Mathematical Resolution of Spectra

In the spectra of macromolecules, the overlapping bands cannot be resolved by instrumental manipulation alone. Instead, mathematical techniques such as deconvolution, derivative spectroscopy, and band fitting are used for improving the spectral quality. 

Deconvolution is manipulation of the interferogram with an exponential weighting function. It may be viewed as the inverse of smoothing. In deconvoluted 

First derivative IR spectra of a softwood and hardwood lignin are shown in Fig. 4.1.12. They display 20-22 positive and negative peaks instead of the 12 to 14 maxima appearing in the original spectra. Broad bands with low intensity are 

Bands labeled with show a maximum A = Absorbance of normalized spectra A for the highest band equals 100 (Instrument Bio-Rad, Digilab FTS 40) 

Band fitting (curve fitting, or band shape analysis) is conveniently performed with commercially available software packages which fit, interactively or automatically, Gaussian or Lorentzian line shapes (or their combinations) to an unknown band profile. The applicability of this technique to lignin chemistry is not known at present. 

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