Ultraviolet Spectral Analysis and Quantitative Detection of Heptafluoroisobutyronitrile (CFN) in a CFN-Carbon Dioxide (CO) Gas Mixture.

As an alternative to sulfur hexafluoride (SF) with great potential for application, heptafluoroisobutyronitrile-carbon dioxide (CFN-CO) gas mixture has been applied in various gas-insulated equipment. The insulation performance of the gas mixture is closely related to the mixing ratio. Therefore, accurate quantification of CFN in the CFN-CO gas mixture has very important engineering significance. At present, there are few reports on the rapid quantitative detection of the concentration of CFN in the gas mixture. In this paper, a rapid analytical method for CFN concentration based on ultraviolet (UV) absorption spectroscopy is constructed. The UV spectral characteristics of CFN molecules are calculated by density functional theory. The appropriate bands that can be detected are determined by analyzing the calculated results. A concentration detection system of CFN based on UV absorption spectroscopy is built. Through analysis of the calculated results and experimental results, a quantitative detection method of CFN in the CFN/CO gas mixture is determined. The method can achieve accurate detection of the concentration of the gas mixture in the conventional application range (including 4-10% CFN). The coefficient of the determination R of the concentration inversion curve reaches 0.999 and the inversion error ratio does not exceed 5%. The related research results provide an important reference for the engineering application of the gas mixture.