METHOD OF MEASURING CIRCULAR DICHROISM, OPTICAL ROTATION AND ABSORPTION SPECTRUM

摘要

In the present invention there is disclosed a method of measuring transmittance, circular dichroism and optical rotation of an optically active substance, and namely by means of harmonic analysis of polarization state of elliptic-modulated measuring beam after its passage through the optically active substance and an analyzer, and namely through the mediation of amplitude changes of electric signal, to which corresponding amplitude changes of the measuring beam are converted. During measurement the zero harmonic component corresponding to optical transmittance (tau) of the optically active substance, the first harmonic component corresponding to circular dichroism (psi) thereof and the second harmonic component corresponding to optical rotation (phi) there, whereby the first harmonic component frequency corresponds to modulation frequency of the measuring beam (4), whereupon the amplitudes of so determined harmonic components are compared with unit values obtained during calibration. The dichrograph according to the present invention is formed by a beam divider (3) from which two parallel beams, i.e. a measuring beam (4) and a reference beam (5) radiate in alternate manner, whereby the reference beam (5) further passes through an ellipticity modulator (6) and an achromatic phase element (9) that is placed during the circular dichroism unit in this reference beam (5). Further the dichrograph is formed by two analyzers, i.e. a measuring analyzer (8) situated in the measuring beam (4) behind a measuring cell (7) and a reference analyzer (10) being situated in the reference beam (5). The measuring analyzer (8) optical axis is angularly displaced by 45 degrees with respect to said modulator (6) optical axis. The reference analyzer (10) is in the course of measurement angularly displaced with respect to said measuring analyzer (8) by a selected unit angle, for instance by 1 degree.