Development of an F-19 NMR method for the analysis of fluorinated acids inenvironmental water samples

This investigation was carried out to evaluate F-19 NMR as an analytical to ol for the measurement of-trifluoroacetic acid (TFA) and other fluorinated acids in the aquatic environment. A method based upon strong anionic exchan ge (SAX) chromatography was also optimized for the concentration of the flu oro acids prior to NMR analysis. Extraction of the analyte from the SAX col umn was carried out directly in the NMR solvent in the presence of the stro ng organic base, DBU. The method allowed the analysis of the acid without a ny prior cleanup steps being involved. Optimal NMR sensitivity based upon T 1 relaxation times was investigated for seven fluorinated compounds in four different NMR solvents. The use of the relaxation agent chromium acetylace tonate, Cr(acac)(3), within these solvent systems was also evaluated. Resul ts show that the optimal NMR solvent differs for each fluorinated analyte. Cr(acac)(3) was shown to have pronounced effects on the limits of detection of the analyte. Generally, the optimal sensitivity condition appears to be methanol-d(4)/2M DBU in the presence of 4 mg/mL of Cr(acac)(3). The method was validated through spike and recovery for five fluoro acids from enviro nmentally relevant waters. Results are presented for the analysis of TFA in Toronto rainwater, which ranged from <16 to 850 ng/L. The NMR results were confirmed by GC-MS selected-ion monitoring of the fluoroanalide derivative .