IR spectra of similar compounds and subtle molecular bond changes are not visible. so based on the literature i thought we will go for derivatization. But after derivatization the peaks are different. The spectra looks different. now how will i use the the value? is it only for making a PCA(principle component analysis)? how do we interpret the wavenumber difference from the derivative spectra? how do we decide when to go for 1st derivative, or 2nd derivative?
In general, derivative of a spectra can highlights small changes that otherwise cannot be seen in a flat or featureless spectra. The general principles including the basic mathematics and generation methods of derivative spectroscopy could be seen in the following reference: http://www.whoi.edu/cms/files/derivative_spectroscopy_59633940_175744.pdf
Derivative spectroscopy is the basis for how modulation spectroscopy (E.g., Photo-reflectance or electro-reflectance) works when the main spectra (Reflectivity or R) may look more or less featureless, but the derivative spectra (Delta R) can highlight or amplify small variations in the spectra when plotting (Delta R) / R. This allows for example to identify band-to-band or impurity-to-band edge transitions in semiconductors.
Similarly, spectroscopic imaging may allow for the analysis of spatial distribution of various materials including biochemical components. Considering that analysis of IR spectra may be complicated due to absorption peaks overlapping with each other, the second derivative spectroscopy can enhance the separation of overlapping peaks, such as that in the following reference:Article Application of second derivative spectroscopy for increasing...
Thank you Prof.Bahram for the detailed answer. i will go through it
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