Second Derivative Photometry

One general effect of plotting the second derivative of a spectrum is an accentuation of its spectral features, the so-called discrimation effect. This effect is particularly useful for the quantitative analyses of mixtures of lignin and certain low molecular weight organic compounds. As an illustration, the absorbance and second derivative spectra of mixtures of a softwood lignosulfonate and phenol at various ratios are shown in Fig. 5.1.6. In the absorbance spectra, 

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