Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Metrological approaches to organic chemical purity: primary reference materials for vitamin D metabolites

Published

Author(s)

Michael A. Nelson, Mary Bedner, Brian E. Lang, Blaza Toman, Katrice A. Lippa

Abstract

Given the critical role of pure, organic compound primary reference standards used to characterize and certify chemical Certified Reference Materials (CRMs), it is essential that associated mass purity assessments be fit-for-purpose, represented by an appropriate uncertainty interval, and metrologically sound. The mass fraction purities (% g/g) of 25-hydroxyvitamin D (25(OH)D) reference standards used to produce and certify values for clinical Vitamin D metabolite CRMs were investigated by multiple orthogonal quantitative measurement techniques. Quantitative 1H-nuclear magnetic resonance spectroscopy (qNMR) was performed to establish traceability of these materials to the International System of Units (SI) and to directly assess the principal analyte species. The 25(OH)D standards contained volatile and water impurities, as well as structurally-related impurities that are difficult to observe by chromatographic methods or to distinguish from the principal 25(OH)D species by one-dimensional NMR. These impurities have the potential to introduce significant biases to purity investigations in which a limited number of measurands are quantified. Combining complementary information from multiple analytical methods, using both direct and indirect measurement techniques, enabled mitigation of these biases. Purities of 25(OH)D reference standards and associated uncertainties were determined using frequentist and Bayesian statistical models to combine data acquired via qNMR, liquid chromatography with UV absorbance and atmospheric pressure-chemical ionization mass spectrometric detection (LC-UV, LC-ACPI-MS), thermogravimetric analysis (TGA), and Karl Fischer (KF) titration.
Citation
Analytical and Bioanalytical Chemistry
Volume
407
Issue
28

Keywords

purity, qNMR, data combination, Vitamin D, primary standard, metrology

Citation

Nelson, M. , Bedner, M. , Lang, B. , Toman, B. and Lippa, K. (2015), Metrological approaches to organic chemical purity: primary reference materials for vitamin D metabolites, Analytical and Bioanalytical Chemistry, [online], https://doi.org/10.1007/s00216-015-9013-7 (Accessed June 10, 2023)
Created September 7, 2015, Updated November 10, 2018