Polarimetry

Polarimetry examines the polarization of shear waves, generally of light waves.

Applications

A polarimeter determines the degree of polarization of homogeneous bodies, such as sugar solutions ( Saccharimeter ). Polarimetry is a methodology for quantifying the optical activity of substances or solutions which are able to rotate the plane of vibration of linearly polarized light. It is the rotation of the polarization plane of linearly polarized light when passing measured by these substances or solutions. As a characteristic measure of the rotation of a sample, the specific rotation, the rotation angle at 10 cm depth layer of a liquid substance or a solution, calculated on a concentration of 1 g · ml - 1 1, indicating serves. The specific rotation depends not only on the chirality of the molecule and on the following variables:

• Wavelength of the polarized light
• Type and purity of the solvent used, if necessary,
• Concentration of the solution
• Measuring the temperature (in ° C).

The conditions of measurement always be reported, only the measure is clearly defined - When specifying the specific rotation α, ie the amount of rotation, must, in addition to the sign (" " or "").

Pharmacy and Chemistry

The specific rotation is often used in pharmacy and chemistry for the identification and quality control of chiral substances. Particular importance has the indication of the specific rotation of natural products such as amino acids, terpenes and sugars, since the majority of these compounds is optically active. For chiral drugs tolerances for the specific rotation, and the measurement conditions (such as wavelength and measurement temperature ) are listed in pharmacopoeias. Example of such a demand for tolerance to the drug penicillamine in the European Pharmacopoeia: " The specific rotation must be between - 61.0 and - 65.0 ° are calculated to the dried substance. "

Partial polarimetry is also used in the pharmaceutical industry for determining the durability of chiral drugs.

Sugar industry

In the sugar industry polarimetry is often used to determine the concentration of aqueous sugar solutions, in part, the measurement is performed continuously with a Durchflusspolarimeter. The polarimeter is sometimes called in the sugar industry also Saccharimeter.

Imaging methods are for example the polariscope or polarizing microscope (see photo), which also have applications in the photoelasticity.