Fluorine-Tagging Strategies for Amino Acid Detection by Low-Field ¹⁹F NMR Spectroscopy

High-field NMR spectroscopy is a cornerstone of metabolomics; however, the high cost and infrastructural requirements of high-field instruments limit its broader applicability. Benchtop LF NMR spectrometers represent an attractive alternative, though sensitivity and resolution remain major challenges. ¹⁹F NMR is particularly attractive for LF NMR, as its large gyromagnetic ratio and wide chemical-shift range, together with the absence of naturally occurring fluorine in biological matrices, allow interference-free analysis.^1–3
Chemoselective tagging strategies reduce spectral congestion and enhance target selectivity in NMR, commonly employing isotope-enriched probes. ^4,5
Reactive ¹⁹F-tags have shown promise for the identification and quantification of amino acids in complex mixtures by ¹⁹F NMR. ^1,2Here, we investigate a ¹⁹F-tagging approach specifically designed for compatibility with benchtop ¹⁹F NMR, targeting a broad panel of proteinogenic amino acids. Amino acid derivatization is performed with selected F-tags, using DMT-MM as coupling agent in liquid media at near-neutral pH. ^6,7
Reaction conditions (pH, buffer composition, temperature, and time) are optimized by both high-field and benchtop ¹⁹F NMR spectroscopy.
Preliminary results show that selected fluorinated tags yield ¹⁹F-labelled amino acid products with well-resolved resonances, detectable and quantifiable on the benchtop spectrometer, supporting the feasibility of this approach at LF. Ongoing work focuses on extending the screening to a wider set of amino acids and evaluating tagging selectivity in more complex mixtures.
This study aims to establish a proof-of-concept for targeted amino acid profiling using fluorine-assisted tagging combined with LF ¹⁹F NMR, bridging established chemoselective derivatization strategies with emerging benchtop NMR technology and laying the groundwork for accessible metabolomics workflows beyond specialized high-field facilities.

1) Duong, Q. H. et al. Anal. Chem. 2024, 96, 1614–1621.
2) Chen, Y.-T. et al. Chem. Commun. 2021, 57, 13154–13157.
3) Ye, T. et al. Anal. Chem. 2009, 81, 4882–4888.
4) Ye, T. et al. Anal. Chem. 2010, 82, 2303–2309.
5) Montgomery, K. et al. J. Fluorine Chem. 2023, 266, 110084.
6) Kunishima, M. et al. Tetrahedron 1999, 55, 13159–13170.
7) Kunishima, M. et al. Tetrahedron 2001, 57, 1551–1558.