Speaker
Description
In spectrophotometric analysis, univariate calibration is often based on the intuitive assumption that the maximum of an absorption band provides the best analytical signal. This practice is closely connected to the Beer–Lambert relation, which suggests a linear dependence of absorbance on concentration and makes the most intense spectral position appear especially attractive because of its high sensitivity. However, peak height alone is not a reliable criterion for optimal calibration.
This lecture examines why the best univariate calibration point is frequently not located at the peak maximum. The discussion is illustrated using UV-Vis spectra of methyl orange and infrared spectra of thermodynamically ideal binary mixtures, including benzene–toluene, benzene–cyclohexane, and benzene–carbon tetrachloride. By comparing calibration performance across spectral positions and relating prediction errors to sensitivity, spectral separation, and curvature of the concentration-dependent response, it becomes clear that band flanks or apparently less prominent regions can outperform the absorbance maximum