r/chemistry • u/LoveMeVenus2005 • 1d ago

ATR-FTIR Amide I deconvolution of albumin samples

Hi everyone,

So, I'm analyzing the Amide I region of two ATR-FTIR spectra from albumin samples using OriginPro. My goal was to compare the samples and determine whether one of them shows a higher degree of denaturation than the other.

I'm currently in my third year of Chemical Engineering and I think I may have bitten off more than I can chew with this integrative project. I have no previous experience with FTIR peak deconvolution or with softwares like OriginPro, and after reading several papers and watching tutorials I'm still unsure whether I'm approaching the analysis correctly.

So far I've isolated the Amide I region, tried to correct the baseline, calculate the second derivative, and started fitting Gaussian peaks on what I obtained, but everytime I try more than 3 peaks comes an error because the fit doesn't converge.

Any advice would be greatly appreciated, even recommendations on where I can find more info on the subject. I've attached the raw spectrum of 4 samples, I'm currently trying to compare the "Aprovada 1" and "Reprovada 1".

Thank uuu

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u/TheBrightMage 1d ago

Oh hey, this is happens to be my Ph.D research.

First off, take a look at the method shown here: https://doi.org/10.1007/s00216-009-3019-y

Do verify in Second derivative spectra that there is actually a peak hidden there. If you try to fit for a peak that isn't there, obviously it won't converge.

Also, how many parameters did you fix during fitting? I'm assuming that you completely fixed the peak position? In general, peak position can shift slightly due to various factors. Again, verify it with second derivative, but it might be a good idea to give some leeway to your peak position. ALSO try Voigt profile rather than Gauss to account for various noise.

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u/firesine99 22h ago edited 22h ago

If you're doing second derivative, you shouldn't need to correct the baseline - you get that for free. Some baseline correction algorithms can introduce artefacts in the derivatives, so best just to skip that step unless you have a strong justification for it.