Air compressor for FID air.

Discussions about GC and other "gas phase" separation techniques.

13 posts Page 1 of 1
Hi all I am looking for an alternative to using zero grade air for my 5890-FID. I believe I've seen references in the past to just using an air compressor I think someone mentioned a Harbor Freight model. What type do you need and how do you hook it up and regulate the flow? Also I assume it would be wise to use a hydrocarbon trap and replace it frequently?
Hi MSCHemist,

I apologize--Do you mean an air compressor or an air generator? Sometimes the air generators have their own compressors...and their own pneumatic controls (to answer the flow regulation question).

And yes...since I've used "house air" for FIDs, I still swap out hydrocarbon traps, roughly quarterly.
MattM
That may have been me, given my propensity to try horrible ideas that occasionally work out well.

Looks like it's a Porter Cable C2002R, an oil-free pancake compressor. It's loud, noisy, obnoxious- and works just fine. It should go without saying that a hydrocarbon trap is a must-have, despite being oil-free. I get a beautiful baseline, running hydrogen carrier gas and a pancake compressor for air.

Tying in the compressor to a larger reservoir will increase the cycle time, meaning the compressor is on longer, but less frequently.
We've used "house air" for FIDs for years, but that is plumbed to a Balston Whatman air purifier designed for FIDs.
To paint the complete picture, at the two jobs I'm thinking of also there were (Parker Balston, I believe) air purifiers upstream of the hydrocarbon trap, pretty much the same as Consumer Products Guy describes.
MattM
Thanks. I assume I'd need a moisture trap as well given the relative humidity in my lab this summer.
When I use an FID (not too often) I use a plain old compressor from Lowes/Home Depot. A hydrocarbon filter for the heavier hydrocarbons will probably help but it will not take out methane (not very long at least) which is present in ambient air. Therefore, you will still see an elevated (but should be relatively stable) baseline. A water trap is probably a good idea.

If you have the money you could invest in a zero air generator but keep in mind that you will need pretty high quality (read dry and halogen free) compressed air to really see the benefit.

You do not regulate the flow, you regulate the output pressure. The flow should be regulated at the instrument (which is sometimes dependent on the line pressure.)

Best regards,

AICMM
AICMM wrote:
If you have the money you could invest in a zero air generator but keep in mind that you will need pretty high quality (read dry and halogen free) compressed air to really see the benefit.

I agree- just found out that "zero air generators" do not remove water, but that doesn't effect FIDs much. Ideally, the setup would be standard air compressor, air dryer, heavy hydrocarbon trap or halogen trap, then zero air generator. I'm ready to scrap ours, more trouble than its worth and go back to tanks.

At the minimum on a house air system, I would use Supelco's suggestions:
http://www.sigmaaldrich.com/analytical- ... =110579105
then hydrocarbon trap, then molecular sieve, then GC. Depends on quality of house air- ours is straight out of the big 'ol oiled compressor.
We were once given a 5890 GC that had been in the warehouse of our manufacturing facility. Once it arrived, we found liquid oil in the FID and air lines to it, it had apparently been connected to a house compressor that was oil lubed, and no way to trap the oil. So we had to clean and replace a bunch of stuff, including the oven insulation which had become oil-contaminated from overflow. Of course, when we heated the oven, the smell was pretty bad as we could not remove all of the oily insulation (we packed with fiberglass tape).

So we used that GC exclusively for an assay that only required heating to 200 C.

In our own lab, when the oilfree house compressor went dead, to save $ it was decided to use an oil-lubed compressor and maintain its oil trap. Well, staffing issues led to this being neglected by facilities, so house air in the lower floors had permanent oil in the lines. We used tubes filled with cotton as a first trap/visual indicator for oil. Luckily, our Blaston GC zero air generator was mounted high on a shelf so the oil couldn't get up to that; we also had a cotton filter in front of that though.
MSCHemist wrote:
Hi all I am looking for an alternative to using zero grade air for my 5890-FID. I believe I've seen references in the past to just using an air compressor I think someone mentioned a Harbor Freight model. What type do you need and how do you hook it up and regulate the flow? Also I assume it would be wise to use a hydrocarbon trap and replace it frequently?


:lol: I am also looking for the alternative air compressor to using zero grade air. Which model is valuable for it?
Olivia Lisa
I have a small portable air compressor for my little nice car. I love my car and take care her beauty. it is an only 2-gallon compressor.

can you tell me which compressor will be perfect for it?
Olivia Lisa
Can you use Inland 45 for lubricating such compressors. At least that oil designed for GC/MS roughing pumps does not putout any significant volatile hydrocarbons.
We have a very large two stage 10hp compressor 140 gallons of storage capacity we use for the entire lab. When we first set it up we had only the coalescing filters and that led to a lot of water in the lines. We once drained probably 20 gallons of water from the lowest lines in the building.

When we went to using Nitrogen and Zero Air generators we installed a hospital grade air refrigerated dryer just after the compressor and have had no problems with moisture or oil in the lines at all. We feed that air into the Balston pressure swing N2 generator and a Balston Zero Air generator. The Zero Air is at the bench where the FIDs are located, the N2 feeds the entire lab. We only have to replace the scrubbers in the generators about every two years. Just be sure you also have the halide scrubber after the compressor if you use halogenated solvents or HCL in the building as those will kill the hydrocarbon traps and ruin the generators.
The past is there to guide us into the future, not to dwell in.
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