A new method for determining peak absorbance of dense pigment samples and its application to the cone oil droplets of Emydoidea blandingii.

A new method measures the spectral absorption of small volume samples having peak optical densities (Dp) too high (up to 50 and higher) to be measured by standard direct or indirect methods. This method specifically corrects for the effect on the microspectrophotometer (MSP) of wavelength-independent light which bypasses the sample. The method involves; (1) measuring by MSP the long wavelength cutoff of the dense samples and the absorption spectrum of thinned samples of the same pigment, (2) calculating Dp from these. The method's application is illustrated for the colored oil droplets in the retinal cones of the turtle, Emydoidea blandingii.