Understanding Resolution in FTIR Spectroscopy

[umalaya]

Hi,

Can anyone help to explain the term of resolution in FTIR spectrocopy machine and...

1) If a sample A show a band centered 1650cm-1 and after some modify, the sample A show a band centered at 1652cm-1, can we consider the sample change in its molecular structure because it has a band shifted (if we have a resolution setting at 4 cm-1) ?

2) is it the resolution setting of 1cm-1 is always better than the resolution of 4cm-1, 8cm-1 and etc...

Thank you very much...

 

[Rajini]

Hi,
After some modify ? what does that mean. Did you modify the sample or instrument?
Resolution: It is the ability of the instrument to resolve peaks.
For you second question, i would say 1 cm^-1 is better than 4 or 5 or 6 cm^-1. But off course it depends on lots of factor.

 

[umalaya]

Hi,

Thank you. Ya, I mean modify the sample.

Hi,
After some modify ? what does that mean. Did you modify the sample or instrument?
Resolution: It is the ability of the instrument to resolve peaks.
For you second question, i would say 1 cm^-1 is better than 4 or 5 or 6 cm^-1. But off course it depends on lots of factor.

 

[Rajini]

I think then in your case the slight change (2 cm^-1) is not encouraging..because it is less than the resolution of your instrument..
May be you can try using high resolution. It is up to you to decide.
good luck

 

[Ravian]

in ftir systems resolution is associated with the distance that the moving mirror travels i.e. a resolution of 2cm-1 means mirror moves 0.5cm from its natural focal focal point called ZPD. Longer the distance traveled by the moving mirror, more sharp features on the sample are explorable. But as it is already explained it depends on your sample and also time you have to perform experiment. Good practice is that you perform experiment at different resolutions and see if there are any fine structures in your sample. If not then stick to the resolution which gives results in less time.
A change in 2cm-1 is too less to deduct any thing, probably something in your sample has changed but not the molecular structue but some impurity. A change of 0.5ev(~4000cm-1) may mean something.