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

Abstract

propanenitrile (C 4 F 7 N) is being researched as an alternative to sulfur hexafluoride (SF 6 ) 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 C 4 F 7 N and its related byproducts. A total of 14 gases were identified with estimated concentrations as low as 20 ppm (ppm) for C 3 F 6 using GC−MS and 7.4 ppm for CH 4 using SRS and as high as 500 ppm for CF 4 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 CH 4 and H 2 . SRS succeeded in detecting CF 4 and C 2 F 6 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.