GC's giving off strange smell, possible malfunction?

[sh0ttychemist2595]

My Lab has recently installed three Agilent 8890's. One is coupled with a Single Quad, another with a QQQ, and the last with an FID. Two share the Same phase column(DB-624) and the last has a HP-5. The flow rate is near optimal conditions for all the columns (1.1 ml/min for the MS systems, 1.4ml/min for the FID) and none of the instruments are temperature programmed past their range, even in post run. I've noticed this strong burning smell coming from all of the instruments during their respective post runs. It smells almost like melting plastic, and but I can't put my finger on what the smell is. All columns have been adequately conditioned. When doing maintenance a few months ago, I had noticed that septa from one instrument had melted. I had assumed that the initial technician that installed the GC's didn't use high temp septa, so I had changed all of the septa to High temp, low bleed septa. The smell still has not gone away. After recently performing a gold seal replacement on the gc single quad, I had noticed that the insulation of the cap leading to the gold seal was more or less melted to the top of the GC. All inlets on the instruments are set to 250C, and I'm not sure what could be the source of the problem. Any help/insight would be appreciated.

[antonk]

* PVC cable in oven exhaust path
* Forgotten thing in thermostat
* Wrong (uncalibrated) inlet temperature (actual >> specified 250)
....
* New plastic with incomplete polymerization

[James_Ball]

If a thermocouple is not reading correctly it can cause the inlets to overheat.

I had Agilent install one of the Gerstel made large volume inlets on our 6890/5975 a few years ago and the first one had a bad thermocouple. While waiting for it to heat up we noticed an odor. I opened the oven door and asked the engineer if the inlet should be glowing. It was cherry red on the bottom and had melted the equivalent of the gold seal to the bottom of the inlet, completely welded it together.

If you have some type of temperature probe you can stick into the gap above the insulation cup on the bottom, see if the temperature reading is near what it should be.

Also, for brand new instruments, there is always an odor for some time as all the oils from manufacturing bake off the stainless steel inside the oven.

[Jake]

If you're melting septa, as James points out, there's clearly an issue with your inlet temp. regulation. At an inlet set-point of 250 C, which is a very typical inlet temp., you should be able to use ANY Agilent septum. The maximum temperature for all but the high-temp/low bleed is 350 C.

I am a bit confused though. All three of the GCs are doing this (melting septa)? Hard to imagine all three new GCs would be having the same issue of the same failed part.