Quantitative FTIR?

[Capiwalter]

First of all, sorry about my english.

Secondly, I would like to ask you, FTIR expert people, about a doubt in my work. I study the degradation of some polymers in processing and I obtained some FTIR data with absorption in 1640 cm-1 and 1720 cm-1. I would like to compare these two chemical groups quantitatively to see which is generated preferentially in function of the variation of temperature of the process. The doubt is about the molar absorptivity:

1. Where can I find the values, roughly, for these two chemical groups?

2. Can I do this comparison with my FTIR data? The major part of the table data I found is about ultraviolet and almost nothing about FTIR.

 

That´s it guys! Sorry if I am so dummy..

 

Thanks!

 

Walter

[John Cuthber]

First, there's nothing wrong with your English that you need to worry about.

 

Second I don't think I have ever seen molar absorbtivity data for IR spectra.

Is the degradation on the surface of the polymer or is it through all the polymer?

 

If it is on the surface then the path length is not well defined.

If the two sorts of degradation are both on the surface then you might be able to compare them. Do you know what the degradation products are? Can you look at the IR spectra of compounds similar to the degradation products and see how strongly they absorb?

 

You can certainly use IR data quantitatively. You need to convert from percent transmittance to absorbance- the same as with UV spectra.