The FT-IR spectrum of precipitated calcium carbonate has been given in the file. The peaks between 2900-2840 are inverted in one of the spectrum. How can we solve this problem??
Dear Ghosh, before taking IR, you have to select which is the mode. there you have to select transmission not absorption. If you are taking absorption then you will get an inverted image.
Other wise large concentration also will make this problem. you can drag the peak in the oppasite direction then you will get the original image.
Agree with Preethanuj above: Transmission always shows an "inverted" type spectrum, as 100% transmission means no absorption, but when the material absorbs the IR, the transmission is reduced and you see an “inverted” peak. A switch to absorption mode will show positive peaks.
It really doesn't matter whether the peaks are facing downwards or upwards, or whether the wavenumbers are left-to-right or right-to-left; it communicates the same information in slightly different ways.
As for the wavenumbers going right to left, it's just a common convention. There's no real reason to do that, given that it's been done any ways. What matters is what the peaks look like. In other words how strong/weak they are, how narrow/wide they are, where they are horizontally because that's how you identify which bond stretches or bends those rotational or vibrational peaks correspond to.
You just need to know what the peak looks like, not which way it's facing.
I agree with Prof. Kalaiselvan. Upward and downward is not a matter. But the position is always a matter of fact. Because each bending or stretching has its own value. So we can plot in both directions. But the scale is always same. The fingerprint region is the identity card of a compound. Also the intensity depends on concentration, the bond they make, and the solvent they used to smear the compounds etc. Some times it's seems to be weak, if we increase the concentration the intensity will increase and the peak become broad..
Thank you all for the answers. But my point is that both the spectrums in the doc file are the spectra of calcium carbonate in the transmission mode not in absorption mode. But in one the spectra some peaks are facing upwards . How can we resolve this problem? Is it the concentration of the sample, pallet transparency, moisture or KBr contamination ?
I am not sure if this will be useful at his point or not.
Even I faced the same problem. I would suggest you repeat the test (that's what i did).
Make different samples and see if has repeating peaks or not.
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