Cannot tune, large leak.

[wenleonard]

About a month ago after a He tank swap, I had a large leak that was very difficult to find because my system seemed air tight. Detector and column (Agilent 5975c) did not contain the leak but as soon as the headspace and GC were hooked up the system couldn't even pass and air and water check. It turned out a Swagelock fitting extending the GC control line to the headspace supply port was leaky. Once I replaced it my leak symptoms disappeared.

The tank was recently changed and immediately afterward I am getting the same kind of response as before, a large leak but my inlet is pressurized and headspace working normally. The fitting I replaced is fine, so now my thinking is that the EPC is leaking because my headspace is detecting Nitrogen.

Has anyone else experienced a leak like this? My next step is to rewire the GC to be used without the headspace but if this sounds like an EPC failure to anyone then I can just order a replacement instead of doing major work just for diagnosing.

Thanks!

[Peter Apps]

Depending how you do cylinder changes there might have been air introduced into the gas lines.

Peter

[wenleonard]

I purged the system for a couple hours and still have enormous hits of 18, 28, 32. Surely a bit of air introduced during a tank change would clear up.

[cleh]

Check your fittings inside the oven (transfer line and inlet). When you cool these down to do your cylinder change, they can loosen up. Use an electronic leak detector to check your regulator and all connections and fittings going to the GC. Also use it to check the inlet and connections to the column. Make sure your cylinder is completely open. If you have a purifier in line, it will take a bit longer to purge the air. If the purifier is old, you may want to replace it (you can take it out of line to see if the leak disappears). If these are all OK, check the transfer line nut and manifold o-ring by spraying some form of Dust Off on them while scanning for the fluorocarbon in the brand you use.

[wenleonard]

I resolved the issue. Turns out our Ultra high purity helium had water in it. Thanks for all of your advice!

[James_Ball]

I resolved the issue. Turns out our Ultra high purity helium had water in it. Thanks for all of your advice!

Even the best suppliers can have one slip through once in a while. Drives you crazy trying to find a leak when it is your gas to begin with

Worst one I had so far was when we had a 800 gallon Argon tank filled and started to see Calcium in all our ICP/MS instruments. Turns out the Argon was contaminated with Xenon, and doubly charged Xenon interferes with Calcium.