JP7093005B2 - Reagent-free total effective chlorine measuring device and its calibration method and reagent-free total effective chlorine measuring method - Google Patents

Description

The present invention relates to a total effective chlorine measuring device, a calibration method thereof, and a total effective chlorine measuring method. More specifically, the present invention relates to a total effective chlorine measuring device capable of evaluating the total effective chlorine concentration of a sample solution containing bromine such as seawater without using a reagent, a calibration method thereof, and a total effective chlorine measuring method.

The total effective chlorine concentration is the concentration of all halogen-based agents having a bactericidal effect. Specifically, it is represented by the amount of halogen (usually the amount of chlorine) corresponding to the amount of iodine released when potassium iodide is reacted.
Total effective chlorine includes free chlorine (hypochlorous acid or hypochlorite ion), bound chlorine such as chloramine.
When sodium hypochlorite is added to water containing bromine such as seawater, hypobromous acid is produced by reaction with bromine, and further reacts with ammoniacal nitrogen in seawater to form bromoamines (bound bromine). Is thought to have been generated. These hypobromous acid, bromoamines, etc. are also included in the total effective chlorine because they release iodine when they react with potassium iodide.

Conventionally, a polarographic method for measuring a redox current is used for continuous measurement of chlorine concentration. As the chlorine concentration measuring device by the polarographic method, there are a reagent-type device that requires the addition of a reagent and a non-reagent type device that does not use a reagent.
The reagent-free device has the advantage that the burden of maintenance work and maintenance costs is small, but the measurement target that can measure the chlorine concentration accurately and stably with the reagent-free device is limited to a specific sample solution such as clean water. The current situation is that (Patent Document 1).
In particular, in the case of seawater or water containing bromine such as boiler cooling water, the chlorine concentration could not be measured accurately and stably by the reagent-free polarograph method.

Japanese Patent No. 3469962

In view of the above circumstances, the present invention can determine the total effective chlorine concentration by a two-electrode polarograph method without using a reagent, and hypobromine in a sample solution containing bromine such as seawater or boiler cooling water. An object of the present invention is to provide a total effective chlorine measuring device capable of accurately and stably measuring the total effective chlorine concentration including acid, a calibration method thereof, and a total effective chlorine measurement method.

In order to achieve the above problems, the present invention has adopted the following configuration.
[1] A two-electrode polarographic method for measuring all effective chlorine.
A gold detection electrode immersed in the sample liquid and a platinum counter electrode,
An applied voltage mechanism that applies an applied voltage selected from the range of 750 ± 250 mV between the detection electrode and the counter electrode, and
A total effective chlorine measuring device comprising: an ammeter for measuring a redox current flowing between a detection electrode and a counter electrode when the applied voltage is applied to the applying voltage mechanism.
[2] Further, a calculation control unit is provided, and the calculation control unit obtains the total effective chlorine concentration of the sample solution based on the redox current measured by the ammeter. The total effective chlorine measuring device according to [1]. ..
[3] A calibration method for calibrating the total effective chlorine measuring device according to [2], wherein a calibration solution containing no halogen other than chlorine and having an electric conductivity of 4 mS / m or more is used. Calibration method.
[4] An applied voltage selected from the range of 750 ± 250 mV is applied between the gold detection electrode immersed in the sample solution and the platinum counter electrode, and the redox current flowing between the detection electrode and the counter electrode is applied. A method for measuring total effective chlorine, which comprises measuring and obtaining the total effective chlorine concentration of the sample solution from the obtained redox current.
[5] The selected applied voltage is applied between the detection electrode and the counter electrode immersed in a calibration solution that does not contain halogen other than chlorine and has an electric conductivity of 4 mS / m or more, and the detection electrode is combined with the detection electrode. The redox current flowing between the counter electrode was measured, and the calibration curve based on the correspondence between the obtained redox current and the total effective chlorine concentration of the calibration solution was obtained.
The method for measuring total effective chlorine according to [4], wherein the total effective chlorine concentration of the sample solution is obtained from the redox current when the sample solution is measured using the calibration curve.
[6] The method for measuring total effective chlorine according to [4] or [5], wherein the sample solution contains bromine.

According to the total effective chlorine measuring device of the present invention, its calibration method, and the total effective chlorine measuring method, the total effective chlorine concentration can be obtained by the two-electrode polarograph method without using a reagent, and seawater or boiler cooling water can be obtained. Even with a sample solution containing bromine such as, the total effective chlorine concentration including hypobromic acid can be measured accurately and stably. Moreover, it can also measure low-concentration total effective chlorine.

It is an overall block diagram of the total effective chlorine measuring apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing of the sensor part in the total effective chlorine measuring apparatus which concerns on 2nd Embodiment of this invention. It is an overall block diagram of the total effective chlorine measuring apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing of the sensor part in the total effective chlorine measuring apparatus which concerns on 4th Embodiment of this invention. It is a calibration curve obtained in Experimental Example 1 of this invention. It is a polarogram when chlorine is added to the seawater obtained in Experimental Example 2 of the present invention. It is a polarogram when chlorine is added to the dechlorinated water obtained in Experimental Example 2 of the present invention. It is a polarogram of the sample liquids A to C obtained in Experimental Example 3 of the present invention. It is a calibration curve obtained in Experimental Example 4 of this invention. It is a measurement result of the total effective chlorine concentration of the experimental example 4 of this invention. This is the result of continuous measurement of the chlorine-added seawater of Experimental Example 5 of the present invention. This is the result of measuring the seawater to which the low concentration chlorine was added in Experimental Example 6 of the present invention.

<First Embodiment>
[Device configuration]
The total effective chlorine measuring apparatus by the two-electrode polarographic method according to the first embodiment of the present invention will be described with reference to FIG. The total effective chlorine measuring device of the present embodiment is roughly composed of a sensor unit 1 and a main body unit 20.

The sensor unit 1 has a measurement cell 11 into which the sample liquid S is introduced, a detection electrode support 12 in which the lower portion is immersed in the sample liquid S, a detection electrode 13 attached to the tip surface of the detection electrode support 12, and a sample in the lower portion. Holds the counter electrode support 14 immersed in the liquid S, the counter electrode 15 attached to the outer peripheral surface on the lower end side of the counter electrode support 14, the motor 16 for vibrating the detection electrode 13 in a circular motion, and the detection electrode support 12. The bearing 17 has a large number of beads 18 for cleaning the detection electrode 13 charged in the sample liquid S. The measuring cell 11 is provided with a mesh-shaped partition plate 11a for partitioning between the detection electrode 13 and the counter electrode 15, so that the beads 18 do not flow out to the counter electrode 15 side.

The main body 20 has an arithmetic control unit 21, a voltage applying mechanism 22, an ammeter 23, and a display device 24. The detection pole 13 and the arithmetic control unit 21 are connected by the wiring L1, the counter electrode 15 and the arithmetic control unit 21 are connected by the wiring L2, and the motor 16 and the arithmetic control unit 21 are connected by the wiring L3. .. The ammeter 23 is provided in the middle of the wiring L1, and the boosting mechanism 22 is provided in the middle of the wiring L2.

The detection electrode 13 is made of gold. Further, the counter electrode 15 is made of platinum.
The detection electrode support 12 is arranged in an inclined state, and a predetermined portion in the intermediate portion in the length direction is held by the bearing 17, and the precession movement can be performed with the holding portion by the bearing 17 as a fulcrum. Further, the base end portion 12a of the detection electrode support 12 and the rotation shaft 16a of the motor 16 are eccentrically engaged with each other. Therefore, by rotating the rotation shaft 16a of the motor 16, the base end portion 12a makes a circular motion, and the detection electrode 13 attached to the tip end portion of the detection electrode support 12 also vibrates (circular motion). .. Further, the wiring L1 can be pulled out from the vicinity of the holding portion by the bearing 17 through the inside of the detection electrode support 12 without being twisted even if the detection electrode 13 is circularly moved.

A large number of beads 18 are arranged in the vicinity of the detection electrode 13 in a non-fixed state. The beads 18 come into contact with the vibrating (circular motion) detection electrode 13 to polish the detection electrode 13. As the material of the beads 18, ceramic or glass is preferable.

The detection electrode 13 and the counter electrode 15 can be washed with a chemical solution according to the composition of the stain component. For example, chemical cleaning using oxalic acid, hydrochloric acid, hydrogen peroxide solution, or the like can be performed. In addition, ozone cleaning may be performed. Further, physical cleaning such as brush cleaning may be performed instead of or together with chemical cleaning or the like.
Further, in order to keep the detection electrode 13 clean, it is preferable to perform electrolytic polishing in addition to mechanical polishing with beads 18. For electrolytic polishing, a well-known method can be appropriately adopted as long as a current flows between the detection electrode and the counter electrode in the direction opposite to that at the time of measurement.
The fully effective chlorine measuring device of the present embodiment may be provided with an automatic cleaning mechanism for cleaning the counter electrode 15 and the detection electrode 13. In that case, regular cleaning can be performed automatically.

[Measurement of total effective chlorine]
In the total effective chlorine measuring device of the present embodiment, the boosting mechanism 22 applies an applied voltage between the detection electrode 13 and the counter electrode 15. The applied voltage is selected from the range of 750 ± 250 mV, preferably selected from the range of 600 to 900 mV, and more preferably selected from the range of 700 to 800 mV.
When the applied voltage is around 750 mV, a plateau region can be obtained regardless of whether the sample solution contains seawater or within the measurement range of the total effective chlorine concentration of normal seawater, so that halogen other than chlorine is not contained. Using a calibration solution such as tap water having an electric conductivity of 4 mS / m or more, a calibration line for measuring the total effective chlorine concentration of seawater or a sample solution containing seawater can be created.
Further, the same calibration curve can be used regardless of whether the total effective chlorine is chlorine or bromine, and regardless of the difference in pH.

The applied voltage is preferably appropriately selected from the range of 750 ± 250 mV according to the measurement range of the total effective chlorine concentration.
Specifically, when the measurement range is 2 mg / L or less, it is preferable to select from the range of 700 ± 200 mV, more preferably to select from the range of 700 ± 100 mV, and select from the range of 700 ± 50 mV. Is even more preferable.
When the measurement range is 2 mg / L or more, it is preferable to select from the range of 800 ± 200 mV, more preferably to select from the range of 800 ± 100 mV, and further preferably to select from the range of 800 ± 50 mV.

Further, the ammeter 23 has come to measure the redox current flowing between the detection electrode and the counter electrode when the applied voltage mechanism 22 applies the applied voltage between the detection electrode 13 and the counter electrode 15. There is.
The sample liquid S to be measured is not particularly limited, but the present invention is particularly suitable when the sample liquid S contains seawater containing bromine (bromine ion or bromic acid) or when the sample liquid S contains seawater such as boiler cooling water. Can be applied to.

In the total effective chlorine measuring method of the present invention, the arithmetic control unit 21 obtains the total effective chlorine concentration from the redox current obtained by the total effective chlorine measuring device of the present invention. The obtained total effective chlorine concentration is given to the display device 24 as a signal D1, and the total effective chlorine concentration is displayed on the display device 24. Further, the value of the total effective chlorine concentration is transmitted as a signal D2 to an external recorder, data logger, memory, printer, computer and the like. The signal D2 may be a digital signal or an analog signal. Further, it may be transmitted by wire or may be transmitted by wireless.
In order to obtain the total effective chlorine concentration from the redox current by the calculation control unit 21, a calibration curve showing the correlation between the redox current and the total effective chlorine concentration obtained in advance using a calibration solution is used for calculation. The calibration solution and the calibration method using the calibration solution will be described later.

Further, the arithmetic control unit 21 may output the current value from the ammeter 23 to the external computer as a signal D2. In that case, the method for measuring the total effective chlorine of the present invention can be carried out by performing an operation of obtaining the total effective chlorine concentration from the redox current in the external computer.
Further, the arithmetic control unit 21 may output the current value from the ammeter 23 to the display device 24 as a signal D1. In that case, if the total effective chlorine concentration is obtained from the redox current based on the current value read from the display device 24 and the calibration curve obtained in advance, the method for measuring the total effective chlorine of the present invention can be carried out. ..

It is preferable to correct the temperature of the redox current used in the calculation. Therefore, it is preferable that the total effective chlorine measuring device of the present invention is provided with a temperature sensor. If the temperature of the sample liquid is kept sufficiently constant, or if the required measurement accuracy is low, the temperature correction may be omitted.
Temperature correction means converting to a redox current at a reference temperature (for example, 25 ° C.) in consideration of the temperature dependence of the redox current measurement. When the reference temperature is 25 ° C., the temperature is specifically corrected by the following formula (1).
I (V) ₂₅ = I (V) _t / (1+ (α × (t-25) / 100)) ・ ・ ・ (1)
t: Sample liquid temperature (° C) at the time of measurement
I (V) _t : Redox current value at voltage V obtained at sample solution temperature t ° C. I (V) ₂₅ : Redox current value at voltage V temperature-corrected at reference temperature 25 ° C. α: 1 ° C. Electrode output change amount (%)

[Proofreading]
In the calibration method for calibrating the total effective chlorine measuring device of the present invention, a calibration solution containing no halogen other than chlorine and having an electric conductivity of 4 mS / m or more is used.
If the sample solution is seawater containing bromine, there is also an idea that the calibration solution should be seawater or the like with a known concentration of chlorine added.
However, the present inventor considered that it is not preferable to use a calibration solution based on seawater because the influence on the calibration value cannot be predicted because seawater contains various components and its composition is constantly changing. .. Then, when an attempt was made to use dechlorinated water, a solution obtained by adding chlorine having a known concentration to the dechlorinated water, or tap water as a calibration solution with the total effective chlorine measuring device of the present invention, the results were accurate and stable. We have found that measurable calibration is possible.

The calibration solution used for the calibration of the present invention has an appropriate electrical conductivity required for the polarographic method. Specifically, it is 4 mS / m or more, and preferably 4 to 5000 mS / m. The dechlorinated water is not pure water, and although it does not contain halogen, it is a liquid containing an ionic component that gives appropriate electrical conductivity.
Since tap water usually contains chlorine and has an appropriate electrical conductivity (usually 4 to 40 mS / m), it can be used as it is as a calibration solution in the present invention. Further, if chlorine is removed from tap water, it can be made into dechlorinated water. Tap water is easily available, and it is convenient and preferable to use it as it is as a calibration solution.
The calibration solution used in the present invention can also be prepared by diluting a stock solution containing chlorine having a known concentration with dechlorinating water.

The calibration using the calibration solution is specifically performed by applying a voltage (same as when measuring the sample solution) selected in the range of 750 ± 250 mV between the detection electrode immersed in the calibration solution and the counter electrode. The applied voltage) is given, and the oxidation-reduction current flowing between the detection electrode and the counter electrode is measured. The external computer that receives the information from the arithmetic control unit 21 or the arithmetic control unit 21 obtains a calibration curve based on the correspondence between the obtained redox current and the total effective chlorine concentration of the calibration solution.
The obtained calibration curve is stored in an external computer that receives information from the calculation control unit 21 or the calculation control unit 21, and is used to obtain the total effective chlorine concentration of the sample solution from the redox current when the sample solution is measured. Will be done.

The calibration curve can be obtained by using two or more kinds of calibration curves having different chlorine concentrations. For example, it is possible to obtain a calibration curve using dechlorinated water and spun solution (a solution obtained by diluting a stock solution containing chlorine of a known concentration with dechlorinated water at a dilution ratio considering the measurement range of a measuring device, or tap water) as a calibration curve. can.
Once a calibration curve has been created, span calibration using the actual sample solution can be performed on a regular basis to maintain a highly accurate calibration curve.

<Second Embodiment>
[Device configuration]
The total effective chlorine measuring device by the two-electrode polarographic method according to the second embodiment of the present invention is the same as the first embodiment except that the sensor unit 1 in FIG. 1 is changed to the sensor unit 2 shown in FIG. Is.

FIG. 2 is a cross-sectional view of the sensor unit 2. The sensor unit 2 shown in FIG. 2 is provided with a substantially cylindrical case 31, and a support base 32 in which a through hole 32a along the axial direction is formed in the center of one opening of the case 31. Is stuck. A pair of upper and lower circular windows 32b, 32b are formed at substantially the center of the support substrate 32 in the axial direction so as to penetrate from one peripheral surface to the opposite peripheral surface at right angles to the axial direction. .. Further, a recess 32c is formed in the circumferential direction near the tip thereof, and a counter electrode 33 is wound over the entire surface of the recess 32c.

Further, below the counter electrode 33, a cap 34 made of a mesh is screwed so as to cover the tip of the support substrate 32. Further, a large number of beads 36 for polishing and cleaning the detection electrode 35, which will be described later, are stored in the cap 34. An inner net 37 is provided at a position that covers the window 32b from the inside to prevent the beads 36 from flowing out.

A motor 38 is attached to the inside of the case 31, and is fixed to the rotating shaft 38a of the motor 38 on the upper side of the eccentric coupling 41. The eccentric coupling 41 is held by the coupling case 42, and the coupling case 42 is held above the support base 32 by a plurality of columns 43.
A substantially rod-shaped connecting shaft 44 is connected to the lower side of the eccentric coupling 41. The angle formed by the rotating shaft 38a and the connecting shaft 44 is set to about 3 degrees, and the portion of the connecting shaft 44 connected to the coupling case 42 makes a circular motion by driving the motor 38.

A little lower side of the connecting shaft 44 in the axial direction is inserted into the bearing 45. The bearing 45 is composed of a cylindrical tubular portion 45a in the direction of the connecting shaft 44 and a flange portion 45b extending in the radial direction around the lower end side of the tubular portion 45a, and is made of a rubber material. The tubular portion 45a is in close contact with the connecting shaft 44 in a watertight state with high pressure. Further, the outer peripheral surface of the bearing 45 is in close contact with the inner peripheral surface of the support substrate 32 in a watertight manner.

The lower end side of the connecting shaft 44 with respect to the bearing 45 is inserted into the upper end side of the substantially cylindrical detection electrode support 46. As a result, the detection electrode support 46 is connected and fixed to the lower end side of the connecting shaft 44, and is hung in the through hole 32a of the support base 32. A detection pole 35 is provided at the lower end of the detection pole support 46.
When the portion of the connecting shaft 44 connected to the coupling case 42 moves in a circular motion due to the drive of the motor 38, the connecting shaft 44 makes an aging movement with the portion where the flange portion 45b is located as a fulcrum. As a result, the detection pole 35 provided at the lower end of the detection pole support 46 fixed to the connecting shaft 44 also moves in a circular motion.

The lead wire 47 of the detection electrode 35 is finally connected to the arithmetic control unit 21 of the main body unit 20 via the connector 48. Further, the counter electrode 33 is connected to the arithmetic control unit 21 of the main body unit 20 via the connector 48. The motor 38 is also connected to the arithmetic control unit 21 of the main body unit 20 via the connector 48.
In FIG. 2, the wiring in the vicinity of the connector 48 of the lead wire 47 is not shown. Further, the wiring from the counter electrode 33 to the connector 48 and the wiring from the motor 38 to the connector 48 are not shown.
Similar to the first embodiment, the detection electrode 35 is made of gold and the counter electrode 33 is made of platinum.

When the lower end of the sensor unit 2 of the present embodiment is immersed in the sample liquid S, the sample liquid S flows in and out from the cap 34 and the window 32b. As a result, the sample liquid S comes into contact with the detection electrode 35 and also with the counter electrode 33 wound around the support substrate 32. That is, the detection electrode 35 and the counter electrode 33 are immersed in the sample liquid S.
The sample liquid S is prevented from entering the case 31 above the bearing 45 by the bearing 45.
The total effective chlorine measuring device according to the second embodiment can measure the total effective chlorine and the like in the same manner as the total effective chlorine measuring device according to the first embodiment. In addition, calibration can be performed in the same manner as the total effective chlorine measuring device according to the first embodiment.

<Third Embodiment>
[Device configuration]
The total effective chlorine measuring apparatus by the two-electrode polarographic method according to the third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals as those in FIG. 1, and detailed description thereof will be omitted.
The total effective chlorine measuring device of the present embodiment is roughly composed of a sensor unit 3, a main body unit 20, and a liquid feeding unit 50.

The sensor unit 3 is the same as the sensor unit 1 of the first embodiment except that the measurement cell 11 of the first embodiment is changed to the flow cell 19. The flow cell 19 is provided with a mesh-shaped partition plate 19a that partitions the detection electrode 13 and the counter electrode 15, so that the beads 18 do not flow out to the counter electrode 15 side.
The liquid feeding unit 50 has an inflow passage 51 for sending the sample liquid S to the flow cell 19, a discharge passage 52 for discharging the sample liquid S from the flow cell 19, and a pump 53 provided in the inflow passage 51.
The pump 53 and the arithmetic control unit 21 are each connected by wiring L4. The pump 53 operates according to an instruction from the arithmetic control unit 21.
The total effective chlorine measuring device according to the third embodiment may measure the total effective chlorine and the like in the same manner as the total effective chlorine measuring device according to the first embodiment, except that the sample liquid S is made to flow in the flow cell 19. can. In addition, calibration can be performed in the same manner as the total effective chlorine measuring device according to the first embodiment.

<Fourth Embodiment>
[Device configuration]
The total effective chlorine measuring device by the two-electrode polarographic method according to the fourth embodiment of the present invention is the same as the third embodiment except that the sensor unit 3 in FIG. 3 is changed to the sensor unit 4 shown in FIG. Is.

FIG. 4 is a cross-sectional view of the sensor unit 4. The sensor unit 4 has a configuration in which a flow cell 60 is added to the sensor unit 2 of the second embodiment. In FIG. 4, the same components as those in FIG. 2 are designated by the same reference numerals as those in FIG. 2, and detailed description thereof will be omitted.
A support substrate 32 is inserted in the flow cell 60. The inner wall on the upper end side of the flow cell 60 and the outer periphery of the support substrate 32 are liquid-tightly fixed via an O-ring 61.
A sample liquid inlet 60a for inflowing the sample liquid is provided in the center of the tip of the flow cell 60, and a sample liquid outlet 60b for flowing out the sample liquid is provided on the side wall near the O-ring 61. The inflow path 51 is connected to the sample liquid inflow port 60a, and the discharge path 52 is connected to the sample liquid outflow port 60b.

When the sample liquid S flows from the sample liquid inlet 60a of the flow cell 60 of the sensor unit 4 of the present embodiment, a part of the sample liquid S invades into the cap 34 and flows out from the sample liquid outlet 60b through the window 32b. do. As a result, the sample liquid S comes into contact with the detection electrode 35. Further, a part of the sample liquid S flows in from the sample liquid inlet 60a, passes outside the support substrate 32, and flows out from the sample liquid outlet 60b. As a result, the sample liquid S comes into contact with the counter electrode 33 wound around the support substrate 32. That is, by flowing the sample liquid S from the sample liquid inlet 60a of the flow cell 60, the detection electrode 35 and the counter electrode 33 are immersed in the sample liquid S.

The total effective chlorine measuring device according to the fourth embodiment can measure the total effective chlorine and the like in the same manner as the total effective chlorine measuring device according to the third embodiment. Further, the calibration can be performed in the same manner as the total effective chlorine measuring device according to the third embodiment.

<Other embodiments>
In each of the above embodiments, a method of positively flowing the sample liquid in contact with the detection electrode with respect to the surface of the detection electrode to obtain the reproducibility of the thickness of the diffusion layer required for the polarographic method is adopted, but the sample liquid is in contact with the detection electrode. A method of obtaining reproducibility of the thickness of the diffusion layer may be adopted by a method of suppressing the flow of the sample liquid in a narrow range. Examples of the apparatus adopting this method include the redox current measuring apparatus described in Japanese Patent Application Laid-Open No. 2015-34740.

Hereinafter, an experimental example for clarifying the effect of the present invention is shown.
[Experimental Example 1]
The total effective chlorine concentration when a known concentration of chlorine was added to seawater was measured using a total chlorine DPD reagent.
(A) Sample solution The total effective chlorine concentration was measured for the following sample solutions.
・ Seawater,
-A sample solution prepared by adding a sodium hypochlorite solution having a known concentration to seawater so that the amount of chlorine added to 1 L of the sample solution is 0.15 mg.
-A sample solution prepared by adding a sodium hypochlorite solution having a known concentration to seawater so that the amount of chlorine added to 1 L of the sample solution is 0.25 mg.
-A sample solution in which a sodium hypochlorite solution having a known concentration is added to seawater so that the amount of chlorine added to 1 L of the sample solution is 0.65 mg.

(B) Total Chlorine Reagent As a DPD reagent for measuring total chlorine, a total chlorine reagent (item code: HACH0582) manufactured by HACH, which contains the following components, was used.
Potassium iodide: 20.0 to 30.0% by mass,
N, N-diethyl-phenylenediamine salt: 1.0-5.0% by mass,
Carboxylate: 40.0-50.0% by mass,
Disodium hydrogen phosphate: 20.0 to 30.0% by mass,
Ethylenediaminetetraacetic acid disodium: less than 1.0% by mass.

(C) Measurement of total effective chlorine concentration A fixed amount of 10 mL to 20 mL of total chlorine reagent and sample solution is taken in an absorption cell with a cell length of 50 mm, and mixed using a photoelectric spectrophotometer (DR2700 manufactured by HACH), and then 10 The absorbance at a wavelength of 510 nm after seconds was measured, and the total effective chlorine concentration was determined from a calibration curve prepared in advance. The results are shown in FIG.

The calibration curve for obtaining the total effective chlorine concentration (measured value) on the vertical axis of FIG. 5 was created by measuring the following dechlorinated water and a standard sample in the same manner as the sample solution.
Dechlorinated water: Water obtained by treating tap water with activated carbon to remove chlorine (the same applies to the following experimental examples).
Standard sample: Prepared by diluting a sodium hypochlorite solution with an effective chlorine concentration of about 12% with dechlorinated water. The total effective chlorine concentration of the prepared standard sample was determined according to the above "(c) Measurement of total effective chlorine concentration" (the same applies to the following experimental examples).

As shown in FIG. 5, the slope of the measured value with respect to the added concentration was as small as 0.5409. The cause of this is unknown, but it is thought that the absorbance was lower than when seawater was not included because the added chlorine was consumed due to the influence of the components in seawater.
However, a good correlation was obtained between the added concentration and the measured value (R ² = 0.9953).
Therefore, it was confirmed that the total effective chlorine concentration obtained by the calibration curve from the absorbance measured using the total chlorine reagent is effective as an index of the total effective chlorine concentration in seawater.

[Experimental Example 2]
Using the total effective chlorine measuring device of the fourth embodiment, the polarogram showing the relationship between the applied voltage and the redox current was investigated. However, as the boosting mechanism 22, a mechanism capable of continuously changing the voltage was used, and a gold electrode having a diameter of 2 mm was used as the detection electrode 13, and rotation was given to such an extent that a linear velocity of about 100 cm / s could be obtained. .. The counter electrode 15 was a platinum electrode. As the sample solution, a sample solution in which chlorine (sodium hypochlorite solution) was added to seawater and a sample solution in which chlorine (sodium hypochlorite solution) was added to dechlorinated water were used.
FIG. 6 shows a polarogram when chlorine is added to seawater, and FIG. 7 shows a polarogram when chlorine is added to dechlorinated water.

In FIG. 6, the numerical value described after T is the total effective chlorine concentration measured using the total chlorine reagent as in Experimental Example 1. For example, the polarogram shown as "T0.493 mg / L" is a polarogram of a sample solution (sample solution in which chlorine is added to seawater) having a total effective chlorine concentration of 0.493 mg / L measured in the same manner as in Experimental Example 1. Shows the logogram.

In FIG. 7, the numerical value described after F is the free chlorine concentration measured in the same manner as in Experimental Example 1 except that the DPD reagent for measuring free chlorine was used. For example, the polarogram shown as "F0.48 mg / L" is a sample solution having a free chlorine concentration of 0.48 mg / L measured in the same manner as in Experimental Example 1 except that the DPD reagent for measuring free chlorine was used. The polarogram of the sample solution) in which chlorine is added to dechlorinated water is shown.
Since the sample solution obtained by adding chlorine (sodium hypochlorite solution) to dechlorinated water does not contain effective chlorine other than free chlorine, the values described after F in FIG. 7 are the free chlorine concentration as well as the free chlorine concentration. It is also the total effective chlorine concentration.

As the DPD reagent for measuring free chlorine, a free chlorine reagent manufactured by HACH (item code: HACH0578) containing the following components was used.
N, N-diethyl-phenylenediamine salt: less than 5.0% by weight,
Carboxylate: 60.0-70.0% by mass,
Disodium hydrogen phosphate: 30.0-40.0% by mass,
Ethylenediaminetetraacetic acid disodium: less than 5.0% by mass.

In both FIGS. 6 and 7, the plateau region (the region where the current hardly changes even if the applied voltage changes slightly) tends to shift to the high voltage side as the total effective chlorine concentration increases. Comparing the polarograms of FIGS. 6 and 7 in which the total effective chlorine concentrations were almost equal, the plateau regions of both were almost equal.
That is, the plateau of the sample solution in which the total effective chlorine concentration in FIG. 6 is 0.493 mg / L and the sample solution in which the free chlorine concentration (total effective chlorine concentration) in FIG. 7 is 0.48 mg / L is around 600 mV. The plateau of the sample solution having a total effective chlorine concentration of 1.202 mg / L in FIG. 6 and the sample solution having a free chlorine concentration (total effective chlorine concentration) of 1.00 mg / L in FIG. 7 was around 700 mV. ..

From this, it was found that the amount of seawater contained in the sample solution did not affect the range of applied voltage, which is a good plateau region.
Therefore, it was found that a calibration curve for measuring the total effective chlorine concentration of seawater or a sample solution containing seawater can be prepared using a calibration solution that does not contain halogens other than chlorine and has an electric conductivity of 4 mS / m or more. rice field.

Further, in any of the sample liquids shown in FIGS. 6 and 7, a good plateau region was obtained at an applied voltage of around 750 mV. Further, from FIG. 7, in the case of a sample solution having a total effective chlorine concentration of about 3 mg / L, it is considered that a plateau region can be obtained at about 900 mV.
Considering this result and the fact that the measurement range of the total effective chlorine concentration of seawater is usually 2 mg / L or less on the low concentration side and 2 mg / L or more on the high concentration side, the applied voltage is in the range of 750 ± 250 mV. I knew what to do.
In addition, in order to perform particularly accurate measurement, the applied voltage should be appropriately selected within the range of 750 ± 250 mV according to the measurement range (the higher the measurement range of the total effective chlorine concentration, the more 750 ± 250 mV. It was found that the applied voltage on the high voltage side should be selected in the range).

[Experimental Example 3]
Using the same equipment as in Experimental Example 2, under the same measurement conditions, the following sample solutions A to C were examined for polarograms showing the relationship between the applied voltage and the redox current. The results are shown in FIG.
Sample solution A: A sample solution obtained by adding a sodium hypochlorite solution having a known concentration to dechlorinated water so that the free chlorine concentration with respect to 1 L of the sample solution after addition is 2 mg / L.
Sample solution B: A sample obtained by adding 0.6 g of potassium bromide to 1 L of sample solution A.
Sample solution C: A sample in which 0.6 g of potassium bromide, 0.2 g of anhydrous sodium acetate, and 0.2 mL of acetic acid were added to 1 L of sample solution A.

The sample liquid A contains free chlorine (hypochlorous acid). On the other hand, the sample liquids B and C contain hypobromous acid due to the added potassium bromide.
The pH of the sample liquid B is about 7.5, but the pH of the sample liquid C containing the buffer component is about 4.0.
As shown in FIG. 8, the current values when the applied voltage was around 750 mV did not have a large difference between the sample liquids A to C.
From this, it was found that if the applied voltage is around 750 mV, the same calibration curve can be used regardless of whether it is free chlorine or hypobromous acid and regardless of the difference in pH. ..

[Experimental Example 4]
The calibration of the total effective chlorine measuring device of the fourth embodiment with an applied voltage of 800 mV was performed using a spun solution consisting of dechlorinated water and tap water (containing free chlorine but not other halogens). .. A gold electrode having a diameter of 2 mm was used as the detection electrode 13 of the all-effective chlorine measuring device, and the rotation was applied so that a linear velocity of about 100 cm / s could be obtained. The counter electrode 15 was a platinum electrode. When the spun solution was measured using a total chlorine reagent in the same manner as in Experimental Example 1, the total effective chlorine concentration was 0.68 mg / L. The obtained calibration curve is shown in FIG.
The obtained calibration curve of FIG. 9 was stored in the total effective chlorine measuring device.

The total effective chlorine concentration of the following sample liquid was measured using the above-mentioned total effective chlorine measuring device in which the calibration curve of FIG. 9 was stored. The results are shown in Table 1 and FIG.
The "additional concentration" in Table 1 and FIG. 10 is the concentration of chlorine added to seawater or the total effective chlorine concentration measured using the total chlorine reagent of tap water. The redox current in Table 1 is a value obtained by using the total effective chlorine measuring device, and the measured values in Table 1 and FIG. 10 are all obtained from the redox current by using the calibration curve of FIG. Effective chlorine concentration.

(Sample solution)
-A sample solution prepared by adding a sodium hypochlorite solution having a known concentration to seawater so that the amount of chlorine added to 1 L of the sample solution is 0.45 mg.
-A sample solution in which a sodium hypochlorite solution having a known concentration is added to seawater so that the amount of chlorine added to 1 L of the sample solution is 1.04 mg.
-A sample solution in which a sodium hypochlorite solution having a known concentration is added to seawater so that the amount of chlorine added to 1 L of the sample solution is 2.75 mg.
-Tap water: Tap water having a total effective chlorine concentration of 0.75 mg / L measured in the same manner as in Experimental Example 1.

As shown in Table 1 and FIG. 10, the measured values were in good agreement with the added concentration, and a good correlation was found between the added concentration and the measured values.
Further, in FIG. 10, it was confirmed that the data of tap water and the data of the sample liquid obtained by adding chlorine to seawater are on the same straight line.
From this, the calibration curve obtained by using a calibration curve that does not contain halogens other than chlorine such as tap water and has an electric conductivity of 4 mS / m or more can also be used for measuring a sample solution in which chlorine is added to seawater. It turned out to be effective.

[Experimental Example 5]
A sample solution prepared by adding a sodium hypochlorite solution having a known concentration to seawater so that the amount of chlorine added to 1 L of seawater is 0.5 mg was calibrated according to Experimental Example 4, and the total effective chlorine measurement of the fourth embodiment was performed. It was measured by the device and the change over time of the measurement result was investigated. The results are shown in FIG.
As shown in FIG. 11, the measured value decreased with the passage of time, but the state of the decrease was along a gentle curve.
This is because hypobromous acid and bromoamines produced by the reaction between the added sodium hypochlorite and bromine and ammoniacal nitrogen in seawater are consumed or decomposed by the components in seawater, resulting in a decrease. It is thought that the situation is correctly captured.

[Experimental Example 6]
While continuously measuring seawater with the total effective chlorine measuring device calibrated according to Experimental Example 4, a fixed amount of a sodium hypochlorite solution having a known concentration was sequentially added, and changes in the measured values were investigated. The results are shown in Table 2 and FIG.
No. in Table 2 and FIG. 1 to 4 indicate that the measurements are made at the following time points.
Further, the DPD values in Table 2 and FIG. 12 are the total effective chlorine concentration measured by using the total chlorine reagent as in Experimental Example 1, and the measured values are the values obtained by the total effective chlorine measuring device.

NO. 1: Before adding the sodium hypochlorite solution.
NO. 2: When the sodium hypochlorite solution in an amount such that the amount of chlorine added to 1 L of seawater is 0.02 mg is added for the first time.
NO. 3: When the sodium hypochlorite solution in an amount such that the amount of chlorine added to 1 L of seawater is 0.02 mg is added for the second time.
NO. 4: When the sodium hypochlorite solution in an amount of 0.02 mg of chlorine added to 1 L of seawater was added for the third time.

As shown in Table 2 and FIG. 12, a good correlation was obtained between the DPD value and the measured value, even though the total effective chlorine concentration was extremely low. Also, for example, NO. It was also found that the DPD value and the measured value can be matched with higher accuracy by correcting the zero point of the calibration curve obtained by the calibration of Experimental Example 4 based on the measurement result at the time point 1.

[Experimental Example 7]
A low-concentration sample obtained by adding a sodium hypochlorite solution in an amount of 0.03 mg to dechlorinated water and dechlorinated water by the total effective chlorine measuring device of the fourth embodiment calibrated according to Experimental Example 4. The liquids were measured alternately, and the reproducibility of the measurement results of the low-concentration sample liquids from the first to the fourth time was examined. The results are shown in Table 3.
As shown in Table 3, although the total effective chlorine concentration was extremely low, high reproducibility was obtained by the total effective chlorine measuring device.

1 to 4 ... Sensor unit, 11 ... Measurement cell, 12 ... Detection pole support, 13, 35 ... Detection pole,
14 ... counter electrode support, 15, 33 ... counter electrode, 16, 38 ... motor, 17, 45 ... bearing,
18, 36 ... beads, 19, 60 ... flow cell, 20 ... main body,
21 ... Arithmetic control unit, 22 ... Voltage mechanism, 23 ... Ammeter, 24 ... Display device,
50 ... Liquid feeding unit, 53 ... Pump, S ... Sample liquid

Claims (5)

It is a reagent-free total effective chlorine measuring device that measures total effective chlorine without using reagents by the two-electrode polarograph method.
A gold detection electrode immersed in the sample liquid and a platinum counter electrode,
An applied voltage mechanism that applies an applied voltage selected from the range of 750 ± 250 mV , with the detection electrode side as minus and the counter electrode side as plus, between the detection electrode and the counter electrode.
An ammeter that measures the redox current that flows between the detection electrode and the counter electrode when the applied voltage is applied by the boosting mechanism .
Equipped with an arithmetic control unit ,
The arithmetic control unit is a reagentless type characterized in that the total effective chlorine concentration is obtained from the oxidation-reduction current measured by the current meter based on a calibration curve showing the correlation between the oxidation-reduction current and the total effective chlorine concentration. Total effective chlorine measuring device. The calibration method for calibrating the reagent-free total effective chlorine measuring device according to claim 1 , wherein the calibration curve is calibrated using a calibration solution which does not contain halogen other than chlorine and has an electric conductivity of 4 mS / m or more. A calibration method characterized by obtaining . An application selected from the range of 750 ± 250 mV between the gold detection electrode and the platinum counter electrode immersed in the sample solution without using a reagent, with the detection electrode side as minus and the counter electrode side as plus. A voltage is applied, the redox current flowing between the detection electrode and the counter electrode is measured, and from the obtained redox current , the redox current is based on a calibration line showing the correlation between the redox current and the total effective chlorine concentration. A reagent-free method for measuring total effective chlorine, which comprises obtaining the total effective chlorine concentration of a sample solution. The selected applied voltage is applied between the detection electrode and the counter electrode immersed in a calibration solution having an electric conductivity of 4 mS / m or more, which does not contain halogen other than chlorine, and the detection electrode and the counter electrode are used. The redox current flowing between the two is measured, and a calibration curve showing the correlation between the redox current and the total effective chlorine concentration is obtained based on the correspondence between the obtained redox current and the total effective chlorine concentration of the calibration solution. ,
The reagent-free total effective chlorine measurement method according to claim 3 , wherein the total effective chlorine concentration of the sample solution is obtained from the redox current when the sample solution is measured using the calibration curve. The reagent-free total effective chlorine measuring method according to claim 3 or 4 , wherein the sample liquid contains bromine.

Images