19F-NMR Analysis of Primary and Secondary Amines Following Chemical Derivatization with Trifluoroacetic Anhydride

Five amines were reacted with trifluoroacetic anhydride (TFAA) as derivatization reagent and subsequently analyzed via ¹⁹F nuclear magnetic resonance (NMR) spectroscopy. The ¹⁹F-NMR spectra of derivatives of aniline, 2,4-dimethyl aniline, and 2-methoxy aniline produce a signal that are very close to TFAA. The peaks resulting from the reaction of TFAA with N-ethyl aniline and N-methyl aniline are shifted much farther downfield than any of the other signals. Optimal ¹⁹F-NMR sensitivity based upon T ₁ relaxation time was investigated for derivatization compound and flurbiprofen as internal standard in toluene. The calibration curve was linear for amines over the range of 9.0–100.0?mg?L^?1, with detection limit (S/N?=?3) of 2.6–2.9?mg?L^?1. Solid-phase extraction cartridges were investigated for preconcentration of water samples. The method was validated through spike and recovery for secondary amines from tap water sample.