Chromatography Forum

I have been reading some Agilent documentation for the vacuum systems and they have very clear prohibitions against any sort of vacuum exhaust filters. Unfortunately, I ran across this documentation after I had bought filtration setups. So, now I am thinking maybe getting filters was a mistake.

Does anyone have strong opinions pro or con about this?

I bought this SIS all in one vacuum pump exhaust trap for my E2M2 backing pumps for my two 8260 P&T GC-MS thinking I would make the air in the lab safer.

Now that I am thinking Agilent might be right I can suppose that purge vent traps are sufficient and what makes it through the column and the MS will likely be absorbed by the pump oil (at least the high boiling compounds). This is a combined oil mist filter with a carbon trap attached. If I remove the carbon trap, then at least I can take care of oil mist and not endanger my turbopump?

All of the Agilent pumps after the E2M2 came with the oil mist filters straight from Agilent, so that should not be a problem.

Ours are vented outside through an exhaust vent which we use to also remove the hot air from the oven. I vent the split and septum purge lines through that also.

The E2M1.5 that came with my 5975 has an Agilent-branded trap/mist filter that came on it new.

It's actually probably about due for replacement-I've never taken a super close look at it to see exactly what it contains. It's a blue plastic cage a few inches tall with a tight cloth gauze visible through it-I don't know if there's more to it than that, or if it just uses the cloth to hold down oil mist. It does get rid of the mist cloud during the first few seconds of pump-down, although long-term I still seem to get a film of oil on the top of the pump and on the bench around it.

So, it sounds like a mist filter is OK. What do you think about the possible back pressure caused by the activated carbon filter?

It should only be pumping a few milliliters per minute, mostly from the carrier so I wouldn't think there should be much back pressure. Only time there is high flow is the first minute or so at pumpdown.

FWIW, this is what's on mine

https://www.agilent.com/store/productDe ... 1099-80039

I agree with James that there really shouldn't be a backpressure concern since there's basically not any perceptible flow out the exhaust even when the foreline is in the range of a few hundred millitorr. I'd only worry about backpressure if the scrubber was completely clogged.