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This method is for determining trace permanent gases in high purity polymer grade ethylene and propylene gas or liquid using a gas chromatograph (GC) equipped with a pulsed discharge helium ionization detector (PDHID). The instrument is preconfigured and capable of determining typical impurities in polymer grade ethylene or propylene, however this method only describes the procedure for measuring carbon dioxide, carbon monoxide, hydrogen, nitrogen, and a composite of oxygen and argon. The instrument uses multiple columns and timed valve switching to eliminate the interference of propylene with the permanent gases. The lower limit of quantitation for nitrogen is 0.05 mol-ppm, carbon monoxide is 0.15 mol-ppm, carbon dioxide is 0.16 mol-ppm, oxygen is 0.25 mol-ppm, and hydrogen is 0.37 mol-ppm.