Dispersion photometer, in particular for the kinetic determinati

Details Dispersion photometer, in particular for the kinetic determinati Dispersion photometer, in particular for the kinetic determinati

1992-12-21

1995-05-02

Rosenberger, Richard A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356341, G01N 2151

Patent

active

054124700

DESCRIPTION:

BRIEF SUMMARY
The invention refers to a dispersion photometer (nephelometer), in particular for the kinetic determination of total proteins, having (a) a light source, (b) an optical system which projects the image of the light source into the sample chamber, (c) a removable optical cell in the sample chamber, into which the liquid to be analyzed can be given, (d) a stirrer, which stirs the liquid to be analyzed during the measurement, (e) a photo-electric sensor which receives light scattered in an forward angle, and (f) an electronic processing and display unit following this photo electric sensor for measuring the values of the dispersed light.
Dispersion photometers of this type are principally known, as an example it is referred to an article of F. Wittmann and G. Traxler "Neue Perspektiven der nephelometrischen Proteinbestimmung (Vorstellung ARRAY)" in Labormedizin 9 (1986) 434-436 ("New perspectives of the nephelometric protein determination" (presentation ARRRAY)). In the market available dispersion photometers are very expensive, their price is currently clearly above DM 100.000, - - . This fact has proven to be an obstacle for the use of dispersion photometers in laboratories for medical analysis, although the analysis with a dispersion photometer is more sensitive, faster, more precise and generally also lower in cost than an analysis following the conventional methods in clinical chemistry.
Reiber has described in Fresenius Z Anal Chem. (1982) 311: 374-375 a new physical-chemical principle for the determination of protein concentrations in biological samples, in which the precipitation of protein is carried out in trichloroacetic acid (TCA), and instead of measuring the absorption (turbidity) the dispersed light is measured. The precipitation of protein molecules causes initially an increase of dispersing particles with a dimension which is small compared to the wavelength 1 of the used light. Therefore the dispersed light intensity I increases, for which is valid I.perspectiveto.1/1.sup.4. In the course of the precipitation more and more larger particles show up, the dimension of the particles is now not any more small compared to the wavelength of the measuring light, whereby a different dispersion is prevalent, for which is valid I.apprxeq.1/1.sup.2.
Due to the dependance of the intensity of the dispersed light from the wavelength so far only more or less monochrome light was applied and in addition only light in the short wavelength range of the visual spectrum has been employed. In order to achieve the required sensitivity, which means a low measurement limit of 20 mg/l or less, which is expected by the users, it is required to apply high standards of technology for optics and electronics. This also explains the high price level for known dispersion photometers.
Starting from these considerations the invention is based upon the task, to further develop and modify a dispersion photometer of the above described type in such a way, that the optical system and the electronic unit is simplified.
This task is solved starting from a dispersion photometer of the type described above by inserting between light source and optical cell and between optical cell and photo-electric sensor only such (optical) elements, which allow a maximum transmission respectively reflection without selective absorption or reflection in the visual spectral range (400 nm to 800 nm).
Based upon this invention the sample in the optical cell is illuminated with white light. This has the advantage, that the light flux of the illuminating light is substantially higher than with so far known instruments. Due to the high light flux of the illuminating light also the intensity of the dispersed light is high, allowing to use low cost, long term stable photo-electric sensors as detectors. Therefore complicated measures for the optic system and for the electronic processing unit are not required.
As a surprise came the fact, that it is possible to leave the up to now as required considered principle of mainly monochrome light and the use of lig

REFERENCES:
patent: 2436262 (1948-02-01), Miller
patent: 4136953 (1979-01-01), Klein et al.
patent: 4157871 (1979-06-01), Anderson et al.
patent: 4250394 (1981-02-01), O'Connor
patent: 4408880 (1983-10-01), Tsuji et al.

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