JP7435172B2 - Reagent and moisture measurement method - Google Patents

Description

The present invention relates to reagents and moisture determination methods.

上記の反応は、Ｍｉｔｃｈｅｌｌ＆Ｓｍｉｔｈにより、ヨウ素１ｍｏｌと水１ｍｏｌとが反応することが知られている。 One of the representative methods for measuring the moisture contained in a substance is the Karl Fischer method, which was published in 1935 by Karl Fischer of Germany. Karl Fischer proposed that a reagent consisting of iodine (I ₂ ), sulfur dioxide (SO ₂ ), a basic substance (Base), and methanol (CH ₃ OH) and water (H ₂ O) react as shown in the following reaction formula. It was announced that the water content of substances can be measured by using this reaction.

In the above reaction, it is known by Mitchell & Smith that 1 mol of iodine and 1 mol of water react.

There are two typical methods for measuring moisture using Karl Fischer reagents: volumetric titration, which determines moisture from the titration amount, and coulometric titration, which determines moisture by generating iodine through electrolytic oxidation. . Regarding the measurement procedure, in any titration method, the solvent in which the sample to be measured is dissolved is made anhydrous with iodine, the sample to be measured is then placed in this anhydrous solvent, and the sample is titrated with a reagent containing iodine. Calculate the moisture concentration.
Generally, volumetric titration method (Patent Documents 1 and 2) is used when the water concentration contained in a substance exceeds approximately 1% by mass, and coulometric titration method (Patent Document 3) is used when the water concentration is less than 1% by mass. and 4) are used.

Japanese Patent Application Publication No. 2002-202299 Japanese Patent Application Publication No. 2014-167455 JP2009-294041A Japanese Patent Application Publication No. 2014-186016

As mentioned above, in moisture measurement, when a sample with a low moisture concentration is used as the sample to be measured, a coulometric moisture measuring device that performs Karl Fischer titration using the coulometric titration method and a coulometric moisture measuring device that vaporizes the moisture in the sample to be measured are usually used. Perform moisture measurement in combination with a vaporizer.
However, when using a sample with a high kinematic viscosity as the sample to be measured, the coulometric titration method makes it impossible to accurately measure the water concentration because the sample adheres to the electrodes in the electrolytic cell of the moisture measuring device. There was a problem in that the sample adhered to the heating tube in the vaporizer, making cleaning after measurement difficult.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reagent that makes it possible to measure the moisture content of a sample with a low water concentration and high kinematic viscosity by a volumetric titration method, and a moisture measurement method using the reagent.

As a result of intensive studies to solve these problems, the present inventors succeeded in reducing the water content of samples with low water concentration and high kinematic viscosity by reducing the water equivalent of the reagent to a specific amount or less. It was discovered that the concentration can be measured by volumetric titration, and the present invention was completed.

That is, the gist of the present invention is as follows.
[1] A reagent for measuring water concentration, which contains iodine and has a water equivalent of 0.9 mgH ₂ O/ml or less.
[2] The reagent for measuring water concentration according to [1], which is a Karl Fischer reagent, further comprising a basic substance, sulfur dioxide, and a solvent.
[3] The reagent for measuring water concentration according to [2], wherein the basic substance is an imidazole compound or an amine compound.
[4] The reagent for measuring water concentration according to [2] or [3], wherein the solvent is an alcohol or a chloroform compound.
[5] A moisture measurement method comprising a titration step of titrating the reagent according to any one of [2] to [4] to a sample to be measured.
[6] The moisture measuring method according to [5], wherein the moisture concentration of the sample to be measured is 500 ppm or less.
[7] The moisture measuring method according to [6], wherein the kinematic viscosity of the sample to be measured at 25° C. is 800,000 mm ² /sec or less.
[8] The moisture measuring method according to any one of [5] to [7], wherein the sample to be measured is selected from the group consisting of oil, resin, and pharmaceutical preparation.

According to the present invention, it is possible to provide a reagent that makes it possible to measure the moisture content of a sample with a low moisture concentration and high kinematic viscosity by volumetric titration, and a moisture measurement method using the reagent.

Embodiments of the present invention will be described in detail below, but these descriptions are only examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents unless the gist thereof is exceeded.
In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits, and "A to B" means A or more. It means that it is below B.

<Reagent>
A reagent for measuring water concentration (hereinafter also simply referred to as "reagent for measuring water concentration" or "reagent") that is an embodiment of the present invention contains iodine and has a water equivalent of 0.9 mgH ₂ O. This is a reagent for measuring water concentration.
The above reagent for measuring water concentration is a reagent that can be used to measure the water concentration of a sample to be measured, and in particular, a reagent that can measure the water concentration by being titrated into the sample to be measured (for water concentration measurement). titration reagent).

上記反応式（１）では、１モルの水分子に対し、１／２モルのＩ_２が消費される。よって、測定対象試料中の全ての水分と反応するヨウ素の量を測定することにより、測定対象
試料中の水分濃度を評価することができる。
測定対象試料中の全ての水分と反応するヨウ素の量を測定する方法は、特段制限されないが、例えば、測定対象試料に接触する試薬の量を徐々に増加させ、測定対象試料と試薬との反応の経過を観測し、測定対象試料の全ての水分の反応が完了する時点での試薬の量から反応に要するヨウ素の量を評価する方法が挙げられる。
このような方法として、具体的には、滴定法が挙げられ、例えば、滴定フラスコ内に測定対象試料を投入した後、該フラスコ内の測定対象試料に対して上記の試薬を滴下し、滴定の終点までに用いられた試薬の量から反応に要するヨウ素を評価することができる。なお、終点の確認は、後述の「水当量評価工程」の項に記載の方法で行ってよく、また、ヨウ素の色が現れるか否かを目視で観察する方法で行ってもよい。 Iodine exhibits an oxidation-reduction reaction with water (moisture in the target sample) as shown in reaction formula (1) below.

In the above reaction formula (1), 1/2 mole of I ₂ is consumed per 1 mole of water molecules. Therefore, the water concentration in the sample to be measured can be evaluated by measuring the amount of iodine that reacts with all the water in the sample to be measured.
The method of measuring the amount of iodine that reacts with all the moisture in the sample to be measured is not particularly limited, but for example, the amount of reagent that comes into contact with the sample to be measured is gradually increased, and the reaction between the sample and the reagent is measured. One method is to observe the progress of the reaction and evaluate the amount of iodine required for the reaction from the amount of reagent at the time when the reaction of all the water in the sample to be measured is completed.
A specific example of such a method is a titration method. For example, after putting a sample to be measured into a titration flask, the above-mentioned reagent is dripped onto the sample to be measured in the flask, and titration is carried out. The amount of iodine required for the reaction can be estimated from the amount of reagent used up to the end point. The end point may be confirmed by the method described in the "Water equivalent evaluation step" section below, or by visually observing whether the color of iodine appears.

上記反応式（２）では、１モルの水分子に対し、１モルのＩ_２が消費される。よって、脱水溶剤に測定対象の試料を溶解させた溶液にカールフィッシャー試薬を滴定し、終点までに要したヨウ素の滴定量から、測定対象の試料中の水分濃度を評価することができる。 One of the methods for measuring water concentration using titration is the Karl Fischer method, and the above reagent can be used as a Karl Fischer reagent.
Karl Fischer reagent is a reagent that further contains a basic substance (Base), sulfur dioxide (SO ₂ ), and a solvent in addition to iodine (I ₂ ), and is quantitatively mixed with water as shown in reaction formula (2) below. oxidation-reduction reaction.

In the above reaction formula (2), 1 mol of I ₂ is consumed per 1 mol of water molecules. Therefore, the water concentration in the sample to be measured can be evaluated from the titration amount of iodine required to reach the end point by titrating the Karl Fischer reagent to a solution of the sample to be measured in a dehydrated solvent.

Furthermore, by using a substance that reacts with Base.SO ₃ in the above reaction formula (2) as a solvent, the equilibrium of the reaction in the reaction formula (2) can be made to proceed to the right. For example, when alcohol (ROH) such as methanol is used as a solvent, the reaction shown in the following reaction formula (3) occurs, and the equilibrium of the above reaction formula (2) can proceed to the right.

Hereinafter, the reagent according to this embodiment will be explained in detail.
The reagent according to this embodiment has a water equivalent (potency) of 0.9 mgH ₂ O/ml or less, and since the amount of iodine that comes into contact with water is small, it reacts with water in just the right amount. Even when titration is employed, the water concentration of a sample with low water concentration and high kinematic viscosity can be measured. The water equivalent (potency) of a reagent is the mass of water that reacts with the reagent per mL.
The water equivalent of the reagent is 0.9 mgH _{2 O/ml or less, but 0.8 mgH 2 O} /ml, from the viewpoint of being able to more accurately measure the water concentration of the sample to be measured and exhibiting the above effects. It is preferably at most 0.5 mgH 2 O/ml, more preferably at most 0.5 mgH ₂ O/ml. In addition, if the water equivalent is low, the amount of titrant consumed to measure the water content of the sample to be measured will increase significantly, or the color of the titrant may change due to a decrease in the amount of iodine, which may make visual end point determination unstable. Therefore, the water equivalent of the reagent is preferably 0.1 mg H ₂ O/ml or more, and more preferably 0.2 mg H ₂ O/ml or more.
The above water equivalent can be decreased by adding water and can be increased by adding iodine.
Additionally, since samples with low water concentrations, such as those on the order of ppm, are generally measured using the coulometric method, reagents with very low water equivalents, such as 0.9 mgH ₂ O/ml or less, are Not used in law. Furthermore, in the coulometric method, the reagent according to this embodiment is not used in the step of measuring the water concentration of the sample to be measured.

The above water equivalent is calculated by dehydrating the dehydrated solvent charged in the titration flask with the relevant reagent, then placing a water standard solution with a guaranteed value into the titration flask, and adding the reagent dropwise. Calculate from the amount of reagent used using the following formula.
F=S×K/T
F: water equivalent (mgH ₂ O/ml)
S: Amount of water standard solution collected (g)
K: Guaranteed value of water standard solution (mgH ₂ O/g)
T: Titration amount of the reagent of the present invention required for titration (ml)

The form of iodine (I ₂ ) contained in the reagent is not particularly limited, and commercially available iodine (I 2 ) can be used.
The concentration of iodine in the reagent is not particularly limited, but from the viewpoint of being able to accurately measure the water concentration of the target sample with a low water equivalent, it is usually 1% by mass or more, preferably 2% by mass or more, and It is usually 8% by mass or less, preferably 4% by mass or less.

The form of sulfur dioxide (SO ₂ ) contained in the reagent is not particularly limited, and commercially available sulfur dioxide (SO 2 ) can be used.
The concentration of sulfur dioxide in the reagent is not particularly limited, but from the viewpoint of ensuring an appropriate pH for the Karl Fischer reaction, it is usually 0.1% by mass or more, preferably 1.0% by mass or more, and 2. It is more preferably at least 10% by mass, usually at most 10% by mass, preferably at most 8% by mass, and preferably at most 5% by mass.

The type of basic substance (Base) contained in the reagent is not particularly limited as long as it exhibits basicity; examples include imidazole compounds, amine compounds, etc., and from the viewpoint of stability of the titration end point and safe handling. Therefore, among these, imidazole compounds or amine compounds are preferred. One type of these substances may be used alone, or two or more types may be used in any combination and ratio.
Examples of imidazole compounds or amine compounds include imidazole and imidazole derivatives, alcohol amines such as diethanolamine, pyridine and alkylaminopyridine, pyridine derivatives, etc. Among these, imidazole or pyridine is used from the viewpoint of versatility. preferable.

Examples of imidazole derivatives include 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, 1-butylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-probylimidazole, 2-butylimidazole, 4- Examples include methylimidazole, 4-butylimidazole, 1,2-dimethylimidazole, 1,2,4-trimethylimidazole, 1-phenylimidazole, and benzimidazole.

Examples of pyridine derivatives include 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, 2,6-dihydroxypyridine, 3-hydroxy-6-methylpyridine, 2-chloropyridine, 3-chloropyridine, 2, Examples include 6-dichloropyridine and methylethylpyridine.

The concentration of the basic substance in the reagent is not particularly limited, but from the viewpoint of ensuring an appropriate pH for the Karl Fischer reaction, it is usually 1% by mass or more, preferably 5% by mass or more, and 12% by mass or more. It is preferable that Further, the content is usually 20% by mass or less, preferably 13% by mass or less.

The type of solvent contained in the reagent is not particularly limited as long as it is a substance that can dissolve the above-mentioned iodine, sulfur dioxide, and basic substances. Examples include alcohols, chloroform compounds, etc., and solvents with high dissolving power In particular, from the viewpoint of promoting the titration reaction and clarifying the end point, alcohols or chloroform compounds are preferred. One type of these substances may be used alone, or two or more types may be used in any combination and ratio.
Examples of alcohols or chloroform compounds include methanol, ethanol, alkyl ethers such as ethylene glycol monoethyl ether and diethylene glycol monoethyl ether, alkylene carbonates such as ethylene carbonate and propylene carbonate, and chloroform. Among these, diethylene glycol monoethyl ether or chloroform is preferred.

The content of the solvent in the reagent is not particularly limited, but is usually 50% by mass or more, and 70% by mass or more from the viewpoint of allowing the equilibrium of the above reaction formula (2) to proceed to the right side at a suitable rate. It is preferable that it is, and it is preferable that it is 80 mass % or more. Further, it is usually 90% by mass or less, preferably 85% by mass or less.

The reagent may contain substances (other substances) other than the above-mentioned iodine, sulfur dioxide, basic substance, and solvent.

The content of components contained in the Karl Fischer reagent can be analyzed by gas chromatography or the like. It can also be calculated from the amount of raw materials for the Karl Fischer reagent.

<Moisture measurement method>
A moisture measurement method (hereinafter also simply referred to as "moisture measurement method") which is another embodiment of the present invention is a moisture measurement method including a titration step of titrating the above-mentioned reagent.
The aspect of the moisture measurement method including the above-mentioned titration step is not particularly limited, and includes, for example, Karl Fischer titration method, and can include each step applied in this titration method. Typical Karl Fischer methods include volumetric titration (volume method) and coulometric titration (coulometric method), but these methods are useful for measuring the water concentration of samples with high water concentration and high kinematic viscosity. However, when a sample with a high kinematic viscosity is used as the sample to be measured, the sample adheres to the electrodes in the electrolytic cell of the moisture measuring device, making it impossible to accurately measure the moisture concentration. The volumetric titration method is more suitable than the coulometric titration method because it does not cause such problems.

Examples of steps that can be carried out by volumetric titration include the following steps.
(1) Reagent preparation step for preparing reagents.
(2) A dehydration step in which water in the dehydrated solvent in the titration flask is dehydrated.
(3) Water equivalent (potency) evaluation step to determine the water equivalent (potency) of the reagent.
(4) A measurement target sample dissolution step of dissolving the measurement target sample in an anhydrous dehydrated solvent.
(4) Titration step of titrating the reagent.
(5) Water equivalent evaluation step of evaluating the water equivalent (potency) of the sample to be measured (including calculating the water concentration of the sample to be measured).
(4) is an essential step, and steps (1) to (5) above do not need to be performed in the order listed, but normally steps (1) to (3) are performed during the titration step. In addition, step (5) is performed simultaneously with the titration step.
In the case of the volumetric method, the water concentration of the sample is calculated from the water equivalent of the titrant and the titration amount required when the titrant reacts with the sample to be measured, as shown in the following formula.
Moisture (%) = {(titrant amount (ml) × water equivalent of titrant (mgH ₂ O/ml)) / (sample amount to be measured (ml) × 1000)} × 100
A commercially available device can be used for the moisture measurement, and examples include devices such as Karl Fischer volumetric titration moisture measurement device CA-310 (manufactured by Mitsubishi Chemical Analytech).

[Reagent preparation process]
The moisture measurement method may include a reagent preparation step of preparing a reagent. The method for preparing the reagent is not particularly limited, but includes, for example, steps such as charging a dehydrated solvent into a titration flask and setting the titrant at the supply site of the moisture measuring device.

[Anhydrous process]
The moisture measuring method may include a dehydration step of dehydrating the water in the dehydrated solvent in the titration flask.
The type of dehydrating solvent is not particularly limited as long as it can dissolve the sample to be measured. For example, a method for making a dehydrated solvent anhydrous includes titration with a Karl Fischer reagent.

[Water equivalent (potency) evaluation process]
The moisture measurement method may include a water equivalent (potency) evaluation step to determine the water equivalent (potency) of the reagent.
As a method for determining or adjusting the water equivalent of a reagent, the method described in the explanation regarding the water equivalent above can be applied.

[Measurement target sample dissolution process]
The moisture measurement method may include a step of dissolving a sample to be measured in an anhydrous dehydrated solvent.
The method of dissolving the sample to be measured in the dehydrated solvent is not particularly limited. For example, the dehydrated solvent, the sample to be measured, and a stirrer are placed in a titration flask, and the dehydrated solvent is dissolved while being stirred by the stirrer. An example of this method is to dissolve the sample to be measured in a solvent.

[Titration process]
The moisture measurement method includes a titration step of titrating the above-mentioned reagent. The titration method is not particularly limited, and a known titration method using a buret or the like can be applied.
By the above titration, the reaction of reaction formula (2) below proceeds, and the water content can be evaluated from the titration amount of iodine required to reach the end point by the water equivalent evaluation step described below.

The titration temperature is not particularly limited, but is usually room temperature.

[Water equivalent evaluation process]
The moisture measurement method may include a water equivalent evaluation step of evaluating the water equivalent (potency) of the sample to be measured.
The method for evaluating the water equivalent of the sample to be measured is not particularly limited, and any known method can be adopted. For example, the water equivalent can be evaluated using a constant voltage polarization amperometric titration device or a constant current polarization potentiometric titration device. can.
When using a constant-voltage polarization current titration device, the current that changes as the moisture measurement reagent is dropped is measured, and as the titration progresses, the current in the circuit changes greatly and then returns to its original position. When the end point of the titration is reached, the change in current continues for a certain period of time, and the end point of the titration is determined when the change in current continues for a certain period of time.
When using a constant current polarization potentiometric titration device, a minute current is passed between the electrodes, and the potential difference that changes when the moisture measurement reagent is dropped is measured.As the titration progresses, the value of the voltmeter in the circuit changes from the polarized state. It suddenly decreases, disappears and transfers, and then returns to its original position. When the end point of the titration is reached, a negative state continues for a certain period of time, and this state is defined as the end point of the titration.
Finally, the water concentration of the sample to be measured is calculated from the amount of reagent consumed by the end point of the titration.

The volumetric titration method includes a titration method called a back titration method, as disclosed in JP-A No. 2015-179057. The titration method in the above description is called a forward titration method as opposed to a back titration method. In the back titration method, a reagent is added in advance to a titration cell that has been subjected to dehydration treatment by preliminary titration in such a manner that it contains more than the water content of the sample. Then, the sample is put in here, the water in the sample is reacted with the excess reagent, and the remaining reagent is mixed with water and methanol standard solution (a standard prepared by adding a specified amount of water to dehydrated methanol to adjust the water concentration). This method measures the water content of a sample by titrating it to the end point (contrary to the end point in the case of forward titration, when no iodine is present and there is a slight excess of water). This method is an effective titration method when the reaction between the reagent and the water in the sample is slow and the end point is unclear. The above-mentioned reagents can be used not only in forward titration but also in back titration.

The reagents mentioned above have lower water equivalents (potency) than the commonly used Karl Fischer reagents, so when dehydrating the initial solvent in the volumetric titration procedure, the titer is increased. Put it away. If the titration amount increases, the frequency of replacing the solvent in the titration flask and the amount of waste liquid tend to increase. In order to reduce the consumption of titration amount due to the use of reagents, reagents with different iodine water equivalents (potency) are added to the titration flask in advance, the water in the solvent is dehydrated to the minimum water content that can be detected by the measuring device, and the remaining water is added to the titration flask. It may be made anhydrous with the reagents mentioned above.
The sample to be measured is not particularly limited, but it is usually preferably selected from the group consisting of oils, resins, and pharmaceutical preparations with low water concentrations.

If the water concentration is high, the titer of the reagent increases, so the water concentration of the sample to be measured is usually 10,000 ppm or less, preferably 500 ppm or less, and more preferably 100 ppm or less. Although it is not necessary to set a lower limit for the water concentration of the sample to be measured, the detection limit is usually 1 ppm or more.

If the kinematic viscosity of the sample to be measured is high, it may not dissolve in the dehydrated solvent, the sample may not mix uniformly, or it may stick to the electrodes of the titration flask, making it difficult to calculate the accurate water concentration. The kinematic viscosity of the sample to be measured is preferably 800,000 mm ² /sec or less, more preferably 600,000 mm ² /sec or less,
It is more preferably 300,000 mm ² /sec or less, and 100,000 mm ²
It is particularly preferably at most 50 mm ² /sec, preferably at least 100 mm ² /sec, and more preferably at least 300 mm ² /sec. The kinematic viscosity can be controlled by adjusting the presence or absence and amount of use of thickeners, solvents, and the like.
The measurement of kinematic viscosity can be carried out according to the Japanese standard JIS Z 8803:2011 method for measuring liquid viscosity.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not interpreted as being limited to the following examples. The materials used in the examples and the measurement methods for evaluation items are as follows. "%" in the examples is based on mass unless otherwise specified.

<Experiment 1>
The following four types of reagents were prepared as titrants.
[Comparative example 1]
Reagent with water equivalent (potency) of 3.0 mg H ₂ O/ml: Karl Fischer volumetric method reagent Aquamicron SS 3 mg (manufactured by Mitsubishi Chemical Corporation; iodine 1-5% by mass, sulfur dioxide 1-5% by mass, pyridine 12% by mass) , chloroform 81% by mass)
[Comparative example 2]
Reagent with water equivalent (potency) of 1.0 mg H ₂ O/ml: Karl Fischer volumetric method reagent Aquamicron SS 1 mg (manufactured by Mitsubishi Chemical Corporation; 1-5% by mass of iodine, 1-5% by mass of sulfur dioxide, 12% by mass of pyridine) , chloroform 83% by mass)
[Example 1]
Reagent with a water equivalent (potency) of 0.5 mg H ₂ O/ml: 250 μL of water was added to 500 ml of the above reagent with a titer of 1.0 mg H ₂ O/ml to prepare a reagent with a titer of 0.5 mg H ₂ O/ml. . [Example 2]
Reagent with a water equivalent (potency) of 0.3 mg H ₂ O/ml: 350 μL of water was added to 500 ml of the above reagent with a titer of 1.0 mg H ₂ O/ml to prepare a reagent with a titer of 0.3 mg H ₂ O/ml. .

Accuracy of measurement of water concentration in commercially available silicone oil KF-54 (manufactured by Shin-Etsu Chemical Co., Ltd.; water concentration 70 ppm, kinematic viscosity 400 mm ² /sec by vaporization analysis) using the above four reagents (repeated measurement 3 times) variation) was evaluated. Accuracy is evaluated by dividing the standard deviation of the water concentrations obtained by three measurements by the average value of the water concentrations, and the lower this value is, the better the accuracy is.
When measuring the water concentration, Karl Fischer volumetric titration type water measuring device CA-310 (manufactured by Mitsubishi Chemical Analytech) was used as the measuring device, and Aquamicron dehydrating solvent CP (manufactured by Mitsubishi Chemical, Chloroform 84) was used as the dehydrating solvent. % by mass, propylene carbonate 5 to 15 mass %, sulfur dioxide 1 to 5 mass %, 2-pyrrolidone 1 to 5 mass %, pyridine 2.4 mass %, and ethanol less than 1 mass %).
The measurement results of the moisture concentration and the accuracy evaluation results are shown in Table 1 below.

From Table 1 above, it can be seen that by lowering the titer of the reagent, the accuracy is better.

<Experiment 2>
Using the reagent of Comparative Example 2 with a titer of 1.0 mg H ₂ O/ml and the reagent of Example 1 with a titer of 0.5 mg H ₂ O/ml, KF-54 (manufactured by Shin-Etsu Chemical Co., Ltd.) with different kinematic viscosities and The table below shows the accuracy of water concentration measurement (variation due to 3 repeated measurements) when measuring the water content of three types of silicone oil of two grades of KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.) with different viscosities. Shown in 2.
Note that the kinematic viscosity of the silicone oil shown in Table 2 is the kinematic viscosity at 25° C. and is a catalog value.

Table 2 shows that, regardless of the difference in viscosity, Example 1 with a titer of 0.5 has better accuracy than Comparative Example 2 with a titer of 1.0.

As described above, according to the present invention, it is possible to provide a reagent that makes it possible to measure the moisture content of a sample with a low water concentration and a high kinematic viscosity by a volumetric titration method, and a moisture measurement method using the reagent. .

Claims (10)

A reagent for measuring water concentration,
The water concentration measuring reagent contains iodine and a basic substance , has a water equivalent of 0.9 mgH ₂ O/ml or less, and has a concentration of the basic substance of 1 to 13% by mass. A reagent for measuring water concentration , characterized by : The reagent for measuring water concentration according to claim 1, wherein the reagent for measuring water concentration is a Karl Fischer reagent further containing sulfur dioxide and a solvent. The reagent for measuring water concentration according to claim 2, wherein the basic substance is an imidazole compound or an amine compound. The reagent for measuring water concentration according to claim 3, wherein the basic substance is one or more selected from pyridine and pyridine derivatives. The reagent for measuring water concentration according to any one of claims 2 to 4 , wherein the solvent is an alcohol or a chloroform compound. A method for measuring moisture content, comprising a titration step of titrating the reagent for measuring moisture concentration according to any one of claims 2 to 5 with respect to a sample to be measured . The moisture measuring method according to claim 6 , wherein the moisture concentration of the sample to be measured is 500 ppm or less. The moisture measuring method according to claim 7 , wherein the kinematic viscosity of the sample to be measured at 25° C. is 800,000 mm ² /sec or less. The kinematic viscosity of the sample to be measured at 25°C is 100 to 100,000 mm. ² The moisture measuring method according to claim 8, which is /sec. The moisture measuring method according to any one of claims 6 to 9 , wherein the sample to be measured is selected from the group consisting of oil, resin, and pharmaceutical preparation.