Page 1 of 1
Injector valve
Posted: Tue Oct 31, 2006 5:16 pm
by delle.82
I have come into the middle of a project where the person that set it up is no longer working on the project. I am also a novice at working with GCs. There is a 6-port HPLC valve hooked up to a GC. The 6-port valve is not hooked up to a pump. We are doing high pressure injections. I was wondering if this setup would work? Can you have an HPLC valve hooked up to a GC? Does the valve need to be hooked up to a pump?
Posted: Tue Oct 31, 2006 5:34 pm
by tom jupille
A six-port, two-way injection valve works the same way in GC and LC (I believe some of the early HPLC injectors were adapted from Valco GC valves). In GC , the "pump" connection would be to the incoming carrier gas. The big concern in using an LC valve for GC is whether it will stand up to the temperatures involved.
Posted: Tue Oct 31, 2006 5:42 pm
by delle.82
Thanks for your quick response. So the system would not need a pump? Will the pressure from the carrier gas keep it regulated?
Posted: Tue Oct 31, 2006 6:07 pm
by tom jupille
I'm not sure what you mean by "regulated". The mobile phase flow (carrier gas flow in GC) is routed either directly to the column or diverted through the sample loop before going to the column. There is a brief description of how these valves operate in the FAQ section (click on the "FAQ" link at the upper left of the screen, just under the Chromatography Forum logo, and drill down through "Questions about Liquid Chromatography . . . Hardware . . . How do autosamplers work?" to the detailed answer.
The valve is switched from one position to the other either manually (with a handle), electically (with an actuator motor), or pneumatically (with a compressed-air-driven actuator).
Posted: Tue Oct 31, 2006 9:30 pm
by promochrom
The seal material is different for gas valve and liquid vavle. the max temperature is also differnt. A LC valve has a lower temperature. If your gas sample need a high temeprature (say above 80 C), you should use a gas vavle.
If the gas sample is pushed to the valve loop by a high pressure, you may add a restrictor at the outlet of the valve loop, or your sampel will flush out very fast.
The most popular supplier of gas valve is Valco. You can find a lot of information from their website
www.vici.ch