JP2980508B2 - Solution analysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for analyzing a solution.

[0002]

2. Description of the Related Art In recent years, as a highly accurate and versatile titration method,
Potentiometric titration has been increasingly used.

[0003] This potentiometric titration method is a method of performing titration utilizing a difference in dissociation state in a solvent, but it has been difficult to separate substances having no difference in dissociation state in an aqueous solution.

[0004]

In order to analyze a substance having no difference in dissociation state in an aqueous solution with good reproducibility and high accuracy, it is necessary to use iron and steel. As disclosed, materials that are difficult to analyze in potentiometric titration are subjected to diffusion dialysis using an ion exchange membrane in advance, and then a target substance is selectively analyzed at each ion electrode using an ion selective electrode.

However, in order to analyze many substances at once, an ion electrode having selectivity for the substances is required. Further, it is necessary to remove in advance a substance that interferes with the ion-selective electrode using an ion-exchange membrane or the like. The present invention provides a solution analysis method for solving the above-mentioned problem.

[0006]

Means for Solving the Problems A method characterized by using a solution in which a substance having a base is dispersed in an organic solvent and analyzing an acidic solution containing three or more components by potentiometric titration, More preferably, a basic aqueous solution in which the solute is dissolved in an amount of 5 mol / L or more and 14 mol / L or less is used as a solvent in an organic solvent at 0.05 mol / L.
This is a method characterized by performing an analysis by potentiometric titration using a solution dissolved at a concentration of not less than 1 liter and not more than 2.00 mol / l.

[0007]

The operation of the present invention will be described below in detail.

In the present invention, a substance having a base as a solute is dispersed in an organic solvent as a solvent as a standard solution for titration. The use of an organic solvent as the solvent is a major difference from the conventional standard solution for titration.

[0009] Organic solvents such as methanol, ethanol and acetone have a lower dielectric constant than water, and according to the Chemical Handbook,
32.6, 24.3, 20.7 at 25 ° C. respectively
And the water is 78.5 at 25 ° C.

For this reason, when the same acidic substance is dissociated in a solvent, it is understood that water having high activity of the solvent is easily dissociated.

On the other hand, dissociation is unlikely to occur in a solvent having a low relative dielectric constant, and it is possible to separate even a substance that is close to a dissociated state in water in a solvent having a low relative dielectric constant.

Table 1 shows an example. Hydrofluoric acid has a pKa of 3.2 in an aqueous solution, and acetic acid has a pKa of 4.8, and the difference is only about 1.6. However, in an ethanol solvent, hydrofluoric acid is 7.2 and acetic acid is 10.2. 2, which is about 3.0. (PKa = -logKa, Ka: dissociation constant) Therefore, it has become possible to separate substances that could not be separated in an aqueous solution by the method of the present invention.

In the present invention, an aqueous solution is defined as a solute for titration because it is a substance which is hardly dissolved in an organic solvent.
This is because when a standard solution for titration is prepared, it is not directly dissolved in an organic solvent but is dissolved as an aqueous solution and then dispersed in an organic solvent.

Further, the lower limit of the aqueous solution in which the solute is dissolved is defined as 5 mol / l. This is because, in the case of dispersing at a concentration of mol / liter or less, the influence of the concentration of the aqueous solution is larger than that of the organic solvent, and accurate analysis cannot be performed.

Further, the upper limit of 14 mol / l is defined as exceeding 14 mol / l approaches the saturated dissolution amount of the solute, making it difficult to dissolve the solute. This is because they cannot be mixed.

In the present invention, the lower limit of the concentration of a solution in which an aqueous solution in which a solute is dissolved is dispersed in an organic solvent is 0.1.
The reason that the molar amount of 05 mol / liter is specified is that it is industrially uneconomical because a large amount of a standard solution for titration is required for titration below 0.05 mol / liter.
This is because the dispersion of the standard solution concentration becomes large.

Further, the upper limit of 2.00 mol / l is defined as the water concentration in the standard solution for titration becomes higher when the concentration exceeds 2.00 mol / l. This is because it becomes difficult to separate substances that do not have any.

Example 1 shows an example in which a mixed solution of hydrofluoric acid, acetic acid and nitric acid was subjected to potentiometric titration with the standard solution for titration of the present invention.

As shown in Example 1, according to the present invention, acid components which could not be separated conventionally can be analyzed with high accuracy.

[0020]

EXAMPLE As a sample solution, 50 wt% hydrofluoric acid, 70 w
Using t% nitric acid and 100 wt% acetic acid, the ratio was prepared as shown in Example 1.

After sufficiently stirring the sample solution, 50 cc of the sample solution was sampled using a micropipette.
Potentiometric titration was performed.

The titration standard solution was prepared by dissolving sodium hydroxide in an aqueous solution to a concentration of 10 mol / l, dispersing this solution in an ethanol solvent, and preparing a 0.10 mol / l ethanol solvent titration solution.

For comparison, the conventional method is 0.1
Potentiometric titration was also performed using an aqueous solution of sodium hydroxide (mol / liter) as a titration standard solution.

FIGS. 1 and 2 show the titration curves when the titration was performed. It has been found that the conventional method cannot separate hydrofluoric acid and acetic acid, but the method of the present invention can successfully separate nitric acid, hydrofluoric acid and acetic acid.

According to the conventional method, the set value and the analysis value of only nitric acid matched the set value and the analysis value, but hydrofluoric acid and acetic acid could not be separated.

On the other hand, according to the method of the present invention, nitric acid, hydrofluoric acid,
Acetic acid is separated and agrees well with the set value.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

According to the present invention, a method for titrating a substance in an aqueous solution, which has been conventionally difficult to analyze, by using an organic solvent as a solvent is made possible, and a method can be performed accurately, quickly, and simply. Things.

[Brief description of the drawings]

FIG. 1 is a diagram showing a titration curve of an analysis example according to a conventional method.

FIG. 2 is a diagram showing a titration curve of an analysis example of the present invention.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tadashi Sakai 1618 Ida, Nakahara-ku, Kawasaki-shi Nippon Steel Corporation Advanced Technology Research Laboratories (72) Inventor Shinji Tarinaga 3434 Shimada, Oaza, Hikari-shi, Yamaguchi Pref. In-company (56) References JP-A-6-66783 (JP, A) JP-A-7-190982 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 27/26 341 G01N 31/16

Claims (2)

(57) [Claims] 1. A method for analyzing a solution, comprising using a solution in which a substance having a base is dispersed in an organic solvent and potentiometrically titrating an acidic solution containing three or more components. 2. A basic aqueous solution having a solute of 5 mol / L or more and 14 mol / L or less is dispersed in an organic solvent so that the concentration is 0.05 mol / L or more and 2.00 mol / L or less. A method for analyzing a solution, comprising analyzing an acidic solution containing three or more components by potentiometric titration using the solution obtained.