I have a few compounds (some are achiral, some are chiral) that marginally absorb at 589nm. Currently the polarimeter in our dept offers only 546 and 589nm. 546nm is not usable because the compounds absorb strongly in this region.
Unfortunately the achiral compounds (D4 symmetry) give optical rotation at 589nm, and those chiral compounds give fluctuating readings. I am sure the temperature has been stabilized and the solutions have been well filtered to discard particulates.
Is fluorescence interfering the measurement? Usually how do you measure the optical rotation of colored compounds?
Thank you.
Dear Ching Tat To,
I am not an expert in this field, but I think the answer is to use polarized light microscopy. Quoting from the book ‘Polarized Light Microscopy’
https://www.med.unc.edu/microscopy/files/2018/06/lm-ch-15-polarized-light.pdf
©Robert Bagnell 2012. ’The simplest polarizing light microscope is one that has an east - west polarizer between the light source and condenser and a north – south “analyzer” between the back focal plane of the objective lens and the eyepiece.’ When the polarizer and analyzer are “crossed” like this, no light will be seen in the microscope in the absence of a specimen. If your samples exhibit optical rotation they will become visible through such a pair of crossed filters when they are rotated to the relevant angle of a measurement.
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