Chromatography Forum

Hi all
I have varian GC 450. Today when we do the sample run, sudden decrease in prssure. i checked leakage in the line but there was no leak in the line. I used TCD detector having packed column. I also checked all the flows at injector point, detector point ) , all are ok.
I also checked FID having capillary column, it shows reday. it has pressure.
whole day i tried to manage this but can't
Can anybody help me?

When you say there is a sudden decrease in pressure when you do the sample run, exactly what do you mean? Is the loss of pressure in the injector, or do you lose makeup flow in your detector? I think you're referring to the injector, but just wanted to clarify.

Can you provide more details, please? Is your method split or splitless? How are you doing the sample run - direct injection, SPME?

Some of the first things to check would be the septum, as well as the injector nut ferrule. If the injector is having a difficult time maintaining only a split state, but does ok in splitless, then you could have a contaminated or partially clogged split line. Also, check your septum purge flow by opening the 450 door and measuring at the appropriate port - it should be around 2-5mL/min.

Hopefully providing more details of your system configuration will help us troubleshoot the problem.