Understanding Resolution in FTIR Spectroscopy

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Discussion Overview

The discussion focuses on the concept of resolution in FTIR (Fourier Transform Infrared) spectroscopy, particularly in relation to changes observed in sample spectra. Participants explore how resolution settings affect the interpretation of spectral data and the implications of slight shifts in band positions.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asks whether a shift in the band position from 1650 cm-1 to 1652 cm-1 indicates a change in the molecular structure of the sample, given a resolution setting of 4 cm-1.
  • Another participant clarifies that resolution refers to the instrument's ability to resolve peaks and suggests that a resolution of 1 cm-1 is generally better than higher settings, though this is dependent on various factors.
  • A different participant notes that a change of 2 cm-1 may not be significant, as it is less than the resolution of the instrument, implying that higher resolution may be necessary for more definitive conclusions.
  • One participant explains that in FTIR systems, resolution is linked to the distance the moving mirror travels, and suggests experimenting with different resolutions to identify fine structures in the sample.
  • Another participant posits that a small change of 2 cm-1 might indicate something has changed in the sample, but not necessarily the molecular structure, possibly suggesting the presence of impurities instead.

Areas of Agreement / Disagreement

Participants express differing views on the significance of a 2 cm-1 shift in band position, with some suggesting it is too small to indicate a structural change, while others imply that it could suggest some alteration in the sample. There is no consensus on the implications of resolution settings or the interpretation of spectral shifts.

Contextual Notes

Participants mention that the effectiveness of resolution settings can depend on the specific sample and the time available for experimentation. There are also unresolved assumptions regarding the definitions of resolution and the conditions under which spectral changes are interpreted.

umalaya
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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...
 
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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.
 
Hi,

Thank you. Ya, I mean modify the sample.





Rajini said:
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.
 
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
 
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.
 

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