Trace Analysis of C₄F₇N Insulating Gas Mixtures by Spontaneous Raman Spectroscopy and Gas Chromatography

2,3,3,3-Tetrafluoro-2-(trifluoromethyl) propanenitrile (C₄F₇N) is being researched as an alternative to sulfur hexafluoride (SF₆) for applications in gas-insulated switchgear. We independently assessed the effectiveness of gas chromatography-mass spectrometry (GC-MS) and a novel method of feedback-assisted multipass cavity spontaneous Raman spectroscopy (SRS) for the trace quantification of impurities in C₄F₇N and its related byproducts. A total of 14 gases were identified with estimated concentrations as low as 20 ppm (ppm) for C₃F₆ using GC-MS and 7.4 ppm for CH₄ using SRS and as high as 500 ppm for CF₄ using GC-MS and 1430 ppm for CO using SRS. While GC-MS is highly effective in selectively detecting and quantifying trace contaminants, it necessitates separate detectors for various gases, such as CH₄ and H₂. SRS succeeded in detecting CF₄ and C₂F₆ at concentrations of 465 and 100 ppm, respectively, and in placing an upper bound of several hundred ppm for the other analytes. Crucially, SRS holds potential for portability-and thus for field applications-in gas-insulated switchgear equipment diagnostics.