Chromatography Forum

Dear Sir,

I have a problem in my TOGA system. The seperation of permanent gases like hydrogen and nitrogen are done with a mol sieves 5 A column. But the H2 and N2 peaks are very small. Inorder to improve, i conditioned the mol sieves column to 300 degeee for 5 hours using argon carrier gas. But still the same problem existis. Leak check was done using soap solution and as such no leak was detected. What could be the problem. The tcd filament temp is 140 degree and that of the detector is 240 degree. Since we wnt to detect Hydrogen we use argon as the carrier gas. Valuable informations will be highly appreaciated.

It appears that your sensitivity to H2 and N2 have changed from your post.

[b]What changed from your earlier analysis where the peaks were larger?[/b]

Perhaps your peaks are supposed to be that small. Why do you believe they are not? Give us a little more information, please. Are your other gases the right size? Did you contaminate your column with something where you felt you had to condition it. Are you injecting directly onto a mole sieve column or is there another precolumn ahead of it. Has it been cleaned?

Did you change gas supply? Have you changed gas cylinders? If your Argon gas is contaminated with air or oxygen your H2 and N2 peaks should get smaller.

Are you running a rotor or diaphram valve? Just because you run a soap test on external connections that does not exclude that you still have a leak internally.

If you had a good analysis originally and it went bad, then you have to find out what changed !

If you never had a good analysis originally, then that is a different problem. Your post does not give us enough information to be as helpful as we would wish.

Good luck.