A reliable gas chromatography-flame ionization detector (GC-FID) method was developed for the accurate determination of trace CO and CO2 in high concentration of SF6. Using a combination of dual Porapak Q chromatographic columns with valve switching, SF6 was separated from the tested samples and blown out of the detection system, with the aim of ruling out the possibility of conversion column poisoning. Meanwhile, CO and CO2 were on-line separated and subsequently converted to CH4 in the presence of a nickel catalyst to increase the sensitivity for the determination of carbon-borne gases. The results showed that neither gas interfered with the determination of the other. Satisfactory linearities were achieved in the range 2-500 μL/L for both CO and CO2, with highly accurate and reproducible determination (RSD<2%). The developed GC-FID method is applicable to the determination of gases lodged in high-voltage circuit breakers toward the analysis of trace CO and CO2, thus providing a tool for probing the potential breakdown of SF6-insulated equipment.
Keywords: breakdown of circuit breaker; carbon dioxide; carbon monoxide; gas chromatography (GC); sulfur hexafluoride.