Separating the Effects of Scatter and Absorption Using the Representative Layer

Abstract

The physical interpretation of the absorbance observed in a non-scattering sample is straightforward; it is a simple function of the concentration of the analyte(s) and its (their) ability to absorb light. In a scattering sample, the phenomena of absorption and scattering affect each other. Consequently, the measured “absorbance” is more difficult to interpret and is not suitable for direct comparison to an “absorbance” obtained from a non-scattering sample. This paper describes a strategy for separating the effects of scatter and absorption. The amount of light absorbed by a sample can be determined by measuring both the amount of light remitted and the amount transmitted by the sample. Using the mathematics of plane parallel layers, it is possible to model the sample as a series of “layers” of any thickness and calculate the absorption, remission and transmission for each of these hypothetical layers. The absorption computed for a layer having a thickness of one particle, which we term the “representative layer”, can be used to benchmark the absorbance that would be observed from the sample in the absence of scatter.