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

Area of Science:

• Analytical Chemistry
• Materials Science
• Electrical Engineering

Background:

• 2,3,3,3-Tetrafluoro-2-(trifluoromethyl) propanenitrile (C4F7N) is a potential alternative to sulfur hexafluoride (SF6) in gas-insulated switchgear.
• Accurate quantification of trace impurities in C4F7N is crucial for its application and safety.
• Existing methods like GC-MS have limitations in detecting certain gases and portability.

Purpose of the Study:

• To assess the effectiveness of gas chromatography-mass spectrometry (GC-MS) and spontaneous Raman spectroscopy (SRS) for trace impurity quantification in C4F7N.
• To identify and quantify impurities in C4F7N and its byproducts.
• To evaluate the potential of SRS for field applications in gas-insulated switchgear diagnostics.

Main Methods:

• Independent assessment of GC-MS and a novel feedback-assisted multipass cavity SRS.
• Identification and quantification of 14 different gases.
• Detection limits down to 7.4 ppm for CH4 using SRS and 20 ppm for C3F6 using GC-MS.

Main Results:

• Both GC-MS and SRS successfully identified and quantified trace impurities.
• GC-MS detected up to 500 ppm of CF4, while SRS detected CF4 at 465 ppm and C2F6 at 100 ppm.
• SRS demonstrated potential for detecting various analytes with upper bounds in the hundreds of ppm and showed promise for portability.

Conclusions:

• GC-MS is effective for selective detection but requires multiple detectors.
• SRS is a viable alternative for trace impurity analysis in C4F7N, with potential for field deployment.
• SRS offers a promising pathway for portable diagnostics in gas-insulated switchgear equipment.