FI64242C - ANORDINATION FOR PHOTOMETRIC MAETNING AV VAETSKOR - Google Patents

Description

1 64242

APPARATUS FOR THE PHOTOMETRIC MEASUREMENT OF LIQUIDS - ANORDNING FOR THE PHOTOMETRIC MEASUREMENT OF A VÄTSKOR

The present invention relates to a device for photometric measurement of liquids, which device consists of a measuring sensor and a photodetector between which the liquid to be measured can be placed in a cuvette made of glass or the like, and which is placed in a cuvette liquid.

Liquid absorbance measurement in clinical chemistry is mainly done in the following ways: 10 a) separate (disposable) cuvette, measurement horizontally through liquid and two cuvette walls (Figure 1) b) separate cuvette, measurement vertically through liquid and one 15 wall (Figure 2) c) solid a continuous flow cell in which the liquid to be measured changes, measurement as in point 1, figure 1 20 d) the so-called centrifugal measurement, in which the cuvettes form a circular rotor which rotates during the measurement, the principle of measurement being the same as in (b), Figure 2

Essential to all measurements is the exact length of the liquid column 25 to be measured: the more accurately the light always travels the same distance in the liquid under study, the more reproducible and error-free the absorbance can be measured. Thus, all the factors that affect the variation in the length of the light path in a liquid cause a measurement error.

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Vertical measurement through a liquid is a commonly used method, however, sensitive to light path length errors: due to the narrowness of the cuvette, the free liquid surface tends to form a curved surface (so-called meniscus) due to the surface-35 tension between the liquid and the cuvette. The curved surface causes the outermost rays of the measuring light beam to travel a longer distance in the liquid 2 64242 than the middle ones. In addition, the curved surface has different shapes with different liquids. This causes a measurement error, which has generally been eliminated e.g. by adding detergents to liquids to reduce surface tension. On the other hand, narrowing the light-5 beam helps somewhat, although the adequacy of the light intensity sets a certain minimum.

In some cases, the measuring sensor is immersed in the cuvette, thus avoiding the above-mentioned problems, see Figure 3. The actual problem 10 in this way is the contamination of the measuring sensor with the liquid to be measured. cuvette causing cross-contamination. The only way to avoid the above-mentioned disadvantages is to wash and dry the sensor between measurements, which is an expensive and time-consuming procedure - especially for an automatic measuring device.

The object of the invention is to eliminate the above-mentioned drawbacks. The device according to the invention is characterized in that there is a stretchable protective film between the an-20 Tur and the liquid. The invention avoids both measuring errors and cleaning operations of the measuring sensor. Measurement errors are overcome because the membrane allows the sensor to be placed in the liquid, resulting in an accurate absorption distance across the entire beam width.

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A preferred embodiment of the invention is characterized in that the protective film is attached to the cuvette system so as to tightly cover all the cuvettes in the cuvette system. The protective film is disposable and thus follows the ky-30 hydration. In this case, the hygienic after-treatment of disposable cuvettes is an additional advantage.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which 35

Figures 1-3 show cuvettes in measurement systems known per se. Their functions and drawbacks have already been described above.

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Figure 4 shows a cuvette according to the invention covered with a protective film.

Figure 5 shows the same cuvette as Figure 4 in the liquid to be measured with the measuring sensor.

Figure 6 shows a top view of the flow of cuvettes in the device.

The device consists of a measuring sensor 1 and a light detector 2, between which the liquid 3 to be measured can be placed in the cuvette 4. During the measurement, the measuring sensor 1 is placed in the liquid 3 in the cuvette 4. Between the sensor 1 and the liquid 3 there is a protective film 5. The protective film 5 is attached to the cuvette 6 so that it tightly covers all the cuvettes 4 in the cuvette. 5 in accordance with the extensible.

The present invention is applicable to both a single-channel measuring sensor and a plurality of parallel sensors 1, as in Fig. 20a. 6. The device is suitable for the entire range of photometric measurement. The need to achieve an accurate absorption distance in the liquid to be measured is essential.

Disposable cuvette 6, for example the so-called a microtiter plate 25 containing 96 cuvettes in a 4, 8 x 12 matrix is dispensed full of patient samples along with the desired reagents. The cuvette plate 6 moves below the fastening position 7 of the protective film. In this case, the film 5 on the roller 8 rests on the plate and adheres to the upper surface. When passing the position 7 the cuvette plate 6 30 moves under the measuring point 9 covered with a membrane. Here, the vertically moving row of measuring transducers 1 descends into the row of cuvettes as shown in Fig. 5, and the first row is measured. The cuvette plate 6 moves forward one row and the next row is measured. This proceeds through the entire disk, with the next disks 35 automatically following the previous ones.

It will be apparent to those skilled in the art that various embodiments of the invention may vary within the scope of the claims set forth below. Thus, the position of the measuring sensor 1 and the light detector 64242 can be changed so that the actual measurement takes place in the liquid in the opposite direction to the example, i.e. from the bottom up.