Quantitative quadrupolar NMR (qQNMR) using nitrogen-14 for the determination of choline in complex matrixes

Ana Belén Ruiz-Muelle; Paula García Moreno; Ignacio Fernández

doi:10.1016/j.talanta.2021.122344

Quantitative quadrupolar NMR (qQNMR) using nitrogen-14 for the determination of choline in complex matrixes

Talanta. 2021 Aug 1:230:122344. doi: 10.1016/j.talanta.2021.122344. Epub 2021 Mar 23.

Authors

Ana Belén Ruiz-Muelle¹, Paula García Moreno¹, Ignacio Fernández²

Affiliations

¹ Department of Chemistry and Physics, Research Centre CIAIMBITAL, University of Almería, Ctra. Sacramento, s/n, 04120, Almería, Spain.
² Department of Chemistry and Physics, Research Centre CIAIMBITAL, University of Almería, Ctra. Sacramento, s/n, 04120, Almería, Spain. Electronic address: ifernan@ual.es.

PMID: 33934793
DOI: 10.1016/j.talanta.2021.122344

Abstract

NMR offers the unique potential to selectively excite the chosen nuclei avoiding in an extraordinary way the matrix effect. Quantitative Nitrogen-14 NMR (¹⁴N qNMR) spectroscopy has been introduced for the first time as a robust and validated method to determine choline in a variety of matrixes including quinoa grains, instant coffee and food supplements. A study about the ion pairing of choline bitartrate in aqueous solution by means of diffusion PGSE, NOESY and HOESY NMR have been also provided. Validation of the method within eight concentrations levels (from 1.58 to 79.0 mM) afforded a limit of detection of 400 μg/mL (1.58 mM), a quantification limit of 1000 μg/mL (3.95 mM), excellent linearity (R² higher than 0.999), intra-/inter-day precisions lower than 1.24% (CV), recoveries of 93.5%-102.5%, and complete absence of matrix effect. The fast and reliable quantification of choline together with the accuracy and simplicity of this new approach make it useful in the development of analytical procedures that could dramatically affect traditional analysis.

Keywords: (14)N NMR; Choline content; Quadrupolar nuclei; Validated method; qNMR.