Continuous method for determining the optical rotation in chiral media with internal referencing

An approach to continuously monitor the optical activity and measure the rotation angle of a sample is proposed. The general setup is similar to the non-continuous method of measuring the angle by a polarizer and an analyzer, which is stepwise rotated. In the new approach, the analyzer is mounted to a motor and rotates at a constant angular velocity. If the sample under investigation is optically active, the sinusoidal signal experiences a phase shift depending on the angle of rotation. This is similar to conventional polarimeters. The key novel feature of the method is the internal referencing utilizing a pinhole in the analyzer, making the orientation angle measurement redundant. The proposed method can deliver information with high temporal resolution up to kHz and can be made fully automatic.