Positive (+) values indicate downfield shifts, lower-shielding, or higher frequency Negative (-) values correspond to upfield shifts, higher-shielding, or lower frequency. Note: Most literature references historically reverse the sign convention (i.e. negative shifts are reported as positive).

2021年6月24日 · To understand the 19 F-NMR spectrum of carbon-13 labeled trifluoroacetic acid (TFA), one has to consider all the interactions that fluorine-19 atoms can have with carbon-13 atoms, both of which have a non-zero nuclear spin, I = ½.

2023年3月22日 · Here, we report a sensitive 19 F-NMR method for the analysis of total PFAS, with a limit of detection of 99.97 nM, or 50 μg/L perfluorosulfonic acid. To demonstrate the capabilities of 19 F-NMR, the technique was compared to two commonly used methods for PFAS analysis: total oxidizable precursor (TOP) assay and LC-high resolution MS analysis ...

2007年3月12日 · This report describes 19 F NMR and CE strategies for determining the TFA content of a variety of compounds with widely different physicochemical properties. It was demonstrated that the strategies are precise, accurate and robust, and amenable to high-throughput analyses.

This investigation was carried out to evaluate 19 F NMR as an analytical tool for the measurement of trifluoroacetic acid (TFA) and other fluorinated acids in the aquatic environment.

2023年10月1日 · Here we demonstrate the utility of 19 F NMR for the quantitation of trifluoroacetic acid in a batch of two in-house compounds (Fig 9). TFA contains a CF 3 group, resonates at δ -73.41 ppm, and is readily identified as the singlet peaks furthest downfield in the spectra.

2021年1月12日 · Trifluoroacetic acid (CF 3 COOH, TFA) is often used as an ion pairing agent in liquid chromatography to separate peptides and small proteins. Like with the 1 H-NMR spectrum of ethane, the “textbook” description of its 19 F-NMR spectrum consists of a single peak near − 76 ppm relative to CFCl 3.

2013年2月19日 · This review examines the variability of chemical shifts observed in 19-fluorine (19F) nuclear magnetic resonance spectra for the trifluoroacetyl (TFA) functional group. The range of 19F...

2012年10月22日 · The 19 F NMR spectrum for trifluoroacetic acid is shown in the figure below with and without 13 C broadband decoupling in the upper and lower traces, respectively. Approximately 98% of the trifluoroacetic acid is the 12 CF 3 - 12 COOH isotopomer, giving rise to a large singlet plotted off-scale in the figure.

2000年2月15日 · This investigation was carried out to evaluate 19F NMR as an analytical tool for the measurement of trifluoroacetic acid (TFA) and other fluorinated acids in the aquatic environment. A method based upon strong anionic exchange (SAX) chromatography was also optimized for the concentration of the fluo …