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.