JP2002257809A - Method and apparatus for detecting tetramethylammonium hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting tetramethylammonium hydroxide(TMAH) included in a liquid whereby the TMAH can be detected in a short time accurately and effects of foreign matter can be eliminated. SOLUTION: The method for detecting the TMAH included in the liquid includes a heating and decomposing process of heating thereby decomposing the TMAH, and a gas-phase detecting process of detecting trimethylamine as a byproduct of the heating and decomposition in a gas phase. The apparatus for detecting the TMAH included in the liquid has a heating and decomposing means for heating thereby decomposing the TMAH, and a gas-phase detecting means for detecting trimetylamine as a byproduct of the heating and decomposition in a gas phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for detecting tetramethylammonium hydroxide, which is a non-volatile and highly toxic quaternary amine.

[0002]

2. Description of the Related Art Tetramethylammonium hydroxide is a strongly alkaline water-soluble organic substance used for developing a photoresist and washing with an alkali in the production of semiconductors and liquid crystals. Since it is mainly used as a 2-3% aqueous solution, it is diluted with other washing water to become about 0.2-1% wastewater. Tetramethylammonium hydroxide is a substance that requires treatment due to its high toxicity, and a biological treatment method represented by an activated sludge method or a combustion method is generally applied. In these treatment methods, it is important to know the concentration of tetramethylammonium hydroxide in the wastewater in order to grasp the treatment characteristics.

The method of detecting tetramethylammonium hydroxide is limited to detection in a liquid phase because tetramethylammonium hydroxide is a non-volatile substance, and liquid ion chromatography is generally used. Specifically, only tetramethylammonium hydroxide is separated from other components by liquid chromatography, concentrated if necessary, ionized by oxidation, and the like, and the concentration is determined from a correlation with electrical conductivity and the like.

FIG. 5 shows a conventional method for detecting tetramethylammonium hydroxide. A sample 41 containing tetramethylammonium hydroxide is introduced into a chromatographic separation unit 42 in a liquid phase, separated from a coexisting substance by a difference in propagation speed in the chromatograph, and then separated into an ionization unit 4.
3 and is quantified by the measuring unit 44.

[0005] The first problem of the above-mentioned conventional method for detecting tetramethylammonium hydroxide is that detection requires a long time. The reason is that tetramethylammonium hydroxide is a stable quaternary amine, is non-volatile, and has no inherent characteristics that can be used for detection. This is because there is no detection method.

The second problem is that it is difficult to analyze at a low concentration of 0.1 mg / L or less. The reason is that chromatographic separation at a low concentration cannot be performed sufficiently. That is, if there is an amine or the like having a similar physical property as a contaminant and a similar diffusion rate in the chromatograph, an error occurs in the measurement due to the influence of the contaminant which cannot be sufficiently separated.

[0007]

DISCLOSURE OF THE INVENTION The present invention overcomes the above problems, provides a method for detecting tetramethylammonium hydroxide which can be detected in a short time and with high accuracy, and which can eliminate the influence of impurities. An object of the present invention is to provide an apparatus capable of suitably performing the method.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for detecting tetramethylammonium hydroxide contained in a liquid, comprising the steps of: heating and decomposing tetramethylammonium hydroxide; A method for detecting tetramethylammonium hydroxide, comprising a gas phase detection step of detecting trimethylamine as a substance in a gas phase.

In this method, trimethylamine and methanol are detected in the gas phase in the gas phase detection step, and a liquid containing tetramethylammonium hydroxide is sprayed in the heated gas phase in the thermal decomposition step. Preferably, the liquid is made alkaline in the thermal decomposition step.

Preferably, prior to the thermal decomposition step, the method further comprises a coexisting substance removing step of heating the liquid to 80 ° C. or more and less than 130 ° C. to volatilize and remove amines and methanol from the liquid. Background after detecting the trimethylamine and methanol contained in the liquid from which the amines and methanol obtained in the coexisting substance removal step have been removed in the gas phase after the coexisting substance removal step and before the thermal decomposition step. It is preferable to have a detection step.

The method of the present invention further comprises the step of oxidatively decomposing the tetramethylammonium hydroxide and the decomposition product generated by the thermal decomposition of the tetramethylammonium hydroxide, thereby obtaining tetramethylammonium hydroxide and the tetramethylammonium hydroxide required for detection. It is also preferable to have a detoxification step of detoxifying the decomposition product.

[0012] The present invention also provides a detecting device for tetramethylammonium hydroxide contained in a liquid, wherein the heating device decomposes the tetramethylammonium hydroxide by heating, and trimethylamine which is a product of the heat decomposition is used. An apparatus for detecting tetramethylammonium hydroxide, comprising a gas phase detecting means for detecting in a gas phase.

[0013] In the apparatus of the present invention, the gas phase detecting means may be means for detecting trimethylamine and methanol in a gas phase, and the thermal decomposition means may include means for spraying a liquid containing tetramethylammonium hydroxide. Preferably, it is provided.

The apparatus of the present invention further comprises a coexisting substance removing means for heating the liquid to 80 ° C. or more and less than 130 ° C. for volatilizing and removing amines and methanol from the liquid prior to the thermal decomposition step. It is preferable to have background detection means for detecting in a gas phase trimethylamine and methanol contained in the liquid from which the amines and methanol obtained by the coexisting substance removal means have been removed.

It is also preferred that the apparatus of the present invention further comprises an oxidative decomposition means for oxidatively decomposing the tetramethylammonium hydroxide and a decomposition product generated by thermal decomposition of the tetramethylammonium hydroxide.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for detecting tetramethylammonium hydroxide according to the present invention, tetramethylammonium hydroxide in a liquid is heated to decompose tetramethylammonium hydroxide into highly volatile trimethylamine and methanol. By detecting trimethylamine transferred to the phase, tetramethylammonium hydroxide is detected.

In the present invention, to detect means to know whether or not there is (the absence means being below the measurement limit) and to know the concentration.

In the present invention, it is preferable to detect methanol in addition to trimethylamine because the accuracy can be improved.

In order to thermally decompose tetramethylammonium hydroxide, it is sufficient to heat to a temperature sufficient to decompose tetramethylammonium hydroxide, for example, by heating a liquid containing tetramethylammonium hydroxide in a container or a tube. Alternatively, the liquid can be introduced into a container having a heated atmosphere inside. It is preferable that the inside of the container is set to a heating atmosphere, and the liquid sample is sprayed here. This is because the liquid becomes fine droplets, the liquid easily evaporates, and the tetramethylammonium hydroxide is thermally decomposed in a short time.

The heat decomposition temperature is preferably 130 ° C. or higher from the viewpoint of the decomposition rate, and 300 ° C. from the viewpoint of suppressing the decomposition product from decomposing into other substances.
Less than is preferred.

The pressure for the thermal decomposition is not particularly limited, but it is not necessary to apply pressure, and it is simple and preferable to carry out the reaction at normal pressure.

When tetramethylammonium hydroxide is thermally decomposed, trimethylamine and methanol are generated as decomposition products, which are transferred to the gas phase. In particular, trimethylamine is highly volatile and easily transitions from a liquid phase to a gas phase.

Next, in the gas phase detection step, methanol is detected in the gas phase in addition to trimethylamine, which is a product of thermal decomposition, or trimethylamine.

For detecting trimethylamine in the gas phase, known methods and means such as a measuring method using a polymer membrane and gas chromatography can be employed. To detect methanol in the gas phase, known methods and means such as a methanol colorimetric method and gas chromatography can be employed. Gas chromatography is preferred in that the concentration can be determined with good accuracy.

For example, knowing the amount of liquid to be charged and the volume of the gas phase inside the container, and determining the concentration of trimethylamine and methanol components in the gas phase in the gas phase detection step, the amount or concentration of tetramethylammonium hydroxide in the liquid can be determined. You can know.

In the thermal decomposition step, it is preferable to make the liquid containing tetramethylammonium hydroxide alkaline, from the viewpoint of promoting the volatilization of trimethylamine. In order to make the liquid alkaline, an alkaline substance such as sodium hydroxide, potassium hydroxide or the like may be added to the liquid. The pH of the liquid is 11
The above is preferable from the viewpoint of the effect of promoting volatilization.

Prior to the thermal decomposition step, the liquid is
When heated to 0 ° C. or higher and lower than 130 ° C., most of the volatile components shift from the liquid phase to the gas phase. Tetramethylammonium hydroxide remains in the liquid phase because it is a non-volatile substance. Therefore, amines and methanol can be volatilized and removed from the liquid, and deterioration of detection accuracy due to these coexisting substances can be prevented, which is preferable.

After the coexisting substance removing step and before the thermal decomposition step, trimethylamine and methanol contained in the liquid from which the amines and methanol obtained in the coexisting substance removing step have been removed are detected in the gas phase. Then, take background data, and then perform a thermal decomposition step, a gas phase detection step on the liquid obtained in the coexisting substance removal step to detect trimethylamine and methanol,
The amount of tetramethylammonium hydroxide can be known as the difference between the detection result after thermal decomposition and the background data, and this effect should be canceled even if there is a coexisting substance that could not be completely removed in the coexisting substance removal step. This is preferable since the detection accuracy can be further prevented from deteriorating due to trimethylamine and methanol originally contained in the sample solution.

In order to detect trimethylamine and methanol in the gas phase in the background detection step, for example, gas chromatography can be used.

The method of the present invention further comprises the step of oxidatively decomposing tetramethylammonium hydroxide and a decomposition product produced by the thermal decomposition of tetramethylammonium hydroxide, thereby obtaining tetramethylammonium hydroxide required for detection and the tetramethylammonium hydroxide. It is preferable to have a detoxification step of detoxifying decomposition products.

The method of performing the oxidative decomposition is not particularly limited as long as it can be oxidatively decomposed, but it is preferable to heat the decomposition product to 300 ° C. or higher together with an oxidizing agent. May be mixed and heated with a heater, or the above substance may be mixed with heated air or the like.

A preferred form of the detoxification step is to burn the liquid and gas that have been detected. Specifically, the liquid and gas that have been detected may be introduced into a flame such as a burner. By the combustion, the thermal decomposition of tetramethylammonium hydroxide and the oxidative decomposition of the decomposition product of tetramethylammonium hydroxide can be performed in a very short time.

By doing so, harmful substances such as tetramethylammonium hydroxide used for detection can be detoxified.

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a processing flow configuration diagram showing a preferred embodiment of the present invention.

The liquid sample 1 containing tetramethylammonium hydroxide is introduced into the coexisting substance removing means 2, and is heated at 80 ° C. or more and less than 130 ° C. under the supply of the heated air 3, so that the coexisting volatile Material is removed. Thereafter, the mixture is heated to 130 ° C. or higher by the heating air supply 5 in the thermal decomposition means 6 to completely decompose tetramethylammonium hydroxide into trimethylamine and methanol.

Since the decomposed trimethylamine and methanol are volatile, they are present in the gas phase. Trimethylamine and methanol in the gas phase are detected by the gas phase detecting means 7.

On the other hand, a part of the liquid from which the coexisting substance has been removed is introduced as background 4 into the gas phase detecting means 7 and detected. Here, the gas phase detection means also serves as the background detection means.

The apparatus of the present invention may be provided with an arithmetic means for automatically calculating the concentration of tetramethylammonium hydroxide in the liquid, which is the original sample, from the gas phase detection results of trimethylamine (and methanol). In this case, as the calculation means, for example, the concentrations of trimethylamine and methanol are input from the gas phase detection means,
Separately, the amount of the original liquid sample and the volume of the gas phase of the container for thermal decomposition are input, and the concentration of tetramethylammonium hydroxide in the liquid is calculated and output (displayed, printed out, etc.). Good.

The gaseous component having been analyzed together with the remaining liquid sample is supplied to the heating and burning unit 9 while receiving the heating air supply 8.
And is completely burned. It is preferable that not only the tetramethylammonium hydroxide and its decomposition product required for detection but also the substance removed by the coexisting substance removing means be rendered harmless by combustion.

Next, another embodiment of the present invention will be described in detail with reference to FIG.

A sample 11 containing only tetramethylammonium hydroxide in water is subjected to heat decomposition means 12
And supply heated air 13 to heat it to 130 ° C. or higher. Thereby, the tetramethylammonium hydroxide is completely decomposed into trimethylamine and methanol. The highly volatile trimethylamine and methanol are present in the gas phase. A gas containing trimethylamine and methanol is introduced into the gas phase detecting means 14 and detected by the gas phase detecting means.

Further, by adjusting the sample 11 in advance to a high alkali by adding sodium hydroxide or the like, even if the amount of tetramethylammonium hydroxide is very small, the generated trimethylamine is easily volatilized. This is preferable because it can be performed with high accuracy. Further, for example, in the path from the thermal decomposition means to the gas phase detection means, when the temperature decreases, the product of the thermal decomposition condenses together with moisture, and the condensation may reduce the measurement accuracy. At this time, when the water is acidic, the heat decomposition product is easily taken in by the water, but is hardly taken in when the water is alkaline. From such a viewpoint, it is preferable that the liquid is alkali.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

The difference from the embodiment shown in FIG. 2 is that the coexisting substance removing means 22 converts the liquid sample 21 to 80 ° C. or higher where tetramethylammonium hydroxide is not decomposed.
Heating at a temperature of less than 30 ° C., the liquid from which coexisting substances have been removed is used as background 24, and trimethylamine and methanol in this liquid are analyzed by gas phase detecting means 27, thereby reducing the influence of coexisting substances. This is particularly advantageous when there is a coexisting substance in the liquid sample because of the advantage of being able to do so.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

The difference from the embodiment shown in FIG. 2 is that trimethylamine, methanol, which is a decomposition product of tetramethylammonium hydroxide, and the remaining liquid sample are burned in the heating and burning section 36, whereby the sample itself is burned. There is an advantage that it can be completely harmless.

[0047]

The first effect of the present invention is that tetramethylammonium hydroxide can be detected in a short time. The reason is that when tetramethylammonium hydroxide is heated to 130 ° C or more, it is instantaneously decomposed into trimethylamine and methanol, and at the same time, under heating, due to its high volatility, trimethylamine and methanol easily transition to the gas phase. I do. In addition, in the gas phase, trimethylamine and methanol can be easily qualitatively and quantitatively determined.

The second effect of the present invention is that a low concentration of tetramethylammonium hydroxide can be detected. The reason is that trimethylamine generated by thermal decomposition of tetramethylammonium hydroxide easily volatilizes even in a very small amount, and can be easily analyzed in a gas phase.

Generally, the lower limit of quantification of tetramethylammonium hydroxide in the liquid phase is 0.1 mg / L by liquid chromatography, whereas the lower limit of quantification of trimethylamine in the gas phase is 1 μl / m ^{3 by} gas chromatography. It is. From 0.1 mg of tetramethylammonium hydroxide, 24.6 μl
Of trimethylamine is produced. Therefore, even if tetramethylammonium hydroxide of 0.1 mg / L or less, which is difficult to analyze by the conventional method, it can be detected by gas phase analysis with about 24 times the sensitivity if trimethylamine is used.

According to the present invention, a method for detecting tetramethylammonium hydroxide which is excellent in such a manner is provided, and an apparatus capable of suitably performing the method is provided.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a flowchart showing another embodiment of the present invention.

FIG. 3 is a flowchart showing another embodiment of the present invention.

FIG. 4 is a flowchart showing another embodiment of the present invention.

FIG. 5 is a flowchart showing a conventional method for detecting tetramethylammonium hydroxide.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Sample 2 Coexisting substance removing means 3 Air supply 4 Background 5 Air supply 6 Heat decomposition means 7 Gas phase detection means 8 Air supply 9 Heat combustion unit 11 Sample 12 Heat decomposition means 13 Air supply 14 Gas phase detection means 21 Sample 22 Coexistence Substance removing means 23 Air supply 24 Background 25 Air supply 26 Thermal decomposition means 27 Gas phase detection means 31 Sample 32 Thermal decomposition means 33 Air supply 34 Gas phase detection means 35 Air supply 36 Heat combustion unit 41 Sample 42 Chromatographic separation unit 43 Ionization Unit 44 Measurement unit

Claims (13)

[The claims] 1. A method for detecting tetramethylammonium hydroxide contained in a liquid, comprising: a heat decomposition step of heating and decomposing tetramethylammonium hydroxide; and trimethylamine as a product of the heat decomposition in a gas phase. A method for detecting tetramethylammonium hydroxide, comprising a gas phase detection step of detecting. 2. The method according to claim 1, wherein in the gas phase detecting step, trimethylamine and methanol are detected in a gas phase. 3. The method according to claim 1, wherein, in the thermal decomposition step, a liquid containing tetramethylammonium hydroxide is sprayed into a heated gas phase. 4. The method according to claim 1, wherein in the thermal decomposition step, the liquid is made alkaline. 5. A co-existing substance removing step of heating the liquid to 80 ° C. or more and less than 130 ° C. to volatilize and remove amines and methanol from the liquid prior to the thermal decomposition step. 4. The method according to claim 1. 6. After the coexisting substance removing step and before the thermal decomposition step, trimethylamine and methanol contained in the liquid from which the amines and methanol obtained in the coexisting substance removing step have been removed are vaporized. 6. The method according to claim 5, further comprising a background detection step of detecting with a background. 7. Tetramethylammonium hydroxide and its decomposition product required for detection by oxidatively decomposing the tetramethylammonium hydroxide and a decomposition product generated by thermal decomposition of the tetramethylammonium hydroxide. The method according to any one of claims 1 to 6, further comprising a detoxifying step of detoxifying the compound. 8. An apparatus for detecting tetramethylammonium hydroxide contained in a liquid, comprising: a heat decomposition means for heating and decomposing tetramethylammonium hydroxide; and trimethylamine, which is a product of the heat decomposition, in a gas phase. An apparatus for detecting tetramethylammonium hydroxide, comprising a gas phase detecting means for detecting by means of: 9. The gas phase detecting means for detecting trimethylamine and methanol in a gas phase.
The described device. 10. The apparatus according to claim 8, wherein said thermal decomposition means comprises means for spraying a liquid containing tetramethylammonium hydroxide. 11. A coexisting substance removing means for heating the liquid to 80 ° C. or more and less than 130 ° C. for volatilizing and removing amines and methanol from the liquid prior to the thermal decomposition step. The apparatus according to any one of claims 10 to 10. 12. The apparatus according to claim 11, further comprising background detection means for detecting in a gas phase trimethylamine and methanol contained in the liquid from which the amines and methanol obtained by said coexisting substance removal means have been removed. 13. An oxidative decomposition means for oxidatively decomposing the tetramethylammonium hydroxide and a decomposition product generated by thermal decomposition of the tetramethylammonium hydroxide.
The apparatus according to any one of claims 12 to 12.