Chromatography Forum

Hello everyone,

I have a problem with my GC8890, which is new. However, it has been not using for several months due to staff shortage and workload. The ASL used to work perfectly fine and after changing the inlet, it bent the needles. I change the ASL to the back inlet and run some blanks to make sure that it's alright to run. However, the baseline is so bad. It keeps rising and dropping, then some ghost peaks appear. I have changed the inlet, gold seal, O-ring. I performed the instrument blank runs again and the baseline is still bad.
[img][IMG]https://thumbs2.imgbox.com/9d/60/hCxsWCja_t.png[/img][/img]

Hello everyone,

I have a problem with my GC8890, which is new. However, it has been not using for several months due to staff shortage and workload. The ASL used to work perfectly fine and after changing the inlet, it bent the needles. I change the ASL to the back inlet and run some blanks to make sure that it's alright to run. However, the baseline is so bad. It keeps rising and dropping, then some ghost peaks appear. I have changed the inlet, gold seal, O-ring. I performed the instrument blank runs again and the baseline is still bad.
[img][IMG]https://thumbs2.imgbox.com/9d/60/hCxsWCja_t.png[/img][/img]

What change was made on the front inlet to cause the bent needles?

If it has been idle with no flow for months it could have some contaminates built up in the flow path. Might just need to use high split flow for a long time to clear out, and if you can use hydrogen carrier that will clean the flow path really well.

Thanks James,

For the front inlet, I just changed the inlet liner/o-ring and the septa, and it just kept bending my needle. That's why I changed to the back inlet.

I tried to run two blank instrument samples, with the inlet temperature lower to 50C and here are the results:



The second run looks better but still has some contamination.

Thanks James,

For the front inlet, I just changed the inlet liner/o-ring and the septa, and it just kept bending my needle. That's why I changed to the back inlet.

I tried to run two blank instrument samples, with the inlet temperature lower to 50C and here are the results:



The second run looks better but still has some contamination.

I bent a few when I installed a cyclo type liner upside down but otherwise never had a problem with the autosampler not aligning well with the inlet nut.

I will have to look at the images at home, can't open them at work

How hot are you running the column out to. I had to replace the inlet tubing
on several 8890's that were doing high temperature applications due to air
ingress.

Best regards,

AICMM

Thank you AICMM,

I only run the inlet up to 230C. The maximum I ran was 300C.
The column I used was the DB-Wax UI, 30m, 0.25, 0.25 from Agilent, and I ran it up to 240C maximum. FID was at 260C.
The method I used:
40C hold for 5 mins
5C/min to 100C
50C/min to 240C

It always has the baseline problem at RT 9 to 10 mins

This is the chromatogram of a blank/instrument run, with no injection.


Thank you,
ChauDang

Thanks James,

For the front inlet, I just changed the inlet liner/o-ring and the septa, and it just kept bending my needle. That's why I changed to the back inlet.

I tried to run two blank instrument samples, with the inlet temperature lower to 50C and here are the results:



The second run looks better but still has some contamination.

I bent a few when I installed a cyclo type liner upside down but otherwise never had a problem with the autosampler not aligning well with the inlet nut.

I will have to look at the images at home, can't open them at work

Thank you James,

You guessed it right. I installed my cyclo type inlet upside down
I changed it back to normal, However the baseline is still bad. Just a blank run, but it has the same drop and rise in the baseline


Thank you,
Chau Dang