I was doing some measurements by FTIR with my protein in buffer acetate 0,1M and when i want substract the buffer from the sample i have problems because i don´t obtein a flat baseline between 2000 and 1700 cm-1.
As Geoffrey Dent says in
https://www.researchgate.net/post/How_to_subtract_water_from_an_ATR-FTIR_spectra_of_a_protein_gel
water subtraction is tricky "...spectral subtraction of water is fraught with difficulties. The water bands can shift with pH , temperature and hydrogen bonding or other interactions with the sample. It only takes about 1cm-1 shift to make subtraction a mess."
efforts to account for salt and pH can be found in:
Article Subtraction of the Water Spectra from the Infrared Spectrum ...
Article Subtraction of the Water Spectra from Infrared Spectra of Ac...
...and it can still be tricky, due to other influences, e.g. temp, hydrogen bonding, etc. Good luck!
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