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Displaying 26 - 50 of 1835

Environmental Protection Agency Blind Audit 2018

May 17, 2021
Christina Cecelski, Cassie Goodman, Jennifer Carney
The U.S. Environmental Protection Agency (EPA) conducted a blind audit of EPA protocol calibration gas mixtures produced by specialty gas manufactures. The objective was to determine the amount-of-substance fraction (concentration) of the analytes in the

Vitamin D Standardization Program (VDSP) intralaboratory study for the assessment of 25-hydroxyvitamin D assay variability and bias

May 17, 2021
Johanna Camara, Stephen Wise, Christopher T. Sempos, Pierre Lukas, Caroline LeGoff, Stephanie Peeters, Carolyn Burdette, Federica Nalin, Grace Hahm, Ramon Durazo-Arvizu, Adam J. Kuszak, Joyce M. Merkel, E. Cavalier
An intralaborabory comparison study to assess the performance of assays for the determination of serum total 25-hydroxyvitamin D [25(OH)D] was conducted in 2017 as part of the Vitamin D Standardization Program (VDSP). The intralaboratory study consisted of

Decision Tree for Key Comparisons

April 27, 2021
Antonio Possolo, Amanda Koepke, David Newton, Michael R. Winchester
This contribution describes a Decision Tree intended to guide the selection of statistical models and data reduction procedures in key comparisons (KCs). The Decision Tree addresses a specific need of the Inorganic Analysis Working Group (IAWG) of the

Determination of Total Arsenic and Hydrophilic Arsenic species in Seafood

March 1, 2021
Caleb Luvonga, Catherine A. Rimmer, Lee L. Yu, Sang Bok Lee
Marine organisms are vital sources of staple and functional food but are also the major dietary route of human exposure to total arsenic. We report the total arsenic content and the mass fractions of hydrophilic arsenic species from five different marine

A Comparison of Measurement Methods for Alcohol-Based Hand Sanitizers

February 26, 2021
Mary Bedner, Jacolin Murray, Aaron A. Urbas, William A. MacCrehan, Walter Brent Wilson
The production and demand for hand sanitizers have increased dramatically during the coronavirus disease 2019 (COVID-19) health emergency. To be deemed effective and safe, hand sanitizers should contain at least 60 % alcohol (typically ethanol) as well as

A new highly enriched 233U reference material for improved simultaneous determination of uranium amount and isotope amount ratios in trace level samples

January 26, 2021
Richard Essex, Ross W. Williams, Kayron T. Rogers, Cole R. Hexel, Tashi Parsons-Davis, Kerri C. Treinen
A highly-enriched 233U reference material (>0.99987 n(233U)/n(U)) has been prepared and characterized for use as an isotope dilution mass spectrometry spike. An ion exchange separation was performed on 1 gram of high purity 233U to further reduce trace

Quantitative Analysis of Zirconium Alloys Using Borate Fusion and Wavelength Dispersive X-Ray Fluorescence Spectrometry

January 26, 2021
John R. Sieber, Anthony F. Marlow, Rick L. Paul, Charles A. Barber, Laura J. Wood, Lee L. Yu, Alaina Rieke, Amy Kutnerian, Jessica McCandless, Candace Wallace
The National Institute of Standards and Technology (NIST) uses borate fusion, wavelength dispersive X-ray fluorescence (WDXRF) spectrometry and synthetic calibration standards for high performance, quantitative analyses of a wide range of materials

Entropic-based separation of diastereomers. Size-exclusion chromatography with on-line viscometry and refractometry detection for analysis of blends of mannose and galactose methyl-alpha-pyranosides at "ideal" size-exclusion conditions

January 11, 2021
Andre M. Striegel, Steven Trainoff
TThe separation of carbohydrate diastereomers by an ideal size-exclusion mechanism, i.e., in the absence of enthalpic contributions to the separation, can be considered one of the grand challenges in chromatography: Can a difference in the location of a

Biomonitoring of emerging DINCH metabolites in pregnant women in Charleston, SC: 2011-2014

January 1, 2021
Abby G. Wenzel, Jessica L. Reiner, Satomi Kohno, Bethany J. Wolf, John W. Brock, Lori Cruze, Roger B. Newman
Due to the mounting evidence that phthalates produce adverse endocrine effects in humans and wildlife, the use of other chemicals as replacements has increased. One of the most commonly encountered phthalate replacement is di(isononyl)cyclohexane-1,2

Identifying risk factors for levels of perfluoroalkyl substances in the placenta in a high-risk pregnancy cohort in North Carolina

December 31, 2020
Jacqueline T. Bangma, Lauren A. Eaves, Kirsi Oldenburg, Jessica L. Reiner, Tracy Manuck, Rebecca C. Fry
Prenatal exposure to perfluoroalkyl substances (PFAS), a ubiquitous class of chemicals, is associated with adverse outcomes such as preeclampsia, low infant birth weight and later-life adiposity. The objectives of this study were to examine PFAS levels in

Relationship between the Pacific Decadal Oscillation (PDO) and persistent organic pollutants in sympatric Alaskan seabird (Uria aalge and U. lomvia) eggs between 1999 and 2010

December 31, 2020
Vrinda Kalia, Stacy Schuur, Keith A. Hobson, Howard H. Chang, Lance A. Waller, Steven Hare, Matthew O. Gribble
Although climate change occurs alongside other anthropogenic ecosystem impacts, little is known about how sea-surface temperature variability influences the ecotoxicology of persistent organic pollutants (POPs). We analyzed POP contaminant levels, and

Comparison of primary laser spectroscopy and mass spectrometry methods for measuring mass concentration of gaseous elemental mercury

December 10, 2020
Abneesh Srivastava, Stephen E. Long, James E. Norris, Colleen E. Bryan Sallee, Jennifer Carney, Joseph Hodges
We present a direct comparison between two independent methods for the measurement of gaseous elemental mercury (GEM) mass concentration: isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS) and laser absorption

Study of the Reactions of OH with HCl, HBr, and HI between 298 K and 460 K.

November 25, 2020
Vladimir L. Orkin, Victor Khamaganov, Igor Larin
The reactions between OH radicals and hydrogen halides (HCl, HBr, HI) have been studied between 298 K to 460 K by using a discharge flow – electron paramagnetic resonance technique. The rate constants at room temperature were found to be kHCl(298 K) = (7.9

Lessons From the NIST Micronutrients Quality Assurance Program for Vitamin C, 1993 to 2015: Sample Stability, Assay Reproducibility, and Use of Controls to Improve Comparability

November 11, 2020
David L. Duewer, Jeanice M. Brown Thomas, Katherine E. Sharpless, S A. Margolis
Vitamin C is a necessary micronutrient that is involved in many biological processes. In preserved human plasma and serum, vitamin C is most meaningfully analyzed as total ascorbic acid (TAA). From 1993 through 2015, the National Institute of Standards and
Displaying 26 - 50 of 1835