EXPLANATION
High purity ethylene is required as a feedstock for some manufacturing processes, and the presence of trace amounts of carbon dioxide and some hydrocarbons can have a deleterious effect. This test method can be used for setting specifications or for use as internal quality control. This test method is applicable over the range of impurities from 1 to 500 ppm by volume. It covers the determination of carbon dioxide, methane, ethane, acetylene, and other hydrocarbons.
TEST SUMMARY
The sample is separated in a gas chromatograph utilizing four different packed chromatographic columns with helium as the carrier gas. Methane and ethane are determined using a silica gel column, propylene and heavier hydrocarbons with a hexamethylphosphoramide column, acetylene in a series of hexadecane and a squalane column, and carbon dioxide with an activated charcoal impregnated with a solution of silver nitrate. Calibrations are done using standard samples containing known amounts of these compounds.
TEST PRECISION
The bias of this method has not been determined.