JP2010216943A - Method and device for measuring concentration of dissolved nitrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for measuring the concentration of dissolved nitrogen, capable of easily and accurately measuring the concentration of dissolved nitrogen in water to be measured. <P>SOLUTION: The method for measuring the concentration of dissolved nitrogen includes a dissolved hydrogen removing step of removing dissolved hydrogen in the water to be measured; and a measurement step of measuring the concentration of dissolved nitrogen in the water to be measured by a thermal conductivity type detector 12 after the dissolved hydrogen removing step. In the dissolved hydrogen removing step, dissolved hydrogen in the water to be measured is preferably removed by making a platinum group catalyst contact with the water to be measured, and this step may include an oxygen addition step of adding oxygen into the water to be measured. A device for measuring the concentration of dissolved nitrogen 10 includes a dissolved hydrogen removing means 11 for removing dissolved hydrogen in the water to be measured; the thermal conductivity type detector 12; and a hydrogen removed water supplying tube 14 for supplying the water treated by the dissolved hydrogen removing means 11 to the thermal conductivity type detector 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for measuring dissolved nitrogen concentration and an apparatus for measuring dissolved nitrogen concentration.

  Conventionally, ionic components, organic matter, fine particles, water for use in various fields such as semiconductor manufacturing fields such as electronic devices, pharmaceutical manufacturing fields, power generation fields such as nuclear power and thermal power, various industries such as food industry and research facilities, etc. Ultrapure water from which impurities such as bacteria are highly removed is used. In particular, a lot of ultrapure water is used in the cleaning process for manufacturing electronic components such as electronic devices. In the manufacturing process of an electronic device, in order to remove impurities such as fine particles, metal impurities, and organic substances from the surface of the electronic device substrate, the substrate surface is washed with ultrapure water. In this cleaning, not only ultrapure water but also so-called functional water in which nitrogen gas, hydrogen gas, ozone gas or the like is dissolved in ultrapure water to enhance the cleaning effect may be used.

  In general, as a method for producing functional water, a method is known in which a gas is dissolved in degassed water through a gas dissolution module using a semipermeable membrane. For functional water, it is required to control the dissolved gas concentration to a predetermined concentration with high accuracy. Moreover, a gas dissolution module may be provided in the ultrapure water production apparatus (subsystem) to always supply ultrapure water in which dissolved nitrogen is controlled. In response to such demands for ultrapure water and functional water, for example, in a method for producing functional water using a gas dissolution module, the pressure of the gas that extrudes condensed water and the amount of condensed water that is extruded are maintained in a predetermined relationship. Thus, an invention that can always supply functional water having a stable dissolved gas concentration has been proposed (for example, Patent Document 1). The dissolved gas concentration of the produced functional water is measured by various detectors, and the dissolved nitrogen concentration is measured by using a thermal conductivity type detector equipped with a thermal conductivity detection terminal (TCD). It is common.

JP 2007-185559 A

However, ultrapure water and functional water are required to further improve the accuracy of dissolved gas concentration. In order to satisfy this requirement, it is necessary to analyze the dissolved nitrogen concentration of ultrapure water and the dissolved gas concentration of functional water with high accuracy. In some cases, the thermal conductivity detector cannot accurately measure the dissolved nitrogen concentration of ultrapure water or functional water that is the water to be measured.
Then, this invention aims at the measuring method of the dissolved nitrogen concentration which can measure the dissolved nitrogen concentration of to-be-measured water simply and correctly, and the measuring apparatus of dissolved nitrogen concentration.

  A general ultrapure water or functional water production line may be configured to supply a plurality of functional water according to the specifications at each use point. When ultrapure water produced in such a production line is used as hydrogen water and is supplied to some use points, facilities are provided to return excess hydrogen water that could not be consumed at those use points to the ultrapure water production line. There may be. In such an ultrapure water production line, even if a degassing device is provided, it is difficult to remove dissolved hydrogen. For this reason, possibility that dissolved hydrogen will be contained in ultrapure water or functional water becomes high.

  Ultrapure water is often provided with an ultraviolet oxidizer for the purpose of oxidizing and removing organic substances in the production process. In the treatment with such an ultraviolet oxidizer, there is a concern that the generated hydrogen may be dissolved in the ultrapure water and the dissolved hydrogen may remain in the ultrapure water or functional water supplied to the use point.

Here, when dissolved hydrogen exists in the water to be measured, the TCD of the thermal conductivity detector measures the thermal conductivity of the hydrogen gas in addition to the thermal conductivity of the nitrogen gas, and the thermal conductivity of the nitrogen gas and the hydrogen gas A value obtained by adding the thermal conductivity of is output as a signal. The thermal conductivity of hydrogen is extremely large compared to the thermal conductivity of nitrogen. The thermal conductivity of hydrogen is 0.1815 W · m ⁻¹ · K ⁻¹ , whereas the thermal conductivity of nitrogen is 0. 02598 W · m ⁻¹ · K ⁻¹ . Due to such a difference in thermal conductivity, the measured value of the dissolved nitrogen concentration in a system in which dissolved hydrogen is present in the water to be measured is extremely higher than the actual dissolved nitrogen concentration. That is, the presence of dissolved hydrogen in the water to be measured becomes a large error factor in the measurement of the dissolved nitrogen concentration.

  In the ultrapure water and nitrogen water produced in the production line as described above, the present inventors remove the dissolved hydrogen in the water to be measured as much as possible, thereby further reducing the dissolved nitrogen concentration with a thermal conductivity detector. The knowledge that it can measure with high accuracy was acquired. And the dissolved hydrogen in to-be-measured water was removed by the simple method, the method which can measure exact dissolved nitrogen concentration was discovered, and it came to the following invention.

  That is, the method for measuring the dissolved nitrogen concentration of the present invention includes a dissolved hydrogen removing step for removing dissolved hydrogen in the water to be measured, and a dissolved nitrogen concentration in the water to be measured by a thermal conductivity detector after the dissolved hydrogen removing step. And a measuring step for measuring. The dissolved hydrogen removal step preferably removes dissolved hydrogen from the water to be measured by bringing the water to be measured into contact with the platinum group catalyst, and may include an oxygen addition step of adding oxygen to the water to be measured.

  The apparatus for measuring dissolved nitrogen concentration of the present invention comprises a dissolved hydrogen removing means for removing dissolved hydrogen in water to be measured, a thermal conductivity detector, and water detected by the dissolved hydrogen removing means for detecting the thermal conductivity. Means for supplying to the vessel.

  According to the method for measuring dissolved nitrogen concentration and the apparatus for measuring dissolved nitrogen concentration of the present invention, the dissolved nitrogen concentration of water to be measured can be measured easily and accurately.

It is a schematic diagram which shows an example of the measuring apparatus of the dissolved nitrogen concentration of this invention. It is a schematic diagram explaining the measurement principle of the thermal conductivity type detector used for this invention. It is a schematic diagram which shows the experimental apparatus used for the Example and the comparative example.

(Measurement device for dissolved nitrogen concentration)
The present invention will be described with reference to FIGS. 1 and 2, but the present invention is not limited to this. FIG. 1 is a schematic diagram of a dissolved nitrogen concentration measuring device (hereinafter referred to as a dissolved nitrogen concentration measuring device) 10. FIG. 2 is a schematic diagram for explaining the measurement principle of the thermal conductivity detector 12.

  As shown in FIG. 1, the dissolved nitrogen concentration measuring device 10 includes a dissolved hydrogen removing unit 11, a thermal conductivity detector 12, and a dehydrogenated water supply pipe 14. A measured water supply pipe 22 is connected to the measured water circulation pipe 20 for extracting the measured water from the measured water circulation pipe 20 as a sample. The measured water supply pipe 22 is connected to the dissolved hydrogen removing means 11 via the valve 24, and the dehydrogenated water supply pipe 14 is connected to the dissolved hydrogen removing means 11. The dehydrogenated water supply pipe 14 conducts heat so that the measured water from which dissolved hydrogen has been removed by the dissolved hydrogen removing means 11 (hereinafter also referred to as dehydrogenated water) is introduced into the sample chamber 102 (FIG. 2). A degree detector 12 is connected. The thermal conductivity detector 12 is connected to a drain port (not shown) by a drain pipe 16.

  “Means for supplying water treated by the dissolved hydrogen removing means to the thermal conductivity detector” is the dehydrogenated water supply pipe 14.

  The dissolved hydrogen removing means 11 is not particularly limited as long as it is an apparatus that can remove dissolved hydrogen in the water to be measured. The dissolved hydrogen removing means 11 is preferably a packed tower packed with a platinum group catalyst. This is because dissolved hydrogen can be easily removed by bringing the water to be measured into contact with the platinum group catalyst.

When a packed tower packed with a platinum group catalyst is used as the dissolved hydrogen removal means 11, the shape of the platinum group catalyst to be packed is not particularly limited, and examples thereof include powders, granules, and pellets.
A known technique can be used as the platinum group catalyst. For example, a material in which a platinum group such as palladium (Pd) or platinum (Pt) is supported on a carrier such as an ion exchange resin, alumina, activated carbon, or zeolite can be used. Among these, it is preferable to use a catalyst having metal Pd supported on a carrier. As the carrier, an anion exchange resin is preferably used. The catalyst using the anion exchange resin as a carrier is stable for a long period of time without contaminating the thermal conductivity detector 12 because it can be obtained by suppressing the mixing of impurities to the extent that it can be applied to the production line of ultrapure water. This is because it can be measured.

  The thermal conductivity detector 12 is a thermal conductivity detector using TCD. As the thermal conductivity type detector, an existing one can be used, and examples thereof include a dissolved nitrogen meter (511 / E T1C0P00J) manufactured by Hack Ultra Co., Ltd.

  An example of the configuration of the thermal conductivity detector 12 will be described with reference to FIG. As shown in FIG. 2, the thermal conductivity detector 12 is roughly configured by a sample chamber 102, a measurement chamber 110, a purge gas supply source 120, an amplifier 130, and a controller 132. In the sample chamber 102, an adjacent measurement chamber 110 is provided via a diaphragm 104 through which only gas passes. A purge gas supply line 122 and a gas discharge line 114 are connected to the measurement chamber 110. The purge gas supply line 122 is connected to the purge gas supply source 120 via a valve 124. The gas discharge line 114 is connected to an exhaust gas port (not shown). A TCD 112 is provided in the measurement chamber 110, and the TCD 112 is connected to the amplifier 130. The amplifier 130 is connected to the controller 132, and the controller 132 is connected to the valve 124.

(Measurement method of dissolved nitrogen concentration)
The method for measuring the dissolved nitrogen concentration of the present invention includes a dissolved hydrogen removing step for removing dissolved hydrogen in the water to be measured, and a measured conductivity of the measured water by a thermal conductivity detector after the dissolved hydrogen removing step. Measuring step.

  The method for measuring the dissolved nitrogen concentration will be described taking as an example the case where the dissolved hydrogen removing means 11 is a packed tower packed with a platinum group catalyst. First, the valve 24 is opened, and the measured water in the measured water circulation pipe 20 is supplied from the measured water supply pipe 22 to the dissolved hydrogen removing means 11. The water to be measured supplied to the dissolved hydrogen removing means 11 circulates in contact with the platinum group catalyst in the packed tower. During this time, when dissolved hydrogen exists in the water to be measured, the dissolved hydrogen is removed by the following two reactions. First, the dissolved hydrogen in the water to be measured is removed by the reaction of dissolved oxygen or the like of the water to be measured with the reaction of the following formula (1) (catalytic reaction). Secondly, dissolved hydrogen in the water to be measured is adsorbed on the platinum group catalyst (adsorption reaction) and removed. In the adsorption reaction, even if the dissolved hydrogen concentration in the water to be measured is stoichiometrically larger than the dissolved oxygen concentration in the water to be measured, platinum group metals such as Pd and Pt can adsorb the dissolved hydrogen. During the period, dissolved hydrogen in the water to be measured can be removed.

2H ₂ + O ₂ → 2H ₂ O (1)

  In this way, when dissolved hydrogen is contained in the water to be measured, the dissolved hydrogen is removed and becomes dehydrogenated water that flows out from the dehydrogenated water supply pipe 14 (dissolved hydrogen removing step).

  The dehydrogenated water that has flowed into the dehydrogenated water supply pipe 14 is supplied to the thermal conductivity detector 12, and the dissolved nitrogen concentration of the dehydrogenated water is measured by the thermal conductivity detector 12 (measuring step).

  A method for measuring the dissolved nitrogen concentration by the thermal conductivity detector 12 will be described with reference to FIG. First, the valve 124 is opened, purge gas (carbon dioxide gas, argon gas, etc.) of the purge gas supply source 120 is supplied from the purge gas supply line 122 to the measurement chamber 110, and the measurement chamber 110 is filled with the purge gas. In this state, the TCD 112 measures the thermal conductivity of the purge gas and outputs the measured value to the amplifier 130 as a signal. At this time, since the inside of the measurement chamber 110 is filled with a specific purge gas, the signal output from the TCD 112 to the amplifier 130 is stable with the thermal conductivity of the purge gas. The signal output from the TCD 112 is sent to the controller 132 via the amplifier 130. In the controller 132, when the signal output from the TCD 112 is stable, that is, when the purge in the measurement chamber 110 is completed, the valve 124 is closed and the supply of the purge gas to the measurement chamber 110 is stopped.

  When dehydrogenated water is supplied to the sample chamber 102 in a state where the measurement chamber 110 is filled with the purge gas, dissolved nitrogen in the dehydrogenated water passes through the diaphragm 112 and moves to the measurement chamber 110. When nitrogen gas moves from the sample chamber 102 to the measurement chamber 110, the purge gas in the measurement chamber 110 is discharged to the gas discharge line 114 by the transferred nitrogen gas. The TCD 112 measures the thermal conductivity according to the nitrogen gas concentration in the measurement chamber 110, and outputs the measured value as a signal to the controller 132 via the amplifier 130. The speed at which the purge gas in the measurement chamber 110 is replaced with nitrogen gas is proportional to the nitrogen partial pressure of the dissolved gas in the sample chamber 102. For this reason, the controller 132 obtains the nitrogen partial pressure in the sample chamber 102 from the change rate of the signal output from the TCD 112, and based on the obtained nitrogen partial pressure, the dissolved nitrogen concentration in the dehydrogenated water, that is, the water to be measured. The dissolved nitrogen concentration is required.

  The water to be measured is all water to be measured for dissolved nitrogen concentration, for example, pure water such as ultrapure water or nitrogen water in which nitrogen gas is dissolved in the pure water, hydrogen in which hydrogen gas is dissolved in pure water Examples thereof include functional water such as ozone water in which ozone is dissolved in water or pure water. Especially, this invention can be used suitably for the ultrapure water and nitrogen water which are required to manage dissolved nitrogen concentration with high precision. In addition, in the dissolved hydrogen removal step in the present invention, the dissolved nitrogen concentration in the water to be measured does not change. Therefore, the water to be measured is not only water that always contains dissolved hydrogen, such as hydrogen water, but also water that does not contain dissolved hydrogen, such as ultrapure water, nitrogen water, or dissolved hydrogen that may be mixed irregularly. There may be.

  When a packed tower packed with a platinum group catalyst is used as a means for removing dissolved hydrogen in the dissolved hydrogen removal step, the residence time of the water to be measured in the packed tower is determined by the catalyst conditions such as the type of catalyst, the amount of catalyst, and the measured value. It can be determined in consideration of dissolved hydrogen concentration and dissolved oxygen concentration in water. Moreover, the temperature of the water to be measured in the dissolved hydrogen removal step is not particularly limited, but is preferably determined in the range of 10 to 50 ° C. This is because the catalytic reaction can be performed efficiently within the above temperature range. In addition, when using an anion exchange resin as a support | carrier, it is preferable to set it as 60 degrees C or less from a heat resistant viewpoint of an anion exchange resin.

  The concentration of dissolved hydrogen in the dehydrogenated water obtained through the dissolved hydrogen removal step is not particularly limited. For example, the dissolved hydrogen concentration in the dehydrogenated water is preferably 2 mass ppb or less, and more preferably 1 mass ppb or less.

  As described above, by providing the dissolved hydrogen removing step of the present invention, the dissolved nitrogen concentration can be measured in the measuring step after removing the dissolved hydrogen from the water to be measured. For this reason, the dissolved nitrogen concentration of the water to be measured can be measured easily and with high accuracy by the thermal conductivity detector. In addition, the dissolved hydrogen removal step can remove the dissolved hydrogen efficiently without bringing about complicated operations by bringing the measured water into contact with the platinum group catalyst to remove the dissolved hydrogen. it can.

(Other embodiments)
The method for measuring the dissolved nitrogen concentration of the present invention is not limited to the above-described embodiment.
In the method for measuring dissolved nitrogen concentration using a packed tower packed with a platinum group catalyst as the dissolved hydrogen removing means 11 in the dissolved nitrogen concentration measuring apparatus 10, an oxygen addition step of adding oxygen to the water to be measured supplied to the packed tower. May be provided. Examples of the oxygen addition step include a method of adding an arbitrary amount of oxygen from the oxygen cylinder to the measured water supply pipe 22. Even if the dissolved hydrogen concentration of the water to be measured is high by adding an excess oxygen to the water to be measured with respect to the dissolved hydrogen concentration of the water to be measured, the platinum group catalyst can dissolve the dissolved hydrogen. Can be removed continuously. In addition, since oxygen has an extremely small influence on the measured value of the dissolved nitrogen concentration at the thermal conductivity detector 12 compared with hydrogen, even if it is excessively added to the dissolved hydrogen to be removed, the dissolved nitrogen concentration The measured value can maintain high accuracy. Moreover, when providing an oxygen addition process, the frequency which adds oxygen to to-be-measured water is not specifically limited, For example, while measuring the dissolved nitrogen concentration, you may always add or add intermittently. Also good. Even when the water to be measured contains dissolved hydrogen in excess of dissolved oxygen, dissolved hydrogen can be removed for a certain period by the above-described adsorption reaction. Then, before the hydrogen adsorption amount to the platinum group catalyst is saturated and dissolved hydrogen leaks from the dissolved hydrogen removing means 11, oxygen is appropriately added to the water to be measured, so that the platinum group catalyst is expressed by the following formula (1). It can be regenerated by catalytic reaction. For this reason, by intermittently adding oxygen, the adsorption reaction and catalytic reaction of the platinum group catalyst can be repeated, and dissolved hydrogen can be removed over a long period of time.

2H ₂ + O ₂ → 2H ₂ O (1)

  In the above-described embodiment, the measured water is supplied from the measured water circulation pipe 20 to the dissolved hydrogen removing means 11 through the measured water supply pipe 22, but the present invention is not limited to this, and the measured water is stored in a water storage tank or the like. A water supply pipe 22 may be connected.

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

(Experimental device)
FIG. 3 is a schematic diagram showing an experimental apparatus 200 of the example and the comparative example. The experimental apparatus 200 includes a primary pure water supply source 202, a subsystem 240, a dissolved nitrogen concentration measuring apparatus 10, a first gas dissolution module 284, and a second gas dissolution module 294.

  The subsystem 240 is a system for producing ultrapure water by further increasing the purity of primary pure water. The subsystem 240 includes a primary pure water tank 242, a pump 244, a heat exchanger 246, a first degassing device 248, an ultraviolet oxidation device 250, a first non-regenerative ion exchange device (hereinafter referred to as CP) 252, a final filter ( A (UF membrane) device 254 is arranged and configured to circulate ultrapure water.

  The primary pure water tank 242 is connected to the primary pure water supply source 202. A branch pipe 251 is provided on the secondary side of the ultraviolet oxidation apparatus 250, and the branch pipe 251 is connected to the second CP 260. The second CP 260 is connected to the second degassing device 262, and the second degassing device 262 is connected to the first gas dissolving module 284 and the second gas dissolving module 294. The hydrogen cylinder 280 is connected to the first gas dissolution module 284 via the first mass flow controller 282. The oxygen cylinder 290 is connected to the second gas dissolution module 294 via the second mass flow controller 292. The first gas dissolution module 284 and the second gas dissolution module 294 are connected to a microfiltration (MF) membrane device 266. The MF membrane device 266 is connected to a drain port (not shown) by the measured water circulation pipe 20, and the measured water supply pipe 22 including the valve 24 is connected to the measured water circulation pipe 20. A dissolved nitrogen concentration measuring device 10 is connected to the measured water supply pipe 22. The dissolved nitrogen concentration measuring apparatus 10 is connected by a dehydrogenated water supply pipe 14 so that the measured water supplied from the measured water supply pipe 22 flows through the dissolved hydrogen removing means 11 and the thermal conductivity detector 12 in order. Has been. The thermal conductivity detector 12 is connected to a drain pipe 16.

  The primary pure water supply source 202 is a primary pure water system that combines an ion exchange device, an MF membrane device, a reverse osmosis membrane device, and the like.

  As the heat exchanger 246, a plate-type heat exchanger was used.

  Membrane deaerators were used for the first deaerator 248 and the second deaerator 262.

  As the ultraviolet oxidizer 250, an ultraviolet oxidizer that irradiates ultraviolet rays having a wavelength of around 185 nm was used.

  As the first CP 252 and the second CP 260, those filled with an ion exchange resin as a mixed bed form of a cation exchange resin and an anion exchange resin were used.

  For the first gas dissolution module 284 and the second gas dissolution module 294, SEPAREL EF002A manufactured by Dainippon Ink & Chemicals, Inc. was used.

  As the first mass flow controller 282 and the second mass flow controller 292, MC-3102E-NC type mass flow controller manufactured by Lintec Corporation was used.

  According to the above specifications, the sub-system 240 can obtain ultrapure water having a specific resistance of 18.1 MΩ · cm or more and a TOC of 2 ppb or less at the outlet of the MF membrane device 266. The specific resistance is a value measured using a specific resistance meter (AQ-11, manufactured by Toa Decay Co., Ltd.). TOC is a value measured using a TOC meter (A-1000XP, manufactured by ANATEL).

(Dissolved hydrogen removal means)
As the dissolved hydrogen removing means 11, a Pd packed tower in which 300 mL of palladium (Pd) resin was packed in a layer height of 60 cm was used. The Pd resin has a moisture retention capacity of 60 to 70% on the basis of OH type, and 970 mg-Pd / LR of Pd in a gel type I strongly basic anion exchange resin (Pd supported amount per 1 L of resin (mg)) The supported one was used. Further, 95% or more of the total exchange capacity of the gel-type anion exchange resin was adjusted to be in the OH form.

(Thermal conductivity detector)
For the thermal conductivity detector 12, a DO / DN meter (model-3621, manufactured by Hack Ultra Co., Ltd.) was used.

(Experimental example 1)
Using the experimental apparatus 200 described above, the primary pure water supplied from the primary pure water supply source 202 to the subsystem 240 was converted into ultrapure water by the subsystem 240 according to a conventional method. While producing ultrapure water, the water extracted from the branch pipe 251 was treated with the second CP 260 and then deaerated with the second deaerator 262 to obtain deaerated water. A part of the degassed water is supplied to the first gas dissolving module 284, and hydrogen gas is supplied from the hydrogen cylinder 280 to the first gas dissolving module 284 to obtain hydrogen dissolved water in which hydrogen is dissolved in the degassed water. It was. In addition, a part of the degassed water is supplied to the second gas dissolving module 294, and oxygen gas is supplied from the oxygen cylinder 290 to the gas dissolving module 294, and oxygen dissolved water in which oxygen is dissolved in the deaerated water is supplied. Obtained. After the obtained hydrogen-dissolved water and oxygen-dissolved water were mixed, the water was circulated from the MF membrane device 266 to the measured water flow pipe 20 and drained. The dissolved nitrogen concentration of the water to be measured was stable at 0.9 to 1.3 mass ppm (steady state) when hydrogen dissolution was not performed. Note that the amount of hydrogen supplied to the gas dissolution module 284 was adjusted by the first mass flow controller 282 so that the dissolved hydrogen concentration of the water to be measured increased with time. The measured water was collected from the measured water flow pipe 20 at an arbitrary time, and the dissolved nitrogen concentration and the dissolved oxygen concentration were measured by a DO / DN meter (model-3621, manufactured by Hack Ultra Co., Ltd.). The results are listed in Table 1.
The dissolved hydrogen concentration of the water to be measured was calculated from the amount of water flow to the MF membrane device 266 and the amount of hydrogen gas supplied by the first mass flow controller 282 (the same applies hereinafter).

Example 1
A part of the degassed water treated in the same manner as in Experimental Example 1 is supplied to the first gas dissolving module 284, and hydrogen gas is supplied from the hydrogen cylinder 280 to the first gas dissolving module 284 to obtain degassed water. Hydrogen-dissolved water in which hydrogen was dissolved was obtained. In addition, a part of the degassed water is supplied to the second gas dissolution module 294, and oxygen gas is supplied from the oxygen cylinder 290 to the second gas dissolution module 294 to dissolve oxygen in the deaerated water. Dissolved water was obtained. The obtained hydrogen-dissolved water and oxygen-dissolved water were mixed and then passed through the MF membrane device 266 to obtain water to be measured having a dissolved hydrogen concentration of 11 mass ppb. Subsequently, a part of the obtained water to be measured is introduced into the dissolved nitrogen concentration measuring device 10 from the measured water supply pipe 22 and the flow rate is 120 L / h (SV = 400 (SV = 400 (SV) to the Pd packed tower (dissolved hydrogen removing means 11)). / H)), and the dissolved hydrogen removal step was performed. Here, SV is represented by a flow rate (L / h) that is circulated in one hour with respect to a unit volume (L) of the Pd resin. After the dissolved hydrogen removal step, the dissolved nitrogen concentration of the water to be measured was measured by the thermal conductivity detector 12. These operations are performed twice, and the measurement results are shown in Table 2 together with the measurement results of the dissolved oxygen concentration.

(Example 2)
Except that hydrogen gas was not dissolved in the degassed water, the dissolved nitrogen concentration and dissolved oxygen concentration of the water to be measured were measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

(Comparative Example 1)
Except that the measured water was not passed through the Pd packed tower, the dissolved nitrogen concentration and dissolved oxygen concentration of the measured water were measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

(Reference Example 1)
Except that the measured water was not passed through the Pd packed tower, the dissolved nitrogen concentration and dissolved oxygen concentration of the measured water were measured in the same manner as in Example 2, and the measurement results are shown in Table 2.

  As shown in Table 1, in Experimental Example 1, although the dissolved nitrogen concentration in the measured water was 0.9 to 1.3 ppm by mass, the dissolved nitrogen concentration increased as the dissolved hydrogen concentration in the measured water increased. The measured value also increased. From this, it was found that when the dissolved nitrogen concentration of the water to be measured in which dissolved hydrogen exists was measured with a thermal conductivity detector, a large error occurred with respect to the actual dissolved nitrogen concentration.

  As shown in Table 2, in Examples 1 and 2 in which dissolved nitrogen concentration was measured with a thermal conductivity detector after passing through a Pd packed tower to remove dissolved hydrogen, the dissolved nitrogen concentration was 1.1 to 1 The measured value was 3 ppm by mass. Considering that the actual dissolved nitrogen concentration of the water to be measured is 0.9 to 1.3 ppm by mass, Examples 1 and 2 are independent of the presence or absence of dissolved hydrogen before passing through the Pd packed tower. It can be estimated that the dissolved nitrogen concentration of the water to be measured can be accurately measured. On the other hand, in Comparative Example 1 where the dissolved nitrogen concentration was measured with a thermal conductivity detector without passing water to be measured having a dissolved hydrogen concentration of 1.1 × 10 mass ppb through the Pd packed tower, The measured values were 6.9 mass ppm and 7.2 mass ppm. From this, it is possible to measure the dissolved nitrogen concentration accurately and simply by passing the water to be measured through the Pd packed tower to remove the dissolved hydrogen and then measuring the dissolved nitrogen concentration with a thermal conductivity detector. understood.

DESCRIPTION OF SYMBOLS 10 Measurement apparatus of dissolved nitrogen concentration 11 Dissolved hydrogen removal means 12 Thermal conductivity type detector 14 Dehydrogenated water supply pipe

Claims (4)

  A dissolved hydrogen removal step for removing dissolved hydrogen in the water to be measured; and a measurement step for measuring the dissolved nitrogen concentration in the water to be measured by a thermal conductivity detector after the dissolved hydrogen removal step. Measuring method.   The method for measuring a dissolved nitrogen concentration according to claim 1, wherein the dissolved hydrogen removal step removes dissolved hydrogen from the water to be measured by bringing the water to be measured into contact with a platinum group catalyst.   The measuring method of the dissolved nitrogen concentration of Claim 2 which has an oxygen addition process which adds oxygen to to-be-measured water.   Dissolved nitrogen having dissolved hydrogen removing means for removing dissolved hydrogen in water to be measured, a thermal conductivity detector, and means for supplying water treated by the dissolved hydrogen removing means to the thermal conductivity detector Concentration measuring device.

Images