Dear Nabillach,

I can't see what detailed FTIR maxima positions are, but I suppose the band with max near 1600cm-1 together with one between 3100 cm-1 and 3700 cm-1 belongs to the H2O spectrum. In this case, the maximum near 1600cm-1 would be rather OH scissoring band of H2O than C=O (may be C=O is overlapping with OH vibrations but rather in the case of sample b in FTIR-1 figure). I don't know the chemical compositions of your samples any way are your samples liquid?

Also, to better compare the spectra (if you have the same concentrations of analyte in both samples), it would be helpful to perform a normalization procedure (using the strongest band maxima - or the one which we assume doesn't change from sample to sample). In the case of FTIR-1 results, the stretching vibrations of H2O perhaps would be appropriate to use - max of the range between 3100 - 3700 cm-1 ).

Also, did you perform the measurement using the same optical length - the same distances of the measuring cuvette- for spectrum A and B in the FTIR-1 case,

because this may be the reason for the different intensities of main bands.

I also suggest cutting out the part of the spectra below 700cm-1(it also looks like one from water absorption, and it's noisy too - which doesn't help in interpretation). And if you do so, it seems the most interesting part of the spectra to interpret is one between 700cm-1 and 1650 cm-1 assuming the CO vibrations are overlapping the OH vibrations.

Good luck!

Maja

In addition to what Maja Mroczkowska-Szerszeń wrote, please keep in mind my answer to your previous question about this problem. The IR spectrum before and after treatment is (mainly) that of water, there are only weak paracetamol peaks in it (if any; we are still talking about paracetamol, right?!). Most probably the concentration of the analyte before the treatment is simply too low. In the UV spectral range, it is the other way round, since water has no bands above 210 nm.

The band with max near 1600cm-1 together with one between 3100 cm-1 and 3700 cm-1 belongs to the H2O spectrum.

So as far as i think the spectrum suggests the presence of OH bonds In FTIR spectra and In UV conjugation also plays a crucial role so please consider the same

Good Luck!

Supriya

The 1635 cm-1 is the deformation vibration (the bond angle changes), which is not possible if you have a single -OH group, which means that paracetamol will not show this type of vibration. That there is no change is just an indication that your electrochemical method leaves the water untouched. How large is the actual concentration of paracetamol? Usually if the volume percentage is below, say, 1 or 2 %, it is hard to see anything in the IR (sometimes even for 5 %...).

What is the sampling technique? ATR crystal? Thin film between salt plates (probably not since it is aqueous).

It is pretty clear that chromophore in the UV has been consumed. Paracetamol is an amide which means the Amide 1 band could be buried under the water band at 1635, but I don't see any Amide 2 band at 1510. I don't see any of the aromatic absorbances. But I do see some negative bands in your overlay spectrum.

Paracetamol is only about 1% soluble in water. I agree with Dr. Mayerhofer that you may have a very low concentration for FTIR without using specialized techniques. You might try taking the background FTIR spectrum with pure water, then collect the sample spectrum of your solution.

https://unitechlink.com/data-analyzer/