The purity and concentration of optically active substances can be determinate with polarimeter. An optically active substance will rotate the polarization plane of of linear polarized light. The amount of rotation is depending on the molecular composition and proportional to the concentration of chiral molecules. Each optically active substance has his specific rotation factor as defined by Biot’s law
The polarimeter is a sensitive instrument for non destructive measurement of the optical activity of organic and inorganic substances. It is also a simple and cheap method for expensive or no replicable samples