Measurement of Flow Rate Disturbance of Carrier Gas in Gas Chromatographic Column Containing Sample

Abstract

Flow rate disturbance of carrier gas at a column outlet, which sometimes perturbs the quantitative analysis, were measured using a orifice type flow meter. In order to avoid the viscosity effect of sample vapor, a long delay tube was connected between the column outlet and the orifice. Pressure fluctuations due to the flow rate disturbance was recorded on a strip chart recorder by means of a diaphragm type pressure transducer and associated electrical circuits.
When helium was used as a carrier gas, flow rate increase caused by (1) an initial surge due to sample introduction, (2) a decrease of the viscosity of gas inside the zone and (3) emergence of vapor from the solution in the column, was observed in the order for benzene, but the increase caused by the three factors was observed evenly for diethyl ether.
Maximum increase in flow rate was reached up to 6% for benzene (1μ;l) using PEG 20 M column (2 m) at 120°C.
For a mixture of ethyl methyl ketone and octane, a fluctuation of flow rate was observed as a sum of individual fluctuation of single runs.
When the special column, where the stationary liquid phase gradually decrease from the column inlet to the outlet, was connected to the outlet of main column in order to decrease the perturbation on quantitative analysis, the increase in flow rate caused by the factor (3) can be reduced.