Structural determination of four manufacturing impurities of D&C Red No. 33

Eugene P Mazzola; Adrian Weisz; Douglas P Ridge; Sarah E Donnelly; Hanwen Zhang; Raquel M Gonzalez; Luke K Ackerman; Kristen L Reese; Clark D Ridge

doi:10.1002/mrc.5160

Structural determination of four manufacturing impurities of D&C Red No. 33

Magn Reson Chem. 2021 Nov;59(11):1107-1115. doi: 10.1002/mrc.5160. Epub 2021 Apr 27.

Authors

Eugene P Mazzola¹, Adrian Weisz², Douglas P Ridge³, Sarah E Donnelly⁴, Hanwen Zhang¹, Raquel M Gonzalez⁵, Luke K Ackerman⁴, Kristen L Reese⁴, Clark D Ridge⁴

Affiliations

¹ FDA Joint Institute for Food Safety and Applied Nutrition, University of Maryland, College Park, Maryland, USA.
² Office of Cosmetics and Colors, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, Maryland, USA.
³ Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA.
⁴ Office of Regulatory Science, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, Maryland, USA.
⁵ Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, USA.

PMID: 33818821
DOI: 10.1002/mrc.5160

Abstract

Four manufacturing impurities of D&C Red No. 33 isolated by counter-current chromatography were analyzed by NMR and ESI mass spectrometry. Three of these impurities were reported previously with minimal details of structural determination. All four are structurally related to the main component of the dye. The fourth exhibited an unusual discrepancy between the NMR structure and its chemical formula suggested by ESI-MS results. Structural determination and assignment of the main component and four impurities are discussed as well as resolution of the discrepancy between the NMR and ESI-MS results of the fourth impurity.

Keywords: D&C Red 33; NMR assignment; azo dyes; food dyes; structure elucidation.

Published 2021. This article is a U.S. Government work and is in the public domain in the USA.