Optics: measuring and testing – By polarized light examination
Patent
1995-07-26
1997-04-15
Pham, Hoa Q.
Optics: measuring and testing
By polarized light examination
356368, 356366, 356327, G01J 400
Patent
active
056215282
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Subject of this invention is the method for measurement of circular dichroism, optical rotation and absorption on spectra on optical active, gyrotropic, substances by way of spectropolarization and construction of an apparatus for performance of this measurement.
Presently circular dichroism spectra can be measured by spectropolarimetric apparatus, dichrographs, which after refitting of its optical system can be used for measurement of other optical properties such as optical rotation and/or absorption on a tested substance as well. For measurement of circular dichroism the apparatus has to contain at least a light source of known wavelength, linear polarizer, modulator of ellipticity, holder and/or couvette for tested substance and detector. For measurement of optical rotation by the same apparatus it is necessary to install before the detector an analyzer which transfers the polarization plane into a change in the ray amplitude. For measurement of absorption, it is advantageous to eliminate, from the optical system, polarization elements i.e. polarizer, ellipticity modulator and analyzer.
Practically it means that by presently used methods with utilization of known types of dichrographs all three above mentioned optical properties cannot be measured simultaneously i.e. in real time. It is not convenient mainly in cases when properties or compositions of tested substances are changing quickly during the chemical reaction or in the cases when non-stable organic substances as e.g. hyaluronidase are measured.
The other imperfection of present dichrographs is in fact that they do not enable utilization of a reference ray for determination of a corresponding unit of the circular dichroism, because in practice there are not available etalon substances showing constant circular dichroism in an acceptably wide spectral area for example in an interval from 300 to 600 nm. This fact limits precision of measurements preformed on presently known dichrographs.
The goal of the invention is to improve the measurement method which substantially reduces the above-mentioned disadvantages and enables, after modification of presently known dichrographs, simultaneous measurement of circular dichroism, optical rotation and absorption spectra in real time and an acceptably wide spectral interval.
SUMMARY OF THE INVENTION
The above mentioned goal is achieved by the subject of this invention, which is a method for measurement of transmittance, circular dichroism and optical rotation of an optical active substance, during which is for determined wavelength, after previous calibration of the measurement system and determination of unit values ascertained by means of harmonic analysis of the state of polarization of a measurement ray with modulated ellipticity after passing through the optically active substance and analyzer where the changes of the measured ray amplitude are transferred into changes in electric signals.
An object of the method according to this invention is to assort the null harmonic, the first harmonic and the second harmonic component which correspond to transmittance, circular dichroism and optical rotation of measured optically active substance, while the frequency of the first harmonic component corresponds to modulation frequency, and the amplitudes of the such determined harmonic components are compared with individual unit values achieved by calibration.
A further object of the method according to this invention is to utilize double ray equipment which forms the second ray as a reference ray such that the reference ray is calibrated and modulated identically with the measurement ray and changes in the amplitude of the reference ray are transformed into changes in the electric signal changes alternatively with transferring of corresponding changes of measurement ray amplitudes, wherein the frequency of alternations of both the rays, the measurement ray and the reference ray, is at least 10.times. smaller than the modulation frequency.
A dichrograph is provided for carrying out
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Pham Hoa Q.
Rokos & Co., Ltd.
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