The column is packed with a substrate that differentially retards the passage of gas components, and therefore separates them. The column used for ethylene analysis is packed with activated alumina, and the carrier gas is nitrogen. There must be a pressure drop across the column for the carrier gas to flow through the column. The gas pressure at the start of the column must be greater than the pressure at the end of the column near the detector. Injection of the sample at the start of the column is therefore injected against a positive pressure.
Ethylene is detected with a flame ionization detector.
A hydrogen flame burns the samples within the carrier gas, forming ions and electrons. The electrical conductivity is then proportional to the concentration of charged particles within the gas. The units are nanoliters per gram fresh weight per hour, which is the same as microliters per kilogram fresh weight per hour. Measrue the weight of fruit in the jar and the volume of the jars after the experiment. Be sure to record the time, weight, and necessary volumes.