JP3274809B2 - Method for analyzing elements in alcohol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel method for analyzing metalloid elements in alcohol. Specifically, a metalloid element which is present in a small amount in alcohol and can form a compound with alcohol, that is, arsenic, boron, germanium, and silicon (hereinafter, collectively referred to as “specific impurities”) is accurately quantified. Is a possible analytical method.

[0002]

2. Description of the Related Art In the semiconductor industry, which is becoming more and more highly integrated in recent years, alcohols such as isopropyl alcohol (hereinafter also referred to as IPA) used in precision cleaning and drying processes are required to have high purity, and strict impurity control is required. Has been requested.

Conventionally, as an analytical method for quantifying trace metal elements in alcohol, a method of evaporating to dryness and then dissolving with hydrochloric acid or nitric acid for quantification has been carried out.

However, the specific impurities form a low-boiling compound with alcohol and volatilize with the alcohol during the evaporation process, so that it cannot be quantitatively recovered in the residue after evaporation to dryness.

Although it is not clear what kind of compound the specific impurities and alcohol form, it is presumed to be an ester compound such as arsenate, borate, germanate and silicate.

[0006] Therefore, for the purpose of eliminating the formation of the compound, there has been proposed a method in which a complexing agent such as mannitol and tartaric acid is coexistent and evaporated to dryness.

[0007]

However, in the method using a complexing agent, not only the volatilization of a specific impurity cannot be sufficiently prevented, but also a large amount of the complexing agent coexists with the sample introduction system. Clogging is liable to occur, and it cannot be measured by a high-sensitivity analyzer such as an inductively coupled plasma mass spectrometer (ICP-MS) due to the interference effect of the complexing agent, and the lower limit of quantification is as low as about 10 ppb. Was. Therefore, there is a problem that it cannot be used for quality control analysis of a chemical solution for the semiconductor industry that requires a high-purity chemical solution.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the behavior of specific impurities during the evaporation of alcohol containing the specific impurities. As a result, it has been found that by performing an evaporation operation in the presence of a specific amount of water in alcohol, the compound is effectively hydrolyzed, and the specific impurities can be quantitatively recovered in the aqueous phase. It was completed.

According to the present invention, an alcohol containing a metalloid element capable of forming a compound with the alcohol is added with an amount of water in which substantially only an aqueous phase remains by evaporation, and then substantially only an aqueous phase remains. A method for analyzing elements in alcohols, comprising performing an evaporation operation until the water phase and analyzing the elements present in the aqueous phase.

The sample to be analyzed to which the method of the present invention is applied is not particularly limited as long as it is alcohol. For example, isopropyl alcohol, methanol, ethanol and the like can be mentioned. In particular, it is suitably used for isopropyl alcohol which forms an azeotropic composition with water.

[0011] In the semiconductor industry, quality control of alcohols such as IPA used in precision cleaning and drying processes is the most typical example of the application requiring the analysis method.

As the metalloid element capable of forming a compound with the alcohol to be analyzed in the present invention, arsenic, boron, germanium, and silicon are typical.

A feature of the method of the present invention resides in that an evaporation operation is performed after an amount of water in which substantially only an aqueous phase remains by evaporation is added to the alcohol containing the specific impurities. Since the specific amount of such water varies depending on the type of alcohol, it cannot be unconditionally limited.

Therefore, it may be determined appropriately for each alcohol to be analyzed. For example, with respect to IPA, water is added so as to have an azeotropic composition with water (water 12% by weight, IPA 88% by weight) in an amount exceeding the water ratio, particularly preferably 15 to 25% by weight. Good.

However, if the amount of water to be added is excessively large, a large amount of energy for evaporating to dryness is required in the analysis described later, which is not economical. Therefore, it is desirable to keep the upper limit of adding water within the above range.

It is desirable that the water to be added has as high a purity as possible. In general, ultrapure water is used. In addition,
In the present invention, the ultrapure water has a specific resistance of 18 MΩ ·
Particles having a size of 1 cm / ml or more and 0.2 μm or more are used.

In the present invention, the operation of evaporating the alcohol to which water has been added is generally carried out by heating the mixture in a container. The container is not particularly limited as long as it does not substantially elute ions. In order to prevent loss due to adsorption of specific impurities to the vessel wall, a material having water repellency is preferably used. Suitable materials include, for example, Teflon, polycarbonate and the like.

The heating may be performed under normal pressure, reduced pressure or increased pressure. In this case, if the evaporation rate is too high, the mist containing the specific impurities is scattered together with the vapor, and therefore it is desirable to adjust the evaporation rate to such an extent that such scatter does not occur.

In the above-mentioned evaporation operation, most of the specific impurities are present in the aqueous phase when only the aqueous phase remains in the vessel.

Therefore, the specific impurities in the aqueous phase may be analyzed by a known method. Illustrating a typical analysis method, the aqueous phase is a known analyzer,
For example, arsenic, boron, and germanium are quantitatively analyzed by an inductively coupled plasma mass spectrometer (ICP-MS) or an inductively coupled plasma emission spectrometer (ICP-AES), and silicon is quantitatively analyzed by an electrically heated atomic absorption spectrophotometer. The method is general. Of course, in the analysis method of the present invention, it is possible to analyze the alcohol of interest even if other elements are present.

[0021]

As will be understood from the above description, according to the present invention, arsenic, boron, germanium, and silicon contained in alcohol are each quantitatively recovered in the aqueous phase, and the sample to be analyzed is water. Therefore, analysis using a conventionally used high-sensitivity analyzer becomes possible, and a trace amount of the element can be accurately quantified.

[0022]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 200 ml of commercially available IPA was sampled, and then the specific resistance was 18
A standard sample was prepared by adding 40 ml of ultrapure water containing particles of MΩ · cm or more and 0.2 μm or more per particle / ml or less.

Next, 200 ml of the above IPA was sampled, 40 ml of ultrapure water was added, and then 10 ng each of arsenic, boron and germanium and 200 ng of silicon were added to prepare a test sample.

Each of the above two samples is 300 ml in volume.
And the evaporation operation was performed until only 1 to 2 ml of the aqueous phase remained.

The resulting aqueous phase was made up to 10 ml with ultrapure water, and arsenic, boron and germanium were measured by an ICP mass spectrometer, and silicon was measured by an electric heating atomic absorption spectrophotometer.

Table 1 shows the analysis values of the standard sample and the test sample.

Further, the difference between the specific elements of the standard sample and the test sample was compared with the amount of addition, determined as a recovery rate by the following formula, and also shown in Table 1.

Recovery (%) = difference (ng) / addition amount (ng) × 100

[0030]

[Table 1]

Comparative Example 1 200 ml of commercially available IPA similar to that of Example 1 was taken and used as a standard sample.
Then, 10 ng of each of arsenic, boron, and germanium and 200 ng of silicon were added thereto to prepare a test sample.

The standard sample and the test sample were each placed in a Teflon container having a volume of 300 ml, and evaporated to dryness. 10 ml of nitric acid was added to dissolve the dried product, and arsenic, boron and germanium were dissolved in ICP Silicon was measured with a mass spectrometer using an electrically heated atomic absorption spectrophotometer.

Table 1 shows the analysis values of the standard sample and the test sample.

The difference between the specific element of the standard sample and that of the test sample was compared with the amount of addition and determined as a recovery rate by the following equation.

Recovery (%) = difference (ng) / addition amount (ng) × 100

[0036]

[Table 2]

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Claims (1)

(57) [Claims] 1. An alcohol containing a metalloid element capable of forming a compound with an alcohol is added with an amount of water in which substantially only an aqueous phase remains by evaporation, and then evaporated until substantially only an aqueous phase remains. A method for analyzing an element in an alcohol, comprising performing an operation and analyzing the element present in the aqueous phase.