Building Gas Chromatograph with Capillary Column: Tips & Guidelines

[lilrex]

I have a project that I want to do; really it is an experiment that would prove useful to another project of mine.

I want to build a gas chromatograph.

The specs.

Capillary column
Helium carrier
Thermal Conductivity Detector

The analyte is a mixture of CH4,N2 (for now)

I already have the TCD made and it is functioning well, I just need some info on the capillary.

Question: what will work well enough for a capillary column? Can I use a copper capillary as used for refrigeration? I know that the norm is a capillary that has a coating on the inside with a Stationary phase but will the walls of a copper or glass capillary suffice in this function? I suspect it all has do with the degree of separation that is needed but I am looking for some guidelines in this respect, just some empirical guidelines to help me get started.

Probably for one to make a recommendation I might give some more information I just need to make an approximation as to the quantity of the components in the anilyte, rarely would I even need to separate a complicated mixture just the simple one that I exemplified.

I guess that I could just buy some capillary and experiment but I just wanted your opinion on the matter.

Thanks, Cheers!

 

[lilrex]

GC anaylisis of CH4

I mentioned in another thread that I wanted to build a Gas chromatograph but I think it was poorly stated so here are more specific questions.

I read that activated alumina is suitable to use as a stationary phase for the detection of hydrocarbons up to pentane, in the examples used the same column was used to separate the isotopes of hydrogen gas.

I am not sure exactly how this works, is it used as a kind of molecular sieve? or is it separating the mixtures by another means? I would like to know but more importantly I need someone with more experience then I that can tell me if activated alumina is capable of separating CH4 from N2 and O2 in a hydrogen or helium carrier?

I would like to use a capillary column but am having trouble selecting the right coating for this task.

 

[lilrex]

Al column

I am thinking about constructing the column out of aluminum, i figure that since the column packing is going to be AlO3 that it couldn’t hurt, of course I am not much of a chemist, but I can't think of any consequence to using the metal.

Normally for the packing one would use 30-120 grit closely separated material but all I have at the moment is 800 grit. So I will use a narrow tube, probably .67 mm in diameter. The problem I am seeing at this time is the dead space of the detector and will have to rebuild it, otherwise it will not resolve well. so if I am going to have any chance of a good measurement for my application I will guess that the dead volume of the detector needs to be 1% of the column,(if anyone else has an opinion on this, I appreciate advice)

 

[lilrex]

I really like projects like this as they teach you a lot if stuff!

cheers!