Optics: measuring and testing – Of light reflection – With diffusion
Patent
1998-11-25
2000-07-04
Rosenberger, Richard A.
Optics: measuring and testing
Of light reflection
With diffusion
356440, 356246, 422 8209, G01N 2103
Patent
active
060846836
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an optical detection apparatus for chemical analyses of small volumes of samples.
Measuring apparatuses for the qualitative and quantitative chemical analyses of samples are known to the specialist in large number. For the analysis in particular of small volumes of samples, techniques are used today which are based for example on electrophoresis or chromatography, or in which the sample is examined optically without prior separation. In both cases, detection of the analytes to be identified is very often effected by means of optical methods, so that the development of new optical detection apparatus plays a very important role in respect of the instrumental improvement in the field of analysis. Even within the bounds of so-called immuno-assay, detection of biologically active substances is frequently effected by means of optical methods. Optical detection apparatuses include inter alia systems for absorption and fluorescence measurements.
In general, depending on type, detection apparatuses comprise a source of light to emit an induction light, a measuring cell for the sample, a photoelectric sensing element to receive the light coming from the sample in the measuring cell, and light-conducting means, on the one hand in order to conduct the induction light from the light source to the measuring cell, and on the other hand to conduct the light coming from the sample in the measuring cell back to the photoelectric sensing element.
In the case of fluorescence measurements, a known process is for example to bring the sample into contact with a sensor layer, e.g. a membrane applied to a substrate, the membrane containing chemical or biochemical recognition elements. As (bio-) chemical recognition elements, affinity partners of the analyte to be identified are immobilised in or on the membrane, and bind the analytes to them, for example by means of an antigen-antibody reaction. The sensor layer, which has selective sensitivity for the analyte to be identified in the sample, for example through the recognition elements, is brought to fluorescence by the induction light. When the sample makes contact with the sensor layer, the interaction between the analyte and the sensor layer or the recognition elements causes a change in the fluorescence light, for example in respect of its intensity, which is recorded by the photoelectric sensing element and is registered as the measured variable.
Frequently in the development of new detection apparatus, the main aim is to be able to carry out the analyses faster and faster and to miniaturize the apparatus more and more, so that the amount of sample employed is as small as possible. At the same time, however, the instrumental sensitivity of measurement should at the very least be maintained. In addition, it is frequently necessary to examine a sample qualitatively and quantitatively as quickly as possible for various analytes. For example, the routine examination of blood in hospitals and laboratories requires that the sample, namely blood, is examined in respect of different analytes, e.g. the partial pressure of so-called blood gases, such as carbon dioxide and oxygen, the concentration of electrolytes, such as H.sup.+ (pH value), Na.sup.+, K.sup.+, Ca.sup.2+, Cl.sup.-, or for its metabolite content, such as lactate, glucose or creatinine. In agro-technology also, it is often necessary to example a sample in respect of several analytes.
An optical detection apparatus, which is equipped for the examination of small volumes of samples, is disclosed in EP-A-0 616 211. The fundamental idea here is to keep to a minimum the number of optical transitions--by which is meant the transitions in the optical path between areas of differing optical density--between the source of light and the photoelectric sensing element. This is achieved, whereby the induction light emitted from the light source is conducted by a special photoconductor, which has a refractive index gradient, for example a gradient index (GRIN) lens, to a capillary
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Czolk, R., "Bewaehrungsprobe fuer Mikrosysteme", F&M Feinwerktechnik & Messtechnik 103, Sep., No. 9, 1995, pp. 492-494.
Barnard Steven Mark
Bruno Alfredo Emilio
Ehrat Markus
Herzig Hans Peter
Nussbaum Philippe
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