JPH0419499Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a flow cell for a solution concentration measuring device used to accurately measure the concentration of a solution.
In particular, it relates to a flow cell using a glass electrode with a glass membrane as a sensitive membrane.

Accurate and
When highly accurate measurements are required, factors that cause measurement errors and stability must be taken into particular consideration. Among these, the ones that have a particularly large impact are
These problems arise from the structure of the detection section, such as the generation of a liquid junction potential difference at the liquid junction of the reference electrode, its fluctuation during measurement, and the adhesion of air bubbles near the electrode sensitive membrane.

In general, such precision measurements are achieved by using a flow cell as a detection section as shown in FIG. 1. In the figure, the first
The flow cell 1 has a sensitive membrane surface of an indicator electrode 4 such as a glass electrode or an ion electrode having an approximately cylindrical outer shape exposed to a direct flow path 3 formed in a flow cell body 2 through which a solution to be measured flows. It has a structure in which the membrane surface is brought into contact with the solution to be measured that is supplied to the flow path 3 through a pipe line (not shown), and a second flow cell 6 having a similar structure and equipped with a comparison electrode 5 is provided, and the second flow cell 6 is connected to the first flow cell. The solution to be measured that has exited the first flow path 3 is caused to flow into the flow path 8 formed in the main body 7 of the second flow cell 6 through a pipe (not shown),
The indicator electrode 4 and the comparison electrode 5 are electrically connected through the solution to be measured, a potential difference corresponding to the concentration of the solution to be measured is generated, and the concentration of the solution to be measured is measured from this potential difference. Of course, a flow cell in which a flow cell 1 equipped with an indicator electrode 4 and a flow cell 6 equipped with a comparison electrode 5 are also in practical use. This makes it possible to reduce the occurrence of the liquid junction potential difference mentioned above, and because the sample to be measured passes through the indicator electrode before coming into contact with the reference electrode, the internal liquid of the reference electrode passes through the liquid junction to the sample to be measured. can be prevented from contaminating and affecting the environment. Furthermore, in order to keep the liquid junction potential small and stable, a method may also be used in which the internal liquid of the reference electrode is merged downstream of the first flow cell 1 from another flow path to form a direct liquid junction.

In such a flow cell, typical examples of conventional methods in which an indicator electrode is attached to the flow cell body are shown in FIGS. 2 and 3. That is, two O-rings 9, 1 are placed on the outer periphery of the cylindrical indicator electrode 4 at intervals in the axial direction.
0, and these O-rings 9 and 10 are attached to the inner wall surface 2a forming the cylindrical through hole 11 of the flow cell main body 2.
The indicator electrode 4 is slidably in contact with the indicator electrode 4 to facilitate attachment and detachment of the indicator electrode 4, and is configured to maintain a fluid-tight state with the solution to be measured flowing through the flow path 3.

In this way, the through hole 11 larger than the outer diameter of the indicator electrode 4 is formed in the flow cell body 2, and the O-ring is slid into contact with the entire surface of the sensitive film 4a of the indicator electrode 4 to contact the solution to be measured. Even when a glass electrode having a glass film as a sensitive film is used as the indicator electrode 4, the glass sensitive film is not pressed, so the glass electrode can be fixed in a predetermined position without being damaged.

However, since a gap exists on the outer periphery of the indicator electrode 4 between the lower O-ring 10 and the flow path 3, the exchange of the solution that has entered this gap is insufficient, and air bubbles are generated. There was a point of contact where it was easy to adhere.

The present invention eliminates these drawbacks and provides a flow cell that allows for easy attachment and detachment of electrodes and allows for stable and accurate measurements.

4 and 5 are a schematic sectional view showing an embodiment of a flow cell for a solution concentration measuring device according to the present invention, and a sectional view taken along the line 5--5 in FIG. 4.

As shown in the figure, the flow cell 20 includes a flow cell body 21 and a glass electrode 22 having a substantially cylindrical outer shape and functioning as an indicator electrode. The flow cell main body 21 is formed with a direct flow path 23 through which the solution to be measured flows, and the glass electrode 22 is connected to the flow path 2 from the top surface of the flow cell main body 21.
It is attached to a cylindrical through hole that reaches 3. When attaching this glass electrode 22, in this embodiment, a packing 24 made of a soft material such as rubber or plastic is fitted around the outer periphery of the glass electrode 22, and is tapered at an acute angle in the direction of the glass sensitive film 22a. On the other hand, a cylindrical recess 25 having an inclined part that engages with the taper angle of the packing 24 is formed in the flow cell main body 21,
The packing 24 is stored in this cylindrical recess 25, and the washer 26 is inserted into the upper part of this packing 24.
A cap nut 27 screwed into a threaded portion formed on the outer periphery of the flow cell main body 21 presses the packing 24 through a washer 26 to bring it into close contact with the outer periphery of the glass electrode 22, thereby fixing the glass electrode 22 in a predetermined position. It is. At this time, the entire surface of the sensitive film 22a of the glass electrode 22 is exposed to the flow path 23, and the degree of exposure is such that the sensitive film surface is at the same position as the upper wall surface of the flow path 23, or slightly more than the upper wall surface of the flow path 23. The glass electrode 22 is positioned so that it protrudes inward.
It is preferable to fix it.

FIG. 6 is a front view with one side of the gasket 24 in cross section of the above embodiment, and FIGS. 7A and 7B are front views with one side of the gasket in cross section showing other shapes of the gasket. Of course, the shape and structure of the gasket 24 are not limited to those shown in the drawings, but it is essential that the gasket 24 be tapered at an acute angle in the direction of the glass sensitive film 22a.

In the above embodiment, the gasket 24 is pressed by the cap nut 27 and the washer 26, and the glass electrode 2
Although the gasket 24 is brought into close contact with the gasket 24, it goes without saying that the gasket 24 may be pressed by a pressing member such as a well-known bayonet mount type, or any other known pressing member may be used. It is also obvious that the washers 26 are not necessarily required. Furthermore, it goes without saying that the present invention can be applied to a flow cell in which a flow cell equipped with a glass electrode and a flow cell equipped with a reference electrode are integrated.

With this invention, (1) Easier attachment and detachment of electrodes to the flow cell.

(2) Positioning of the electrode sensitive membrane on the flow path surface can be easily determined without requiring any skill.

(3) There are no voids around the electrode sensitive membrane, making it easy to exchange liquid.
It is easy to clean and does not cause air bubbles to adhere.

(4) The tightening effect of the packing is strong due to the above-mentioned taper, together with its airtight effect.

It has the following effects and is extremely useful for precision measurements.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an example of a flow cell used in a conventional solution concentration measuring device, FIG. 2 is a sectional view showing the configuration of a typical example of a conventional flow cell, and FIG. 3-line sectional view, FIG. 4 is a sectional view showing one embodiment of the flow cell according to the present invention, and FIG.
The figure is a sectional view taken along the line 5-5 in Figure 4, Figure 6 is a partially cut-away front view of the packing used in the flow cell of Figure 5, and Figures 7 A and B each show other shapes of the packing. FIG. 3 is a partially cutaway front view. 20...Flow cell, 21...Flow cell main body, 22...Glass electrode, 22a...Glass sensitive membrane, 23...Flow path, 24...Packing, 25...
...Cylindrical recess.

Claims (1)

[Scope of utility model registration request] A glass electrode having a substantially cylindrical outer shape is attached to a through hole formed in the flow cell body that reaches a direct flow path through which the solution to be measured flows from one surface of the flow cell body, and a glass sensitive membrane of the glass electrode is attached. In a flow cell for a solution concentration measuring device that measures the concentration of a solution to be measured by exposing its surface to the flow path and bringing it into contact with the solution to be measured, the outer periphery of the glass electrode is tapered at an acute angle in the direction of the glass sensitive film. A cylindrical recess is formed in the flow cell main body, and a cylindrical recess having an inclined portion that engages with a taper angle of the cylindrical recess is fitted into the cylindrical recess, and the cylindrical recess accommodated in the cylindrical recess is pressed by a pressing member. A flow cell for measuring solution concentration, wherein the gasket is brought into close contact with the outer periphery of the glass electrode, and the glass electrode is fixed at a predetermined position.