scanning Electrochemical Microscopy-Atomic Force Microscopy (SECM-AFM) Probes to Image Surface Topography and Reactivity at the Nanoscale

January 27, 2017
Author(s)
Jeyavel Velmurugan, Amit K. Agrawal, Sang M. An, Eric A. Choudhary, Veronika A. Szalai
Electrocatalysts, used in energy applications, rely on the solid-liquid interface to carry out productive chemistry. This interface is generally less amenable to standard surface-science characterization methods, making the investigation of the surface

Spatial variation in perfluoroalkyl acids in a population of wild American alligators (Alligator mississippiensis) at Merritt Island National Wildlife Refuge (MINWR) surrounding the Kennedy Space Center (KSC)

January 26, 2017
Author(s)
John Bowden, Jacqueline T. Bangma, Martin Jones, Russell H. Lowers, Frances Nilsen, Jessica L. Reiner, Thomas R. Rainwater, Stephen E. Somerville, Louis J. Guillette Jr.
This study aimed to quantify fourteen perfluoroalkyl acids (PFAAs) in the plasma of a population of alligators located at Merritt Island national Wildlife Refuge (MINWR). Male (n = 117) and female (n = 112) alligators were sampled in every month during

Least Squares Moving-Window Spectral Analysis

January 20, 2017
Author(s)
Young J. Lee
Least squares regression is proposed as a moving-windows method for analysis of a series of spectra acquired as a function of external perturbation. The least squares moving-window (LSMW) method can be considered an extended form of the Savitzky–Golay

Determination of Liquid Density

January 12, 2017
Author(s)
Lane C. Sander, Lorna T. Sniegoski
The determination of solution density is required for conversion of liquid solution levels from a mass fraction basis to a volume fraction basis. This presentation will provide information about three approaches in common use for the determination of

Liquid Chromatography: Introduction and Instrumentation

January 12, 2017
Author(s)
Lane C. Sander
Chromatography is an example of a process by which a mixture is separated into at least two fractions with different compositions. This presentation will provide a brief overview of the practice of liquid chromatography (LC), with an emphasis on

Measurement of Uranium-236 in Particles by Secondary Ion Mass Spectrometry

January 12, 2017
Author(s)
David S. Simons, John D. Fassett
The determination of the relative isotopic abundance by secondary ion mass spectrometry of 236U in uranium-containing material is complicated by the presence of 235U1H+ ions at the same nominal mass as the uranium isotopic peak. The net intensity of the

Plumbing for Liquid Chromatography

January 12, 2017
Author(s)
Lane C. Sander
The setup and maintenance of liquid chromatographic equipment requires a basic knowledge of chromatographic hardware. Tubing connections are an essential component in liquid chromatography instrumentation. System function and performance depend on the

Preparation of Calibration Solutions

January 12, 2017
Author(s)
Lane C. Sander, Michele M. Schantz
Calibration solutions provide the basis for quantitation for most instrumental techniques. The instrumental responses for analytes in calibrants of known composition are compared with corresponding responses in samples to provide quantitation of the

Pressurized Fluid Extraction

January 12, 2017
Author(s)
Lane C. Sander
Pressurized fluid extraction (PFE) is one of several sample preparation methods that can be used to extract targeted analytes from a sample matrix into a solvent, to permit subsequent analysis. With PFE, samples are extracted with solvent in a pressurized

Principles of Quantitation: Chromatography

January 12, 2017
Author(s)
Lane C. Sander
The accurate characterization of the chemical composition of a sample depends on a variety of factors that must be considered by the analyst. Knowledge of how different approaches to quantitation affect the measurement accuracy is requisite to the
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