Chromatography Forum

Hello all,

We were recently able to fix our GC/MS because of a leak we had found. We baked out the trap for 12 hours and let the levels get back to normal and ran an Air/Water check. The air level was fine, but the water level was at 'Massive.' We baked out the system for a longer time (24 hours) and this morning I ran another Air/Water check with the same outcome (Massive water level). Any ideas as to what the problem might be? Would I need to bake out the system for a longer period time and/or at a higher temperature? We've been using ~230 C for the temp.

Any info would be great.

Is the water level dropping at all ? If the vacuum chamber has been opened it can take several days to bake the water off the internal surfaces if the ambient humidity is high - and it tends to sit where it is coolest.

Peter

Luckily I found that our gas clean filter was spent. I changed that and will bake out the system over night to see if that will help any. We did have the system open for a long time so maybe it just needs more time to get rid of the water. Thanks for the comment!

Also make sure your PFTBA vial has calibrant solution in it.

It doesn't need to bakeout everytime to get rid of water, you will ruin the instrument.
If you have high levels of water and low levels of air it can only be a saturated filter or water residues after a vent, just keep it idle for 1 day and it will be ok.

Thanks for the responses! I tried another air and water check this morning, but we still have the high water level. The professor that is helping me says that we should possibly ramp up the column temperature on the GC for some time to see if that would help, although I tend to believe that since we had the instrument open for a while (and that it's fairly old), giving it some time would be the better option. Thanks again for the comments!

I have same the problem on my Saturn 2200. Did you fix the problem already? Please show me the way to fix it.
Thank you.

Tran Ngoc Dinh

Dear Adam & Tran Ngoc

For air /water ratio problem you assure following thing with your GCMS
1) Check gas clean filter for air and water signal, saturated or not
2) Instrument back out normally 10 to 12 hr.
3) After above mention step adjust first Cal Gas and RF tuning than Auto tune except air water
4) After pass Trap, Mass, EM test then tune air water and check status

If again water or air level is high
Then you separate mass end with GC and block mass transfer line with block nut and check air water level after 2 to 4 hr. if water persist and constant then your leakage is in mass end and clean trap and adjust properly with manifold and trap.

If water and air level down then leakage in GC side

Then you just decrease your flow rate 1 to 0.2 ml/min and check air water if it decrease it miens leakage in gas line and correct it. Before it you replace your septa and liner or assure your injector end is leakage free.

Hope this information helps you to understand your problem

Hi!

Please, you load the method "DailyCheck" original from Varian, after that, you put the electron multiplier in 1500 Volt.
Go to the "manual control" screen and select segment one (air and water) and turn on the trap, please take a print screen of it and put it here.
thanks

Removing/lowering moisture level (<10%) from GC-MS can be daunting. Sometimes, after leak checking, baking it for 16-24 hrs will correct the problem. Sometimes you need to do more troubleshooting like changing your pencil filters, gas line moisture/oxygen filters, gas source, and cleaning your multiplier housing and changing the seal. We have just recently resolved our problem doing these things.

Ditto on what shiva_kant said.

You can also sonicate the trap in methanol to remove the water. Do this only as a last resort because you can degrade you electrodes.

What is your fore line pressure? Try replacing your quad rings (trap and transfer line). The older the instrument the more issues you will have with keeping a vacuum

You might also have a leak somewhere in you GC. Doing what shiva_kant said earlier (isolating the GC) has helped me in the past

Good luck,

Jones