Bulding my own carbon traps

[Vox]

Hello, another post in search for low-budget solutions. My company makes CO2 scrubbers, so there is plenty of activated carbon sitting around. Does anybody see any problem with me building my own charcoal traps?

I was thinking of building some traps out of 2" or so pipe, 6-8" long and loading it with pelletized carbon with mesh screens on both ends. Since this would only cost like 10 bucks a piece

I was thinking of putting one on my Zero Air, my HE and H2, for my 5890 GC-FID. There are also some small traps built into the GC (I've no clue exactly what kind of trap they are).

I will gladly accept any input you have to give. Thanks.

[chromatographer1]

Well, I like to save money too.

Leaks....... will your homemade traps not leak gases into your pneumatics?

If you wish to trap hydrocarbons, when will you know the trap needs replacing? How do you know it traps well?

If other gases leak in or are desorped from the carbon you are using (is it really really clean enough? ) how will you know?

Those other little traps are for water and oxygen. They don't last too long, just long enough so the original user has good gas for the first few months of use, assuming the gas was pretty good to begin with when the GC was first installed.

Removal of carbon containing gases is important for FID response at very sensitive levels, but if you leak in oxygen (and maybe water) into your He carrier will that damage your very expensive columns? Will you know they are damaged and how?

Whatever you decide, please use indicating purity traps to see if anything is getting to your GC after your homemade traps and fittings remove it.

They remove water, oxygen, and hydrocarbons at very low levels.

best wishes,

Rod

[Bruce Hamilton]

I've almost always built my own carbon traps, I used some 1/2" stainless tubing with 1/8-1/2" brass swagelock fittings at the end.

The tubing was about 15" long, and I stuffed some glasswool in one end- filled with granulated activated charcoal ( about 2 - 4 mm size ), carefully tamped (sp?) it down by tapping gently on the bench, then add more glass wool and the fittings.

I'd purge with nitrogen for about an hour before connecting to the system. Note that some GCs have mole sieve traps on some carrier lines inside them, so the effect of changing the carbon traps isn't always obvious.

As they just have 1/8" fittings, you can substitute with a piece of copper tube, and a new trap should reduce the FID background signal after several hours. You know when the traps are dying, because the FID background signal will creep up slowly over about a month, but I used to just replace them regularly.

Used to last about 2-3 years on FID and carrier gas lines - but I used factory air with a Norgren moisture trap and carbon filter in the regulator at the takeoff point. The Norgren carbon filter was also changed every 3-4 years.

Quite easy to do, and the brass swagelock ferrules onto the stainless seldom leak, and are easily demountable. you could use PTFE ferrules as an alternative.

Please keep having fun,

Bruce Hamilton

[HW Mueller]

This is from some time ago, but I doubt too much has changed in this respect: Commercial traps for H2O and O2 were installed in an attempt to clean up N2 (4.6 grade ~ 99.999% or better). The traps did not change color, indicating that H2O and O2 were too low for trapping, but the baseline (FID detector) got worse. The traps were taken out, the baselines immediatly improved, and the following years FA were analyzed without any problems attributable to carrier gas. Later we used H2 without any traps....., no problem. It seems that the high grade commercial gases payed for themselves.

[sassman]

OT, but this reminds me of a mishap I had as a grad student. I wanted to build my own carbon trap to catch organics coming out of my LC/MS roughing pump, so I filled a 2x15 inch glass tube with black carbon and put glass wool on both ends. I connected the trap to the outlet of my pump and turned the pump on. Poof! Black carbon shot out all over the lab. That lab probably still has black stains from it. What I learned: when you first turn on the vacuum pump for a mass spec, it pumps out lots of air very quickly. Hahahaha!