Chromatography Forum

I was in the process of reactivating a Autosystem GC that has been in storage for a while, and while testing it, I had a student worker misunderstand me and inject about 1 mL of hexane into the injector.
About 10 minutes later, I started to smell a terrible burning smell and eventually noticed the collector was burning up, with the inside literally deformed and melted.

I ordered a new collector, polarizer and jet - but I'm concerned there is something else wrong with this machine that i've missed. H2 flow rate was ~40 ml/min and Air was ~450 ml/min, with a carrier flow of about 3 ml/min He. Since we were just testing, I had an old 0.25 mm column in. Would injecting 1 mL of Hexane be enough to destroy the collector like this- or is something else wrong?

I have put several hundred microliters of hexane through Varian FIDs with nothing more spectacular than a large blue flame in the body of the injector and no damage. These Varian FIDs are very robust - no insulators anywhere near the hottest parts, or in the way of larger than usual flames. If your FID had plastic insulators they could have ignited with a larger than usual flame but my gut feel is that there is somethig else not right. Have you checked all the gas flows with a flow meter (not the GCs onboard controls and meters) ?. As an outside chance, you are using air and not oxygen ?. If oxygen I would have expected the whole GC to combust.

Peter

Yes, all gas flows have been checked with digital flowmeter, and we are using UHP grade compressed air, not oxygen.

unhpian,

I would be most suspicious of the heater and RTD being separated from each other in the detector. The RTD is nice and cool so it says apply power to the FID heater ad nauseum. Pretty soon you have a glowing hot heater and an RTD that is still saying that I am pretty cool, so apply more heat..... The other thing I have seen is flipped heaters, that is, what I thought was a valve heater actually in the injector and vice versa. Still, neither of them got so hot as to melt an insulator.....

One microliter of hexane will not generate the amount of heat you are considering so on re-start I would follow the instrument very closely.

Best regards.

Was everything OK before the supercharged injection ?

Peter

hydrogen and air attached in reverse?

Aldehyde,

My observation has been, mostly on 5890's and such, that reversed connections leads to problems lighting and staying lit, not extreme temperature. For what that is worth....

Best regards.

Woops, I responded awhile back but I guess it didn't go through. I agree that it would be rare but have actually heard of this happening to a customer. They attached in reverse and then tried and tried to get it to light, finally getting a nice flame in the collector until they turned off the gases. Oops.

That would do it .

Peter

OP Here: It's been a few months, and while there haven't been any problems with the replacement collector, we still haven't figured out why the first one melted. The hydrogen and air are hooked up correctly, and the flow rates are within their accepted ranges. At this point, I'm guessing it was some fluke occurence, or perhaps the tech injected more hexane than he thought.