How to know the wavelength that i should use to measure the optical rotation? What is the difference between optical rotation and optical ellipticity? thanks
to measure optical rotation of a substance you need to use a device called polarimeter.
as for the wavelength, i think it should be from that part of spectrum where the substance does not absorb strongly, for you want to have quite a lot of light transmitted by the sample.
you will use by default 589nm, which is D ray emission of sodium. The optical rotation is the angle you will mesure with your polarimeter.
Optical rotation can be determined by using Polarimeter. For that you have to make a known concentration (say 0.5 g/100 mL). Then you can measure the optical rotation as well as specific rotation at 589 nm. 1st of all you have to add the solvent (in which you have diluted your sample) in the sample cell and make it zero. Then add your sample and note down the optical rotation value.
Yes as above. However, if what you have has no literature value and you have no idea which wave length to use. You could could carryout a wavelength scan if you can get your hands on a polarimeter equipped with multiple wavelengths. If your sample is optically active and pure, you should get the optical rotation with one or more of the wave lengths. Most are measured at the sodium D line 589nm.
Nurul I hope you have now found the answers your were looking for. What did you do in the end?
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