The researchers used a special machine called a Helium Ionization Chromatograph to analyze impurities in carbon tetrafluoride gas. They compared two methods, one using a Pulsed Discharge Helium Ionization Detector and the other using a combination of thermal conductivity and flame ionization detectors. The results showed that the PDHID method was more sensitive, had lower detection limits, and was better for analyzing high-purity CF4 gas.