Chromatography Forum

Dear collaques

We have a problem with our GC/MS, the turbomolecular pump does not move from low to high pressure and the instrument autoshut down. and the pressure lower gradually. There is not leak from injectio port or column connection. We do not know the reason. could any one tell us.

Thanks.

What type of gc/ms

Hi xxx

Our GC/MS is Shimadzu QP 2010.

Hi, I don't understand what does it means when you say

"the turbomolecular pump does not move from low to high pressure"

.
Does the turbo pump start working? Does it make its normal sound?
Does the rotary pump work properly?

Thank you and good luck

regards

DL

Hi DL,
I mean that:,

Vacuum working begins with rotary pump then turbomolecular pump works, gradually the vacuum decrease to about 5 pascal (lower vacuum) then the vacuum reachs to about 1 e-3 (high vacuum). when vacuum reachs to this values the instrument gives message that vacuum is completed and GC/MS is ready to analysis. This operation must be happeen through 5 minutes, otherwise shout down is happened.

Our problem is, the turbo molecular pumb stopped before it reachs to high vacuum 1 e-3 and making shout down to the vacuum operation.

Thanks

Hi DL,
I mean that:,

Vacuum working begins with rotary pump then turbomolecular pump works, gradually the vacuum decrease to about 5 pascal (lower vacuum) then the vacuum reachs to about 1 e-3 (high vacuum). when vacuum reachs to this values the instrument gives message that vacuum is completed and GC/MS is ready to analysis. This operation must be happeen through 5 minutes, otherwise shut down is happened.

Our problem is, the turbo molecular pumb stopped before it reachs to high vacuum 1 e-3 and making shut down to the vacuum operation.

Thanks

sounds like you have a big leak, check the MS or see if the column is broken if all the connections are ok.

HI JI2002,

The column is OK (not broken),
The conection between coulum, injector and detector is OK.

By the way, what do you mean with "check your MS" ?

Thanks

safwatali,

if MS shut down automatically, the leak should be between the column and MS, it shouldn't be injector port or anything before that. I was thinking maybe the O-ring is demaged if you have any in the MS.

Hi JI2002,

There is O-ring around the door of MSD but it is OK.
Do you mean other O-ring.

Thanks

You have a very large air leak into the mass spec. The most likely location is the ferrule going into the mass spec interface. If you are using a 0.25 mm id column be sure you are using a 0.4 mm hole ferrule. If you are using a 0.5 mm hole ferrule the sealing may not be good. If you have QP-5000 series instrument the ferrules for these are different and will not seal on the QP-2010. One other issue involves sealing the door. To seal the door properly do not try to use the screw to seal before pumping down. Leave the screw fairly loose, and after the rotary pump starts gently push the door closed and let the vacuum seal the door.

Hi Ron,

I will done your suggestions, especially about sealing the door. By the way is it differ if we use the screw to seal before pumping down:?:

Thanks

If you let the vacuum seal the door the sealing force around the entire O-ring will be uniform. If you try to seal with the screw the sealing force will not be equal around the entire O-ring since you are applying pressure at only three point. In rare cases this may cause a leak, especially if the O-ring is pinched.

Hi again, safwatali, do you have a blank nut to block column end on the interface? Can you take off the column and put this nut?
I agree with the others that the problem is in the interface or in the door. Maybe you can have more sources of air like IG valve connection (I suppose you have one because you can measure high vacuum), and the reservoir where the PFTBA is. Check that nuts also (tight them a little).
Good luck

DL