JPH07253410A - Flow cell type ion sensor - Google Patents

Abstract

PURPOSE:To secure the measuring accuracy of a magnesium selective electrode by disposing a calcium ion selective electrode on the downstream side of a magnesium ion selective electrode. CONSTITUTION:Holders 3A, 3B are provided in a flow cell housing 1, and a magnesium ion selective electrode 5A and a calcium ion selective electrode 5B are respectively engaged with the holders 3A and 3B. In this case, liquid to be measured flows from a left side to a right side in a housing 1 tube. The electrodes 5A and 5B are respectively provided on the upstream and downstream sides. When a magnesium ion concentration included in the liquid to be measured is measured in the presence of calcium ions of various concentrations, a measuring accuracy is + or -7% or less. On the contrary, when the electrodes 5A, 5B are replaced to be disposed, the measuring accuracy is reduced to about + or -18%. This is considered that a constituent ingredient of the electrode 5B is dissolved to be interfered with the electrode 5A. Thus, the electrode 5B is disposed on the downstream side, thereby equalizing the measuring accuracy of the electrode 5A to that in the case of the single electrode 5A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow cell type ion sensor for measuring the ion concentration of ions existing in a solution, and more particularly to a flow cell type ion sensor for simultaneously detecting a plurality of ion concentrations.

[0002]

2. Description of the Related Art Conventionally, an ion-selective electrode used in an ion concentration measuring device or the like is such that the potential of the electrode measured with reference to a reference electrode changes in proportion to the logarithm of the activity of the ion to be measured. Is used to detect the ion concentration. Such ion-selective electrodes have hitherto been widely used in fields such as specific ion monitoring and water quality analysis.

In particular, recently, there is an increasing demand for simultaneous analysis of the concentrations of a plurality of different ions present in the liquid to be measured. In such simultaneous measurement, needless to say, a plurality of ion-selective electrodes that respond selectively to individual ions to be measured are required. For example, a magnesium ion-selective electrode and a calcium ion-selective electrode are required to simultaneously detect magnesium ions and calcium ions present in the liquid to be measured.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
When each ion concentration is measured using a liquid membrane type magnesium ion selective electrode and a PVC liquid membrane type calcium ion selective electrode at the same time, the measurement accuracy of the magnesium ion selective electrode may be magnesium ion selective depending on the measurement conditions. In some cases, it was lower than when measured with the sex electrode alone.

The present invention has been made in view of the above problems, and in a flow cell type ion sensor including a magnesium ion-selective electrode and a calcium ion-selective electrode as constituent elements, the measurement accuracy of the magnesium ion-selective electrode is magnesium. It is an object of the present invention to provide a flow cell type ion sensor having a structure that does not deteriorate compared to the case of using an ion selective electrode alone.

[0006]

In order to achieve the above object, a flow cell type ion sensor of the present invention has a concentration of ions to be measured in a flow channel of a flow cell in which a liquid to be measured containing at least magnesium ions and calcium ions is flowed. Arranging multiple ion-selective electrodes for detection,
In the flow cell type ion sensor for measuring the ion concentration in the liquid to be measured, the concentration of calcium ion is detected on the downstream side of the magnesium ion selective electrode for detecting the concentration of magnesium ion arranged in the flow path. The point is to arrange a calcium ion selective electrode for the purpose.

[0007]

The flow cell type ion sensor of the present invention is provided on the downstream side of the magnesium ion selective electrode for detecting the concentration of magnesium ion in the flow channel of the flow cell through which the liquid to be measured containing at least magnesium ion and calcium ion flows. By disposing the calcium ion selective electrode for detecting the concentration of calcium ion, the measurement accuracy of the magnesium ion selective electrode is ensured.

Hereinafter, it will be described that the measurement accuracy of the magnesium ion selective electrode is ensured by the present invention. The present inventors reduce the measurement accuracy of a magnesium ion-selective electrode, such as a PVC (polyvinyl chloride) liquid membrane-type magnesium ion-selective electrode, which occurs in a flow cell type ion sensor in which a plurality of ion-selective electrodes are arranged at the same time. The phenomenon was examined. As a result, it was found that this decrease in measurement accuracy was due to a decrease in the selectivity of the magnesium ion-selective electrode for calcium ions when used in combination with the calcium ion-selective electrode.

As a result of studying this phenomenon in more detail, the magnesium ion-selective electrode and the calcium ion-selective electrode were arranged in the flow path through which the liquid to be measured containing at least magnesium ion and calcium ion was passed to determine the respective ion concentrations. When a calcium ion-selective electrode is placed upstream of the flow channel and a magnesium ion-selective electrode is placed downstream, the measurement accuracy of the magnesium ion-selective electrode is higher than that of the magnesium ion-selective electrode alone. It was found that the measurement accuracy of the magnesium ion-selective electrode does not decrease when the magnesium ion-selective electrode is arranged upstream of the flow channel and the calcium ion-selective electrode is arranged downstream of the flow channel.

From this, the decrease in the measurement accuracy of the magnesium ion-selective electrode when the calcium ion-selective electrode is also used is due to the fact that the constituent components of the liquid membrane type calcium ion-selective electrode are eluted into the liquid to be measured and the magnesium ion selectivity is lowered. It is thought to be caused by interfering with the electrodes. The most likely interfering components are the membrane solvents decane-1-ol, di-n-octylphenyl phosphonate, di-octyl phosphonate, tri-n-octyl phosphate, tri-, which are membrane solvents contained in the calcium ion selective electrode. Substituted phosphonates such as -n-decyl phosphate and phosphates. It is highly possible that these interfered with the magnesium ion-selective electrode via the liquid to be measured and reduced the selectivity of the magnesium ion-selective electrode for calcium ions.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a flow cell type ion sensor according to the present invention.

As shown in FIG. 1, in the flow cell type ion sensor of the present embodiment, at least two holders 3A and 3B are provided in a row in a cylindrical flow cell housing 1, and the holders 3A and 3B are respectively provided in the holders 3A and 3B. The magnesium ion-selective electrode 5A and the calcium ion-selective electrode 5B are fitted into each other, so-called fitting. At this time, the tips of the ion-selective electrodes 5A and 5B are surely brought into contact with the liquid to be measured flowing in the flow cell casing 1. The same applies when a corresponding ion-selective electrode is arranged to detect other ions. Further, in addition to these ion selective electrodes, a reference electrode 7 is provided so as to be in contact with the same liquid to be measured. Lead wires 9A, 9B and 9C are connected to the ion selective electrodes 5A and 5B and the reference electrode 7, respectively. In addition, in the present embodiment, it is assumed that the liquid to be measured flows through the inside of the flow cell casing 1 from the left side to the right side in FIG. 1, and the magnesium ion selective electrode 5A is arranged on the upstream side (left side in the figure). A calcium ion selective electrode 5B was provided on the downstream side.

In this embodiment, the reference electrode 7 is provided on the downstream side of the calcium ion selective electrode 5B, but its position is between the magnesium ion selective electrode 5A and the calcium ion selective electrode 5B. Alternatively, it may be on the upstream side of the magnesium ion selective electrode 5A. Further, the positions of the other ion-selective electrodes are not limited as in the reference electrode 7. However, it is needless to say that the calcium ion-selective electrode 5B should be located at the downstream side of the magnesium ion-selective electrode 5A, but it is better to separate the distance.

Next, the operation of this embodiment will be described with a specific configuration. In the present example, each ion concentration of magnesium ion and calcium ion was continuously measured using a flow cell type ion sensor. In FIG. 1, the liquid to be measured containing magnesium ions and calcium ions in the flow cell casing 1 flows from the left side to the right side in the figure as described above.

The magnesium ion selective electrode 5A provided on the upstream side of the flow path of the flow cell is, for example, N-heptyl-N ', N'-bis {8-[[3- (heptylmethylamino) -1,3. -Dioxopropyl] amino] octyl} -N-methyl-propanediamide was used as a sensitizer to construct a PVC liquid film type electrode using o-nitrophenyl octyl ether as a film solvent. In addition, a calcium ion selective electrode 5 provided on the downstream side of the flow channel of the flow cell
In B, bis [di- (n-octylphenyl) phosphato] calcium was used as a sensitive substance, and di-n-octylphenylphosphonate was used as a membrane solvent, and a PVC liquid membrane type electrode was similarly constructed. A silver-silver chloride electrode was used as the reference electrode 7. The potential of each of the ion selective electrodes 5A and 5B was measured with the reference electrode 7 as a reference.

When the concentration of magnesium ions contained in the liquid to be measured was measured in the presence of various concentrations of calcium ions, the measurement accuracy was within ± 7%, and at least continuous 4
It was usable for a month.

On the other hand, magnesium ion selective electrode 5A
When the disposition of the calcium ion selective electrode 5B and the measurement of the magnesium ion concentration were performed under the same conditions, the measurement accuracy decreased to ± 18%, and at the same time, the service life also decreased to about one month.

Next, a second embodiment will be described with reference to FIG. The second embodiment shows a conceptual diagram of a vertical cross section of a flow cell type ion sensor for simultaneously measuring four different kinds of ions. In this flow cell type ion sensor, each ion selective electrode 15 and reference electrode 17 are provided inside the outer package 11. Exterior 1 of this ion sensor
1 is provided with a measured liquid inlet 11a and a measured liquid outlet 11b, respectively. An opening for taking out the lead wire 19 is provided on the side wall surface of the outer package 11 near the measured liquid outlet 11b.

Further, the exterior 1 of the flow cell type ion sensor.
Magnesium ion selective electrode 15 installed inside 1
A, the potassium ion-selective electrode 15B, the calcium ion-selective electrode 15C, the nitrate ion-selective electrode 15D, and the reference electrode 17 are formed in substantially the same shape, and their appearances are disk-shaped bodies having substantially the same radius. There is a through hole in the center.

Similarly, each of these ion-selective electrodes 15 is
Electrical insulating members 13A, 13B interposed as spacers between A, 15B, 15C, 15D and the reference electrode 17,
Each of 13C, 13D, 13E, and 13F is formed in substantially the same shape, and its appearance is similar to that of the ion-selective electrode 15 with a through hole provided in the center. These electrical insulating members 13A, 13B, 13C, 13D, 13
E, 13F and electrical insulation member 13A interposed between the measured liquid inlet 11a and the magnesium ion selective electrode 15A and electrical insulation interposed between the reference electrode 17 and the measured liquid outlet 11b. The thickness of the member 13F is not particularly limited and can be appropriately selected.

Further, each of the ion selective electrodes 15 described above
A, 15B, 15C, 15D, reference electrode 17, and electrical insulating members 13A, 13B, 13C, 13D, 13E, 13
The Fs are integrally connected to each other such that the holes provided at the centers thereof are aligned with each other, that is, the through holes 27 are formed thereby and the respective board surfaces are brought into close contact with each other. That is, the through holes 27 provided in the electric insulating member 13, each ion-selective electrode 15, and the reference electrode 17 are provided between the measured liquid inlet 11a and the measured liquid outlet 11b.
It functions as a single flow path that penetrates and allows the liquid to be measured to flow.
The measured liquid flowing in from the measured liquid inlet 11a flows through the through hole 27 toward the measured liquid outlet 11b, and can be discharged from the measured liquid outlet 11b without leaking on the way.

In this embodiment, not only the magnesium ion selective electrode 15A is arranged upstream of the calcium ion selective electrode 15C, but also the magnesium ion selective electrode 15A and the calcium ion selective electrode 1
By disposing the potassium ion selective electrode 15B between the electrodes 5C and 5C, it is possible to avoid the adjacency and to keep the distance. Thus, three or more ion selective electrodes 1
In the flow cell type ion sensor having 5A, 15B, and 15C, it is more preferable that the magnesium member-selective electrode 15A and the calcium ion-selective electrode 15C are not adjacent to each other.

Next, the structure of the ion selective electrode 15 will be described. In addition, each ion selective electrode 15A, 15B,
Since the configurations of 15C and 15D are substantially the same, the magnesium ion selective electrode 15A will be described as an example.

This magnesium ion selective electrode 15A
Is a substrate (preferably made of polyvinyl chloride resin) 21A
A magnesium ion-selective film 23A (potassium ion-selective film 23B, calcium ion-selective film 23C, nitrate ion-selective film 23D) is formed along the through-holes of (21B, 21C, 21D) and further formed on the film. The lead wire 19 is formed through the conductive members 25A (25B, 25C, 25D) formed in close contact with each other. Further, although the structure and arrangement of the reference electrode 17 are not particularly specified, it is preferable to arrange the reference electrode 17 at the most downstream side of each ion selective electrode 15 as shown here.

With such a structure, a plurality of ion-selective electrodes can be integrated compactly, and the flow rate of the liquid to be measured can be small, which is of great practical value and is particularly suitable for online measurement. A suitable ion sensor can be provided.

In the second embodiment shown in FIG. 2, the electrode structure is classified as an ion-selective electrode, which is a so-called coated wire type, which has no internal liquid, but the present invention is not limited to this. Needless to say, the present invention is not limited to this electrode structure and applies to all liquid film type electrodes having an internal liquid.

[0027]

As described above, according to the present invention, in the flow cell type ion sensor body including the magnesium ion-selective electrode and the calcium ion-selective electrode as constituent elements, the measurement accuracy of the magnesium ion-selective electrode is It is possible to make it almost the same as the case of the selective electrode alone.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a basic configuration of a flow cell type ion sensor according to the present invention.

FIG. 2 is a conceptual sectional view of a flow cell type ion sensor showing an embodiment example according to the present invention.

[Explanation of symbols]

 1 Flow Cell Housing 3 Holder 5A, 15A Magnesium Ion Selective Electrode 5B, 15B Calcium Ion Selective Electrode 7,17 Reference Electrode 9,19 Lead Wire 11 Ion Sensor Body Exterior 11a Measured Solution Inlet 11b Measured Solution Outlet 13 Electric insulating member 15C Calcium ion selective electrode 15D Nitrate ion selective electrode 21A Magnesium ion selective electrode substrate 21B Potassium ion selective electrode substrate 21C Calcium ion selective electrode substrate 21D Nitrate ion selective electrode substrate 23A Magnesium ion selective membrane 23B Potassium ion selective membrane 23C Calcium ion selective membrane 23D Nitrate ion selective membrane 25A, 25B, 25C, 25D Conductive member 27 Through hole

Claims (1)

[Claims] 1. A plurality of ion-selective electrodes for respectively detecting the concentrations of ions to be measured are arranged in a flow path of a flow cell in which a liquid to be measured containing at least magnesium ions and calcium ions is flowed, and the liquid to be measured is arranged. In a flow cell type ion sensor for measuring the ion concentration in, a calcium ion for detecting the concentration of calcium ion on the downstream side of a magnesium ion selective electrode for detecting the concentration of magnesium ion arranged in the flow path A flow cell type ion sensor having a selective electrode.