JPS5952980B2 - measurement cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measurement cell for analyzing liquid components using electrodes, and in particular, to an improved support structure for a stirrer that stirs a sample liquid.

In recent years, analysis cells that use electrodes have become popular as devices for analyzing inorganic ions, organic substances, and gas molecules contained in liquids due to their analytical principle, ease of operation, and shortened analysis time. .

Conventionally, an analysis cell using this electrode has been constructed by filling a test liquid containing the component to be analyzed into a cell container, and placing a stirrer containing a magnet or a metal that can be moved by a magnet inside the cell container. throw into. Next, the stirrer is rotated by the magnetic force of a magnetic stirrer provided outside the container to keep the liquid to be tested in an agitated state. In this state, an electrode is inserted into the liquid to be tested and an electrical signal corresponding to the concentration of the component in the liquid is extracted to perform analysis and measurement of the liquid component. In a measurement cell with this structure, the stirrer is rotated by external magnetic force, so electrodes can be inserted throughout the opening of the cell container, and multiple electrodes can be inserted at the same time for multi-component analysis. Moreover, since there is no need for a rotating shaft passing through the bottom of the cell container, there are advantages such as no damage to the sealing material or no liquid leakage.

However, this structure generates large noise during measurement, making it impossible to analyze low-concentration components with high precision, and the rotation of the magnetic force of the magnetic stirrer and the rotation of the stirrer inside the cell container are not synchronized. There were problems such as the stirrer flying up, down, left and right, and damaging the electrodes.

The inventor of the present invention conducted various studies on the causes of this noise generation and found that this noise is caused by fluctuations in the rotational state of the stirrer.

In other words, since the stirrer is simply placed in the cell container and is not supported in any way, the stirrer is not in a fixed position but rotates eccentrically. It was discovered that the noise generation is caused by fluctuations in the flow rate and concentration distribution of the test liquid due to fluctuations in the distance between the two. For this reason, in conventional measurement cells, components can only be analyzed in areas where the electrical signals taken out from the electrodes are sufficiently large in response to the noise level caused by the eccentric movement of the stirrer. Moreover, analysis is impossible at liquid component concentrations below which the electrical signals extracted from the electrodes correspond to the same amount as the noise level, and even concentrations that can be analyzed contain errors equal to the noise level. It was hot. The present invention was made based on this knowledge, and its purpose is to place a stirrer at a predetermined distance from the electrode, and to support the stirrer so that it rotates in a fixed position. It is an object of the present invention to provide a measurement cell that is structured to include an eccentricity prevention body that allows even low-concentration components to be analyzed with high precision, and that prevents damage to electrodes due to splashing of a stirrer.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

・Figures 1 to 3 show an embodiment of the present invention, and this measurement cell 1A includes a cell container 2 with an open top and a stirrer rotatably provided at the bottom of the cell container 2. 3A
and an eccentricity prevention body 4 attached to the bottom side of the cell container 2 so as to support this.

As shown in the perspective view in FIG. 2, the stirrer 3A includes a large-diameter disk portion 6 containing a keychain-shaped magnet 5, a small-diameter cylindrical portion 7 protruding from the center of its upper surface, and this cylindrical portion. It is integrally formed with a plurality of blade parts 8 which are provided radially projecting from the upper surface of the part 7.

Further, as shown in FIG. 3, the eccentricity prevention body 4 has a hole 9 in the center having a slightly larger inner diameter than the cylindrical portion 7 of the stirrer 3A, and is further opened along the circumferential direction so as to surround this hole. It is formed of a disc-shaped frame 11 comprising a plurality of small-diameter holes 10.

The eccentricity prevention body 4 formed of the disk-shaped frame 11 is fitted into and fixed to a step 12 formed on the bottom side of the cell container 2, and is inserted into the central hole 9 to form a cylinder of the stirrer 3A. A portion 7 is inserted through the stirrer 3A to support the stirrer 3A from above. The cell container 2, stirrer 3A, eccentricity preventer 4, and other members constituting the measurement cell 1A may be made of metal, plastic, glass, etc., but the stirrer 3A in particular is made of Teflon or other materials that are made of friction-free material in order to rotate smoothly. Preferably, less material is used.

As shown in FIG. 1, an electrode 13 for analyzing liquid components is inserted into the upper opening of the cell container 2, and this electrode 13 is further connected to a recorder 15 via an amplifier 14. Further, a magnetic stirrer 16 is arranged at the bottom of the cell container 2 so as to place the cell container 2 thereon.
A magnet (not shown) provided inside the device is rotated by a motor. Further, as the electrode 13, for example, an oxygen electrode is used when analyzing dissolved oxygen, a sodium electrode is used when analyzing Na+, and a chloride electrode is used when analyzing carbon.

Next, the operation of the analysis cell having the above structure will be explained.

The test liquid 17 is placed in the cell container 2, and the electrode 13 is further inserted.

Next, when the magnet of the magnetic stirrer 16 is rotated, as the magnetic force rotates, the stirrer 3A containing the magnet 5 rotates, stirring the test liquid 17 from the blade part 8 to achieve a uniform concentration distribution state. to hold. In this state, an electrical signal corresponding to the concentration of the component in the test liquid 17 is extracted from the electrode 13, amplified by the amplifier 14, and recorded on the recorder 15, from which the concentration of the component is measured. In this case, since the stirrer 3A is supported by the eccentricity preventer 4 made of a ring-shaped frame 11, vertical and horizontal movement is restrained, and only rotational movement is performed smoothly.

Therefore, since the stirrer 3A only makes smooth rotational motion without eccentric movement, the distance between the stirrer 3A and the substance-sensitive part of the electrode 13 is kept constant, so that the flow rate of the liquid to be measured,
The concentration distribution becomes uniform, and the noise of the electrical signal taken out from the electrode 13 can be significantly reduced by 1/3 to 1/20. In addition, it is possible to analyze low-concentration liquid components from the old age with little noise, and it is also possible to analyze low-concentration liquid components. The measurement error caused by this method is also reduced to 1/3 to 1/20, and highly accurate analysis is also possible. Further, according to the present invention, since the eccentricity preventing body 4 supporting the stirring bar 30A acts as a resistance against the movement of the liquid to be tested 17 within the cell container 2, an effective stirring state can be obtained.
In cases where the test liquid 17 is diluted and analyzed,
The responsiveness of the electrode 13 can be maintained at its best. In addition, since the stirrer 3A is restrained by the eccentricity prevention body 4,
The stirring bar 3A does not jump up as in the conventional case, and damage to the electrode 13 can also be prevented. Figures 4 and 5 show stirrers 3B and 3C of different shapes, respectively, and Figure 4 shows a large-diameter disc part 6 containing a magnet 5 and a small-diameter cylindrical part protruding from the upper surface of the disc part 6. 18 and four triangular blade portions 8 provided inside the blade portion 8. In addition, FIG. 5 shows a semi-circular 2
This is a stirrer 3C provided with two blades 8. Furthermore, Figure 6,
7 shows a modified example of the eccentricity preventing body 4 composed of a disc-shaped frame 11. In FIG. 6, a large-diameter hole 9 is opened in the center, and a square shape A plurality of holes 10 are opened.

Further, the disk-shaped frame 11 shown in FIG. 7 has a hole 9 opened only in the center. Next, in order to confirm the effectiveness of the present invention, a measuring cell 1A as shown in Fig. 1 was assembled using stirrers 3A, 3B, and 3C of different shapes shown in Figs. 2, 4, and 5, respectively. Ion-exchanged water is poured into this as the test liquid 17, and an oxygen electrode 13 with a Teflon (registered trademark) membrane as a diaphragm is inserted into the liquid to generate an oxygen reduction current corresponding to the dissolved oxygen concentration in the liquid. (signal) and noise levels were measured respectively.

As a result, the signal value corresponding to the dissolved oxygen concentration was 8.0 μA.
, and the noise level is 0.0 for the stirrer 3A.
006 μA, 0.008 μA for stirrer 3B, and 0.010 μA for stirrer 3C.

In this way, the present invention can reduce noise to about 1/1000 of the signal value for dissolved oxygen concentrations that are almost saturated under open air conditions, so an oxygen concentration of 1/1000 or more of the saturated value is sufficient. It was confirmed that detection was possible.
FIGS. 8 to 20 show other different embodiments of the present invention.

The measuring cell 1D shown in FIGS. 8 and 9 has a V-shaped cross section so that the center of the bottom of the cell container 2 is deepest, and a threaded groove 19 is formed on the lower periphery of the inner surface.

The stirrer 3D is composed of a disc part 6 whose lower part protrudes conically in accordance with the V-shape, and a blade part 8 provided at the upper part of the disc part 6. The eccentricity preventing body 4 that supports the stirrer 3D includes a cylindrical body 21 having a thread 20 formed on its outer periphery, a disc part 22 provided horizontally inside the cylindrical body 21 and having a hole 9 in the center thereof, and The frame body 11 is integrally formed with rod-shaped projections 23 provided at intervals on the upper peripheral edge of the disk portion 22, and this frame body 11 is screwed and attached to the bottom of the cell container 2. In this structure, the rod-shaped protrusion 23 acts as a resistor for the liquid 17 to be tested, and a more uniform stirring state can be obtained.

In addition, in the measurement cell 1E shown in FIGS. 10 and 11, the cell container 2 is formed in almost the same shape as in FIG. It is formed into a rod shape.

The eccentricity prevention body 4 includes a cylindrical body 21 having a thread 20 formed on its outer periphery, a hole 9 provided horizontally on the upper part of the cylindrical body 21, and a hole 9 in the center.
The frame body 11 is integrally formed into a ring shape with a disc portion 22 having an open opening. This frame 11 includes a disc portion 2
The cell container 2 can be screwed onto the bottom of the cell container 2 by inserting a tool into a screw-in recess 24 opened on the top surface of the cell container 2 .

Further, in the measurement cell 1F shown in FIG. 12, the bottom of the cell container 2 is formed in a cross-sectional shape, and an L-shaped drainage hole 25 is provided in the bottom wall.

The stirrer 3F includes a disc part 6 containing a magnet 5, a blade part 8 provided on the upper surface of the disc part 6, and a drainage hole 26 inserted through the center part of these parts.
It is formed by. Furthermore, the eccentricity preventing body 4 that supports the stirrer 3F includes a frame body 11 that is integrally formed in a ring shape with a cylindrical portion 21 and a disk portion 22 provided on the top thereof and having a hole 9 in the center. It consists of In the measurement cell 1F having this structure, the liquid to be measured 17 can be easily discharged through the drainage holes 25 and 26.

Furthermore, the measuring cell 1G shown in FIGS. 13 and 14 has a structure in which the center of the bottom of the cell container 2 is higher than the surrounding area, protrudes in a curved manner, and has a drainage hole 25 provided at the peripheral edge.

The stirrer 3G has a built-in magnet 5 and is formed into a disk shape with a conical groove 27 at the center of the upper part of the disk 6 and a radial groove 27'' extending from there toward the outer periphery. As shown in FIG. 14, the eccentricity prevention body 4 is formed of a mouth-shaped frame 11, and has a conical protrusion 28 protruding from the center of the bottom.
This protrusion 28 fits into the groove 27 of the stirrer 3G to support it. Measuring cell 1 of this structure
Since the contact portion of the stirrer 3G is dotted, there is little rotational resistance, and the liquid 17 to be tested can be easily discharged. In the above embodiments, the frame body 11 is used as the eccentricity prevention body 4, but in the embodiments shown in FIGS. 15 and 16, the fixed shaft 11 is used as the eccentricity prevention body 4.
9 was used.

This measurement cell 1H has a cross-shaped stirrer 3H containing a built-in magnet 5, which is rotatably fixed to the bottom of the cell container 2 by a fixed shaft 29. Furthermore, FIG. 17 and FIG. 18 show a modification of the above, in which a cross-shaped stirrer 31 is rotatably supported at the bottom of the cell container 2 by a fixed shaft 29, and a cylindrical shape in which the electrode 13 is inserted and supported. A support frame 31 having a support body 30 provided thereon is attached inside the cell container 2.

In the measurement cell 11 having this structure, it is easy to maintain a constant relative positional relationship between the electrode 13 and the stirrer 31.

Furthermore, the measurement cell 1J shown in FIGS. 19 and 20 has a stirrer 3J provided with a plurality of substantially hemispherical protrusions 32 on the upper surface of the disk portion 6, and an annular protrusion 33 on the lower surface. The cell container 2 has an integral structure, and an annular groove 34 into which the annular protrusion 33 fits is formed at the bottom of the cell container 2.

；；゛２＝＝＝〒±゛しヰ＝{“・：！、、An annular groove 3 provided at the bottom of the cell container 2 so as to be rotatably inserted therein.
It consists of 4. Next, measurement cell 1D of each structure above
. . . 1J, specific examples will be described.

Example Using each of the above measurement cells 1D...1J, the following (
1). (11). Measurements were carried out under the conditions of (111).

(1) An oxygen electrode is used as the electrode 13, and the test liquid 1
Using ion-exchanged water as 7, the signal S of the electrode 13 corresponding to the dissolved oxygen concentration (air equilibrium) in the ion-exchanged water,
The ratio to the noise level N was measured. (11) As the electrode 13, a glucose electrode was used, which was equipped with a porous membrane on which glucose oxidase was immobilized on the surface of the oxygen-permeable diaphragm of the oxygen electrode on the liquid-contacting side.

In addition, the test liquid 17 has a pH of 6. A 50-fold dilution of serum containing 1 g/1 glucose in O phosphate buffer was used. The ratio between the electrode signal S and the noise level N corresponding to the glucose concentration in this case was measured.

A Na+ ion electrode was used as the (111) electrode 13, and a 100 ppm (7) NaCl solution was used as the test liquid 17. The ratio between the electrode signal S and the noise level N corresponding to the Na+ ion concentration in this case was measured. Under each of the above conditions, the measurement cell 1D, No. 1 shown in FIG. 1, measurement cell 1E.1 shown in FIG. No. 2, measurement cell 1F. shown in FIG. No. 3, measurement cell 1G. shown in FIG. N0
．． 4. Measurement cell 1H shown in FIG. N0.5, 17th
Measuring cell 11 shown in the figure. No. 6 and measurement cell 1J shown in FIG. Measurements were made for each case of N0.7, and the results are shown in Table 1.

In this case, the liquid temperature of the test liquid 17 is 25°C, and the stirrer 3 is
The rotation speed of D to 3J is 600r. p. It was set as m.

Comparative Example Measurement cell No. 1 with a conventional structure in which a rod-shaped stirrer was simply inserted into the cell container without using an eccentricity preventer. 8, and measurement cell No. 8 with a conventional structure in which a disc-shaped stirrer was introduced. 9 is also described in (1) of the above example. (11). The ratio between the signal S and the noise level N was measured under each condition (111), and the results are also listed in Table 1.

As is clear from the results in the table above, according to the measurement cell according to the present invention, by supporting the stirrer with an eccentricity prevention body, the horizontal movement of the stirrer is restricted and only rotational movement is possible. I can do it. As a result, the distance between the electrode and the stirrer is maintained constant, and the noise generated is reduced to approximately 1/3 to 1/3 of that of conventional rice.
Since it can be reduced to 1/20, it is possible to perform high-precision analysis, and it is also possible to analyze low-concentration components, and since there is no splashing of the stirrer, damage to the electrodes can be prevented. It has a great effect. Please note that NO
．． By restricting the vertical movement of the stirrer as shown in FIGS. 1 to 6, the generated noise can be further reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a measuring cell showing an embodiment of the present invention, FIG. 2 is a perspective view showing the stirrer shown in FIG. 1, FIG. 3 is a plan view showing the eccentricity prevention body shown in FIG. 4 and 5 are perspective views showing stirrers of different shapes, FIGS. 6 and 7 are plan views showing eccentricity preventers of different shapes, and FIGS. 8 to 20 are perspective views showing stirring bars of different shapes, respectively. Different embodiments are shown, and FIG. 8 is a cross-sectional view of a measurement cell in which the eccentricity prevention body is formed into a frame shape.
Figure 9 is a plan view of Figure 8, Figure 10 is a cross-sectional view of a measuring cell with a rod-shaped stirrer, Figure 11 is a cross-sectional view of Figure 10, and Figure 12 is a stirrer and drainage water into the cell container. 13 is a sectional view of a measuring cell with holes provided, FIG. 13 is a sectional view of a measuring cell using an L-shaped frame as an eccentricity prevention body, FIG. 14 is a perspective view of the frame shown in FIG. 13, and FIG. The figure is a sectional view of a measurement cell in which a fixed shaft is used as an eccentricity prevention body and supports a cross-shaped stirrer.
Figure 7 is a cross-sectional view of the measurement cell with the support frame attached, Figure 18 is a perspective view of the support frame shown in Figure 17, and Figure 9 shows the eccentricity prevention body and the protrusion provided on the stirrer, and when this is inserted. FIG. 20 is a cross-sectional view of a measurement cell configured with an annular groove formed at the bottom of a cell container, and FIG. 20 is a perspective view showing the stirrer shown in FIG. 19. 1A, 1D...1J...Measurement cell, 2
...Cell container, 3A...3J...
... Stirrer, 4... Eccentricity prevention body, 5...
・Magnet, 6... Disc part, 8... Blade part, 11... Frame body, 13... Electrode, 14
...Amplifier, 15...Lucoder 1, 16
...Magnetic Star 1, 17...
...Test liquid, 21... Cylindrical part, 22...
... Disc part, 25, 26... Drain hole, 29...
... Fixed shaft, 31 ... Support frame, 33 ...
... protrusion, 34 ... groove.

Claims (1)

[Claims] 1. A stirrer placed in a cell container is rotated by the magnetic force of a magnetic stirrer provided outside the cell container, and the liquid components are analyzed using electrodes while stirring the test liquid. The measuring cell is characterized in that a stirrer is disposed in the cell container at a predetermined distance from the electrode, and an eccentric prevention body is provided to support the stirrer so that it rotates in a fixed position. measurement cell. 2. The measurement cell according to claim 1, wherein the eccentricity prevention body is constituted by a frame. 3. The measuring cell according to claim 1, characterized in that a fixed shaft rotatably supporting the stirrer is used as the eccentricity prevention body. 4. The measurement cell according to claim 1, wherein the eccentricity prevention body is constituted by a protrusion provided on the stirrer and an annular groove provided at the bottom of the cell container into which the protrusion fits. .