Determination of Trifluoroacetic Acid Using Ion Chromatography Mass Spectrometry

Perflourinated organic acids are ubiquitous and found at relatively low concentrations in the environment (1). Trifluoroacetic acid (TFA) is the persistent atmospheric degradation product of hydrofluorocarbons (HFCs) that are increasingly used as an alternative to banned, ozone-damaging chlorofluorocarbons (CFCs). However, debate surrounds the use of HFCs because of their potential to contribute to global warming and demonstrated toxicity to the environment (2). TFA is also widely used in pharmaceutical and biotechnology purification processes. It is crucial to monitor for TFA in environmental risk assessment and in products intended for human use. TFA can be measured by gas chromatography (GC) after sample preparation and chemical derivatization (3), ion chromatography (IC) (4), and capillary electrophoresis (5). This paper describes an IC-MS method to separate TFA from common anions based on Reagent-Free™ IC (RFIC™ ) technology with sensitive and selective mass spectrometric detection.

Results and Discussion

Figure 1 displays TFA well separated from common anions to minimize charge competition and ionization suppression. The deprotonated molecular ion ([M-H]^- = -113 m/z) was detected as the dominant species in full-scan MS spectra, and used for quantification in SIM detection mode. Figure 2 shows the suppressed conductivity and MS SIM chromatograms of a bottled water sample with TFA spiked at 10 ppb. The method detection limit (MDL) was estimated to be 1.64 ppb with replicate injections of TFA spiked at 10 ppb in bottled drinking water (n = 5, %RSD = 4.39%).

Figure 1: (a) Ion chromatography separation of TFA and common anion standards detected using suppressed conductivity, and (b) Full scan MS spectrum of TFA standard (15–200 m/z).

Conclusion

This IC-MS method provides the sensitive and selective determination of TFA in drinking water.

Figure 2: Ion chromatography separation of TFA and common anions in bottled water spiked with 10 ppb TFA, detected using a) suppressed conductivity, and b)MS SIM. Low concentrations of TFA that are not detected with suppressed conductivity can be easily quantified using MS.

MSQ Plus is a trademark of Thermo Fisher Scientific, Inc.

Reagent-Free and RFIC are trademarks and IonPac is a registered trademark of Dionex Corporation.

References

(1) Ellis, D.; Moody, et al. In Organofluorines, Neilson, A.H., Allard, A-S., Eds.; Springer: New York. 2002, pp 103–120.

(2) Boutonnet, J. C.; et al. Hum. and Ecol. Risk Assess.: An Int. J. 1999, 5, 59–124.

(3) Wujcik, C. E.; Cahill, T. M.; Seiber, J. N. Anal. Chem. 1998, 70, 4074–4080.

(4) Kaiser, E.; Rohrer, J. J Chromatogr., A 2004, 1039, 113–117.

(5) Hettiarachchi, K.; Ridge, S. J Chromatogr., A 1998, 817, 153–161.

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