I am working on UV-visible measuements of some powder samples (dark colored ones), the absorbance measurements gives us values higher than 1, which we think isn't logical, and when I try to calculate the Reflectance by the mean of this equation: R=1-sqrt(T.exp(A)), it gives me high values (up to 70% Reflectance) which are in contradiction with the high absorbance measured, assuming that the Trasmittance values that are under 25% are correct.
Should I go through some type of normalization for my absorbance values? or do i do the UV-Visble measurements again adding Barium Sultfate (BaSO4) to the samples?
Actually it makes a lot of sense and is to be expected for dark samples.
- The transmittance value has an upper limit of 1 (or 100%) for completely transparent samples and a lower limit of 0 (or 0%) for totally dark samples.
- The absorbance value has a lower limit of 0 for completely transparent samples, but no upper limit (in theory)! In practical use, the upper limit depends on your spectrometer's detector quality and the light path characteristics around the sample. High-end spectrometer can measure up to absorbance values around 6, which means that only 10^-6 of the incident light is transmitted...
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