JP2003279557A - Method and instrument for measuring boron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an instrument for measuring boron by which concentration of boron contained in a drain or environmental water can be measured accurately and easily though borofluoride ions exist. <P>SOLUTION: After a first reagent containing at least aluminum ions and/or iron ions is added to a sample liquid, a color reaction is caused by adding a second reagent containing at least 1-amino-8-hydroxynaphtalene-3,6-disulfonic acid-based azo dye and a chelating agent to the sample liquid. Thereafter, absorbance of the sample liquid is measured. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a boron measuring method and a boron measuring apparatus. More specifically, the present invention relates to a boron measuring method and a boron measuring apparatus capable of accurately and easily measuring boron, which is a regulated substance of waste water, even when borofluoride ions are present.

[0002]

2. Description of the Related Art Atomic absorption spectroscopy, ICP, titration, and colorimetry are known as methods for measuring boron. Among these, the atomic absorption spectrometry and ICP require constant use of high-pressure gas such as hydrogen and argon, which requires a large-scale apparatus and is concerned about safety. Further, the titration method can be used only under a very limited condition that the concentration is high and there is no coexisting component.

Further, in the colorimetric method, since the reactivity of borate ions in an aqueous solution is poor, it is unavoidable to use a strong acid, and complicated operations are often involved. For example, when using a coloring reagent such as carminic acid or quinalizarin, the reaction must be carried out in concentrated sulfuric acid. Further, when curcumin is used as the color-developing reagent, it is necessary to carry out an operation of evaporation to dryness, and when methylene blue is used, it is necessary to carry out an operation of solvent extraction. Further, in the case of the azomethine H absorptiometry, the color developing solution is easily oxidized, and even if it is stored in a cool and dark place with a reducing agent coexisting, the life is only about 1 week and it is interfered by many metal ions. I will end up.

In contrast to these colorimetric methods, the method using H-resorcinol as a color-developing solution can react with borate ions under mild conditions of pH 5.5. In this case, in order to prevent interference of coexisting substances in the sample solution, an ethylenediaminetetraacetato complex (hereinafter referred to as “E
DTA ”. ) Etc. are added.

[0005]

However, since it is the borate ion that can react with H-resorcinol, it is not possible to measure the boron bonded to fluorine. That is, in the case of a fluorine compound, it becomes 4BF ₃ + 3H ₂ O → 3BF ₄ ⁻ + B (OH) ₃ + 3H ⁺ in water, and stable tetrafluoroborate ion BF ₄ ⁻ (hereinafter referred to as “borofluoride ion”) is present. But
This borofluoride ion does not react with H-resorcinol. Therefore, the method using H-resorcinol as the color-developing liquid cannot accurately measure the boron concentration in the presence of borofluoride ions. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a boron measuring method and a boron measuring apparatus capable of accurately and easily measuring even in the presence of borofluoride ions.

[0006]

According to the method for measuring boron of the present invention, after adding a first reagent containing at least aluminum ions and / or iron ions to a sample solution, at least 1-amino-8-hydroxynaphthalene- A second reagent containing a 3,6-disulfonic acid azo dye and a chelating agent is added to cause a color reaction, and then the absorbance is measured.

The boron measuring apparatus of the present invention further comprises a reaction space, means for introducing the sample solution and the first reagent into the reaction space, and means for further introducing the second reagent into the reaction space. Means for measuring the absorbance of a mixed solution of the sample solution in which the first reagent and the second reagent are added in the reaction space, wherein the first reagent is aluminum ions and / or The second reagent contains iron ions, and the second reagent is 1-amino-8-hydroxynaphthalene-3,6-
It is characterized by containing a disulfonic acid azo dye and a chelating agent.

According to the boron measuring method or the boron measuring apparatus of the present invention, by adding aluminum ion and / or iron ion as the first reagent, the borofluoride ion is changed into the borate ion, and the second reagent is added. Coloring reagent (1-amino-8-hydroxynaphthalene-3,6-
Disulfonic acid type azo dye).
Further, the aluminum ion and / or the iron ion can be masked by the chelating agent in the second reagent, although an excessively added amount can be an interfering ion in the reaction with the color forming reagent. Therefore, the boron concentration can be accurately measured regardless of the presence or absence of borofluoride ions. Note that iron ions are specifically iron (II
I) ion, but iron (II) ion may coexist.

In the boron measuring method or the boron measuring apparatus of the present invention, both aluminum ions and iron ions form a precipitate of a basic complex salt under alkaline conditions, resulting in poor reactivity. The addition of ions is preferably performed under acidic conditions. Specifically, it is preferable to add aluminum ion at pH 4 or less, preferably pH 2 to 3, and iron ion at pH 3 or less, preferably pH 2 to 2.5. Therefore, it is preferable that the first reagent contains a pH adjusting agent so that the pH after adding the first reagent to the sample solution satisfies the above condition.

In the boron measuring method or the boron measuring apparatus of the present invention, either one or both of aluminum ion and iron ion can be added, but it is preferable to add aluminum ion. Aluminum ions are preferable because aluminum ions have milder pH conditions as described above. Further, it is because a higher sensitivity (change in absorbance per unit concentration of boron) can be obtained in the reaction with the coloring reagent than in the case of adding iron ions. Furthermore, when iron ions are used, the change of borofluoride ions to borate ions does not proceed sufficiently unless they are added in a large excess as compared with the case of using aluminum ions.

In the boron measuring method or the boron measuring apparatus of the present invention, it is preferable that the first reagent is added and then heated to react. Thereby, the change of borofluoride ion to borate ion can be advanced in a short time. In this case, the heating temperature is preferably 40 to 100 ° C. Considering the heat resistance of the reaction vessel, etc., 8
It is more preferable that the temperature is 0 ° C. or lower. Further, considering that the reaction proceeds promptly, the temperature is more preferably 60 ° C. or higher.

In the method for measuring boron of the present invention, the color reaction by adding the second reagent is carried out at pH 4 to 7.
It is preferable to carry out. Similarly, in the boron measuring apparatus of the present invention, the pH of the mixed solution is adjusted by the second reagent.
Is preferably adjusted to 4-7.

If the pH during the color-developing reaction is lower than 4, color development with the borate ion and the color-developing reagent cannot be sufficiently obtained. The pH during the color development reaction is more preferably 4.5 or higher. On the other hand, if the pH during the color development reaction is higher than 7, the sensitivity due to the reaction between the borate ion and the color reagent cannot be sufficiently obtained. The pH during the color development reaction is more preferably pH 5.4 or less. When the pH is higher than 5.4, masking of coexisting metal ions in the sample solution and added aluminum ions and / or iron ions with the chelating agent becomes insufficient. Further, the pH during the color development reaction is more preferably less than 5.3, and further preferably pH 5.1 or less. With this, the metal ions in the sample solution or the first reagent can be sufficiently masked while maintaining the sensitivity of the color-forming reagent, so that the coloration accurately corresponding to the borate ion concentration can be obtained.

In the boron measuring method or the boron measuring apparatus of the present invention, it is preferable that the second reagent contains sodium ion and / or potassium ion. In this case, the interference can be eliminated by keeping the influence of the alkali metal ion in the sample solution on the sensitivity constant. That is, this makes it possible to eliminate the interference of sodium ions and / or potassium ions, and to obtain a color accurately corresponding to the borate ion concentration.

In the boron measuring method or the boron measuring apparatus of the present invention, it is preferable that the reaction after the addition of the second reagent is stopped midway to measure the absorbance. Thereby, the absorbance having good linearity can be obtained, accurate measurement can be performed over a wide measurement range, and the measurement time can be shortened.

In this case, the reaction with the second reagent is
Proceed by heating at 100 ° C, then 0 ° C
Above, it is preferable to stop by cooling to a temperature lower than 40 ° C. By heating at 40 to 100 ° C, the reaction proceeds and sufficient color development is obtained.
Further, by cooling to a temperature of 0 ° C. or higher and lower than 40 ° C., the reaction can be surely stopped, so that measurement with good reproducibility becomes possible. Considering the heat resistance of the reaction vessel, the more preferable heating temperature is 80 ° C.
It is the following. Further, a more preferable heating temperature is 60 ° C. or higher in order to enhance the masking effect of the interfering component and to promote the reaction promptly. In order to more surely stop the reaction, a more preferable cooling temperature is 30 ° C or lower,
More preferably, it is 25 ° C. or lower. Further, considering the fear of freezing and the dew condensation inside the apparatus, the more preferable cooling temperature is 10 ° C. or higher.

Further, when cooling the mixed solution, it is preferable to add pure water to the mixed solution to accelerate the cooling.
As a result, the temperature of the mixed solution can be drastically lowered, and more reproducible and quick measurement can be performed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. FIG. 1 is a schematic configuration diagram of a boron measuring apparatus according to this embodiment. As shown in FIG. 1, the boron measuring apparatus according to the present embodiment includes a reaction cell 10 that constitutes a reaction space, a sample liquid introducing pipe S1 for introducing a sample liquid into the reaction cell 10, and a reagent for introducing a reagent. Introductory pipe R1, R
2a, R2b, R2c and a lead-out pipe S2 for leading out the mixed liquid of the sample liquid and the reagent in the reaction cell 10 are inserted.

The reaction cell 10 is arranged in a constant temperature bath 20 having a heater (not shown) and is heated to a predetermined temperature. Further, the constant temperature bath 20 is provided with an inlet 20a and an outlet 20b for supplying cooling water to the inlet 20a.
The mixed solution in the reaction cell 10 can be cooled by flowing the mixed solution in the reaction cell 10 to the outlet 20b. Further, a stirring means (not shown) for stirring the mixed liquid in the reaction cell 10, such as a stirrer or a magnetic stirrer, is appropriately provided.

The sample liquid introducing pipe S1 has a sample liquid measuring device M1.
And the dilution water meter M2 are interposed, and the sample solution measured by the sample solution meter M1 is swept over the pure water measured by the dilution water meter M2 and introduced into the reaction cell 10. It is like this. In addition, the reagent introducing tubes R1, R2a, R2
b and R2c have reagent injection pumps RP1 and RP2, respectively.
a, RP2b, RP2c are interposed, and as will be described later, the reagent 1 forming the first reagent and the reagents R2a to R2c forming the second reagent are placed in the reaction cell 10 at a predetermined timing. It is being introduced. Further, the colorimeter 30
Is provided.

The reagent 1 constitutes the first reagent of the present invention, and is introduced into the reaction cell 10 prior to the second reagent. The reagent 1 contains aluminum ions and / or iron ions and a pH adjuster. In order to obtain a reagent containing aluminum ions and / or iron ions, aluminum sulfate, aluminum nitrate, iron sulfate, alum represented by M ₁ Al (SO ₄ ) ₂ .12H ₂ O, M ₂ Fe (SO ₄ ) ₂ -Iron alum or the like represented by 12H ₂ O can be used, but aluminum nitrate can be particularly preferably used. In the above chemical formula, M ₁ and M ₂ are monovalent cations such as K and NH ₄ .

The preferred concentration of the aluminum ion and / or iron ion of the reagent 1 during the reaction depends on the expected borofluoride concentration, but in the case of the aluminum ion, it is 1000 to 7000 mg / L, for example, 150.
It can be 0 mg / L. In the case of iron ions, the preferable concentration during the reaction is 1500 to 120.
It is 00 mg / L, and can be set to 3500 mg / L, for example. Thus, it is desired to add a sufficient amount of aluminum ions and / or iron ions in advance.

The pH adjusting agent contained in the reagent 1 is used for preventing the precipitation of the basic complex salt of aluminum ion and / or iron ion, and an acid such as hydrochloric acid, sulfuric acid or nitric acid is appropriately used. By the addition of the first reagent, the pH of the solution in the reaction cell 10 is 4 or less, preferably pH when the first reagent contains aluminum ions.
When iron ions are contained in 2-3, the pH is 3 or less,
It is preferably adjusted to pH 2 to 2.5.

As will be described below, this reagent 1 is capable of converting a borofluoride ion into a borate ion B (OH) ₄ ⁻ capable of reacting with the coloring reagent of the reagent 2. That is, as described above, the borofluoride ion BF ₄ ⁻ is a stable ion, but as shown in the following formula, it gradually hydrolyzes in water to show acidity, and finally borate ion B
It is known that the reaction for obtaining (OH) ₄ ⁻ proceeds reversibly. BF ₄ ⁻ + 4H ₂ O → B (OH) ₄ ⁻ + 4H ⁺ + 4F ⁻ That is, if the product of this reversible reaction, F ⁻ , can be removed from the reaction system, the above reaction formula is forced to proceed to the right. And borate ion B capable of reacting with reagent 2a
(OH) ₄ ^- can be varied.

On the other hand, the aluminum ion and / or iron ion contained in the reagent 1 forms a stable complex with the fluoride ion as shown in the following formula. Al ³⁺ + 6F ⁻ → AlF ₆ ³⁻ Fe ³⁺ + 6F ⁻ → FeF ₆ ^{3 −} Therefore, by adding reagent 1, F ⁻ is removed from the reversible reaction system, and borate ion B (OH) ) ₄ ^- can facilitate the change to.

As a method of removing F ⁻ from the above reversible reaction system, a method of adding a calcium ion or the like to generate a precipitate can be considered. However, it is complicated to separate the generated precipitate and it is difficult to adopt it in an automatic analyzer. In addition, the measurement target component may coprecipitate, which is not an appropriate method.

Reagents R2a to R2c constitute the second reagent of the present invention and are introduced into the reaction cell 10 after the first reagent. As described in detail below, the reagent 2a is a coloring liquid, the reagent 2b is a chelating agent,
Reagent 2c is a pH buffer solution.

The reagent 2a, which is a color forming liquid, is 1-amino-8-hydroxynaphthalene-3,6 having the structure shown in [Chemical Formula 1].
A disulfonic acid type azo dye (hereinafter referred to as “H acid type azo dye”).

[Chemical 1]

In [Chemical formula 1], Ar is an aryl group, and examples of the aryl group include the following [Chemical formula 2] to
[Chemical formula 3] is mentioned.

[Chemical 2]

[Chemical 3]

The H acid azo dye reacts with boric acid H ₃ BO ₃ to form a 1: 1 complex. Especially when the aryl group is
1- (2,4-dihydroxy-1-phenylazo) -8-hydroxynaphthalene-3,6-disulfonic acid (hereinafter referred to as "H-resorcinol") is the most sensitive and preferred. H-resorcinol and boric acid are
By reacting as shown in [Chemical formula 4], the absorption maximum wavelength is 510
nm 1: 1 complex is formed.

[0031]

[Chemical 4]

Boric acid H in [Chemical Formula 4]₃BO₃Is the pole
It is a weak acid, part of which is OH in aqueous solution.^-Base
Receive, H₃BO₃(OH)^-Becomes These ho
Since all (OH) groups bonded to the element are equivalent, boric acid H₃
BO₃Is B (OH)₃And boric acid hydrate ion H₃BO₃(O
H)^-Is B (OH)_Four ^-Can be written respectively. That is,
In [Chemical Formula 4], the chemical species that actually contributes to the reaction is B
(OH)₃Or B (OH)_Four ^-Is.

The reagent 2b is a chelating agent, which masks excess aluminum ions and / or iron ions in the first reagent and metal ions contained in the sample solution to prevent interference with the reaction with the coloring reagent. Can be eliminated. As the chelating agent, EDTA disodium salt (dihydrate), EDTA tetrasodium salt (tetrahydrate), CyDTA (trans-1,2-cyclohexanediamine tetraacetate), GEDTA (glycol ether diamine tetrahydrate) (Acetic acid salt) and the like, and mixtures thereof. Particularly, EDTA / disodium salt (dihydrate), ED
TA / tetrasodium salt (tetrahydrate) and a mixture thereof are preferable because they can mask a high concentration of metal ions. Examples of metal ions that can be masked by the chelating agent include iron ions, aluminum ions, and copper ions.

The AlF ₆ ^3- complex or FeF ₆ ^{3 -} complex formed by the reaction of the reagent 1 with borofluoride ion is sufficiently stable, and those which have already formed the complex by the usual chelating agent. The aluminum ions and iron ions of will not be taken away. Therefore, the addition of the reagent 2b will not release the fluorine ion F ⁻ again and the borofluoride will not be regenerated.

The reagent 2c is a pH buffer solution, so that the pH during the reaction is 4 to 7, preferably 4 to 5.4, more preferably 4.5 or more and less than 5.3, and further preferably 4.5.
A buffer solution that can adjust the pH to 5.0 or less, for example, pH 5.0 is selected. As such a buffer solution, an acetic acid-based buffer solution can be preferably used. Especially pH 4 ~
By reacting under the conditions of 5.4, it is possible to promote the complex formation of metal ions such as aluminum ions and iron ions with the chelating agent and enhance the masking effect. On the other hand, even under such pH conditions, sufficient color development by the reagent 2c can be obtained. Therefore, metal ions such as iron ions can be sufficiently masked while maintaining the sensitivity of the color forming reagent, so that the absorbance corresponding to the borate ion concentration can be accurately obtained.

Further, this pH buffer solution contains sodium ions and / or potassium ions. As the buffer solution capable of adjusting the pH range as described above and containing both sodium ion and potassium ion, for example, acetic acid-sodium acetate buffer solution to which potassium nitrate is added is preferably used. In addition, the preferable concentration of sodium ion in the buffer at the time of reaction is 2000 to 6000 mg / L, more preferably 3000 to 5000 mg / L, and for example, 40
It can be 00 mg / L. The preferable concentration of potassium ion in the buffer solution at the time of reaction is 20
00-7000 mg / L, more preferably 2500-5
It is 500 mg / L, and can be set to 4600 mg / L, for example. In this way, by adding a sufficient amount of alkali metal ions in advance, interference can be eliminated by keeping the influence of the alkali metal ions in the sample solution on the sensitivity constant, and the absorbance corresponding to the borate ion concentration can be obtained accurately. be able to.

When measuring boron in the sample liquid with the boron measuring apparatus of the present embodiment, the sample liquid measured by the sample liquid measuring device M1 and the pure water measured by the dilution water measuring device M2 are mixed with the sample liquid introducing pipe S1. Is introduced into the reaction cell 10. Also,
The reagent injection pump RP1 is operated to introduce the reagent 1 using the reagent introduction pipe R1.

Then, the water in the constant temperature bath 20 is heated to heat the mixed liquid of the sample solution and the reagent 1 in the reaction cell 10 so that the borofluoride ion in the sample solution and the reagent 1 are reacted. The preferable heating temperature at this time is 40 to 100 ° C.,
The temperature is more preferably 60 to 80 ° C, and can be 70 ° C, for example. By heating at such a temperature, the conversion of borofluoride to borate ion is promoted,
The reaction can be completed in a short time. For example, 10
When heated at 0 ° C, the reaction can be completed almost completely in about 10 minutes.

Next, the reagent injection pumps RP2a, RP2
b, RP2c is operated, and reagent introduction tubes R2a, R2
b, R2c is used to introduce the reagents 2a to 2c into the reaction cell 10. Then, the water in the constant temperature bath 20 is heated to heat the mixed liquid in the reaction cell 10. As a result, the borate ion originally contained in the sample solution and the borate ion derived from the borofluoride ion contained in the sample solution react with the reagent 2a (color developing solution). The preferable heating temperature at this time is 40 to 100 ° C., and more preferably 60.
It is -80 degreeC, For example, it can be 70 degreeC. Further, a preferable reaction time (heating time) is 20 to 40 minutes,
It is more preferably 25 to 35 minutes, and may be 30 minutes, for example. By selecting such temperature and reaction time, it is possible to obtain the absorbance with sufficient sensitivity and good linearity.

After that, cooling water is poured into the constant temperature bath 20. At the same time, pure water measured by the diluting water meter M2 is injected into the reaction cell 10. Thereby, the reaction cell 10
The mixed solution inside is cooled both from the outside and from the inside to stop the reaction between the borate ion in the mixed solution and the reagent 2a (color developing solution). The preferred cooling temperature at this time is 0 ° C or higher and lower than 40 ° C, more preferably 10 to 30 ° C.
℃, more preferably 10 to 25 ℃, for example 20
It can be ° C. Further, the cooling time may be, for example, 5 to 10 minutes, although it depends on the temperature and the flow velocity of the cooling water. By cooling to such a temperature, the reaction is surely stopped and a highly reproducible absorbance is obtained. In particular, by injecting pure water into the inside of the reaction cell 10, the temperature of the mixed solution can be drastically lowered, and more reproducible and quick measurement becomes possible.

After the reaction is completed, the mixed solution in the reaction cell 10 is
It is led out by the lead-out pipe S2 and led to the colorimeter 30. And
Absorbance is measured by this colorimeter 30. The absorbance is preferably measured at 510 nm which is the maximum absorption wavelength of the complex formed by the borate ion and the reagent 2a (coloring liquid), but can be measured in the range of 490 to 530 nm.

With the boron measuring apparatus of this embodiment, the blank value can be measured by the following procedure. In the measurement of the blank value, the same amount of the sample solution and pure water as in the case where the reaction by the first reagent and the reaction by the second reagent are respectively heated and proceeded, from the sample solution inlet pipe S1 to the sample solution meter M1.
And the dilution water meter M2 to measure and introduce into the reaction cell 10. Further, the same amount of reagents 1, 2a to 2c is continuously introduced from the reagent introduction pipes R1, R2a, R2b, R2c by operating the reagent injection pumps RP1, RP2a, RP2b, RP2c.

Then, the reaction step of heating the water in the constant temperature bath 20 is omitted, and the same amount of pure water as that added when the reaction is stopped is measured by the dilution water meter M2 and injected into the reaction cell 10. . Immediately thereafter, the mixed liquid in the reaction cell 10 is led out to the colorimeter 30 by the lead-out pipe S2. Then, with this colorimeter 30, the absorbance is measured at the same wavelength as in the case of heating to allow the reaction to proceed.

By subtracting the blank value measured in this way from the measured value when the reaction was advanced by heating, accurate absorption was obtained by removing the absorption of the color originally possessed by the reagent or sample solution. Various measurements are possible. In the present embodiment, the reagent 2a (coloring liquid) itself has a considerably large absorption in the absorbance measurement wavelength region, so that measurement of this blank value is important. Further, the absorption of the reagent 2a (color-developing liquid) itself largely changes in a short period with the deterioration of the reagent 2a. Therefore, it is desirable to measure the blank value as often as possible, preferably each time. As a result, the replacement frequency of the reagent 2a can be set to about 30 days.

In the present embodiment, the second reagent is divided into the reagents 2a to 2c, and the reagent injection pumps R are separated from each other.
P2a, RP2b, and RP2c were used to introduce them into the reaction cell 10. However, if there is no problem in consideration of the storage stability and stability of the reagents, they may be added together or separately. For example, the reagents 2b and 2c may be combined together in advance and supplied by one reagent injection pump. Further, the addition of pure water in the blank measurement may be performed once instead of two times if there is no particular problem due to circumstances such as a measuring device. Further, in the present embodiment, the absorbance was measured by deriving the mixed solution into a colorimeter arranged outside the reaction cell, but the reaction cell itself was used as a colorimetric cell, or a light guide probe was inserted into the reaction cell. Therefore, the mixed solution may be measured without being led out of the reaction cell.

Further, in the above embodiment, the so-called batch measurement, in which the sample solution or the like is retained in the reaction cell to carry out the reaction, is a so-called batch injection analysis (FIA) in which the sample solution is reacted while flowing in the tube. It may be a simple flow measurement. In this case, the inside of the tube becomes the reaction space.

[0047]

[Example] 1. Confirmation of pretreatment effect [Experimental Example 1] As a sample solution, boric acid was dissolved in pure water,
A borate ion solution having a boron concentration of 1 mg / L and sodium borofluoride were dissolved in pure water to give a boron concentration of 1
A borofluoride ion solution of mg / L was prepared. Further, 0.4 g of H-resorcinol was dissolved in pure water to obtain 10
The color-developing liquid (reagent 2a) was used as 00 mL. Also, ED
215 g of TA disodium salt (dihydrate) and ED
150 g of TA / tetrasodium salt (tetrahydrate) was dissolved in pure water to make 5000 mL, which was used as a chelating agent (reagent 2b). In addition, 185 mL of acetic acid (JIS standard product), 1000 g of sodium acetate, and 500 g of potassium nitrate were mixed with pure water to give 5
000 mL was used as the pH buffer solution (reagent 2c).

8 mL of each sample solution obtained as described above, 5 mL of a chelating agent, and 5 mL of a pH buffer solution were added and stirred, and then 4 mL of a color developing solution and 20 mL of pure water as dilution water were put into a reaction cell and mixed by stirring. This mixed solution had a pH of 5.0. This mixed solution was reacted in a boiling water bath at 100 ° C. for 30 minutes. Then, after 30 minutes, 28 mL of pure water was added into the reaction cell, and cooling water at about 15 ° C. was poured into the thermostat and cooled for 10 minutes. This was measured for absorbance at 510 nm. The absorbance was measured using a 10 mm quartz cell. The results of three measurements for each are shown in Table 1.
In Table 1, the difference in absorbance is the difference from the absorbance at zero boron concentration (pure water).

[0049]

[Table 1]

[Experimental Example 2] As a sample solution, sodium borofluoride was dissolved in pure water to obtain a boron concentration of 0 to 3.75.
A borofluoride ion solution of mg / L was prepared. Further, 80 g of aluminum sulfate dodecahydrate was dissolved in pure water, and 15 mL of (2 + 1) hydrochloric acid was added to make 1 L to prepare a pretreatment reagent (reagent 1). In addition, a coloring liquid (reagent 2a),
The same chelating agent (reagent 2b) and pH buffer solution (reagent 2c) as those used in Experimental Example 1 were used.

8 mL of each sample solution obtained as described above and 4 mL of the pretreatment reagent were put in a reaction cell and mixed with stirring. The pH of this mixed solution was 2.5. Then, this mixed solution was reacted in a boiling water bath at 100 ° C. for 10 minutes. 10
After the lapse of minutes, 5 mL of the chelating agent and 5 mL of the pH buffer solution were added and stirred, and then 4 mL of the coloring solution and pure water as dilution water 16
mL was placed in the reaction cell and mixed with stirring. This mixture is p
It was H4.9. This mixed solution was reacted in a boiling water bath at 100 ° C. for 30 minutes. Then, after 30 minutes, 28 mL of pure water was added into the reaction cell, and about 1
Cooling water at 5 ° C. was injected and the mixture was cooled for 10 minutes. 51 this
Absorbance was measured at 0 nm. The absorbance was measured using a 10 mm quartz cell. The results are shown in Table 2. In Table 2, the absorbance difference is the difference from the absorbance at zero boron concentration.

[0052]

[Table 2]

[Experimental Example 3] The same as Experimental Example 2 except that boric acid was dissolved in pure water as a sample solution and a borate ion solution having a boron concentration of 0 to 2.0 mg / L was used. The absorbance was measured under the conditions. The results are shown in Table 3. In Table 3, the difference in absorbance is the difference from the absorbance at zero boron concentration.

[0054]

[Table 3]

[Experimental Example 4] As a sample solution, boric acid and sodium borofluoride were dissolved in pure water to give a boron concentration of 0 to 0.
Absorbance was measured under the same conditions as in Experimental Example 2 except that a mixed solution of 3.25 mg / L was used. The results are shown in Table 4. In Table 4, the difference in absorbance is the difference from the absorbance at zero boron concentration. The mixing ratio of borofluoride ion and borate ion of each sample liquid is shown in the second column of Table 4.

[0056]

[Table 4]

[Summary of Experimental Examples 2 to 4] The relationship between the boron concentration and the absorbance difference of each sample solution obtained in Experimental Examples 2 to 4 is summarized in FIG. That is, in FIG. 2, data described as “borofluoride ion solution” is shown in Experimental Example 2 (Table 2), data described as “borate ion solution” is shown in Experimental Example 3 (Table 3), and “mixed solution”. The data described as are based on Experimental Example 4 (Table 4), respectively.

[Results] As shown in Experimental Example 1 (Table 1),
When measured without pretreatment, even with the same 1 mgB / L, the difference in absorbance of the borofluoride ion solution was only about 9% of the difference in absorbance of the borate ion solution. It is considered that this is because in the borofluoride ion solution, most of the borofluoride ions remain as “BF ₄ ⁻ ” and do not form a complex with H-resorcinol. On the other hand, in Experimental Examples 2 to 4 (Tables 2 to 4) in which the pretreatment of adding aluminum ions was performed, the absorbance difference per unit concentration of boron was sufficient (sensitivity of the borate ion solution of Experimental Example 1). Of about 70%) was obtained. Moreover, as shown in FIG. 2, good linearity was obtained on the same straight line. That is, it was found that the difference in absorbance obtained between the borofluoride ion solution and the borate ion solution was equivalent, and in the case of the mixed solution, the difference in absorbance was obtained as the total amount of both. It is considered that this is because the borofluoride ion was changed to borate ion by the pretreatment, and the complex formation with H-resorcinol became possible.

2. Examination of Pretreatment Reagent [Experimental Example 5] As a sample solution, boric acid was dissolved in pure water,
A borate ion solution having a boron concentration of 1 mg / L and sodium borofluoride were dissolved in pure water to give a boron concentration of 1
A borofluoride ion solution of mg / L was prepared. Further, as a pretreatment reagent (reagent 1), aluminum sulfate 1
Dissolve 80 g of dihydrate in pure water, (2 + 1) hydrochloric acid 15 m
What was made into 1 L by adding L (hereinafter referred to as "aluminum sulfate solution"), and aluminum nitrate nonahydrate 8
Two kinds were prepared by dissolving 0 g in pure water to make 1 L (hereinafter referred to as “aluminum nitrate solution”). The same color developing solution (reagent 2a), chelating agent (reagent 2b), and pH buffer solution (reagent 2c) used in Experimental Example 1 were used.

8 mL of each sample solution obtained as described above and 4 mL of the pretreatment reagent were put in a reaction cell and mixed with stirring. This mixed solution had a pH of 2.5 for the aluminum sulfate solution and a pH of 3 for the aluminum nitrate solution. Then, this mixed solution was reacted in a boiling water bath at 100 ° C. for 10 minutes. After 10 minutes, 5 mL of the chelating agent and 5 mL of the pH buffer were added and stirred, and then 4 mL of the color-developing solution and 16 mL of pure water as dilution water were put into the reaction cell and mixed with stirring.
This mixed solution has a pH of 4.9 when the pretreatment solution is an aluminum sulfate solution, and also has a pH value when it is an aluminum nitrate solution.
It was 4.9. This mixed solution was reacted in a boiling water bath at 100 ° C. for 30 minutes. After 30 minutes, 28 mL of pure water was added to the reaction cell and about 15 minutes was added to the thermostat.
Cooling water at 0 ° C. was added and the mixture was cooled for 10 minutes. 510 this
Absorbance was measured at nm. The absorbance was measured using a 10 mm quartz cell. The results are shown in Table 5. In Table 5, the difference in absorbance is the difference from the absorbance at zero boron concentration (pure water).

[0061]

[Table 5]

[Experimental Example 6] As a sample solution, sodium borofluoride was dissolved in pure water to obtain a boron concentration of 0 to 3.00 m.
A borofluoride ion solution adjusted to g / L was prepared. Further, as a pretreatment reagent (reagent 1), 10 g of ammonium iron sulfate dodecahydrate was dissolved in pure water, and 0.8 mL of nitric acid was added to make 100 mL (hereinafter referred to as “iron ion solution”). . The same color developing solution (reagent 2a), chelating agent (reagent 2b), and pH buffer solution (reagent 2c) used in Experimental Example 1 were used.

8 mL of each sample solution obtained as described above and 4 mL of the pretreatment reagent were placed in a reaction cell and mixed with stirring. This mixture had a pH of 2. Then, add this mixed solution to 10
The reaction was carried out for 10 minutes in a boiling water bath at 0 ° C. After 10 minutes, 5 mL of the chelating agent and 5 mL of the pH buffer were added and stirred, and then 4 mL of the color-developing solution and 16 mL of pure water as dilution water were put into the reaction cell and mixed with stirring. The pH of this mixed solution was 4.7. This mixed solution was reacted in a boiling water bath at 100 ° C. for 30 minutes. After 30 minutes, 28 mL of pure water was added to the reaction cell and about 15 minutes was added to the thermostat.
Cooling water at 0 ° C. was added and the mixture was cooled for 10 minutes. 510 this
Absorbance was measured at nm. The absorbance was measured using a 10 mm quartz cell. The results are shown in Table 6. In Table 6, the absorbance difference is the difference from the absorbance at zero boron concentration.

[0064]

[Table 6]

[Comparison between Experimental Example 2 and Experimental Example 6] Experimental Example 2
And the relationship between the boron concentration and the absorbance difference of each sample solution obtained in Experimental Example 6 are summarized in FIG. That is, in FIG.
The data described as "aluminum ion solution" is based on Experimental Example 2 (Table 2) and the data described as "iron ion solution" is based on Experimental Example 6 (Table 6).

[Results] As shown in Experimental Example 5 (Table 5),
When using either aluminum sulfate solution or aluminum nitrate solution as the pretreatment reagent, the difference in absorbance when the sample solution is a borofluoride ion solution and the difference in absorbance when the sample solution is a borate ion solution are almost the same. It was equivalent.
Further, in each case, a sufficient difference in absorbance per unit concentration of boron was obtained. The cause of the difference in the absorbance per unit concentration of boron between the aluminum sulfate solution and the aluminum nitrate solution is unknown. Further, as shown in FIG. 3, linearity was obtained even when the iron ion solution was used, but the value was lower than the absorbance per unit concentration of boron when the aluminum ion solution was used. Therefore, it was found that as the pretreatment reagent, both a solution containing aluminum ions and a solution containing iron ions can be used, but a solution containing aluminum ions is more preferable.

3. Examination of Reaction Conditions of Pretreatment [Experimental Example 7] As a sample solution, boric acid was dissolved in pure water,
A borate ion solution having a boron concentration of 1 mg / L and sodium borofluoride were dissolved in pure water to give a boron concentration of 1
A borofluoride ion solution of mg / L was prepared. The same pretreatment reagent (Sample 1) as in Experimental Example 2 was used. Color developing solution (reagent 2a), chelating agent (reagent 2
b), the pH buffer solution (reagent 2c) is described in Experimental Example 1,
The same thing as Experimental example 2 was used.

8 mL of each sample solution obtained as described above and 4 mL of the pretreatment reagent were placed in a reaction cell and mixed with stirring. This mixture had a pH of 2.5. And, this mixed liquid,
As shown in Table 7, the reaction was performed for a predetermined time in a water bath at a predetermined temperature. After a predetermined time, chelating agent 5m
L, 5 mL of pH buffer solution was added, and the mixture was stirred, and then color developing solution 4
mL and pure water 16 mL as dilution water were put into the reaction cell and mixed with stirring. This mixed solution had a pH of 4.9. This mixed solution was reacted in a boiling water bath at 100 ° C. for 30 minutes.
Then, after 30 minutes, 28 mL of pure water was added into the reaction cell, and cooling water at about 15 ° C. was injected into the constant temperature bath to
Cooled for 0 minutes. This was measured for absorbance at 510 nm.
The absorbance was measured using a 10 mm quartz cell. The results are shown in Table 7.

[0069]

[Table 7]

[Results] As shown in Experimental Example 7 (Table 7),
The ratio of the absorbance difference in the case of the borofluoride ion solution to the absorbance difference in the case of the borate ion solution is 100 ° C.
It was almost 100% under the condition of minutes. On the other hand, it was 70% after 10 minutes at room temperature and about 85% after 30 minutes. From this, it was found that the decomposition of fluoride ions was accelerated by heating.

4. Examination of Influence of Fluoride Ion [Experimental Example 8] As a sample solution, sodium borofluoride and sodium fluoride were dissolved in pure water to obtain a boron concentration of 0 mg.
/ L or 1 mg / L, fluorine ion concentration 0 to 50 mg
A borofluoride ion solution coexisting with fluorine ions was prepared. The same pretreatment reagent (Sample 1) as in Experimental Example 2 was used. The same color developing solution (reagent 2a), chelating agent (reagent 2b), and pH buffer solution (reagent 2c) were used as in Experimental Examples 1 and 2.

For each sample solution obtained as described above,
The absorbance was measured under the same conditions as in Experimental Example 2. The results are shown in Table 8 and FIG.

[0073]

[Table 8]

[Results] As shown in Experimental Example 8 (Table 8, FIG. 4), a slight increase in absorbance was observed as the fluorine ion concentration in the sample solution increased, but this is within the error range during analysis. it is conceivable that. From this, it was found that the coexistence of fluorine ions did not become a major obstacle.

[0075]

According to the boron measuring method and the boron measuring apparatus of the present invention, the boron concentration can be measured accurately and easily even when borofluoride ions are present. Therefore, it is highly practical in monitoring the boron concentration in water in the wastewater treatment process and environmental water, and is useful from the viewpoint of environmental protection.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a boron measuring apparatus according to this embodiment.

FIG. 2 is a graph showing the results of Experimental Examples 2 to 4.

FIG. 3 is a graph showing the results of Experimental Examples 2 and 6.

FIG. 4 is a graph showing the results of Experimental Example 8.

[Explanation of symbols]

10 ... Reaction cell, 20 ... Constant temperature bath, 30 ... Colorimeter,
S1 ... Sample introducing pipe, S2 ... Delivery pipe, R1 ... Reagent introducing pipe, R2a ... Reagent introducing pipe, R2b ... Reagent introducing pipe, R2c ... Reagent introducing pipe, M1 ... Sample liquid measuring instrument, M
2 ... Diluent meter, RP1 ... Reagent injection pump, RP
2a ... Reagent injection pump, RP2b ... Reagent injection pump, RP2c ... Reagent injection pump,

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G042 AA01 BB15 CA02 CB03 DA06                       DA08 FA03 FA06 FA11 FB02                       GA01 GA05 HA02 HA07                 2G054 AA02 AB10 BA02 CA10 EA06                       GB05

Claims (4)

[Claims] 1. A first reagent containing at least aluminum ions and / or iron ions is added to a sample solution, and then at least a 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid azo dye is mixed with a chelate. A method for measuring boron, which comprises adding a second reagent containing an agent to cause a color reaction, and then measuring absorbance. 2. The method for measuring boron according to claim 1, wherein the color development reaction is performed at pH 4 to 7. 3. A reaction space, means for introducing a sample solution and a first reagent into the reaction space, and a second means in the reaction space.
The means for introducing the reagent and the means for measuring the absorbance of the mixed liquid in the reaction space obtained by adding the first reagent and the second reagent to the sample liquid,
The reagent of (1) contains aluminum ions and / or iron ions, and the second reagent contains 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid azo dye and a chelating agent. Boron measuring device. 4. The boron measuring apparatus according to claim 3, wherein the pH of the mixed solution is adjusted to 4 to 7 by the second reagent.