Vacuum Injections and Throttling

[mugrad.2011]

I'm doing natural gas analysis using a vacuum injection system. The cylinder attaches to an introduction valve that connects to the GC via 1/8" stainless steel tubing. 1mL is injected just below atmospheric pressure (-5 in HG). Talking with an engineer, we began to debate the potential for throttling at the introduction valve to cool the gas enough for condensation in the tubing. Anybody care to weigh in with some thoughts?

Thanks

[muGC]

If you are performing natural gas analysis, you should always be heat tracing the sampling line all the way from the sample cylinder to the GC injection valve. Regardless of pressurized or vacuum injections, the heavy hydrocarbons can condense if the cylinder and lines are not heated, causing a bias in your results.