JP2009244283A - Method of measuring water and aqueous solution with ultraviolet ray - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To identify water containing micro amounts of various dissolved components. <P>SOLUTION: A method of measuring an aqueous solution with ultraviolet ray includes: preliminarily measuring an ultraviolet spectroscopic spectrum for each of a plurality of standard aqueous solutions in a prescribed wavelength range at the longer wavelength side of an absorption peak at around 160 nm of the water; and then measuring the ultraviolet spectroscopic spectrum of an aqueous sample solution containing the microamount of component in the prescribed wavelength range to determine whether the ultraviolet spectroscopic spectrum of the aqueous sample solution is in agreament with the ultraviolet spectroscopic spectrum of which standard aqueous solution. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to identification and quantitative analysis of water or water-soluble components.

  In the discrimination / quantitative analysis of water or water-soluble components, spectroscopic analysis is widely used as a very effective means. The spectroscopic analysis methods are roughly classified into ultraviolet-visible spectroscopy, near-infrared spectroscopy, and infrared spectroscopy depending on the measurement wavelength region.

  In particular, in near-infrared spectroscopy, an absorption spectrum reflecting water-specific hydrogen bonds is remarkably observed at 800 nm to 1400 nm. For example, JP-A-3-175341 discloses a method for measuring dissolved components in water using this spectrum. Proposed. Water molecules are hydrogen bonded to each other in the liquid state, but when other dissolved components are mixed in water, the hydrogen bond state changes very sensitively. Then, by examining the state of the change, it becomes possible to quantitatively analyze the mixed components. More specifically, when an inorganic electrolyte is ionized in an aqueous solution, hydrogen bonds are broken or distorted between water molecules in the vicinity of ions and bulk water molecules generated by ion hydration, and water molecules are generated by the electric field of ions. Due to the influence of the polarization of water, the bonding state of water molecules themselves and the bonding state of water-bonded water molecules are affected, and the near-infrared absorption spectrum differs from that of pure water. Therefore, by calibrating the change in advance, the concentration of ionic species having no absorption spectrum in the near infrared can be determined from the change in the absorption spectrum of water.

  For example, in today's semiconductor manufacturing process, circuit miniaturization advances and the concentration of the inorganic electrolyte in the chemical solution used tends to decrease accordingly. In addition, from the viewpoint of environmental problems related to waste liquid treatment, component analysis at a very low concentration is required. However, the absorption spectrum of water appearing in the near infrared is inherently forbidden transition and weakly absorbed, and the concentration of trace components cannot be measured. Therefore, it is necessary to measure the concentration of a very small amount of dissolved component for which a significant difference cannot be obtained in the near-infrared spectrum.

As will be described later, the present invention uses far-ultraviolet spectroscopy, but JP-A-3-220452 describes a method for determining hydrogen peroxide in coexistence with ammonia or sodium hydroxide using the absorbance of ultraviolet light. Has been. What is measured here is a hydrogen peroxide concentration of 0 to 10% by weight, an ammonia concentration of 0 to 15% by weight, and a sodium hydroxide concentration of 0 to 8% by weight. We do not analyze trace components.
JP-A-3-175341 JP-A-3-220452

  An object of the present invention is to enable identification of water containing various trace amounts of dissolved components using the absorption spectrum of water appearing in the far ultraviolet.

  The absorption spectrum due to the n → σ * transition of water having a peak near 160 nm shifts to the longer wavelength side due to the effect of the electric field formed between the water itself and the hydrated ion dissolved in the water, and part of the spectrum is The aqueous solution is identified by utilizing the fact that it appears in a region that can be measured with a regular spectrometer (a spectrometer that does not require vacuum).

  In the aqueous solution measurement method using ultraviolet light according to the present invention, the wavelength dependence of the ultraviolet spectrum of a plurality of standard aqueous solutions is determined within a predetermined wavelength range (for example, a range of 180 to 210 nm) on the long wavelength side of the absorption peak near 160 nm of water. Measure in advance. Next, the ultraviolet spectrum of the aqueous solution sample containing a trace component is measured in a predetermined wavelength range, and it is determined which standard aqueous solution the ultraviolet spectrum of the aqueous solution sample matches.

  It is possible to clearly identify which standard aqueous solution the ultraviolet spectrum of the aqueous solution sample matches with.

Water spectrum Graph showing how the ultraviolet spectrum changes with respect to the temperature change of pure water Graph showing the state of water spectrum change in nitrite aqueous solution Diagram of ultraviolet spectrometer Far ultraviolet spectra of distilled water and 8 aqueous solutions

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In general, in the spectroscopic analysis using visible / ultraviolet rays, the absorption spectrum extends to the energy level of the electronic transition of the substance to be measured, so that it involves a much larger energy change than the absorption spectrum of near infrared rays. The history of spectroscopic analysis using this fact is deep, and it has been applied to qualitative and quantitative analysis of various luminescent groups. Today, the spectrum of most chromophores is known. As described above, UV-visible spectroscopy has been widely used, but has been applied only to solutions having an absorption band in the 200 nm to 800 nm region. For example, nitrate ions (NO ₃ ²⁻ ) and nitrite ions (NO ₂ ⁻ ) in precipitation are known to have absorption peaks at 201 nm and 210 nm, respectively, and detection and measurement using those wavelengths are performed. ing.

By the way, the water molecule has an unpaired electron in the oxygen atom in the molecule, and this unpaired electron can participate in the covalent bond with other molecules, and the antibonding property formed at that time An energy change in the ultraviolet region called an n → σ ^* transition is accompanied with the molecular orbital σ ^* . The absorption spectrum of water is known to have a peak at a wavelength of 167.0 nm in a gas state, and shows a peak around 160 nm in a liquid. However, no attempt has been made so far to detect or measure substances dissolved in water using the absorption spectrum of the water itself. This is because when the amount of the component dissolved in the water is very small, it is obvious that the main component is water, and it is obvious that the change in the absorption amount of the spectrum of the water itself due to the mixing of the trace component is negligibly small. .

The inventor of the present invention pays attention to the fact that the energy required for the n → σ ^* transition of water shows an inherent change in the hydrated ion in a state where the dissolved component is hydrated in water. The state of change of n → σ ^* transition spectrum of water related to ions was systematically investigated. As a result, in a state where the dissolved component is hydrated in water, the electric field of the hydrated ions affects the bottom of the absorption peak near 160 nm due to the n → σ ^* transition (with a 180 to 210 nm common spectrometer). Ascertaining that the intensity, position, and band width of the absorption band appearing in the measurable region change very sensitively to hydrogen bonding and hydration of water, and use this for the identification and quantitative analysis of aqueous solutions. It was proved that it was possible to measure the concentration of trace components dissolved in water and the change in water quality. That is, the absorption spectrum due to the n → σ ^* transition of water has a very steep slope in the wavelength region of 180 nm to 210 nm as shown in FIG. 1, but the position of this slope changes the state of water. Even if the concentration of the substance dissolved in water is very small, and the magnitude of the absorption peak of water hardly changes, a slight shift in the spectrum can cause the state of the change to be 10 ³ to. It will be magnified 10 ⁵ times and reflected.

Example 1: Temperature change in the ultraviolet spectrum of pure water.
The ultraviolet spectrum of pure water changes with temperature. For example, the ultraviolet spectrum shown in FIG. 2 shows the bottom of the absorption of water having a peak near 160 nm when the temperature of pure water is changed at eight temperatures every 5 ° C. within the range of 20 ° C. to 55 ° C. It is an absorption spectrum of. As the temperature of pure water rises and the hydrogen bond strength of water itself is relaxed, the ultraviolet spectrum shifts to the longer wavelength side, and the water spectrum in this region reflects changes in the bonding state between water molecules. It shows that.

Example 2: Change in the ultraviolet spectrum of water due to a trace amount of dissolved components.
Moreover, the ultraviolet spectrum of water changes with respect to the concentration of a very small amount of components dissolved in water. For example, FIG. 3 shows a measurement example of the change in the far ultraviolet spectrum of water found in an aqueous nitrite ion solution. Here, sodium nitrite is dissolved in pure water at 25 ° C. at a concentration of 20 μmol / l within a range of 20 μmol / l to 200 μmol / l. As the concentration of sodium nitrite increases, the amount of absorption at the absorption peak (wavelength 210 nm) of nitrite ions (NO ₂ ⁻ ) increases, while the absorption in the region of 190 nm to 200 nm is proportional to the increase in nitrite ions. It can be seen that it has increased. This can be understood as a spectrum in which the long-wavelength shift of the absorption spectrum of water due to hydration of sodium nitrite overlaps the original absorption spectrum of nitrite ions (the spectrum estimated by the dotted line in the figure). That is, the change in the spectrum from 190 nm to 200 nm is caused by the hydration of sodium nitrite in pure water, so that the binding state of water molecules is relaxed, and the water absorption spectrum is shifted in correlation with the concentration of sodium nitrite. This shows that the concentration of sodium nitrite can be quantified from the change in the amount of absorption in the region of 190 nm to 200 nm due to this shift. In the measurement of Examples 1 and 2, the apparatus shown in FIG. 4 was used.

  FIG. 4 shows the configuration of an ultraviolet spectroscopic measurement apparatus used for measuring ultraviolet spelling of water. Ultraviolet rays generated from the light source 10 pass through the measurement sample in the optical cell 12. The measurement light transmitted through the optical cell enters the spectroscopic unit 14 and is split into a plurality of wavelengths. (A grating may be used for the spectroscopic method, or an interference filter may be used.) The signal processing unit 16 calculates a concentration by calculating a signal at each measurement wavelength. Further, the data output unit 18 displays or outputs the calculation result. This device configuration is the same as the conventional one. Specifically, as the signal processing unit 16 and the data display unit 18, a conventional spectroscopic device capable of measuring at a wavelength of 190 nm to 280 nm can be used. Here, an ultraviolet / visible spectroscopic analyzer 3100PC manufactured by Shimadzu Corporation was used.

  In one measurement method, instead of using a calibration curve, the wavelength dependence of the ultraviolet spectrum is obtained for a plurality of standard aqueous solutions within a predetermined wavelength range on the long wavelength side of the absorption peak near 160 nm of water (for example, within a range of 180 nm to 210 nm). ) Measure in advance. Next, the ultraviolet spectrum of the aqueous solution sample containing a trace component is measured in a predetermined wavelength range, and it is determined which standard aqueous solution the ultraviolet spectrum of the aqueous solution sample matches.

  An example of measurement will be described below.

Example 3: Identification of commercial natural water.
Eight types of commercially available natural waters W1 to W8 and distilled water were analyzed. Table 1 shows the ion concentrations and pH values of these eight types of commercially available natural waters W1 to W8. Pure water was prepared by distilling water twice and passing through activated carbon and a reverse osmosis filter. Of the natural waters available on the market, W1 is “Delicious water from Rokko” (trademark) (house food), W2 is “natural water from Southern Alps” (trademark) (Suntory), and W3 is “Natural of Tateyama mountain range” "Water" (trademark) (Sapporo Beer), W4 is "News from Forest Water" (trademark) (Coca-Cola), W5 is "Evian" (trademark) (Calpis), W6 is "alkaline ion" “Water” (trademark) (Kirin Beverage), W7 is “Echizen no Mizu” (trademark) (High Peace), and W8 is “Yuyu Shusui” (trademark) (Nestlé Japan).

Table 1 shows the cation and anion concentrations (mg / 100 ml) and pH values of eight natural water samples.

  In the measurement using the apparatus shown in FIG. 4, the temperature of water was 25 ° C. A quartz cuvette cell having an optical path length of 10 mm was used as the optical cell 12, and water or an aqueous solution as a measurement sample was placed in the quartz cuvette cell 12. And the ultraviolet spectrum in the wavelength range of 180 nm-310 nm was measured.

FIG. 5 shows the far-ultraviolet spectral patterns of these eight kinds of commercially available natural waters W1 to W8 and pure water (distilled water) in the wavelength range of 190 nm to 250 nm. The wavelength range of 190 nm to 210 nm of these spectra overlaps with the bottom of the absorption band near 160 nm due to the n → σ ^* transition of water.

As can be seen by comparing the spectral pattern of FIG. 5 with Table 1, there is no simple relationship between the spectral pattern and the amount of dissolved component (mineral). This is because the spectral pattern in FIG. 5 is not formed only by the absorption of the dissolved component itself but reflects the difference in hydration of the dissolved component in each sample. That is, the data show that the intensity, peak position, and bandwidth of the n → σ ^* transition change sensitively due to the hydration of the dissolved component.

  As is clear from FIG. 5, these eight kinds of natural waters W1 to W8 can be clearly identified from the difference in their spectral patterns, and no preprocessing of the spectrum is required for identification. Therefore, the wavelength dependence of the ultraviolet spectral spectrum is measured in advance for the eight types of standard aqueous solutions of natural water, the ultraviolet spectral spectrum of a certain aqueous solution sample is measured, and the ultraviolet spectral spectrum obtained is the ultraviolet spectrum of which standard aqueous solution. By judging whether or not it matches the spectrum, it is possible to identify which natural water the aqueous solution sample is. In contrast, although not shown, the near-infrared spectra of the eight types of water measured by the present inventor appear to be the same with the naked eye, and are completely discernible even when performing sophisticated and complex principal component analysis. could not.

  DESCRIPTION OF SYMBOLS 10 Light source, 12 Optical cell, 14 Spectrometer, 16 Signal processing part, 18 Data output part

Claims (2)

For a plurality of standard aqueous solutions containing a plurality of trace components having different compositions, the wavelength dependence of the ultraviolet spectrum is previously measured in a predetermined wavelength range on the long wavelength side of the absorption peak near 160 nm of water,
Measure the ultraviolet spectrum of an aqueous solution sample containing trace components in the specified wavelength range,
An aqueous solution measurement method using ultraviolet light to determine which standard aqueous solution the ultraviolet spectrum of an aqueous solution sample matches. The method for measuring an aqueous solution according to claim 1, wherein the wavelength region is in a range of 180 nm to 210 nm.

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