JPH03115849A - Formation of liquid junction in flow-through type ion concentration measuring apparatus - Google Patents

Abstract

PURPOSE:To stabilize a liquid junction part within a short time by providing a stop valve to either one of a comparing electrode solution introducing pipe and an ion sample introducing pipe and connecting the pipe provided with the stop valve to the other pipe in a T-shape. CONSTITUTION:When a stop valve 18 is opened to drive a pump 12, the electrode solution from a comparing electrode solution tank 19 and the sample solution from a sample introducing port 11 are respectively sucked through introducing pipes 13, 14 to meet with each other at a junction part 17. At the confluent point of time, the valve 18 is closed to close the pipe 14. By this mechanism, the sample solution flows so as to tear off the end surface of the comparing electrode solution and, after tearing-off, the pump 12 is stopped. Since the comparing electrode solution uses the pipe 14 as a sleeve to come into contact with the sample solution only at an end surface part, a stable liquid junction is formed and the valve 18 is again opened to form the electric circuit of a comparing electrode 16 and an ion selecting electrode 15 and, by detecting the potential between the electrodes showing a steady valve, a stable liquid junction part can be formed within a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a technique for forming a liquid path in a flow-through type ion concentration measuring device.

(Prior art) In order to intermittently measure the ion concentration of a sample solution whose amount can be collected for measurement intermittently, the sample solution is usually connected to the pump 2 from the sample inlet 1 as shown in Fig. 1. Sample introduction pipe 3
An intermittent flow-through type ion concentration measuring device is used, in which a comparison electrode solution introduction pipe 4 is connected to the middle of the ion flow, and an ion selection electrode 5 and a comparison electrode 6 are immersed in each introduction pipe 3.4. Then, the sample solution and the reference electrode solution are sucked by the pump 2, and when the two solutions meet to form a liquid junction, the pump 2 is stopped and the ion selective electrode 5 is sucked.
The interelectrode potential difference E between and the comparison electrode 6, that is, the unit potential E r of the ion selection electrode 5 and the comparison electrode 6
A method is adopted in which the potential difference E ise - E ref with respect to ef is measured by the potential difference Ej between the liquids at the liquid junction.

(Problem to be Solved by the Invention) However, in this type of device, since the bosib is stopped when the sample solution and the reference electrode solution meet, as shown in Fig. 2, the comparison electrode solution and the sample solution are separated. The state of contact with the liquid is unstable, and until this state stabilizes, the liquid potential difference Ej fluctuates, so the interelectrode potential difference E does not show a steady value (FIG. 3).

For this reason, not only does it take time for the electrode potential difference E to stabilize after the pump is stopped, but also the stable state of the liquid contact is not constant, resulting in a problem of low reproducibility of measurement results.

The present invention was made in view of these problems, and its purpose is to provide a method for forming a liquid junction in a flow-through type ion concentration measuring device that can form a stable liquid junction in a short period of time. It is to make a proposal.

Means for Solving Section C M) In order to solve such problems, in the present invention, one of the reference electrode solution introduction pipe equipped with the reference electrode and the sample introduction pipe equipped with the ion selection electrode is A stop valve is provided to open and close the flow path of the inlet pipe, and one inlet pipe is connected to the other inlet pipe orthogonally in a "T" shape to form a joint, and the other inlet pipe is connected to a pump. connecting to form an analysis flow path, opening the stop valve and driving the pump, closing the stop valve when they merge at the junction, and suctioning the test N sample solution or reference electrode solution. The method includes a step of stopping the pump after scraping off the reference electrode solution or sample solution in contact with the joint portion.

(Operation of the invention) By opening the stop valve and driving the pump, the sample solution and the reference electrode solution are sucked through the respective introduction pipes and merge at the connecting portion. When these two liquids meet, the stop valve is closed to block the passage of the reference electrode introducing pipe, and when a small amount of one liquid, for example, the sample solution, is aspirated, the other liquid, the reference electrode liquid, flows into the end surface of the pipe. is forcibly scraped off with the sample solution. Thereafter, when the pump is stopped, the reference electrode solution comes into contact with the sample solution only at its end face using the introduction pipe as a sleeve, so that a stable liquid junction is formed within a short time.

(Example) The details of the present invention will be described below based on illustrated examples.

FIG. 4 shows a piping system of an apparatus that constitutes an embodiment of the present invention, in which a comparison electrode liquid introduction pipe 14 is connected in the middle of a sample introduction pipe 13 from the sample introduction port 11 to the pump 2. In a flow-through type ion concentration measuring device, a stop valve 1 is installed between the reference electrode 16 and the T-shaped joint 17 of the reference electrode liquid introduction pipe 14.
8. In addition, the reference numeral 15 in the figure indicates the ion selection electrode immersed in the sample solution introduction pipe 13.
9 indicates a comparative electrode liquid tank such as potassium chloride.

In the embodiment described above, the stop valve 18 is opened and the pump]2
When the reference electrode solution tank 19 and the sample solution are sucked from the sample introduction port 11 through the respective introduction pipes 13 and 14, they merge at the junction 17. When these two liquids meet, the stop valve 188 is closed to close the passage of the comparison electrode introduction pipe 14. As a result, the sample solution that is still being sucked flows as if peeling off the end surface of the reference electrode solution. After scraping off the reference electrode solution, pump 1
Stop 2. As a result, as shown in FIG. 5, the reference electrode solution comes into contact with the sample solution only at its end face using the introduction pipe 14 as a sleeve, so that a stable liquid junction is formed. When the stop valve 18 is opened again from this state to form an electric path between the comparison electrode 16 and the ion selection electrode 15, an interelectrode potential E (FIG. 6) indicating a steady value can be detected.

In the above-mentioned embodiment, a stop valve 1 is provided in the comparative electrode liquid introduction pipe 14.
The second embodiment of the present invention shown in FIG. The sample solution introduction pipe 13 is connected to the electrode solution introduction pipe 14 in a linear shape, and a stop valve 28 is installed on the sample solution introduction pipe 13 side.
In this embodiment, the stop valve 28 is closed when the reference electrode solution and the sample solution merge, and the reference electrode solution is allowed to flow down. let As a result, the end surface of the sample solution is washed away with the reference electrode solution, and the sample solution is brought into contact with the reference electrode solution only at the end surface portion.

In each of the embodiments described above, the electrode is immersed on the upstream side of the stop valve, but similar effects can be obtained even if the electrode is immersed on the downstream side.

(Effects of the Invention) As explained above, in the present invention, a stop valve is provided on either the reference electrode solution introduction pipe or the ion sample introduction pipe, and a stop valve is provided on the other introduction pipe in a single-character shape. Since the structure was configured to connect the pipes, a stop valve was installed on either side, and after the two liquids had merged, the stop valve was operated to allow one solution to flow for a short period of time, allowing both pipes to be connected. A stable liquid junction can be easily and quickly formed by contacting the liquid at the joint surface and washing one solution with the other at the confluence of the two liquids, which can be reproduced in a short measurement cycle. It is possible to obtain highly accurate measurement results.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the piping system of a conventional flow-through type ion concentration measuring device, Fig. 2 is an explanatory diagram showing the liquid contact state of the liquid junction in the above device, and Fig. 3 is a diagram showing the response characteristics of the conventional blind. Fig. 4 is a piping diagram showing an example of the device used in the present invention, Fig. 5 is an explanatory diagram showing the liquid contact state of the liquid junction according to the present invention, and Fig. 6 is a piping diagram showing an example of the device used in the present invention. FIG. 7, which is a diagram showing response characteristics, is a piping diagram of an apparatus showing another embodiment of the present invention. 11...Sample introduction port 12...Pump 13
... Sample introduction pipe 14 ... Reference electrode solution introduction pipe

Claims (1)

[Claims] A stop valve is provided to open and close the flow path of either a reference electrode liquid introduction pipe equipped with a comparison electrode or a sample introduction pipe equipped with an ion-selective electrode, and one of the introduction pipes is connected to the other introduction pipe. Connecting orthogonally in a "T" shape to form a joint, and connecting the other introduction pipe to a pump to form an analysis flow path, and opening the stop valve to drive the pump. , a step of closing a stop valve when they merge at the junction, and a step of stopping the pump after scraping off the reference electrode solution or sample solution in contact with the junction by suctioning the sample solution or reference electrode solution. A method for forming a liquid junction in a flow-through type ion concentration measuring device.