New Variants in the Derivative Method

A further variant of evaluation, preferred for standardization and comparison, is the log A method of derivativation. In the past, logarithms of spectra were used when the absorbance extended to a broader region. Beyond that, spectra of the same substances, but of different concentrations, have an identical shape. The curves are only shifted along the y-axis [72]. Theoretically, this advantage, applied to differentiation, leads to congruent signals [72, 73]  

With the log A method, even the smallest differences in the shape of the spectra are obvious. Equations analog to Eq. (2-77) and (2-78) are valid for the natural logarithm In. 

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