Chromatography Forum

Greetings,

I am new to the Chromatography Forum and also to GC-MS and FTIR. I am a semiconductor FA Engineer and my expertise is in SEM/EDS, FIB, GFAA, ICPMS, and semiconductor wet and plasma deprocessing and delineation.

I currently work with a medical device company. We have a Nicolet 6700 FTIR and use it for polymer analysis and also have a gas cell for laser gas analysis. I am trying to put together a justification for a GC-MS system for gas analysis, thermal desorption and head space analysis.

Being fairly new to these techniques I would appreciate the pro's and con's of each system. perhaps a side-by-side comparison? Does such a table (instrument/technique comparison) exist anywhere?

Any expertise and tutelage would be greatly appreciated.

Thanks kindly, in advance!!!

Burgie

In short - FTIR gives you an analysis of the sample as a whole and provides a measurement of vibrational frequencies. It is like listening to a symphony - you get the whole and can pick out some of the parts, but they must be sufficiently significant. And while you can pick out that there is a violin section, you will not really be able to figure out if there is a Stradivarius among them. With molecules, FTIR gives you an indication of functioality in a sample - carbonyls, amines, hydroxyls, etc.

GC/MS separates volatile compounds and provides identities of each - more like standing by the stage door to see who comes out (and some may not use that door). You can see each violinist and see if any is carrying a Stradivarius. - You can get a lot of detail about the parts, but you must figure out the relationship to the whole.

IR has some advantages for looking at polymers - you will never get a polymer intact through a GC column. The GC/MS is good for looking at small molecules, such as plasticizers or monomer, which you might miss in the spectrum of the entire polymer. It is also able to clearly differentiate between types of molecules that would be hard to tell apart by FTIR.

So, this should give you some perspective. You are talking about two different technologies which do different jobs. To make the proposal, you need to figure out the objective of applying GC/MS to your materials. And, understand that it takes some training to use a GC/MS and to interpret the data.

I would strongly suggest you go to the literature and look to see if anyone has been working on problems like what you want to solve with the GC/MS.

Burgie,

A minor comment to add. In my opinion, GC-MS is not the best way to do light gases (fixed gases.) There are a number of posts on this site about why but suffice it to say that you are looking for compounds that the MS is constantly trying to suck in and you are best served in this type of analysis by columns that a GC-MS doesn't really like.

Best regards,

AICMM

Nice Analogy Don Hilton---viz, GC and FTIR to a symphony.