Chromatography Forum

Hi everyone,

I am doing a workplace health assessment of our lab. Does anyone know what is contained in the exhaust gas that a GC-MS system vents after each run? I imagine most of it is hot air from the oven. Has there been any research done on how toxic these exhaust gases are or what they contain?

Thanks for any assistance.

If by "exhaust gas" you mean what comes out of the MS roughing pump then it is helium plus whatever sample has been run, plus some vacuum oil vapour. The split and septum purge vents put out sample vapour in helium.

If you are worried about the hot air that comes out of the back of the GC oven as the oven cools ? - it is air, the same air as in the lab. If it is contaminated you have a huge leak that would stop the whole instrument working.

Peter

... plus some vacuum oil vapour...

Some say oil mist. No doubt vapour accompanies mist.

... plus some vacuum oil vapour...

Some say oil mist. No doubt vapour accompanies mist.

Good point, I would guess that if they are at the stage of worrying about the toxicity of hot air they probably have a mist catcher on the pump.

Peter

Thanks for the replies.

If by "exhaust gas" you mean what comes out of the MS roughing pump then it is helium plus whatever sample has been run, plus some vacuum oil vapour. The split and septum purge vents put out sample vapour in helium.

If you are worried about the hot air that comes out of the back of the GC oven as the oven cools ? - it is air, the same air as in the lab. If it is contaminated you have a huge leak that would stop the whole instrument working.

Peter

There is a mist filter on the roughing pump for the MS, so I'm not worried about that. I am talking about the air vented out of the GC. While I know it is mostly air, it is air that has been heated in the system and smells very unpleasant - like a burned plastic kind of smell. So I just want to know if there have been any studies done to see what else is in it. If it were purely air then I wouldn't think it would smell like it does.

Hello

I believe all vendors do tests to check if there is any potential risk of environment and health and safety issue.
I would check GC oven inside. If you smell plastic perhaps there is some plastic part inside (ferrules box, jet box etc).
For example in Agilent GCs (6890/7890) there is chance that small part can stuck at the back of oven.
Sometimes if GC has not been used for a while if you heat it to high temperature you can smell "smoke" from oven heater - but it should be gone after few runs.
Also check back of the oven (oven flaps) perhaps there is something you cannot see from GC front.

Regards

Tomasz Kubowicz

This smell is typical if you install a new column. It should be gone in a few runs as already said.

Thanks for the replies.

The system has been like this for the past year - so it's not a smell coming from a new part. I am using a Shimadzu QP2010 Ultra. Perhaps this is just how Shimadzu ovens operate? I'm not sure.

If you had told us in your first post that there was a smell we would have known that there was more to the problem than hot air.

A persistent hot plastic smell might point to overheated electricals - possibly a badly wired mains plug or something. The smell might get stirred up when the vent flaps open which is why it is noticeable when the oven cools. Alternatively there might be something slowly cooking to death in the electricals of the GC - varistors which are just above their rated voltage get hot for long periods. Check also that the hot air is not blowing on anything behind the instrument that might generate a smell. To check that the smell is actually coming from the oven turn the heater and fan off while it is hot, open the door and sniff.

Peter

Hi

Just to summarise

You have a burnt plastic smell coming from the oven vent rather than from the pump exhausr?

Is this most noticeable on cool down after each run?

Is the odour level the same each time?

The other replies that you have are very helpful.

Regards

Ralph

As an aside I once had this problem because I forgot to remove the elastic band attaching the column label

Somewhere in the archives there are pictures of what used to be plastic rulers and screwdriver handles before they were accidentally left in a GC oven during a temperature programme.

Peter

Somewhere in the archives there are pictures of what used to be plastic rulers and screwdriver handles before they were accidentally left in a GC oven during a temperature programme.

Peter

Even worse is a plastic flashlight that was left in the oven

Had a similar issue of a smelly (putrid) GC oven on a Thermo PolarisQ
since new, the other Thermo Polaris Q we had, had no smell.

It would sink out the entire Instrument room, so it was decided that it would only be allowed to run overnight/weekend with the fume hood on, and the last sample injected must be 2 hrs before anyone showed up to work the next day, so that the room air would have been flushed clean by the fume hood.

Nobody could figure out the cause for years, problem went away when it was sent off to disposal.

Thanks for the further replies.

I have checked and there are definitely no foreign objects in the system.

The smell is most noticeable on cool down after each sample run. and the odour level is the same. There is no smell coming from the instrument otherwise. The rear of the instrument is clear of obstructions so the hot air is hitting nothing except the exhaust duct.

At this stage I will wait until the next service interval and ask the Shimadzu engineer. While it doesn't seem to be a problem it does seem strange.

But back on the original topic, by the sounds of it there is nothing inherently toxic about typical GC-MS exhaust gas. So thanks for the replies answering that question.

We have encountered a similar problem with the 6-year-old Agilent 6890. The smell of burnt oil appears when the thermostat heater is turned on. The device was not in operation for a while (a couple of months). Now I'll have to disassemble the thermostat elements to see the heater and the fan. Is it possible that the oil from the fan bearings gets on the heating spiral?