Methane & Methanol Separation, air sampling

[AZBiodiesel]

Hey all,

I need to take a sample from an exhaust vent off of a water treatment skid and try to ID methanol, methane and maybe any other VOC. I have never done any air sampling before. Only things I have onsite are 25 mL headspace vials and gas tight syringes. I have a 30m Stabiliwax column that I am planning on using.

I will probably take a sample for a few seconds in the exhaust stream, and a background sample far away. This is going to be a crude test. Any thoughts/help? Thanks

[chromatographer1]

Are you using FID?

If the air is humidified a water peak will be close to the methanol. The hydrocarbons C1-C4 will have almost no separation, and their 'plug' may be distorted or 'flattened' by a large amount of water or methanol.

Methanol should elute after THF, acetone, and methyl acetate and almost coelute with MEK.

DCM should elute after methanol.

Good luck hunting.

Rod

[AZBiodiesel]

Yes its FID with a SSL injection. I have another GC with On column injection port but my needles don't fit the stabiliwax ID. So i have to use the split splitless. I was afraid this column wouldn't separate the low carbon volatiles... and i forgot that water can interfere on the fid. There will most likely be some moisture carry over. I guess I will have to use something like a VOCOL column?

[chromatographer1]

Vocol, or 1301 is a better choice, me thinks.

The water interferes at the head of the column, not so much at the FID end. But only if it is a large amount (steamy air would qualify). If it can separate at the head giving a narrow plug, it may spread out the hydrocarbons which will tend to smear as the HC won't retain forming a plug until they pass the water plug. (water and oil don't mix, right?)

good hunting

Rod

[Johnny Rod]

How about a PoraPLOT Q or similar? Should separate out the light components?