JPS625297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the electrophoretic velocity of visibly suspended particles.

Various methods have been proposed for measuring the electrophoretic velocity of suspended particles when an electric field is formed in a cell suspension, generally a suspension of visible particles.

The electrophoretic velocity of visible suspended particles varies even among particles of the same type, so in order to improve the measurement accuracy of electrophoretic velocity and distinguish between similar particles, it is necessary to observe the distribution of electrophoretic velocity for a large number of particle groups. Must.

The principle of conventional measurement of electrophoretic velocity distribution of visible suspended particles is as follows. FIG. 1 explains the principle. 1 is an electrophoresis cell in which a visible particle suspension is placed and an electric field is applied. Reference numeral 2 denotes a lens system which focuses on one surface within the cell 1 and forms an image of floating particles within that surface on the grating 3. The visible particle suspension is illuminated from above with strong light, and the particles are projected onto the grid 3 as a bright point image. Floating particles are electrophoresing to the right in the figure. Therefore, the floating particle image on the grid 3 is moving to the left on the grid. The grid lines of the grid 3 extend in a direction perpendicular to the moving direction of the particle image and are arranged in parallel to the left and right. Each time the bright particle image crosses a grid line, the amount of light transmitted through the grid decreases. Therefore, considering one floating particle, the amount of light incident on the light receiving element 4 arranged behind the grating 3 changes periodically, and the period is inversely proportional to the electrophoretic velocity of the particle. Actually, on the grid 3 is the cell 1 where the lens 2 is focused.
Since there are many particle images, the fluctuation component of the output of the light-receiving element 4 is not an alternating current of a single frequency, but a superimposition of alternating current components of various periods. The waveform is irregular. When this output waveform is frequency-analyzed to determine the frequency spectral distribution, this spectrum shows the distribution of electrophoretic velocity of suspended particles.

In the conventional method described above, the suspended particles observed are only within one plane of the electrophoresis cell 1, and therefore only a very small number of particles are observed compared to the total number of suspended particles in the cell. .

An object of the present invention is to eliminate the drawbacks of the conventional methods described above, and to improve the accuracy of electrophoretic measurements by making it possible to measure the electrophoretic velocity of a larger number of suspended particles. The present invention will be explained below with reference to Examples.

FIG. 2 shows a top view of an apparatus according to an embodiment of the present invention. 1 is an electrophoresis cell, and 5 and 6 are electrodes. The cell 1 is a flat container with a square plate electrode 5,
6 are facing each other. The distance between the electrodes is smaller than the length of one side of the electrodes. Floating particles are electrophoresing in the direction of the arrow in the figure. The solution in cell 1 is illuminated from above. Floating particles are observed from between the opposing electrodes 5 and 6. That is, floating particles are observed from the right side of cell 1 in the figure. A lens 2 forms an image of floating particles within the cell 1 on the grid 3. The particle image light transmitted through the grating 3 is received by the light receiving element 4. The lens 2, the grating 3, and the light receiving element 4 are fixed on one pedestal 7. The pedestal 7 is movable in the horizontal direction in the figure, and the lens 2 forms an image of the plane x inside the cell 1 on the grating 3.
When the pedestal 7 is moved left and right, the plane x moves left and right within the cell 1. Therefore, set the pedestal 7 so that the plane x is located near the left end of the electrodes 5 and 6 in the figure, inject the particles to be measured into the liquid in the cell 1, and apply a voltage between the electrodes 5 and 6 to remove the injected particles. mount 7 while performing electrophoresis.
When moving to the right, the surface x scans the space between the electrodes 5 and 6 from left to right. . While performing this scanning, the output of the light receiving element 4 is recorded. In the case of cells, they sediment with electrophoresis and the sedimentation speed is faster, so the measurement needs to be completed within 10 to 20 seconds, and the above-mentioned scanning is performed so as to be completed within this time. The electrodes 5 and 6 are square and each side is 2 cm.
Assuming that one scan takes 20 seconds, the time required to scan a distance of 1 mm is 1 mm with the depth of focus of lens 2 being 1 mm.
The electrophoretic distance of particles during this time is about 20μ in seconds. If the projection magnification of lens 2 is 10 times and the pitch of grating 3 is 0.01 mm, the image of one particle will be 20 times per second.
Cross the grating lines. Therefore, the output of photodetector 4 is 20
It is a combination of many signals with frequencies around Hz. Since the frequency of 20 Hz is too low to be electrically processed, it is possible to move the grating 3 to increase the speed of movement of the particle image relative to the grating.

In the above embodiment, scanning is performed by moving the device for observing floating particles relative to the electrophoresis cell, but scanning can also be performed optically. Figure 3 is an example. 1 is an electrophoresis cell, and 2 is a lens. A particle observation system such as a lens 1 is fixed to the cell 1. Two glass wedges 8 and 9 are interposed between the cell 1 and the lens 2. Glass wedge 8,9
can be moved in the direction of the arrow, and the mutual overlap rate can be changed. Parallel plane glass has the effect of bringing the object point closer to the lens by a fraction of the refractive index of its thickness, so by changing the overlapping ratio of glass wedges 8 and 9, the viewpoint in cell 1 of lens 2 can be moved left and right. It can be moved and scanned. Instead of changing the overlapping ratio of the glass wedges 8 and 9, as shown in Figure 4, two parallel flat glass plates 8' and 9' are made to face each other and rotated in the direction of the arrow in the figure to determine the glass thickness as seen from the light beam l. You may change it.

When the electrophoresis cell is tubular, the presence of electroosmotic flow must be considered. When an aqueous solution comes into contact with glass, the surface of the glass that is in contact with the aqueous solution becomes negatively charged, and positive ions gather in a thin layer near where the aqueous solution comes into contact with the glass. When a voltage is applied between the electrodes inserted at both ends of the tube, the positive ions in the thin layer of aqueous solution in contact with the inner surface of the glass tube are attracted toward the negative electrode, and as a result, the aqueous solution in this layer flows toward the negative electrode. . Since the aqueous solution in the tube is generally stationary, a flow toward the positive electrode is formed in the center of the tube as a result of the surface layer flowing toward the negative electrode. The convection of the solution that occurs in this way is an electroosmotic flow. Floating particles perform electrophoresis while moving along with this flow, but it is not possible to distinguish between electrophoretic movement and electroosmotic movement during measurement. Since the direction of electroosmotic flow is opposite between the surface layer and the center of the tube, there exists a cylindrical layer in which the electroosmotic flow is zero.
In the conventional apparatus, the viewpoint of the particle observation system is aligned with a single line on the layer of the electroosmotic flow 0. Therefore, the number of particles observed is very small. FIG. 5 shows an example in which a tubular electrophoresis cell is used. Reference numeral 1 denotes an electrophoresis cell which is tubular in shape and has electrodes 5 and 6 inserted at both ends. 2 is a lens, 3 is a grating, 4 is a light receiving element, and 10 is a laser light source, which are fixed on the arm 11. The arm 11 can rotate around the center line of the electrophoresis cell 1 as shown by the arrow. Lens 2 focuses on the layer of electroosmotic flow with a flow velocity of 0,
Laser illumination is also focused onto this layer.
By rotating the arm 11, scanning is performed along the layer. In a configuration in which flat plate electrodes are placed close to each other and faced each other as shown in FIG. 2, the influence of electroosmotic flow is negligible.

In the conventional device, using Fig. 2, lens 2
The number of particles that can be observed is small because the viewpoint of is not moved to match one fixed plane x. According to the present invention, the plane x is moved to observe all the particles contained within the three-dimensional space, thereby dramatically increasing the number of particles observed and improving the accuracy of electrophoretic velocity measurement. Even in the embodiment shown in FIG. 5, the number of observed particles can be increased because particles on one plane are observed, whereas conventionally only particles on a certain line were observed. In each of the above embodiments, a lens is used in the particle observation system, so the line or plane in the electrophoresis cell that is conjugate with the image of the lens is the viewpoint of the observation system. When using the Doppler heterodyne method, which illuminates with a laser beam from a direction and detects the pulsations in the photometric output of a local oscillation laser beam that intersects with the same beam, the viewpoint of the particle observation system is the local oscillation laser beam and the illumination laser. This is called the intersection with the luminous flux.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of a conventional device, FIG. 2 is a plan view of an embodiment of the device of the present invention, and FIGS. 3 and 4 are only essential parts of devices of other embodiments of the present invention, respectively. FIG. 5 is a perspective view of still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Electrophoresis cell, 2... Lens, 3... Grid, 4... Light receiving element, 5, 6... Electrode, 7... Mount, 10... Laser light source, 11... Rotating arm.

Claims (1)

[Claims] 1. An electrophoresis velocity measuring device which is provided with a means for making a viewpoint within an electrophoresis cell of an observation system for observing suspended particles movable within the cell and scanning the inside of the cell with the said viewpoint.