WO2018186104A1

WO2018186104A1 - Method for quantifying urea and analyzing device

Info

Publication number: WO2018186104A1
Application number: PCT/JP2018/009051
Authority: WO
Inventors: 一重高橋; 菅原　広; 史生須藤; 勝久島田
Original assignee: オルガノ株式会社
Priority date: 2017-04-04
Filing date: 2018-03-08
Publication date: 2018-10-11
Also published as: JP2018179545A; TW201842333A; CN110462398B; TWI760465B; CN110462398A; KR20190108616A; KR102304396B1; JP6866211B2

Abstract

Provided is a method for quantifying urea in a sample solution with a colorimetric method using diacetylmonoxime, wherein a reagent formulated for use in reaction is refrigerated, and the refrigerated reagent is used to quantify urea. In particular, an antipyrine-containing reagent solution is maintained at, for example, 20^oC or lower after being formulated and until the solution is used to quantify the urea.

Description

Urea determination method and analyzer

The present invention relates to a method and an analyzer for quantifying urea in water.

There is a demand for accurately quantifying a small amount of urea in water. For example, when pure water is produced from raw water by a pure water production system, it is difficult to remove urea in the raw water with an ion exchange device or an ultraviolet oxidation device constituting the pure water production system. It is necessary to supply raw water to the pure water production system. As a method for removing urea, there is known a method in which a chemical that generates hypobromite is added to raw water and urea is selectively oxidized by hypobromous acid. However, a chemical that generates hypobromite is also purified water. Since it is a load on the manufacturing system, the smaller the amount of medicine input, the better. Therefore, it is desired to determine the necessity of urea treatment by quantifying the urea concentration in the raw water, and to supply an appropriate chemical when treatment is necessary. Further, there is a demand for measuring the urea concentration in pure water obtained from the pure water production system.

As a urea quantitative method, a quantitative method based on a colorimetric method using diacetyl monooxime is known. As an example of this quantification method, there is a method described in “Hygiene Test Method” (Non-Patent Document 1) issued by the Japanese Pharmaceutical Association. In the colorimetric method using diacetyl monooxime, other reagents for the purpose of accelerating the reaction, such as a mixed solution of antipyrine and sulfuric acid, an aqueous solution of semicarbazide hydrochloride, an aqueous solution of mixed manganese chloride and potassium nitrate, sodium dihydrogen phosphate A mixed solution of sulfuric acid and sulfuric acid can be used in combination. When antipyrine is used in combination, diacetyl monooxime is dissolved in an acetic acid solution to prepare a diacetyl monooxime acetic acid solution, and antipyrine (1,5-dimethyl-2-phenyl-3-pyrazolone) is dissolved in, for example, sulfuric acid. An antipyrine-containing reagent solution is prepared, a diacetyl monooxime acetic acid solution and an anripyrine-containing reagent solution are sequentially mixed with the sample water, the absorbance at a wavelength near 460 nm is measured, and quantification is performed by comparison with a standard solution.

The colorimetric urea determination method using diacetyl monooxime is intended for the determination of urea in swimming pool water and public bath water, for example, so that raw water supplied to the pure water production process, etc. Sensitivity is poor for quantitative determination of urea. Therefore, in Patent Document 1, by measuring the absorbance by applying flow injection analysis (FIA) based on a colorimetric method using diacetyl monooxime, urea is continuously added online in a concentration range of ppb or less to several ppm. A method for quantification is disclosed.

JP 2000-338099 A

The method described in Patent Document 1 is a method capable of continuously quantifying a small amount of urea online, but has a problem that the urea concentration cannot be stably measured over time.

An object of the present invention is to provide a method and an analysis apparatus capable of continuously quantifying urea on-line stably over a long period of time.

The inventors of the present invention, when quantifying a trace amount of urea continuously on-line by a colorimetric method using diacetyl monooxime, by refrigerated storage of a reagent used for the reaction, particularly an antipyrine-containing reagent solution after preparation, The present inventors have found that the urea concentration can be quantified stably over a long period of time, and the present invention has been completed.

Therefore, the method of the present invention is a method for quantifying urea in a sample water by a colorimetric method using diacetyl monooxime, wherein the reagent prepared for use in the reaction is refrigerated and the urea is quantified using the refrigerated reagent. It is characterized by doing.

The analyzer of the present invention is an analyzer for continuously quantifying urea in sample water by a colorimetric method using diacetyl monooxime, a storage tank for storing a reagent prepared for use in a reaction, and a storage tank And cooling means for cooling.

In the present invention, in refrigeration of a reagent prepared for use in the reaction, it is preferable to maintain the temperature of the reagent at 20 ° C. or lower after the preparation of the reagent, and further to maintain at 3 ° C. or higher and 20 ° C. or lower. Preferably, it is more preferably maintained at 5 ° C. or more and 15 ° C. or less. These reagents are preferably stored in the dark. If the refrigeration temperature is too low, the reagent may freeze. In the determination of urea using diacetyl monooxime, a reagent for accelerating the reaction is used together with diacetyl monooxime, and it is preferable to use antipyrine as the reagent used in combination. When antipyrine is used in combination, a diacetyl monooxime acetic acid solution and an antipyrine-containing reagent solution are used. In this case, in the present invention, one or both of the diacetyl monooxime acetic acid solution and the antipyrine-containing reagent solution are used. However, it is particularly preferable to store the antipyrine-containing reagent solution in a refrigerator. The antipyrine-containing reagent solution is, for example, a solution obtained by dissolving antipyrine in sulfuric acid.

As will be described later, the method of the present invention is suitable for, for example, continuously quantifying urea over a period of several days or more. In particular, the urea is quantified by measuring the absorbance by applying the FIA method. Suitable for

According to the present invention, it is possible to perform continuous online quantitative determination of urea stably over a long period of time.

It is a figure which shows the structure of the analyzer of one Embodiment of this invention. It is a graph which shows the relationship between the water passage days in Example 1 and peak intensity.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an analyzer according to an embodiment of the present invention. Here, the present invention will be described by taking as an example a case where the amount of urea contained in raw water used for pure water production or pure water itself is quantified online. However, the water to be quantified by the present invention including urea is not limited to these, and the pure water used here is pure water when pure water is circulated and used. Also included is recovered water recovered from the process.

As shown in FIG. 1, a raw water line 20 used for pure water production is provided. In this line 20, the raw water is fed by a pump P0. A sample pipe 21 branched from the raw water line 20 is provided. The sample pipe 21 is a pipe of sample water branched from the raw water, and includes an on-off valve 22 and a flow meter FI. A sampling valve 10 (also referred to as an injector or an injection valve) is provided at the tip of the sample pipe 21. The portion downstream from the sampling valve 10 including the sampling valve 10 has a configuration as a flow injection analysis (FIA) apparatus and is actually a portion related to urea determination.

The sampling valve 10 has a configuration generally used in the FIA method, and includes a six-way valve 11 and a sample loop 12. The six-way valve 11 has six ports indicated by [1], [2], [3], [4], [5] and [6] in the figure. The sample pipe 21 is connected to the port 2. A pipe 23 to which carrier water is supplied via the pump P1 is connected to the port 6, and a pipe 25 for draining the sample water is connected to the port 3 via the pump P4. A sample loop 12 for collecting a predetermined volume of sample water is connected between the port 1 and the port 4. One end of a pipe 24 serving as an outlet of the sampling valve 11 is connected to the port 5. Carrier water is water substantially free of urea.

When the communication between the port X and the port Y in the six-way valve 11 is expressed as (XY), the six-way valve 11 is (1-2), (3-4), (5-6) The first state and the second state (2-3), (4-5), and (6-1) can be switched. In FIG. 1, the connection relationship between the ports in the first state is indicated by a solid line, and the connection between the ports in the second state is indicated by a dotted line. In the first state, the carrier water flows from the sampling valve 10 to the downstream side through the pipe 23 → the port 6 → the port 5 → the pipe 24. The sample water flows through the sample pipe 21 → port 2 → port 1 → sample loop 12 → port 4 → port 3 and is discharged from the pipe 25. When the first state is switched to the second state, the sample water flows through the sample pipe 21 → port 2 → port 3 and is discharged from the pipe 25, and the carrier water is pipe 23 → port 6 → port 1 → Sample loop 12 → Port 4 → Port 5 → Pipe 24 and then flow downstream. At this time, the sample water that has already flowed in and filled the sample loop 12 in the first state flows into the pipe 24 from the port 5 prior to the carrier water, and goes downstream of the sampling valve 10. Flowing. The volume of the sample water flowing in the pipe 24 is defined by the sample loop 12. Accordingly, by repeatedly switching between the first state and the second state, for example, by rotating the six-way valve 11 in the direction of the arrow in the figure, a predetermined volume of sample water can be repeatedly fed into the pipe 24. Switching between the first state and the second state can be performed every predetermined time in consideration of a residence time necessary for a reaction described later and a time until urea is detected by the detector 32. It is also possible to perform switching by detecting that the sample water introduced into the detector 32 is discharged from the detector 32. In this way, urea can be continuously quantified by automatically switching between the first state and the second state.

In this analyzer, the FIA method is applied to the determination of urea by a colorimetric method using diacetyl monooxime. Therefore, a diacetyl monooxime acetic acid solution (hereinafter also referred to as “reagent A”) and an antipyrine-containing reagent solution (hereinafter also referred to as “reagent B”) are used as reaction reagents used for the determination of urea. These reagents are stored in

storage tanks

41 and 42 provided in the refrigerator 40, respectively. The reagent A is prepared by dissolving diacetyl monooxime in an acetic acid solution. In this embodiment, the preparation itself is performed in the storage tank 41, or the reagent A is stored in the storage tank 41 after its preparation. Similarly, the reagent B is prepared by dissolving antipyrine in, for example, sulfuric acid, but the preparation itself is performed in the storage tank 42, or the reagent B is stored in the storage tank 42 after its preparation. The refrigeration unit 40 shields the

storage tanks

41 and 42 and cools the

storage tanks

41 and 42, whereby the temperatures of the reagents A and B in the

storage tanks

41 and 42 are 20 ° C. or less, preferably 3 ° C. or more and 20 ° C. Hereinafter, it is more preferably maintained at 5 ° C. or more and 15 ° C. or less. Note that the storage tank 41 for storing the reagent A is not necessarily arranged in the refrigeration unit 40 as long as it can be stored in a shaded manner. Further, even if the refrigeration temperature of the reagent is less than 5 ° C., there is no problem as long as crystals do not precipitate in the reagent. Non-Patent Document 1 describes that an antipyrine sulfuric acid solution in which antipyrine is dissolved in sulfuric acid can be used for 2 to 3 months if stored in a brown bottle, and refrigerated because crystals precipitate and do not dissolve again even at room temperature. Although it is described that storage is not suitable, the present inventors have confirmed by experiment that the antipyrine sulfate solution prepared according to the method described in Non-Patent Document 1 does not crystallize even at 3 ° C.

One end of the pipe 26 is connected to the storage tank 41, and the other end of the pipe 26 is connected to the pipe 24 by the mixing unit 43. The pipe 26 is provided with a pump P2 for feeding the reagent A into the pipe 24 at a predetermined flow rate. Similarly, one end of a pipe 27 is connected to the storage tank 42, and the other end of the pipe 27 is connected to the pipe 24 by a mixing unit 44. The pipe 27 is provided with a pump P3 for feeding the reagent B into the pipe 24 at a predetermined flow rate. The mixing

units

43 and 44 have a function of uniformly mixing the reagent A and the reagent B with the liquid flow in the pipe 24, respectively. The other end of the pipe 24 is connected to an inlet of a reaction coil 31 provided in the reaction thermostat 30. The reaction coil 31 causes a color development reaction between urea and diacetyl monooxime in the presence of antipyrine in the inside thereof, and the length and the flow rate inside the reaction coil 31 are the residence time required for the reaction. It is appropriately selected depending on The reaction thermostat 30 is for raising the temperature of the reaction coil 31 to a temperature suitable for the reaction, and for example, heats the reaction coil 31 to a temperature of 50 to 150 ° C., preferably 90 to 120 ° C. .

At the outlet of the reaction coil 31, a detector 32 for measuring the absorbance of the color produced by the color reaction is connected. For example, the detector 32 determines the peak intensity or peak area of the absorbance near the wavelength of 460 nm. By using the absorbance when the carrier water is flowing as a baseline and obtaining a calibration curve from the absorbance with respect to a standard solution with a known urea concentration, the concentration of urea in the sample water can be obtained from the absorbance with respect to the sample water. At the outlet of the detector 32, a back pressure coil 33 is provided for applying a back pressure to a pipe line extending from the pump P 1 to the detector 32 through the sampling valve 10, the pipe 24 and the reaction coil 31. A pressure gauge PI is connected to a position between the outlet of the detector 32 and the inlet of the back pressure coil 33. The drainage of this FIA apparatus flows out from the outlet of the back pressure coil 33.

In the analyzer of this embodiment, urea in the sample water can be measured online by the colorimetric method using diacetyl monooxime using the FIA method. At this time, as reagent A (that is, diacetyl monooxime acetic acid solution) and reagent B (that is, antipyrine-containing reagent solution) used in the reaction, those that are maintained at 20 ° C. or lower after the preparation of those reagents are used. can do. As a result, as will become clear from the examples described later, it is possible to perform continuous quantitative determination of urea stably over a long period of time.

In the above description, the case where an antipyrine-containing reagent solution is used as a reagent used in combination with diacetyl monooxime in a method for quantifying urea by a colorimetric method using diacetyl monooxime has been described. It is not limited to an antipyrine-containing reagent solution.

Next, the results of experiments conducted by the inventors to show the effects of the present invention will be described.

[Example 1]
The apparatus shown in FIG. 1 was assembled. However, a portion from the line 20 to the flow meter FI was not provided, and a standard solution prepared with a urea concentration of 60 ppb could be continuously supplied to the sampling valve 10 as sample water. The urea concentration was continuously monitored for this standard solution. Here, it was examined how the urea concentration obtained as the measured value of the absorbance detection peak in the detector 32 changes when the standard solution is continuously measured. In this example, 2 g of diacetyl monooxime was dissolved in 100 mL of 10% acetic acid to prepare reagent A (ie, diacetyl monooxime acetic acid solution), 0.2 g of antipyrine was taken and dissolved in 9 mol / L sulfuric acid, and the total amount was 100 mL. Reagent B (that is, antipyrine-containing reagent solution) was prepared, and immediately after the preparation, these reagents were respectively stored in the

storage tanks

41 and 42, and each reagent was continuously supplied from the

storage tanks

41 and 42 toward the pipe 24. . After each reagent was injected into the

storage tanks

41 and 42 at the beginning of the continuous measurement, the reagent was not replenished during the continuous measurement. The reagent A storage tank 41 was maintained at room temperature. For reagent B, experiments were conducted in two ways: when the storage temperature after preparation was 10 ° C and when it was 25 ° C. The change in urea concentration was confirmed by the peak intensity of absorbance at a wavelength of 460 nm. The results are shown in FIG. In FIG. 2, measured values when measuring the same standard solution with the peak intensity when measuring 60 ppb of urea standard solution immediately after preparing reagent A and reagent B and storing them in

storage tanks

41 and 42, respectively, as 100%. Shows how it has changed over time.

As shown in FIG. 2, when the reagent B, that is, the antipyrine-containing reagent solution is maintained at 25 ° C., the peak intensity gradually decreases, and the peak intensity reaches 72% during the 10-day operation for continuous measurement. Declined. In other words, urea cannot be quantified stably. In contrast, when the antipyrine-containing reagent solution was refrigerated and maintained at 10 ° C, the peak intensity did not decrease even after 10 days of continuous operation, and it was found that continuous quantification of urea could be performed stably over a long period of time. It was.

[Example 2]
After preparing reagent B in the same manner as in Example 1, it was stored at 5 ° C, 10 ° C, 15 ° C, 20 ° C and 25 ° C for 10 days, respectively. And after this storage, the reagent B was supplied to the apparatus of FIG. Immediately after supplying reagent B to the apparatus, a standard solution with a urea concentration of 60 ppb was measured using this apparatus, and the peak intensity was determined. At that time, the peak intensity when the standard solution was measured immediately after the preparation of the reagent B was set to 100%. Reagent A was prepared in the same manner as in Example 1 and then stored at room temperature. The results are shown in Table 1.

As shown in Table 1, when the storage temperature is 5 ° C. and 10 ° C., the peak intensity is hardly reduced, and when stored at 15 ° C., the peak intensity is reduced by about 10%. It was observed. When stored at 20 ° C., the peak intensity decreased by about 20%, but at 25 ° C., the peak intensity decreased by nearly 30%. From these, in order to continuously measure a trace amount of urea concentration, at least the antipyrine-containing reagent solution of the reagents used in the reaction, here, diacetyl monooxime acetic acid solution and antipyrine-containing reagent solution should be stored in a refrigerator. In that case, the temperature of the antipyrine-containing reagent solution is preferably maintained at 20 ° C or lower, more preferably maintained at 3 ° C or higher and 20 ° C or lower, and more preferably maintained at 5 ° C or higher and 15 ° C or lower. It was.

[Example 3]
A test similar to that of Example 2 was performed, except that the reagent A of Example 2 was stored at the same storage temperature as that of the reagent B of Example 2.

When both the reagent A and the reagent B were refrigerated and measured, the same result as that obtained when the reagent B alone was refrigerated (Table 1) was obtained.

DESCRIPTION OF SYMBOLS 10 Sampling valve 11 Sample loop 31 Reaction coil 32 Detector 33 Back pressure coil 40

Refrigeration part

41,42

Storage tank

43,44 Mixing part

Claims

In a method for quantifying urea in sample water by a colorimetric method using diacetyl monooxime,
Refrigerate the reagents prepared for use in the reaction,
A method characterized in that urea is quantified using a refrigerated reagent.
The method according to claim 1, wherein the temperature of the reagent is maintained at 20 ° C or lower after the preparation of the reagent.
The method according to claim 1 or 2, wherein the refrigerated reagent is an antipyrine-containing reagent solution.
The method according to any one of claims 1 to 3, wherein urea is continuously quantified using the refrigerated reagent.
The method according to claim 4, wherein urea is quantified from the absorbance by applying a flow injection analysis method.
The method according to any one of claims 1 to 5, wherein the sample water is water used for producing pure water or pure water.
An analyzer for continuously quantifying urea in sample water by a colorimetric method using diacetyl monooxime,
A reservoir for storing reagents prepared for use in the reaction;
Cooling means for cooling the storage tank;
An analysis device comprising:
The analyzer according to claim 7, wherein the cooling means maintains the storage tank at a temperature of 20 ° C or lower.
The analyzer according to claim 7 or 8, wherein the storage tank cooled by the cooling means is a storage tank for storing an antipyrine-containing reagent solution.
A sampling valve that continuously feeds carrier water and sample water and continuously discharges the carrier water, and replaces and discharges a constant amount of the sample water with the carrier water by a switching operation;
A mixing unit that is provided downstream of the sampling valve and that mixes the reagent from the storage tank with water discharged from the sampling;
A reaction coil which is provided downstream of the mixing unit and in which the sample water and the reagent react;
A detector connected to the outlet of the reaction coil;
The analyzer according to any one of claims 7 to 9, further comprising: