Laws Kubelka-Munk relationship

Diffuse reflectance R is a function of the ratio K/S and proportional to the addition of the absorbing species in the reflecting sample medium. In NIR practice, absolute reflectance R is replaced by the ratio of the intensity of radiation reflected from the sample and the intensity of that reflected from a reference material, that is, a ceramic disk. Thus, R depends on the analyte concentration. The assumption that the diffuse reflectance of an incident beam of radiation is directly proportional to the quantity of absorbing species interacting with the incident beam is based on these relationships. Like Beer s law, the Kubelka-Munk equation is limited to weak absorptions, such as those observed in the NIR range. However, in practice there is no need to assume a linear relationship between NIRS data and the constituent concentration, as data transformations or pretreatments are used to linearize the reflectance data. The most used linear transforms include log HR and Kubelka-Munk as mathemati-... 

Because the incident monochromatic light is absorbed, reflected, and scattered by the opaque layer material, the theoretical relationship between amount of absorption and amount of substance does not follow the simple Beer-Lambert law that is valid for solutions. The Kubelka-Munk equation is the most accepted theoretical relationship for TLC, but its use is not necessary because of the ability of densitometer software to handle empirical nonlinear regression functions. 

This expression is comparable with Beer-Lambert s law for the absorption of non-scattering samples. Both in the theory of Kubelka and Munk and in Beer-Lambert s law the relationship derived from the measurement value is proportional to the coefficient of absorption and hence proportional to the concentration (c) and coefficient of extinction Sn of the absorbing material ... 

The theory of Kubelka and Munk is used in calculating the concentration for the systems of Boehringer Mannheim, Hoffmann-La Roche and Bayer Diagnostic and Electronic (Ames-Miles). If modifications of the theory have been made, these are stated in the description of the instrument. If the relationship between reflection and concentration (calculated by means of the theory of Kubelka and Munk) is represented graphically, the curve obtained is similar to that for the relationship between transmission and concentration calculated by Beer-Lambert s law (Fig. 3). 

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