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Process Polarimeter for Monitoring Chiral Compounds
in Preparative LC and Process Applications

The POLARmonitor is a high resolution, sensitive polarimetric detector for online monitoring the Optical Rotation of chiral compounds. State-of-the-art microprocessor technology and "no moving parts" mechanical design have resulted in a detector yielding excellent baseline stability and high reproducibility.

The optical unit is separated form the controller unit, providing short warm up time and maximum protection in rough environments. Measuring cells, made of stainless steel or other biocompatible materials, are available for a wide spectrum of flows rates and pressures, enabling all applications in preparative LC, SFC and biotechnology process.

The POLARmonitor uses the Faraday Effect to compensate the optical rotation given by the sample:
       sample= alfacomp= V*d*Icomp*N
Thus, the compensation current Icomp is proportional to alfasample.
The determination of the optical rotation is therefore a simple current measurement and does not necessitate any mechanical moving parts.
After corresponding calibration, the measured rotation angle is indicated in millidegrees (m°).
In addition,a Faraday Modulation takes place in the same coil in order to obtain a definite balancing criterion independent to the light source intensity or the absorbtion of the sample.
The application of an alternating current (AC) with frequency f1 produces a modulation of the polarized light with twice of this frequency.
If an optically active sample is present, its oscillation is superposed by the frequency f1 and fed to an integrator which is phase-sensitive to f1.
This integrator modifies the compensation current Icomp taking into account the correct sign of rotation, until the oscillation component f1 becomes zero, i.e. until the device is in balanced condition.
This process is extraordinary fast which means that Icomp is proportional in real time to the rotation of the optically active sample in the cell.
Icomp is then transformed to a calibrated readout for the serial and analog interface.