A New Realization of SI for Organic Chemical Measurement: NIST PS1 Primary Standard for Quantitative NMR (Benzoic Acid)

Abstract

Metrological traceability to common references supports the comparability of chemical measurement results produced by different analysts, at various times, and at separate places. Ideally, these references are realizations of base units of the International System of Units (SI). ISO/IEC 17025 (Clause 6.5) states that traceability of measurement results is a necessary attribute of analytical laboratory competence, and as such, has become compulsory in many industries, especially clinical diagnostics and healthcare. Historically, claims of traceability for organic chemical measurements have relied on calibration chains anchored on unique reference materials with linkage to the SI that is tenuous at best. A first-of-its-kind National Institute of Standards and Technology (NIST) reference material, ultrapure and extensively characterized PS1 Benzoic Acid Primary Standard for quantitative NMR (qNMR), serves as a definitive, primary reference (calibrant) that assuredly links the qNMR spectroscopy technique to SI units. As qNMR itself is a favorable method for accurate, direct characterization of chemical reference materials, PS1 is a standard for developing other traceable standards and is intended to establish traceability for the measurement of thousands of organic chemical species. NIST PS1 will play a critical role in directly promoting accuracy and worldwide comparability of measurement results produced by the chemical measurement community, supporting the soundness of clinical diagnostics, food safety and labeling, forensic investigation, drug development, biomedical research, and chemical manufacturing. Confidence in this link to the SI was established through (i) unambiguous identification of chemical structure; (ii) determinations of isotopic composition and molecular weight; (iii) evaluation of the respective molecular amount by multiple primary measurement procedures, including qNMR and coulometry; and (iv) rigorous evaluation of measurement uncertainty using state-of-the-art statistical methods and measurement models.

Quantitative determination and validation of 17 cannabinoids in cannabis and hemp using liquid chromatography-tandem mass spectrometry

“…CBD was purchased from Toronto Research Chemicals and certified for purity at NRC using quantitative NMR (qNMR) [ 30 ] with NIST SRM 350b benzoic acid as internal standard [ 31 ]. Reference standards of the other cannabinoids and isotopically labeled cannabinoids were purchased from Cerilliant (Round Rock, Texas, USA).…”

Certification of Standard Reference Materials 2969 and 2970 :

“…The chemical purity of these materials had been determined in 2014, however subsequent measurements made in 2016 indicated that the 25(OH)D2 content had changed substantially and re-investigation of mass purity was warranted for contemporary use. The results are traceable to the International System of Units through the determination of chemical structure and use of NIST PS1 Primary Standard for qNMR (Benzoic Acid) [4,5,6] 5.1. Materials Chemical purity was determined for the following materials, stored at -20 °C in a glass jar desiccator prior to and after the purity analysis: Calcifediol (25-hydroxyvitamin D3); USP Lot G1E064 Ercalcidiol (25-hydroxyvitamin D2); IsoSciences Lot RT-4-2013-062A1…”

Expanding NIST Calibration of Fluorescent Microspheres for Flow Cytometry to More Fluorescence Channels and Smaller Particles

“…The internal standard used for all samples was 1,3,5-trimethoxybenzene (Sigma-Aldrich, TraceCERT ® , Lot BCBW3670). The certified mass fraction of this standard is traceable to the International System of Units (SI) through NIST PS1 Primary Standard for qNMR (Benzoic Acid) [7][8][9].…”