Argon as Carrier

[Schmitty]

Hey all,

We had a bit of an issue here yesterday, as a tank of Ar was put on the house manifold for the UHP He lines. I have purged the Ar out of a couple of the systems, but there are issues with others.

These are all 5973, 5975 Agilent systems and a Waters Quattro Micro.

Does anyone have any solutions, other than waiting, in order to get these systems free from Ar? Are there any common side-effects, like toasted electron multipliers from a situation like this?

Thanks!

[haiedc]

Ar is inert and difficult to condense or adsorb, so you just purge your systems with He for some time. The ion source can not ionize the Ar atom to the extent that they destroy the EM. So I don't think there are any side effect.
Anyway, to be on the safe side, I should think you'd better reduce the EM voltage before testing the condition.

[Peter Apps]

HI Schmitty

When purging the gas system you need to do it all at once - otherwise the argon in the unpurged sections just diffuses back into the parts that have been purged. I would be surprised in a low % of argon in the helium would make a significant difference to chromatography or MS.

Peter

[Schmitty]

Thanks.

Peter, the manifold system we have has about 10 cylinders connected and split in half, so we can swap out 5-6 at a time without disturbing the flow. I did notice that the retention time did not shift significantly on my instruments, but on a GC/FID, it was very apparent. The only way I noticed that the error had occurred was that my backround was going up and up, since I was collecting in scan mode (15-350amu).

Currently, I cannot get the Ar out of my manual tune window for several of the instruments. For the ones that do show no sign, or very little sign of Ar, have a lot (300-600) of background peaks in the stune or atune. We normally have 100-200 background peaks only.

Additionally, this did happen last year as well, however the tank that was put on the UHP He line was Nitrogen instead. In that instance, it didn't take nearly a long to resolve.

Regards

[Don_Hilton]

If you have any microchanel plate detectors, it might be a good idea to leave them off until the argon has cleared. Argon will form a plasma at low pressures and high voltage. It is suspected in the demise of a detector.

[BZK]

If you have an in-line carrier gas filter filled with molecular sieve this could be the critical point. Argon is easily adsorbed and then purged out. Try to disconnect the GC carrier filter and purge at high flow rate direct into the air for several minutes. Check after clean.
I don't know if also Agilent GC contain a molecular sieve INSIDE the GC carrier line ( as Shimadzu GC-2010, for example) but if yes also this filter must be cleaned or replaced.
On my GC-2010 to avoid periodical increase of M/Z 40 i have replaced the inside carrier filter with an empty tube.

Roberto Barcarolo, Italy