JP3188772B2 - Coulometric detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coulometric detector, and more particularly to a natural environment, contamination monitoring, and production line capable of absolutely quantifying a substance to be determined in a fluid sample by potentiostatic coulometry. The present invention relates to a coulometric detector suitable for continuous measurement for monitoring.

[0002]

2. Description of the Related Art In recent years, there has been proposed a method of measuring an electric change amount when a substance to be determined is electrolyzed in an electrolytic cell and quantifying the substance to be determined quickly and with high accuracy. Electrolyte is impregnated into the electrode made of a conductive porous body in the working electrode chamber, and a substance to be determined in the sample is diffused into the working electrode chamber from the working electrode chamber and a sample chamber provided through a diaphragm. And a method for quantification (JP-A-3-13-1).
No. 81850). According to this method, the substance to be determined in the gas or liquid sample can be quantified in a short time and with high accuracy. However, the flow of the sample supplied to the sample chamber is likely to be non-uniform, and the diffusion efficiency of the substance to be determined in the electrode chamber is unidirectional, so that the diffusion efficiency is poor, and therefore the response is not sufficient. It is necessary to set up a sample chamber, and it is difficult to make the detector compact.
Since it is a three-chamber stacked detector of the working electrode chamber and the counter electrode chamber,
The configuration is complicated, and special considerations are required for the inflow structure of the electrolyte and measures against liquid leakage, and the handling is inferior.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and to provide excellent permeation and diffusion of a substance to be determined in a fluid sample, high responsiveness, and a simple structure. An object of the present invention is to provide a sample flow type coulometric detector which is easy to handle.

[0004]

According to the present invention, there is provided a coulometric detector in which a working electrode chamber having a porous electrode impregnated with an electrolyte and a counter electrode chamber are opposed to each other with a diaphragm interposed therebetween. A tube composed of at least one of an exchange membrane, a semipermeable membrane, and a microporous membrane is loaded, and a fluid sample is passed through the tube to detect a substance to be determined in the sample.
The present invention relates to a coulometric detector characterized by being transmitted and diffused into a working electrode chamber .

Examples of the tube used in the present invention include ion-exchange membrane tubes such as Nafion 117 tube (trade name, manufactured by DuPont), semipermeable membrane tubes such as cellulose membrane, and microporous membrane tubes made of polyethylene, polypropylene, Teflon, etc. And a microporous membrane tube such as a porous ceramic membrane. These are appropriately selected according to the type of the substance to be determined, and these tubes may be used in combination.

[0006] The cross-sectional shape of the tube is not particularly limited.
The length of the tube loaded in the working electrode chamber is preferably 10 mm to 500 mm, depending on the tube diameter and the like.
A range of mm is preferred.

In the present invention, the working electrode or the counter electrode includes:
A cloth or a felt, which is an aggregate of conductive fibers, specifically, a carbon cloth or a carbon felt is used. As the electrolytic solution, an aqueous solution or a non-aqueous solution containing a supporting electrolyte or a supporting electrolyte and a reaction reagent is used.
When a non-aqueous solution is used, it can be used to measure a high-temperature sample of 100 ° C. or higher. As the diaphragm, a polystyrene sulfonic acid membrane, an ion exchange membrane, or the like is used.

FIG. 1 is an explanatory diagram of a coulometric detector according to one embodiment of the present invention. In the figure, a working electrode chamber 3 and a counter electrode chamber 4 are opposed to each other on a coulometric detector 1 with a diaphragm 5 interposed therebetween. The working electrode chamber 3 is filled with a porous electrode made of a carbon cloth or the like impregnated with an electrolytic solution, and the sample transmission tube 2 is loaded therein. Both ends of the sample transmission tube 2 are connected to a sample supply port 6 and a sample outlet 7 through a current collector 10. On the other hand, a counter electrode solution is supplied to a counter electrode chamber 4 having a porous electrode from a counter electrode liquid supply port 8 and discharged from the counter electrode outlet 7 to the outside of the system.

[0009] In such a coulometric detector, flowable sample is introduced from the sample-supplying port 6 to continuously transmit a specimen tube 2 at a constant flow rate out of the system from the sample flow outlet 7 through the inside the tube 2 Is discharged. While the sample passes through the sample permeation tube 2, the substance to be determined in the sample permeates and diffuses from the entire periphery of the tube into the working electrode chamber 3, and undergoes electrolysis. Absolute quantification is possible because all substances to be quantified can pass through the tube. Also, since only the substance to be determined is supplied to the working electrode chamber, the electrolysis is not affected by other components contained in the sample,
Measurement accuracy is improved.

[0010]

The present invention will be described below in more detail with reference to examples. Examples 1 to 5 The configuration of the coulometric detector shown in FIG. Determination, determination of soluble COD components in water,
Determination of water in methanol, SO _{2 in} flue gas
And the ozone in the gas were determined. The results are shown in Table 1. In the measurement of each sample, the materials of the counter electrode solution, the diaphragm, the working electrode solution, and the sample permeation tube are shown in Table 1.
The length of the tube loaded in the working electrode chamber was 150 mm. Table 1 shows that the detector of the present invention can easily perform high-precision absolute quantification.

[0011]

[Table 1]

* 1: It was consistent with the value measured by the iodine titration method. * 2: COD content measured by heating and evaporating water is 11p
pm. * 3: The value was consistent with the value measured by the Karl Fischer method. * 4: In agreement with the value measured by the NDIR method (non-dispersive infrared method). * 5: It was consistent with the values measured by absorption and iodine titration.

[0013]

According to the coulometric detector of the present invention, a tube made of an ion-exchange membrane or the like is loaded into the working electrode chamber and the sample is allowed to pass through, so that only the substance to be determined in the sample can be efficiently used in the working electrode chamber. Can be transmitted and diffused, so that the following effects can be obtained. (1) Continuous absolute quantification is possible, and therefore no standard sample is required. (2) Since the diffusion efficiency of the analyte is excellent, the response is excellent and almost real-time online measurement is possible. (3) By selecting the tube material and the electrolytic solution, it becomes possible to measure the substances to be determined contained in various samples (gas, aqueous solution, non-aqueous liquid, slurry). (4) It is possible to provide a detector that is easy to maintain and maintenance-free for a long time. (5) The structure of the detector is simple, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a coulometric detector according to one embodiment of the present invention.

[Explanation of symbols]

1: Coulometric detector, 2: Sample transmission tube, 3
... working electrode room, 4 ... counter electrode room, 5 ... diaphragm, 6 ... sample supply port,
7: sample outlet, 8: counter electrode supply port, 9: counter electrode outlet.

Claims (1)

(57) [Claims] 1. A coulometric detector in which a working electrode chamber having a porous electrode impregnated with an electrolyte and a counter electrode chamber are opposed to each other with a diaphragm interposed therebetween. A tube comprising at least one porous membrane is loaded, and a fluid sample is passed through the tube.
The substance to be determined in the sample into the working electrode chamber
Coulometry detector, characterized in that the causes manner.