An Analysis of Fourth Derivative Spectra

Abstract— –Fourth derivative spectra of chloroplast at – 196°C, obtained by four sequential differentiations of the absorption spectrum, were examined to determine the conditions for optimal signal‐to‐noise ratio and resolution. An appreciable improvement in the signal‐to‐noise ratio was found when the four differentiating intervals were nearly but not exactly equal. The process of differentiating digitized data with the computer was explored in order to define the rules for optimization of the fourth derivative curves.