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Search Publications by: David L. Duewer (Assoc)

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Displaying 101 - 125 of 172

Development and Certification of Green Tea-Containing Standard Reference Materials

November 30, 2011
Author(s)
Lane C. Sander, Mary Bedner, Michael C. Tims, James H. Yen, David L. Duewer, Barbara J. Porter, Steven J. Christopher, Russell D. Day, Stephen E. Long, John L. Molloy, Karen E. Murphy, Brian E. Lang, Rachel A. Lieberman, Laura J. Wood, M. Payne, M. C. Roman, J. M. Betz, A. NguyenPho, Katherine E. Sharpless, Stephen A. Wise
A suite of three green tea-containing Standard Reference Materials (SRMs) has been issued by the National Institute of Standards and Technology (NIST). The materials are characterized for catechins, xanthine alkaloids, theanine, and toxic elements. As many

Dietary Supplement Laboratory Quality Assurance Program: The First Five Exercises

August 17, 2011
Author(s)
Melissa M. Phillips, Catherine A. Rimmer, Laura J. Wood, Katrice A. Lippa, Katherine E. Sharpless, David L. Duewer, Lane C. Sander, J. M. Betz
The National Institute of Standards and Technology (NIST) has established a Dietary Supplement Quality Assurance Program (DSQAP) in collaboration with the National Institutes of Health (NIH) Office of Dietary Supplements (ODS). Program participants measure

Certification of Vitamins and Carotenoids in SRM 3280 Multivitamin/Multielement Tablets

April 24, 2011
Author(s)
Lane C. Sander, Katherine E. Sharpless, Stephen A. Wise, Bryant C. Nelson, Karen W. Phinney, Barbara J. Porter, Catherine A. Rimmer, Jeanice M. Brown Thomas, Laura J. Wood, James H. Yen, David L. Duewer, R. Atkinson, R. Chen, R. Goldschmidt, W.R. Wolf, I-P Ho, M. Betz
A new multivitamin/multielement dietary supplement Standard Reference Material (SRM) has been issued by the National Institute of Standards and Technology (NIST) with certified and reference concentration values for 13 vitamins, 24 elements, and two

Standard Reference Materials for Analysis of Dietary Supplements

June 1, 2010
Author(s)
Katherine E. Sharpless, David L. Duewer
NIST, in collaboration with the National Institutes of Health Office of Dietary Supplements (NIH-ODS) and the Food and Drug Administration (FDA) is producing Standard Reference Materials (SRMs) for dietary supplements. This paper describes the how these

Strategies for Concordance Testing

May 1, 2010
Author(s)
Carolyn R. Steffen, David L. Duewer, Margaret C. Kline, John M. Butler
Concordance evaluations are important to conduct to determine if there are any allelic dropout or “null alleles” present in a data set. These studies are based on the fact that there are a variety of commercial short tandem repeat (STR) multiplex kits

CCQMK62: Nutrients in Infant/Adult Formula Vitamins

April 24, 2010
Author(s)
Katherine E. Sharpless, Catherine A. Rimmer, Karen W. Phinney, Bryant C. Nelson, David L. Duewer, Stephen A. Wise
Key Comparison CCQM-K62 was designed to enable demonstration of the equivalence in capabilities for measurement of vitamins in a food matrix. A milk-based fortified human infant/adult formula was selected as the matrix based upon material availability and

CCQMK62: Nutrients in Infant/Adult Formula Vitamins: Final Report

April 24, 2010
Author(s)
Katherine E. Sharpless, Catherine A. Rimmer, Karen W. Phinney, Bryant C. Nelson, David L. Duewer, Stephen A. Wise
Key Comparison CCQM-K62 was designed to enable demonstration of the equivalence in capabilities for measurement of vitamins in a food matrix. A milk-based fortified human infant/adult formula was selected as the matrix based upon material availability and

Demonstrating the Comparability of Certified Reference Materials

July 24, 2009
Author(s)
David L. Duewer, Katrice A. Lippa, Stephen E. Long, Karen E. Murphy, Katherine E. Sharpless, Lorna T. Sniegoski, Michael J. Welch
Certified Reference Materials (CRMs) enable the meaningful comparison of measurement results over time and place. When CRMs are used to calibrate or verify the performance of a measurement system, results produced by that system can be related through the

Visualization Technique for Uncertainty Budgets: Onion Charts

October 16, 2008
Author(s)
Kenneth W. Pratt, David L. Duewer
A concise graphical depiction, the onion chart, is described for presenting uncertainty budgets for any measurand, y, having a set of component variances, ui2(y). The onion chart consists of a concentric series of rings. Each ring is constructed from the

Commutability of NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum With Selected Total Homocysteine Immunometric or Enzymatic Assays

March 1, 2008
Author(s)
B C. Nelson, Christine M. Pfeiffer, Ming Zhang, David L. Duewer, Katherine E. Sharpless, Katrice Lippa
Background: The National Institute of Standards and Technology (NIST) and the Centers for Disease Control and Prevention (CDC) have recently developed Standard Reference Material (SRM) 1955 Homocysteine and Folate in Frozen Human Serum with certified

k=2 and Other Sometimes Hidden Assumptions in Chemical Measurement Uncertainty Intervals

April 24, 2006
Author(s)
David L. Duewer, S L. Ellison, William F. Guthrie, D B. Hibbert, C Jackson, A Kallner, Stefan D. Leigh, Reenie M. Parris, Kenneth W. Pratt, Michele M. Schantz, Katherine E. Sharpless
A recent interlaboratory study that required individual analysts to estimate uncertainty intervals for their results revealed that some experienced chemical analysts have difficulty with measurement uncertainty calculations. To help validate assumptions
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