MS vs TCD

[ilham]

Hi,

I have the HP-MOLESIEVE column that requires TCD to detect permanent gases. I have MS instead of TCD but when I tried running my samples, no peaks were detected.

Do you know if MS can/cannot detect CO, CO2, H2, CH4? can I use the above column with MS instead of TCD? Is there any limitation on the minimum mass range that the MS is capable of detecting?

As far as I understand, if the column is capable of separating the gases, then the MS should detect them (of course with the proper method)

Finally, do you know if the GC-MS library doesn't include CO and H2, is there any way to update or add new library?

Too many questions, but I am new to this machine and need some help

Thank you!
ilham

[chromatographer1]

Every MS I ever saw could see almost everything but for good reasons there is a lower limit of the mass any analyst would want to detect using an expensive MS.

Fixed gases are in the range of analytes analysts never even try to measure quanitatively. and hydrogen?



Don't you have any? other detector other than MS?

Golly, maybe it is time to spend a little money for a TCD (6-10K) compared to that MS you have costing 50-150K.

Or buy a helium ionization detector (AIC Valco Gow-Mac) ?

I mean you wouldn't buy a limo if you only wanted to cross the street?

At least not with my budget, you wouldn't.

best wishes,

Rod

[AICMM]

ilham,

You are, unfortunately, going to have a tough time with this application unless you have a residual gas analyzer for your MS. If you have a standard MS (5973, ion-trap, etc...) this not a good way to use it.

For starters, column flow rates for Plot's don't match MS. Then you want to measure very low MW compounds (H2 is 2, helium is 4, yech!) Then you want to measure stuff you find in air and more importantly stuff with the same M/Z as what you find in air: CO is 28 and N2 is 28...

I once set up a GC with an HID in less time than it took to not develop an MS method that was being attempted at the same time...

There are more posts on this subject for your review but Rodney is right, see if you can't get a TCD or HID somehow (my standard disclaimer about HID's applies here.)

Best regards,

AICMM