Nonlinear Beer’s law

Most chemists and spectroscopists expect that in the absence of these distinct phenomena causing nonlinearity, Beer s Law provides an exact description of the relationship between the absorbance and the analyte concentration. Unfortunately the world is not so simple, and Beer s Law never holds exactly, EVEN IN PRINCIPLE. The reason for this arises from thermodynamics. 

Strong derived it by the use of the probability of photon capture, with extension of the monochromatic case to that of a finite band width. Holleran offered a derivation based on the combination of proportional dependences. Goldenberg presented a formula for the rectification of nonlinear Beer s law plots. 

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