FI96365C - Method and sensor for photometric analysis of a substance - Google Patents

Description

924741 .DOC 96365

Method and sensor for photometric analysis of a substance

The invention relates to a method for analyzing a substance photometrically, in which light energy is introduced into a sample space and as a result the light energy from the sample is measured, forming a precipitate from the analyte or a reaction product dependent thereon and measuring the intensity of light scattered back from the precipitate. The invention also relates to a sensor for carrying out the method in question.

10

Several assay methods based on light intensity measurement are known. In this case, it is advantageous that the intensity of the light obtained from the sample at a certain wavelength depends on the concentration of the analyte or the compound obtained therefrom by a particular reaction. This is used, for example, in spectrophotometry and fluorescence-based measurements.

The foregoing methods generally require a certain wavelength at which light is conducted to the sample and / or at which measurement of light from the sample is performed. Naturally, this sets precise requirements for instrumentation. In addition, WO 87/03960 discloses a method using precipitate formation and light scattering, in which the measurement is performed on the precipitate in the cuvette of an automatic analyzer. Here, the light scattered from the sample 25 at an angle of 70 ° from the direction of light travel is measured. The sample and reagent, in this case the antibody, are placed separately in the cuvette acting as the sample space. It is a complex automatic analyzer for laboratory use, where the conduction of light to the sample and the measurement of scattered light take place by means of traditional optics. The method allows wavelengths to be selected more freely, and if desired, measurement data can be collected at even more different wavelengths.

The object of the invention is to provide a method and a sensor with which a scatter-based measurement can be simplified, in which the wavelengths to be used can be chosen more freely and which, in addition, diversifies the assay methods available for different substances. To achieve this purpose, the method according to the invention is mainly characterized in that in order to perform the measurement the precipitate itself is formed in the sample space 924741 DOC ^ UUL v 2 by means of a reagent placed therein by placing the sample space in the sample and introducing the analyte or dependent reaction product into the sample space. -nut light for measurement along the same or separate optical fiber or fiber bundle 5, the sample space being located in front of the outer end of the optical fiber.

It is essential in the invention to utilize the solid precipitate formed by the action of the analyte instead of the indicators being bound to e.g. latex spheres, glass beads, etc. in which the resulting color reaction 10 is measured at a certain wavelength. The precipitate is formed in the sample space itself, in which case the measurement is performed by pushing the sample space into the sample. Optical fiber provides simple optics, allowing the method to be used in many measurement applications.

According to a preferred embodiment, the reagent-containing sample space is sealed with a membrane, whereby the membrane is contacted with the analyte medium from which the analyte or the reaction product dependent therefrom is allowed to enter the sample space through the membrane.

20

The sensor for carrying out the method according to the invention is in turn characterized in that a reagent is formed in the sample space which forms a precipitate with the analyte or the product dependent on the product for measurement by means of light scattered back from the precipitate, and that the sample space is placed in the sample space at the end of the same or separate optical fiber or fiber bundle in front of the outer end of the optical fiber so that it can be placed in the sample to be analyzed. According to a preferred embodiment, the sample space is enclosed by a membrane permeable to 30 analytes of the environment or the product of a reaction dependent thereon. According to one alternative, the filling space can also be accessed into the environment inside an open capillary tube.

The invention will be described in more detail below with reference to the accompanying silicon-35 drawings, in which Figure 1 shows the head of a sensor according to the invention,

924741 .DOC

96365 3 Fig. 2 shows a second sensor head in cross section, Fig. 3 shows a third sensor head in cross section and 5 Fig. 4 illustrates a measurement method with the sensor according to Fig. 3.

Figure 1 shows the sensor head. Inside the body of a rod-shaped sensor of suitable material passes an optical fiber 1, the core 2 of which protrudes from the end of the protective cover of the fiber 10. A sample space 3 is formed at the end of the core by closing its end with a membrane 4. The sample space 3 contains a reagent which causes a precipitate with the substance to be measured in the analysis. This substance is any substance which causes a precipitate reaction with a reagent in the sample space, and is not necessarily the substance whose concentration is to be measured, but may be, for example, the reaction product thereof, as will be described later.

When measuring the environment to be analyzed, the sensor immerses its end, i.e. the sample space 3, in the environment to be analyzed, such as a liquid volume. In this case, the desired substance diffuses through the membrane 4 and forms a precipitate with the reagent in the sample space 3. The light is conducted from the light source along the fiber 1 to the sample space 3, and the light scattered back from the precipitate formed therein is returned to the detector along the same optical fiber 1. The light source and detector are located in an instrument unit at the other end 25 of the fiber, which can operate in fiber optics and optics instrumentation according to principles known per se.

Figure 2 shows another type of sensor, in which the core 2 coming out of the protective shell of the optical fiber 1 is surrounded by a membrane 4 which extends in a cylindrical manner over the outer end of the fiber. The open end of the membrane is closed by a light-absorbing piece 5, whereby the sample space 3 remains between the end of the fiber and the piece 5 inside the membrane. In this sample space 3, there is a reagent operating as described above.

Figure 3 shows a sensor with two optical fibers 1, one conducting light from the light source to the sample space 3 and the other leading back to the scattered light detector. The fibers are introduced in parallel inside the sample space 3. The walls of the sample space are formed in this case by a cylindrical Q A 7 A k 924741 .DOC .7 U O U v ..

4 capillary tube 6 walls. The capillary tube is open at the end, allowing the analyte to come into contact with the reagent in sample space 3. Alternatively, the capillary tube 6 may be closed at its end, allowing its wall to be porous, allowing the analyte to pass through.

Figure 4 schematically shows the measurement arrangements when using the sensor of Figure 3. From the light source 7, light is connected to the fiber 1 by means of optics 10 and along it light is conducted along the fiber 1 to the sample 8, where 10 the sensor described above is located. The light scattered back from the precipitate formed in the sensor is conducted along the second fiber 1 to the detector 9. A wide-spectrum, non-coherent miniaturized component, e.g. an LED, can be used as the light source. A conventional commercial luminometer can be used as a detector of light scattered back from the area defining the numerical aperture of the optical fiber head. The light source 7 and the detector 9 can be integrated in the same portable instrument unit.

When one fiber is used, light can be continuously applied to the sample space 3 and the light scattered back along the same fiber in the instrument unit-20 can be reflected to the detector 9 by means of a beam splitter.

A single optical fiber that brings light into the sample space 3 and / or takes it to the detector 9 can also be replaced by a fiber bundle, in the fibers of which light energy can be simultaneously transported.

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Regardless of the method used to conduct light into and out of the sample space, it is possible to monitor the formation of the precipitate, e.g. as a function of time. In this case, for example, the rate of increase of the intensity of the scattered light can be used as an aid in the quantitative analysis of the analyte.

In practice, the reagent can be placed in the sample space 3 either in the solution phase or it can be bound to the gel.

35 As one example of the application of the method, the measurement of the enzyme substrate from solutions can be used. The precipitate-forming agent is then the reaction product of the substrate, which is obtained from the substrate by an enzyme-catalyzed reaction. As the precipitating reagent, a precipitate-forming reagent is used with the reaction product 924741 Doc 96365. In this case, the enzyme can be in the sample space 3 or it can also be immobilized on the membrane 4, whereby the substrate diffuses through the membrane and at the same time becomes a reaction product. This method can be applied, for example, to the measurement of biochemicals in clinical chemistry. The sensor can then be made suitable for field conditions, intensive care, home care or a doctor's office, in which case it is not necessary to use the services of central laboratories when performing analyzes.

The invention can also be applied to the analysis of other substances. For example, many metals precipitate with suitable anions into clearly detectable fines, in which case a solution containing such an anion can be used as a reagent in the sample space and the membrane can, for example, be selectively permeable to the metal ion in question. Suitable metal ion-containing solutions for analyzing the concentration of certain anions can also be used as reagents.

Claims (6)

924741.DOC 96365 A method for photometrically analyzing a substance, in which light energy is introduced into the sample space 5 (3) and consequently the light energy from the sample space is measured, forming a precipitate of the analyte or a reaction product dependent thereon by measuring the intensity of light scattered back that, in order to carry out the measurement, the precipitate is formed in the sample space itself (3) by means of a reagent placed therein by placing the sample space (3) in the sample space (8) and introducing the analyte or its dependent reaction product into the sample space; along a separate optical fiber (1) or a bundle of fibers, the sample space (3) being located in front of the outer end of the optical fiber 15. Method according to Claim 1, characterized in that the sample space is closed by a membrane (4), the membrane being brought into contact with the medium to be analyzed, from which the analyte or the reaction product dependent therefrom is allowed to pass through the membrane into the sample space (3). A sensor for photometric analysis of a substance comprising a sample space (3) and a bus directed thereon for light energy and for passing light energy from the sample space 25 to the measurement space, characterized in that a reagent is formed in the sample space (3) to form a precipitate for measuring with the light scattered back from the precipitate, and that the sample space (3) is located at the front end of the same or separate optical fiber (1) or fiber bundle bringing light energy into the sample space (3) and the light scattered to the sample (3) so that it can be placed in the sample to be analyzed (8). Sensor according to Claim 3, characterized in that the sample space 35 (3) is closed by means of a membrane (4) which allows the substance to be analyzed from the environment or the product of the reaction dependent thereon. 924741 .DOC 96365 Sensor according to Claim 3, characterized in that the sample space (3) is accessible to the environment inside an open capillary tube (6). A sensor according to claim 3, characterized in that the sample-5 space (3) is inside a porous capillary tube (6) closed at its end. • · 924741 DOC 96365