Deconvolution, properly applied, can yield additional information regarding the sample. Unfortunately, it is extremely easy to misuse deconvolution technique, and very often only experience will temper the result and its interpretation. Derivative spectra are obtained through extended use of the Savitzky-Golay algorism for digital filtering. Although the Savitzky-Golay method is a famous line-smoothing technique utilizing adopted polynomials, it is converted to calculate derivative spectra and peak positions by incorporating suitable adopted functions. Derivative spectroscopy has an advantage in emphasizing weak spectral features which are buried beneath dominant spectral features. When a poorly resolved spectral band is observed for quantitative study, it may be desirable to separate the spectral features, into a sum of component bands, all of which have a different peak position, line shape, linewidth, and peak intensity. Major progress in quantitative analysis was achieved when the multivariant statistical methods utilizing factor analysis became available to fourier transform infrared users.