Analysis system and analysis method

Abstract

To more precisely measure the concentration of a trace amount of metal contained in treated water.SOLUTION: An analysis system 300 for analyzing a metal concentration of a liquid includes a pretreatment device 100 for decomposing an organic substance contained in the liquid, and a measurement device 200 for measuring the metal concentration of the liquid in which the organic substance is decomposed by the pretreatment device 100.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an analytical system and an analytical method. [Background technology]

[0002] The metal concentration in ultrapure water is used as one of the indicators for evaluating the quality of ultrapure water used for cleaning in semiconductor manufacturing. Analytical devices typically used to measure metal concentration use a portion of ultrapure water produced by a secondary pure water production system, known as a subsystem, as a sample to measure the metal concentration in the sample. One method for analyzing metal concentration is to measure the ion concentration in a target liquid that has been concentrated using an ion exchange membrane (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-45351 Summary of the Invention [Problem to be solved by the invention]

[0004] When measuring the metal concentrations in treated water, such as ultrapure water, where the metal concentration is at the ppt level, even a small error can significantly affect the water quality assessment. Therefore, precise measurement of the metal concentrations in treated water is necessary. The analytical method described in Patent Document 1 assumes that the metals in treated water are ionized and uniformly dispersed throughout the treated water. In actual treated water, in addition to ionized metals, metals may also exist in a stable state by bonding with metal particles or other elements, resulting in metals that are not uniformly dispersed throughout the treated water. When the target metal element for concentration measurement is in an unionized state, quantitative analysis is impossible because the metal element is not uniformly dispersed throughout the treated water. Therefore, there is a problem in that it is difficult to precisely measure the concentrations of extremely small amounts of metals in treated water.

[0005] An object of the present invention is to provide an analytical system and analytical method that can more precisely measure the concentration of trace amounts of metals contained in treated water. [Means for solving the problem]

[0006] The analytical system of the present invention comprises: 1. An analytical system for analyzing a metal concentration in a liquid, comprising: a pretreatment device for decomposing organic matter contained in the liquid; and a measuring device for measuring the metal concentration of the liquid obtained by decomposing the organic matter in the pretreatment device.

[0007] The analytical method of the present invention further comprises: a pretreatment process for decomposing organic matter contained in the liquid; A measuring step is carried out in which the metal concentration of the liquid in which the organic matter has been decomposed in the pretreatment step is measured. [Effects of the Invention]

[0008] In the present invention, the concentration of trace amounts of metals contained in treated water can be measured precisely. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a water treatment system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating an example of components included in a subsystem. [Figure 3] 1 is a diagram showing an analysis system 300 according to the present embodiment. [Figure 4] FIG. 2 is a schematic diagram of a part of the interior of the measuring device. [Figure 5] 10 is a flowchart illustrating an analysis method in the analysis system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiments of the present invention will be described below with reference to the drawings. The analytical system according to this embodiment is a system for analyzing ultrapure water produced in a subsystem (secondary pure water production system) provided in a water treatment system (ultrapure water production system or ultrapure water production equipment). FIG. 1 is a diagram showing the water treatment system according to this embodiment. As shown in FIG. 1, the water treatment system according to this embodiment includes a pretreatment system 1, a primary pure water production system 2, and a subsystem 3. The pretreatment system 1, the primary pure water production system 2, and the subsystem 3 are connected in series in this order in the flow direction of the water to be treated (e.g., service water). The pretreatment system 1 includes water treatment devices such as a raw water tank, a filter, and a filtered water tank. The primary pure water production system 2 includes water treatment devices such as a cation exchange resin tower, a decarbonation tower, an anion exchange resin tower, a pure water tank, a degassing membrane, and a reverse osmosis membrane (RO membrane) device. Subsystem 3 is equipped with water treatment equipment such as a primary pure water tank, ultraviolet (UV) oxidation equipment, non-regenerative ion exchange resin equipment (CP), and ultrafiltration membrane (UF membrane) equipment, and produces secondary pure water (ultrapure water) from the primary pure water produced in the primary pure water production system 2. The ultrapure water produced in subsystem 3 has, for example, anion and metal concentrations at the ppt level (less than 10 ppt).

[0011] Fig. 2 is a diagram showing an example of components included in the subsystem 3. As shown in Fig. 2, the subsystem 3 includes a primary pure water tank 30, a pump 31, a heat exchanger 32, an ultraviolet (UV) oxidation device 33, a non-regenerative ion exchange resin device (CP) 34, a membrane degassing device 35, and an ultrafiltration membrane (UF membrane) device 36.

[0012] The primary pure water produced in the primary pure water production system 2 is stored in a primary pure water tank 30. The water to be treated (primary pure water) stored in the primary pure water tank 30 is pumped out by a pump 31 and supplied to a heat exchanger 32. The water to be treated, whose temperature has been adjusted by passing through the heat exchanger 32, is supplied to an ultraviolet oxidation device 33 where it is irradiated with ultraviolet light, thereby decomposing total organic carbon (TOC) in the water to be treated. The water to be treated is then subjected to ion exchange treatment in a non-regenerative ion exchange resin device 34 to remove ionic components such as metal ions. The water to be treated from which ionic components have been removed is then subjected to membrane degassing device 35 to remove dissolved gases, and then subjected to an ultrafiltration membrane device 36 to remove fine particles. In this embodiment, the ultrapure water obtained in this manner is analyzed by an analysis system 300.

[0013] 3 is a diagram showing an analysis system 300 according to this embodiment. As shown in FIG. 3, the analysis system 300 according to this embodiment includes a pretreatment device 100 and a measurement device 200.

[0014] The pretreatment device 100 is a device that decomposes organic matter contained in the liquid to be measured (for example, ultrapure water produced by the subsystem 3 shown in FIG. 1). The pretreatment device 100 according to this embodiment decomposes organic matter contained in the liquid to be measured by a thermal acid decomposition treatment. The thermal acid decomposition treatment will be described in detail later. In this embodiment, the pretreatment device 100 decomposes the organic matter contained in the liquid to be measured by a thermal acid decomposition treatment, and ionizes metals bonded to the organic matter. In this way, a liquid to be measured can be obtained in which metals that are bonded to other organic matter and not ionized are also ionized.

[0015] The measuring device 200 measures the metal concentration contained in the measurement target liquid that has been subjected to thermal acid decomposition treatment in the pretreatment device 100. Examples of metals whose concentrations are to be measured include sodium (Na), calcium (Ca), and tin (Sn). At least a portion of the measurement target liquid that has been subjected to thermal acid decomposition treatment in the pretreatment device 100 is introduced into the measuring device 200 as a sample. The measuring device 200 measures the ion mass of the metal ions contained in the introduced sample. The measuring device 200 calculates the metal concentration based on the measured ion mass (response value) and a calibration curve calculated in advance using a standard solution. Examples of measuring devices that can be used for the measuring device 200 include inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry, and ion chromatography.

[0016] FIG. 4 is a schematic diagram of a portion of the interior of the measuring device 200. As shown in FIG. 4, the measuring device 200 has an inlet section 210, a path 220, and an analytical section 230. The inlet section 210 is a section that introduces at least a portion of the measurement target liquid that has been subjected to thermal acid decomposition treatment in the pretreatment device 100 as a sample. The inlet section 210 introduces the sample atomized using, for example, a nebulizer into the measuring device 200. The path 220 is a flow path that guides the sample introduced into the inlet section 210 to the analytical section 230. The analytical section 230 measures the metal concentration as described above. Note that the path 220 may be provided with a component that applies high energy to the sample introduced into the inlet section 210 to turn it into a plasma state.

[0017] The analysis method in the analysis system according to this embodiment will be described below: Fig. 5 is a flowchart for explaining the analysis method in the analysis system according to this embodiment.

[0018] First, the pretreatment device 100 performs a pretreatment step of subjecting the liquid to be measured to a thermal acid decomposition treatment (step S1). Specifically, acid is added to the liquid to be measured, and microwaves are applied to the liquid to which the acid has been added. If the liquid to be measured has an impurity concentration below the lower limit of quantitation, the pretreatment device 100 heats and concentrates the liquid to which the acid has been added, adds acid to the concentrate obtained by the heat concentration, and irradiates the concentrate to which the acid has been added with microwaves. Alternatively, the pretreatment device 100 passes the water to be measured through an adsorbent (impurity adsorbent) to adsorb and concentrate the impurities in the adsorbent, then passes an eluent (acid solution) through the adsorbent to elute the impurities, and irradiates the eluent containing the eluted impurities with microwaves. The eluent used here functions as the acid added in the thermal acid decomposition treatment. Alternatively, if the liquid to be measured has an impurity concentration not below the lower limit of quantitation, the pretreatment device 100 adds acid to the liquid to be measured and irradiates it with microwaves. The acid to be added can be selected based on the properties of the analytical sample, and examples include nitric acid and hydrochloric acid. For microwave irradiation, for example, the eluent or the measurement target liquid to which the acid has been added is placed in a container and placed in a microwave irradiation device, and the microwave irradiation amount is controlled so that the temperature of the measurement target liquid reaches a predetermined temperature within a predetermined time. While microwave heating is used as an example of the heating method for the thermal acid decomposition treatment in this embodiment, for example, if the measurement target liquid contains a larger amount of organic matter than ultrapure water, a heating method using a gas burner or a hot plate can also be used.

[0019] Next, the measuring device 200, which will be described below, performs the measurement step. The introduction section 210 of the measuring device 200 introduces, as a sample, at least a portion of the ultrapure water irradiated with microwaves by the pretreatment device 100 (step S2). The sample introduced into the introduction section 210 reaches the analysis section 230 via the path 220, and the analysis section 230 measures the mass of metal ions contained in the sample (step S3). Then, the analysis section 230 calculates the concentration of metal ions contained in the sample based on the measured mass of the metal ions (step S4).

[0020] The pre-processing step and the measurement step are independent steps, i.e., the measurement step may be performed consecutively after the pre-processing step, or the pre-processing step and the measurement step may be performed discontinuously (at timings unrelated to each other).

[0021] When organometallic compounds used in manufacturing components that come into contact with ultrapure water leach into the ultrapure water, conventional methods have been found to be unable to accurately determine the metal concentrations in the sample. For example, if the sample introduced into the inlet 210 contains organic matter, the organic matter adheres to the inside of the measuring device 200, including the inlet 210 and the path 220, leading up to the analytical device 230. As a result, at least some of the metals that are not ionized and bound to the organic matter cannot reach the analytical device 230. This phenomenon is evident when a sample that has not been irradiated with microwaves (i.e., the organic matter has not been decomposed) is introduced into the measuring device 200 and analyzed, and then a cleaning solution (e.g., a nitric acid solution) is introduced through the inlet 210 to clean the inlet 210 and the path 220. This phenomenon is evident when a metal concentration (e.g., tin concentration) exceeding the specified concentration is detected in the analytical device 230. Therefore, if the sample introduced into the inlet 210 contains organic matter, the analytical device 230 cannot accurately determine the metal concentration in the sample. Examples of organic substances include dimethyltin compounds and dibutyltin compounds.

[0022] Therefore, as in this embodiment, the liquid to be measured is subjected to a thermal acid decomposition treatment in the pretreatment device 100, which decomposes the organic matter contained in the liquid to be measured and ionizes the metals bound to the organic matter. Then, in the measuring device 200, the liquid to be measured is measured, in which the metals bound to the organic matter and not ionized have also been ionized. This makes it possible to more precisely measure the concentration of trace amounts of metals contained in the liquid to be measured (for example, ultrapure water produced in subsystem 3). [Explanation of symbols]

[0023] 1 Pretreatment System 2. Primary pure water production system 3 Subsystems 30 Primary pure water tank 31 Pump 32 Heat exchanger 33 Ultraviolet oxidation equipment 34 Non-regenerative ion exchange resin device 35 Membrane degassing device 36 Ultrafiltration device 100 Pretreatment device 200 Measuring Equipment 210 Introduction 220 Routes 230 Analysis Department 300 Analysis System

Claims

1. 1. An analytical system for analyzing a metal concentration in a liquid, comprising: a pretreatment device for decomposing organic matter contained in the liquid; and a measuring device for measuring the metal concentration of the liquid in which the organic matter has been decomposed by the pretreatment device.

2. 10. The analysis system according to claim 1, The pretreatment device is an analytical system that irradiates the liquid with microwaves to decompose organic matter contained in the liquid.

3. 3. The analysis system according to claim 2, The liquid is an analytical system obtained by passing an eluent through an adsorbent that has adsorbed metals contained in ultrapure water produced by an ultrapure water production apparatus.

4. 3. The analysis system according to claim 2, The liquid is an analytical system obtained by adding an acid solution to ultrapure water produced by an ultrapure water production apparatus.

5. 3. The analysis system according to claim 2, The liquid is an analytical system obtained by heating ultrapure water produced in an ultrapure water production apparatus and then adding an acid solution.

6. The analysis system according to any one of claims 1 to 5, The measuring device is an introduction section for introducing, as a sample, at least a portion of the liquid obtained by decomposing organic substances in the pretreatment device; an analysis unit that measures the ion mass of metal ions contained in the sample introduced by the introduction unit and calculates the metal concentration based on the measured ion mass and a pre-calculated calibration curve.

7. 7. The analysis system according to claim 6, The introduction section is an analytical system that introduces the sample in a mist form.

8. a pretreatment process for decomposing organic matter contained in the liquid; and a measuring step of measuring the metal concentration in the liquid in which the organic matter has been decomposed in the pretreatment step.

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