JPS6267452A - Apparatus for measuring organic carbon in water - Google Patents

Abstract

PURPOSE:To measure a low-concentration organic carbon, by extracting carbon dioxide generated when organic carbon in water is oxidized, with limited gas extraction. CONSTITUTION:A sample water (a) fed by liquid feed pumps 1-a to 1-e is mixed with a potassium persulfate solution (b) and diluted sulfuric acid and the mixed liquid is sent continuously to a decarbonator 2, where helium d-1 is bubbled. Carbon dioxide in the mixed liquid is discharged and removed together with a helium gas as exhaust gas f-1. The mixture is sent by the pump 1-d to a reaction tube 3 kept at a constant pressure and temperature with a pressure adjustor 7 and a thermostatic vessel 4 to oxidize organic matters in the sample water (a) by potassium persulfate. Thereafter, the heated mixed liquid is mixed with helium d-2 in a carbon dioxide extractor 8 and furthermore, carbon dioxide formed is separated while being cooled by a cooling water 9 to be extracted into helium. Water in helium is separated with a water separator 10 and sent to a detector 11, with which the concentration of organic carbon is measured from the concentration of carbon dioxide in helium.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an apparatus for measuring organic carbon in water, and particularly to an apparatus for measuring organic carbon in water suitable for analyzing organic carbon in water with high sensitivity. .

[Background of the invention]

A conventional apparatus for measuring organic carbon in water consists of a means for oxidizing organic matter 'fr: to carbon dioxide, and a means for detecting the carbon dioxide. The method for oxidizing organic matter is the high-temperature oxidation method (JI
S KO102) and a mixed bath of sample water and oxidizing agent rf
A UV oxidation method using K ultraviolet rays is used. In addition, an ampoule containing sample water and reaction reagent and '11
A wet oxidation method (JISKO 102) in which the process is heated in an autoclave at 70C8 degrees is known, but it is not used much because the extraction of carbon dioxide produced from an ampoule is complicated. On the other hand, methods such as an infrared analysis method, a gas chromatography method, and a conductivity side-to-side method are used to quantify extracted carbon dioxide.

Examples of measuring devices for organic carbon in water include fS, mono? Carbon dioxide produced by high-temperature oxidation is ejected using infrared analysis, or carbon dioxide? Is it converted to methane and detected with a gas chromatograph equipped with a hydrogen ionization detector, or is it carbon dioxide generated by irradiating sample water with ultraviolet rays to oxidize organic matter? There are methods that detect it using infrared analysis, and methods that measure total conductivity by absorbing carbon dioxide into a solution.

However, the lower limit of quantification of organic carbon by these measuring devices is 10 to s o ppb, so when it is necessary to quantify organic carbon at even lower concentrations, such as in ultrapure water used in semiconductor manufacturing, etc., Improvements are needed. by the way,
In the high @ oxidation method, if the sample supply +# is increased in order to quantify low concentration organic carbon, a problem arises in that the oxidation catalyst tends to deteriorate.

Furthermore, in the UV oxidation method, a large amount of extraction gas is required to increase the extraction rate of generated carbon dioxide, so there is a problem that the concentration of carbon dioxide in the extraction gas becomes low. For this reason, organic matter is oxidized without using a solid oxidation catalyst, and carbon dioxide is generated. There is a strong demand for the development of a measuring device that can quantify low-concentration organic carbon by extracting with a small amount of extraction gas.

[Purpose of the invention]

An object of the present invention is to provide an apparatus for measuring organic carbon in water that can measure low-level agricultural organic carbon in water with high sensitivity.

[Summary of the invention]

The present invention aims at measuring low concentrations of organic carbon by extracting carbon dioxide produced when organic carbon in water is oxidized using as little extraction gas as possible to prevent the carbon dioxide concentration from decreasing. is important, and when extracting carbon dioxide with extraction gas, extracting carbon dioxide from water vapor or hot water is better than extracting carbon dioxide from water, even if the amount of extraction gas is reduced, the extraction rate will be higher. This method was developed with an eye to the fact that the sample water and reaction solution do not decrease, and includes an inorganic carbonation removal means that removes inorganic carbonate by transferring the sample water and reaction solution to a total inorganic carbonation removal tank, and the sample water and reaction solution from which inorganic carbonate has been removed. an organic substance oxidizing means for transferring the organic substances in the sample water to a reaction tube maintained at high temperature and high pressure and oxidizing the organic substances in the sample water with the reaction liquid; 2. Carbon extraction, in which carbon dioxide produced by oxidation of organic matter is extracted into the extracted gas by introducing a mixture of carbon dioxide and carbon dioxide, and cooled and separated from the hot water containing the water vapor. means, a moisture separation and removal means for separating moisture in the extracted gas, and a carbon dioxide detection means for detecting carbon dioxide in the extracted gas from which moisture has been separated and removed by the main separation and removal means,
Provided is an apparatus for measuring organic carbon in water, characterized in that the concentration of organic carbon in water is determined from the difference of 1 degree between the concentration of carbon dioxide when the reaction liquids are mixed and the concentration of carbon dioxide when the reaction liquids are not mixed. It's about doing.

[Embodiments of the invention]

Example 1 Figure 1 is a block diagram of the water organic carbon measuring device of the present invention.
2 is a liquid sending pump, 2 is a decarbonator that removes all the carbon dioxide dissolved in the sample water, 3 is a reaction tube that oxidizes the organic matter in the sample water a, 4 is a constant temperature bath that keeps the reaction tube 3 at a constant temperature, 5 is 1℃l
A temperature regulator for the hot tank 4, a pressure gauge 6 for monitoring the internal pressure of the reaction tube 3, and a pressure gauge 7 for keeping the pressure inside the tube higher than the water vapor pressure of the water so that the water does not turn into steam even when the temperature of the reaction tube 3 is increased. 91
4 pressure regulators, 8 a speciation carbon extractor for extracting carbon dioxide produced when organic matter is oxidized;
9 is cooling water for cooling the steam or hot water flowing into the carbon dioxide extractor 8; 10 is a moisture separator consisting of a U-shaped tube filled with magnesium perchlorate to remove moisture from the extracted gas; 11 is a gas chromatograph that detects carbon dioxide in extracted gas.

a is sample water, b is potassium persulfate solution to oxidize organic matter, C is dilute sulfuric acid to reduce the solubility of carbon dioxide in water, d is helium gas, and d-1 is to drive out carbon dioxide in sample water d-2 is an extraction gas for extracting the generated carbon dioxide gas, e is a drain, and f is an exhaust gas.

Sample water a sent by liquid sending pump l-a and liquid sending pump 1
Potassium persulfate solution 1b sent by -b and liquid pump l-
The dilute sulfuric acid sent in step c is mixed and sent continuously to the decarbonator 2, where helium d-1 is bubbled and carbon dioxide in the mixed liquid is discharged and removed together with helium gas as exhaust gas f-1. The mixed liquid from which carbon dioxide gas has been removed is fed to a constant pressure by the pressure regulator 7 and the constant temperature bath 4 using the liquid sending pump ld.

The organic matter in the sample water a is oxidized with perfCII potassium. Then a heated mixture containing water vapor and a constant flow of helium d-2
ft. A heated mixed liquid containing water vapor is mixed in a carbon dioxide extractor 8 and is separated while being cooled with cooling water 9.
The carbon dioxide produced is extracted into helium. Water in the helium from which carbon dioxide has been extracted is separated by a water separator 10, and the helium from which carbon dioxide has been extracted is sent to the detector 11, and the concentration of organic carbon in the sample water a is measured from the concentration of carbon dioxide in the helium. do.

According to the embodiment of the present invention described above, when extracting carbon dioxide generated by oxidizing organic carbon in sample water a,
Since the sample water is heated to hot water containing water vapor and supplied with helium d-2i, which is an extraction gas, a small amount of helium d-2 is sufficient for extraction.69
．． Helium d-2 with a high concentration of carbon dioxide can be obtained.

Therefore, low verticality organic carbon in sample water a can be measured with high accuracy.

Embodiment 2 FIG. 2 is another configuration diagram of the underwater M machine carbon measuring device of the present invention. The measuring device in FIG. 2 consists of the decarbonator 2 and liquid pump 1-d (i) in FIG. 1, which have been removed.
BP, in which potassium persulfate sent by liquid sending pump 1-b is mixed at regular intervals with the mixed solution with dilute sulfuric acid C sent by c,
The sample water a
Oxidize the organic matter in with potassium persulfate. Then a heated mixture containing water vapor and a constant flow of helium d
-2i The heated mixed liquid mixed in the carbon dioxide extractor 8 and stored in steam is separated while being cooled with cooling water 9, and the generated carbon dioxide is extracted into helium. Water in the helium from which carbon dioxide 2 has been extracted is separated by a moisture separator 10, and the helium from which carbon dioxide has been extracted is sent to the gas chromatograph 11. The concentration of organic carbon in sample water a is measured from the difference.

According to this example, the concentration of carbon dioxide in the extracted gas when potassium persulfate in the reaction db is fed is the concentration of carbon dioxide in the sample water a.
It corresponds to one time of organic carbon and inorganic carbon (CO2) in
Since the concentration of carbon dioxide in the reaction solution bf and the extracted gas when no liquid is fed corresponds to the concentration of inorganic carbon in sample water a, the organic carbon concentration in sample water a can be determined by finding the difference between the two. I can do it. Therefore, according to the embodiment of the present invention, the analysis time is short because there is no decarboxylation device, and helium can be saved because there is no bubbling, and it is effective for samples with low % inorganic carbon bankruptcy.

Example 3 FIG. 3 shows a chromatogram of the extracted gas analyzed by the apparatus of FIG. 1. FIG. 3 shows a chromatogram obtained when ion-exchanged water was analyzed as sample water a under the analytical conditions shown in Table 1. Carbon dioxide was detected at a retention time of 1.5 minutes, corresponding to an organic carbon concentration of about 40 ppb. This example shows that this device is effective as an analyzer for low concentration organic carbon.

Example 4 FIG. 4 shows a calibration curve obtained when analysis was performed using the analyzer of Example under the analysis conditions shown in Table 1. In order to create a calibration curve, it is necessary to prepare a standard solution with water that is not contaminated with organic carbon. ppb for pure water with high organic carbon concentration
Since it was not possible to create a calibration curve for vbell, I decided to purify water for convenience. Since the device of the present invention oxidizes organic matter in pure water, there should be no organic matter mixed in the deV/ from the dioxide US extractor 8, so this water is commonly used as a standard material for organic carbon. Added a certain amount of 7-tal cough hydrogen potassium, and the organic carbon concentration was 5~100
A standard solution was prepared to give ppb. This 42A
%liquid? 6j in Table 1:] Analyzed under fixed conditions.

Table 1 The test results showed linearity up to 100 ppb. This is a good method for analyzing this glaze. According to the above examples, it is understood that organic carbon in pure water (1 to 100 ppE) can be analyzed with high accuracy.

Example 5 When analyzed using the apparatus of Example under narrow 1 analysis conditions,
Analysis results of samples containing various organic substances (recovery rate of each organic substance)
are shown in Table 2. The calibration curve in Figure 4 is based on potassium hydrogen phthalate as the standard, but since devitrified pure water contains various types of organic substances, the slope of the calibration curve will differ depending on the type of organic substance. is possible. Therefore, various water-soluble organic substances were added to the drain of a carbon dioxide extractor to prepare sample water with a known organic carbon concentration, and this sample was analyzed to determine the recovery rate of organic carbon. The recovery rate was defined as the ratio between the added concentration of organic carbon and the detected concentration of carbon dioxide (detected concentration) obtained from the calibration curve diagram in FIG. The recovery rate of each organic substance is 95 to 106 cm, which is a nearly constant value regardless of the type of organic substance, indicating that even the samples shown in Table 2 can be analyzed using the detection line in Figure 4, even though various organic substances are mixed. Recognize.

Example 6 Shadow of reaction greenhouse on carbon dioxide concentration generated when analyzed using the analyzer of Example 1 under the analysis conditions shown in Table 1 #
The results of the investigation are shown in Figure 5. The pressure inside the reaction tube was set to be 10 kg/cm" higher than the saturated water vapor pressure of water at each temperature to prevent water from evaporating even at high temperatures. The sample water used was ion-exchanged water, but the produced COtt
The m degree shows a substantially constant value at 120C, indicating that the reaction is complete, and it is clear that the apparatus of the present invention is effective as a method for oxidizing organic matter in pure water and converting it into carbon dioxide.

Example 7 Table 3 shows the results of examining repeatability in Experiment 5 when analysis was performed using the analyzer of Example 1 under the analysis conditions shown in Table 1. The average value of organic carbon concentration is 5.36 and 57.04
The repeat accuracy at ppb was 3.5% and 1.6% in relative standard deviation. 5 Table 4 1) Since it was not possible to obtain a sample with a concentration of 5 pb or less,
It was not possible to experimentally confirm the degree of repeatability below ppb. However, since the standard deviation at 1 ppb is considered to be about the same as at 5 ppb, the coefficient of variation can be estimated to be 19 chi. This example shows that 1 ppb of organic carbon in pure water can be quantified with an analytical accuracy of 20% or less.

Example 8 Table 4 shows a comparison of the analysis results when analyzed using the analyzer of Example 1 and Example 20 shown in FIG.

Both results are in good agreement, and it can be seen that both Example 1 and Example 2 are effective as methods for analyzing low-concentration organic carbon.

Example 9 A chromatogram of hydrogen, oxygen, and nitrogen in the extracted gas when analyzed using the analyzer of Example 2 is shown in FIG.

This result was obtained when Molecular Sheep 5A (inner diameter 3 holes, outer diameter 4 holes, length 2 m) was used as a gas chromatograph packing material. According to this example, it can be seen that the analyzer shown in FIG. 2 is also effective as an analyzer for hydrogen, oxygen, and nitrogen in water.

〔Effect of the invention〕

As explained above, according to the present invention, low concentration organic carbon in water can be measured with high precision, and the present invention has the advantage that it is suitable as an apparatus for measuring organic carbon in ultrapure water.

[Brief explanation of drawings]

Figures 1 and 2 are block diagrams showing an example of an apparatus for measuring organic carbon in water, Figure 3 is a chromatogram of extracted gas, Figure 4 is a calibration curve, and Figure 5 is temperature dependence on oxidation reaction. Figure 6 shows hydrogen. It is a chromatogram diagram of oxygen and nitrogen.

Claims (1)

[Scope of Claims] 1. An inorganic carbonation removing means for transferring the sample water, acidic solution and reaction liquid to an inorganic carbonation removal tank to remove inorganic carbonic acid; an organic substance oxidizing means for transferring the mixed liquid to a reaction tube maintained at high temperature and high pressure and oxidizing the organic substances in the sample water with the reaction liquid; and hot water containing the water vapor in which the organic substances from the organic substance oxidizing means have been oxidized. and carbon dioxide extraction means for cooling and separating the hot water containing water vapor while extracting carbon dioxide generated by oxidation of organic matter into the extraction gas by feeding an extraction gas into a mixed liquid of and a moisture separation/removal means for separating moisture in the extracted gas, and a carbon dioxide detection means for detecting carbon dioxide in the extracted gas from which moisture has been separated and removed by the moisture separation/removal means. Features: A measuring device for organic carbon in water. 2. A reaction liquid is added at regular intervals to a mixed solution of sample water and an acidic solution, and the mixture is transferred to a reaction tube maintained at high temperature and pressure, and the organic substances in the sample water are oxidized with the reaction liquid. an oxidizing means, and an extraction gas is fed into a mixed solution of carbon dioxide and hot water containing the steam in which the organic matter from the organic matter oxidizing means has been oxidized, and the carbon dioxide generated by the oxidation of the organic matter is transferred to the extraction gas. a carbon dioxide extraction means that cools and separates the hot water containing water vapor while extracting it; a water separation and removal means that separates water from the extracted gas; and a water separation and removal means that separates water by the water separation and removal means. A carbon dioxide detection means detects carbon dioxide in the removed extracted gas, and detects organic A water organic carbon measuring device that measures carbon.