Split flow problem

[tinsang]

Hello all,
I've an issue with Gas chromatography Thermo series Trace 2001. I can’t run my samples because the GC gives an error that the split flow isn’t reaching. The split flow should be set 93 ml/min. but the split flow can reach up to 80 ml/min. The leak check and the K- value test passed.
Here are the current conditions:
Detector:260°C
Injector: 230°C
Carrier gas: He
Split flow: 93 ml/min.
Column Pressure : 0.55 [bar]
Oven: initial Temp. 195 [°C], heat up to 220°C (2,5 °C/min.), end temp. 220°C (hold 12 min.)
My instrument is limited to a split flow of 200ml/min and this analysis ran 100 times successfully with this condition as mentioned above.

A leak in or around the inlet? I didn't believe, because the leak check passed.
Is a blockage in the split vent trap? If yes, how can I check it?

Thanks for your support.
Dao

[Peter Apps]

The first thing you need to do is to measure the split flow with an independent flow meter to eliminate the possibility that there is a fault in the onboard flow control.

If the split flow really is too low then it is almost certainly due to a restriction in the split plumbing - swapping the trap would be the logical next step. I assume from your temperature programme that you are analysing high boilers - these are the kind of things that clog up split vents.

Peter

[tinsang]

Dear Peter,

I've swapped the split liner filter. The analysis run well. Thanks for your reply.

[Peter Apps]

Good to hear. Thanks for the feedback.

Peter

[Frenky77]

Hi!

I probably have the same issue: the system can't reach the split flow I set or the split flow begins to go down after some minutes it seems to work.

I'm using an old Perkin Elmer Autosystem XL GC that analyzed during the last months a lot of high boiling substances.
I've seen that there is probably a trap on the split vent line: you can find it on the web (Charcoal Trap for Capillary Injectors and Programmed-Temperature Split/Splitless Inlet Systems - part #N6100275).

What do you mean "swap the trap"?

Is there a possibility to clean/regenerate it?
The new part is quite expensive...

Here two pictures of ther part.
https://www.dropbox.com/s/4kwxgdaxh85qg ... G.jpg?dl=0
https://www.dropbox.com/s/r35k7a6l1byo6 ... 4.jpg?dl=0


Francesco

[Peter Apps]

Hi Francesco

By "swap the trap" I mean put a new one in the place of the old one.

You might be able to regenerate the trap. You could try backflushing it (in other words with a gas flow in the opposite direction to the direction that the gas flows when the GC is operating) with nitrogen while heating it to at least 400 C. Backflushing with a series of solvents (at room temperature) might also help, you then need to evaporate the solvents with a flow of clean nitrogen.

Note that you will not be able to heat it if has polymer seals in the connections.

Peter

[abdurahman alkaff]

I had the same case back then. And Peter is right,it is due of the split vent. You could sometime see an indication of higher of head pressure of your injector or if your IQC data is moving higher than your average.
The solution is by changing the split vent with new one, or in my Shimadzu GC i just swap it with purge trap.
Another thing that I had done was, you can take small portion of your split trap on input side by scratch it.
Cheers,

Abdurahman

[Frenky77]

Thank you Peter Apps: I'll try to regenerate it before buy a new one.

abdurahman alkaff: if you see the picture you can see I can't open the trap to scratch it.


Do you think I can install a different trap instead of the Perkin Elmer one?

Francesco

[abdurahman alkaff]

Hi Francesco

Sorry I miss your picture.
I had seen your picture, and the trap in that picture probably the carrier in rather than split vent trap.
I am sorry, i am not familiar with perkin elmer GC. Best thing is to refer the manual thought.

Cheers,

Abdurahman

[Peter Apps]

Thank you Peter Apps: I'll try to regenerate it before buy a new one.

abdurahman alkaff: if you see the picture you can see I can't open the trap to scratch it.


Do you think I can install a different trap instead of the Perkin Elmer one?

Francesco

You can try using other traps, but you have two different size connectors, and at least one welded joint to take into account, so it may not be simple. Also, the resistance and internal volume of the substitute trap will need to be similar to the PE one for the gas controls to work properly.

Peter

[Frenky77]

I simply solved by carefully cleaning the liner.

I tried to change the split rate (20:1-80:1) and everything went well.

Thank you all for the support!

[Peter Apps]

Thanks for the feedback - what kind of liner was it ?

Peter

[Frenky77]

Thanks for the feedback - what kind of liner was it ?

Peter

It's a 2-mm Split Mode Quartz Liner for Programmable Split/Splitless (PSS) Injector, 86mm x 4mm OD x 2mm ID, Product number N6121004.
I think it's quite easy to clean. You can find the picture on different catalogues (#N612-1004).