Understanding Polarimeters

- Mar 30, 2018 -

Understanding Polarimeters  

  Polarimeters are precise optical instruments that measure purity and concentration through the optical activity exhibited in inorganic and organic compounds. Compounds are considered to be optically active if linearly polarized light is rotated when passing through them. This optical rotation in general means that the polarization of the direction of light is rotated at a specific angle proportionate to the concentration of the optically active substance being tested. Optical rotation is measured in degrees of angle. At point zero, a polarizer and analyzer are set in an angle of 90 degrees toward each other, which means that no light reaches the detector (0% transmission). When an optically active substance is then placed in the measuring tube, the transmission will rise as a result of the plane polarization. To measure the angle, the analyzer is rotated up to the point where the transmission of the detector is again at minimum. Polarimetry is a mature technique and today’s automatic instrumentation provides features and benefits that purely manual-optical systems do not. Busy labs processing multiple samples have the option of automated data capture, variable wavelength and temperature with circular polarimeters having 0.005 accuracy and 0.001 resolution. These instruments are suited for quality control, process control, and research for demanding applications in many industries including beverage, cosmetic, chemical, food, essential oils and pharmaceutical


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