Chromatography Forum

Hello, We are using TD-GC/MS in our lab (TD-100, 7890A, 5977A).

When analyzing some sorbent tubes, the foreline value increases from 80 to 300.

And the light on the filament goes out (MS off).

At first, I thought it was due to the high concentration of the sample.

However, it happened with a conditioned sample [there is no problem with the conditioner].

The engineer told me that the diffusion pump is weaker than the turbo pump, so if you change the pump, it shouldn't happen again.

I don't want to replace the pump because it is too expensive.

Is there any other alternative or am I missing something?

Just wondering if anyone else has experienced the same thing I have.

What you describe would indicate that the flow through the analyzer is too high. What is the flow through the TD when desorbing? If you are trying to send more than 3ml/min through the column then you may be overloading the vacuum system.

Can you set a solvent delay until after the vacuum returns to normal? That may be a solution if it is just a sudden jump in pressure as it desorbs.

I confirm that with a turbo molecular pump I never had problems.
Good luck