Theory of Dual-Wavelength Spectrophotometry for Turbid Samples

Abstract

Dual-wavelength spectrophotometry of turbid samples requires detection of the difference between changes in transmittance occurring at two different wavelengths as, for example, when a chemical or physical change in the sample takes place. Equations are derived to show that, if a linear detection scheme is used, interpretation of the experimental data is difficult unless the changes in transmittance are small. If a ratio detection scheme is used, however, the interpretation of large changes in transmittance becomes easier. Ratio detection is also useful for measuring small absorbance changes in the presence of relatively large background-scattering change.