JP2006258491A - Device and method for measuring concentration of acid solution including peracetic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new measuring method of the acid concentration in aqueous solution, and a device therefor. <P>SOLUTION: In order to perform optical density measurement of the aqueous solution including peracetic acid, a sample of the aqueous solution having a plurality of components including peracetic acid having a known concentration is introduced into a cell, and light having a different wavelength in an ultraviolet zone including the wavelength below 190 nm is transmitted through the sample in the cell, and the intensity value of transmitted light is measured. The measurement is repeated relative to the plurality of samples. The absorbance is operated from each intensity value of the plurality of samples, and a calibration curve expression between the concentration and the absorbance of the plurality of components including peracetic acid is determined. Then, the aqueous solution including peracetic acid which is a measuring object is introduced into the cell, and light having a different wavelength is transmitted through the aqueous solution in the cell, and the intensity value of transmitted light is measured. The absorbance is operated from the intensity value, and the concentration of the plurality of components including peracetic acid in the aqueous solution is determined by using the absorbance and the calibration curve expression. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to optical measurement of concentration in an aqueous solution.

  Measurement of the concentration of components in an aqueous solution is necessary for various applications. An acid solution (chemical solution) is used in applications such as sterilization and cleaning. For example, peracetic acid-containing drugs are used for sterilization and cleaning of medical devices, food containers, and the like. In the process of using such an acid solution, the concentration of the acid solution is measured in order to manage the acid solution. As a method for measuring the concentration of peracetic acid and hydrogen peroxide water in peracetic acid-containing drugs with high accuracy, the iodine titration method, analysis using an electrochemical sensor, and electrical conductivity method are mainly used ( For example, see JP-A-6-130051, JP-A-4-45798, JP-A-2001-13102).

JP-A-6-130051 JP-A-4-45798 JP 2001-13102 A

  As described above, iodine titration method, analysis using an electrochemical sensor, electrical conductivity method, and the like are used for monitoring the concentration of an acid solution. However, in the iodine titration method, since the reagent is added to the peracetic acid-containing chemical solution as a sample, the collected acid solution cannot be actually used. Furthermore, since the concentration cannot be measured instantaneously, it is not suitable for in-line use at cleaning and sterilization sites. In addition, the electrochemical sensor method is suitable for instantaneous measurement, but in actual measurement, a buffer solution is used and measurement is performed after mixing with an acid solution, so that the acid solution is completely altered. It ’s hard to say. Therefore, it is desirable that the acid concentration in the acid solution can be accurately determined without contact without altering the acid solution. It is also desirable to allow inline use.

  An object of the present invention is to provide a novel method and apparatus for measuring the acid concentration of an aqueous solution.

For the above purpose, the inventors paid attention to ultraviolet spectroscopy.
In the method for measuring the optical concentration of an aqueous solution containing peracetic acid according to the present invention, (1) a sample of a multi-component aqueous solution containing a known concentration of peracetic acid is introduced into the cell, and a wavelength of 190 nm or less with respect to the sample in the cell. The light of different wavelengths in the ultraviolet region including is transmitted, and the intensity value of the transmitted light is measured. This measurement is repeated for a plurality of samples. Then, (2) absorbance is calculated from the intensity values of the plurality of samples, and a calibration curve formula between the concentration and absorbance of a plurality of components including peracetic acid is obtained. Next, (3) an aqueous solution containing peracetic acid to be measured is introduced into the cell, the light of the different wavelengths is transmitted through the aqueous solution in the cell, and the intensity value of the transmitted light is measured. Then, (4) the absorbance is calculated from the intensity value, and the concentration of a plurality of components including peracetic acid in the aqueous solution is determined using the absorbance and the calibration curve equation. For example, the multiple components are peracetic acid, hydrogen peroxide and acetic acid. Moreover, the said ultraviolet wavelength range is 180-210 nm, for example.

  The concentration measuring apparatus according to the present invention irradiates a cell with a cell into which a multi-component aqueous solution containing peracetic acid is introduced, and light in an ultraviolet wavelength region including a wavelength of 190 nm or less (for example, light in a wavelength region of 180 to 210 nm). Including a light source, a light receiving element (for example, a diamond thin film sensor) that detects light intensity of transmitted light from the cell with a wavelength resolution of 5 nm or less and greater than 0.2 nm, and a wavelength of 190 nm or less in the optical path from the light source to the light receiving element And a spectroscopic element that splits light into different wavelengths.

  In the concentration measuring apparatus, preferably, the spectroscopic element is composed of a plurality of filters that reflect shorter wavelengths than different design wavelengths and transmit longer wavelengths than the design wavelengths. 6. The concentration measuring apparatus according to claim 4 or 5, wherein light having a specific wavelength reflected from one of the filters is selected and emitted in order of design wavelengths.

  Preferably, the concentration measuring device further includes a storage means for storing a calibration curve expression indicating a relationship between the concentration and absorbance of the plurality of components including the peracetic acid, and a light intensity signal output from the light receiving element. Concentration calculating means for calculating the absorbance and determining the concentration of a plurality of components including peracetic acid from the absorbance based on the calibration curve equation.

  In the concentration measuring device, preferably, the cell is a flow cell into which a sample is continuously introduced, and the concentration measuring device further includes a diluting device for diluting the sample introduced into the flow cell with water. Prepare.

Since the absorption spectrum depending on the concentration of peracetic acid is rapidly increased in a short wavelength region of 190 nm or less, the concentration of a plurality of components including peracetic acid in an aqueous solution is measured using spectroscopic measurement in the ultraviolet wavelength region. Can be accurately quantified in a non-contact manner without altering the aqueous solution.
In addition, since the concentration can be accurately determined in a short time, in-line measurement can be performed by using a flow cell.

  Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

  In recent years, peracetic acid-based sterilizing detergents used in aseptic filling systems for PET bottle beverages are always used as a three-component mixed aqueous solution of peracetic acid, hydrogen peroxide solution and acetic acid for purification. Although it is desired to realize an apparatus capable of accurately measuring the peracetic acid concentration in a sterilizing detergent in-line, in the methods that have been studied in the past, the peracetic acid concentration in a peracetic acid-based sterilizing detergent is one of the mixed components. It was difficult to measure without being affected by hydrogen peroxide. Also, an apparatus for continuously supplying samples in-line and continuously measuring the concentration has not been put into practical use.

  Inventors measured the ultraviolet spectroscopy data about various aqueous solution, as shown in FIG. 1 and FIG. 2, in order to examine the possibility of the ultraviolet spectroscopy measurement about the density | concentration of various aqueous solution. Here, in addition to the acetic acid aqueous solution and the hydrogen peroxide aqueous solution, a diluted peracetic acid-based sterilizing detergent was also measured. FIG. 1 shows (a) a 1.7 wt% acetic acid aqueous solution, (b) a 0.2 wt% hydrogen peroxide aqueous solution, and (c) a diluted peracetic acid-based disinfectant (0.86 wt%). Shows the absorbance in the ultraviolet region of active 90) containing 2% peracetic acid, 0.23% by weight hydrogen peroxide, 0.22% by weight acetic acid. FIG. 2 shows the second derivative of the absorbance shown in FIG. In this absorbance measurement, a commercially available spectroscopic measurement apparatus (Shimadzu Corporation UV-visible spectrometer UV-2550) that measures an ultraviolet region of 190 nm or more was used. A cuvette cell having an optical path length of 10 mm was used as the cell. These aqueous solutions were found to have large absorption at about 300 nm or less, and the concentration of various components in the aqueous solution could be measured by ultraviolet spectroscopy.

  Conventionally, the use of an ultraviolet absorption spectrum for measuring the concentration of peracetic acid in the above-described sterilizing detergent has not been noticed. The reason is that, in the ultraviolet region measured by a commercially available ultraviolet spectrometer, the absorption coefficient of peracetic acid is very small at a concentration of 0.2% by weight or less. The typical concentration range is 0.1 to 0.2% by weight for peracetic acid and 0.5 to 2.0% by weight for hydrogen peroxide. This is because it is interfered by hydrogen peroxide. However, from the data of FIGS. 1 and 2, it is presumed that the characteristic absorption band due to peracetic acid is below 190 nm. This is because in the data (c) of the diluted peracetic acid-based disinfectant, the intensity of absorption by hydrogen peroxide increases as the wavelength becomes shorter as shown in (b), and the intensity of absorption of acetic acid is (a As shown in FIG. 1 and FIG. 2, the absorption intensity of the diluted peracetic acid-based disinfectant detergent tends to increase as the wavelength decreases. This is because it cannot be attributed to hydrogen peroxide or acetic acid. Therefore, these data suggest that the quantitative accuracy of measurement of peracetic acid components in an aqueous solution containing peracetic acid is greatly improved by spectroscopic measurement to a wavelength region lower than 190 nm.

  Therefore, the inventors have developed an ultraviolet spectroscopic measurement apparatus capable of performing spectroscopic measurement even in a wavelength region of 190 nm or less, and measured the far ultraviolet spectrum of a peracetic acid-based disinfectant cleaning agent containing peracetic acid, hydrogen peroxide, and acetic acid. It was found that peracetic acid produces a sharp absorption band in the ultraviolet region of 190 nm or less, whereas hydrogen peroxide produces a gentle absorption band in the ultraviolet region. And from the result of the spectral analysis, it discovered that the density | concentration of all these 3 components could be quantified simultaneously and accurately. Specifically, this apparatus can measure, for example, in the far ultraviolet region of 175 to 280 nm, but a wavelength region of 180 to 210 nm is sufficient. Moreover, although absorption became large at a wavelength of 190 nm or less, it was found that measurement was possible with a cell having an optical path length of 0.5 mm.

  FIG. 3 shows a configuration of a spectroscopic unit that performs spectroscopic measurement in the ultraviolet spectroscopic measurement apparatus manufactured by the inventors. A commercially available ultraviolet spectrometer can measure light having a wavelength in the range of 190 nm to 350 nm, but this ultraviolet spectrometer can perform spectroscopic measurement in the far ultraviolet region of 180 to 220 nm. Further, it was found that, in the ultraviolet spectroscopic measurement, the concentration can be measured with high accuracy using a sensor having a wavelength resolution of 5 nm or less without using a photomultiplier having a resolution of 0.5 nm or less. This measuring apparatus has a simple configuration, and can be manufactured in a small size at low cost. Moreover, the measurement time can be set to 30 seconds or less, which is suitable for in-line continuous measurement.

The ultraviolet spectroscopic measurement apparatus will be further described. As the ultraviolet light source 10, a deuterium lamp having a transparent window in a spectral region of 180 to 220 nm is used. The far ultraviolet light generated by the ultraviolet light source 10 is collected by a condenser lens (MgF ₂ lens) 12 and irradiates a flow cell (light absorption cell) 14. A sampled aqueous solution is introduced into the flow cell 14. The far ultraviolet light transmitted through the flow cell 14 passes through the slit 16 and enters the monochromatic grating spectrometer 18. Here, the transmitted light is reflected by the mirror 20a and the collimating mirror 22, then diffused by the grating mirror (spectral element) 24, further reflected by the collimating mirror 22 and the other mirror 20b, and then passed through the slit 26. Is incident on the ultraviolet light receiving element 28. Since it is difficult to manufacture an interference filter capable of efficiently separating ultraviolet light having a wavelength of 200 nm or less, the grating mirror 24 is used here as a spectroscopic element. The groove pitch of the grating mirror 24 is 2400 / mm, and the blaze wavelength is 250 nm. The grating mirror 24 is placed on a rotating stage (not shown) for changing the wavelength. The ultraviolet light receiving element 28 converts the incident ultraviolet light into a photocurrent corresponding to its intensity. The time required to measure the spectrum in the wavelength range of 180 to 220 nm is as short as 30 seconds, and real-time measurement in line is possible. The optical system described above is accommodated in the hermetic container 28, and nitrogen gas or argon gas is introduced into the container 30 from the inlet 32 and discharged from the outlet 34 at a flow rate of, for example, 0.1 liter / min. This gas introduction is for removing oxygen gas from the optical system in the container 28, thereby eliminating the influence of absorption in the ultraviolet region by the oxygen gas.

  As shown in FIG. 4, a sample liquid from an aqueous solution to be measured (not shown) is introduced into the flow path 14 a in the flow cell 14. 4 shows a cross section perpendicular to the paper surface of FIG. By using such a flow cell, the concentration can be continuously measured in-line. The optical path length of the flow cell 14 is as short as 0.5 mm because of the large absorption in the far ultraviolet region. In addition, the transmittance | permeability of the light irradiated to the penetration depth of the aqueous solution in the flow cell is about 45% at a wavelength of 182 nm.

  The light receiving element 28 used in this apparatus is a diamond thin film sensor, which is used for excimer laser illuminance measurement and the like. Measurement is performed with a wavelength resolution of about 5 nm using a 0.6 mm slit 24 and a diamond thin film sensor. This resolution is inferior on the order of one digit as compared with a photomultiplier tube (resolution of 0.5 nm or less) used in a commercially available ultraviolet spectrometer. However, since the absorption band of peracetic acid or the like to be measured is wide and measurement is performed at the shoulder of the absorption band, such a high resolution is not necessary for this measurement. In addition, the size of the light receiving element 28 is as small as 3 × 3 × 1 cm including the electric circuit, and the operation is stable. Since such a small light receiving element 28 is used, the measuring apparatus can be downsized and used for in-line measurement. On the other hand, a commercially available ultraviolet spectroscopic measuring apparatus using an optical image doubling tube has a large size because it requires cooling or the like, and must often be calibrated. A vacuum motor for exhausting oxygen from a large volume is also required. For this reason, a commercially available ultraviolet spectrometer cannot be used for in-line measurement.

  A band pass mirror may be used instead of the grating mirror 24. A bandpass mirror refers to a mirror that reflects light having a shorter wavelength than the design wavelength and transmits light having a longer wavelength. In the example shown in FIG. 5, the transmittances of five types of filters 40, 42, 44, 46 and 48 are shown in the upper part. The first filter 40 reflects light having a wavelength of 180 nm or less and transmits light having a wavelength of 183 nm or more. The second filter 42 reflects light having a wavelength of 185 nm or less and transmits light having a wavelength of 188 nm or more. The third filter 44 reflects light having a wavelength of 190 nm or less and transmits light having a wavelength of 193 nm or more. The fourth filter 46 reflects light having a wavelength of 195 nm or less and transmits light having a wavelength of 198 nm or more. The fifth filter 48 reflects light having a wavelength of 200 nm or less and transmits light having a wavelength of 203 nm or more. As shown in FIG. 6, by combining these filters and selectively switching the optical path, it is possible to sequentially irradiate the sample with light of a specific wavelength. Specifically, these five types of filters 40 to 48 are sequentially arranged so that the light transmitted through the first filter is incident on the second filter, and the light transmitted through the second filter is incident on the third filter. Let Thereafter, incidence and reflection are performed in the same manner. As a result, five types of band transmission characteristics can be realized. That is, a bandpass optical path that transmits light having a wavelength of 180 nm or less, a bandpass optical path that transmits light having a wavelength of 183 to 185 nm, a bandpass optical path that transmits light having a wavelength of 188 to 190 nm, and light having a wavelength of 193 to 195 nm A bandpass optical path that transmits light and a bandpass optical path that transmits light having a wavelength of 198 to 200 nm can be formed. Further, in the configuration shown in FIG. 6, the spectral performance is improved by using two of the five types of filters 40 to 48 and reflecting (transmitting) each measurement light twice with the filter of the same design (transmission). (Rate 5% × 5% = 0.25%). Further, by inserting a disk 52 having an opening 50 (only one is shown in FIG. 6) provided in a position for selectively switching the optical path in the optical path, and rotating the disk 52, the measurement wavelength is measured. Select (switch).

  FIG. 7 shows a data processing unit of the ultraviolet spectrometer. The electric signal input from the light receiving element 28 described above is an intensity signal of light transmitted through the flow cell 14. The amplifier 60 amplifies the intensity signal input from the light receiving element 28, and the A / D converter 62 converts the analog signal output from the amplifier 60 into a digital signal. The density calculation unit 64 calculates the density of each component based on the digital signal of the transmitted light intensity. The density calculation unit 64 is a personal computer including a CPU 66, for example. The CPU 66 stores a ROM 68 that stores programs and the like, a RAM 70 that is a work area, a keyboard that inputs data and various commands, an input device 72 such as a mouse, an output device 74 that outputs signals to the outside, and various programs and data. A hard disk drive 76, which is an auxiliary storage device, is connected. The ROM 68 stores a program for operating the CPU 66 and the like. The RAM 70 stores a calibration curve type and various data. The CPU 66 calculates the absorbance at each wavelength from the input digital signal, and calculates the concentration of the acid in the chemical solution from the calculated absorbance of the light at each wavelength using a calibration curve formula. The output device 74 is a printer, a display, a data output interface, or the like that outputs data processing results.

  The concentration calculation unit 64 receives a transmitted light intensity signal, which is a digital signal, from the A / D converter 62, and then calculates the absorbance of ultraviolet light of each wavelength. Then, based on the calculated absorbance of ultraviolet rays of each wavelength and a calibration curve formula stored in advance, the concentrations of the three components peracetic acid, acetic acid and hydrogen peroxide are calculated. A calibration curve is a multivariate measurement using a multi-degree polynomial of absorbance that measures the absorbance of light of multiple wavelengths for multiple samples of known concentrations and contains a constant term between the absorbance and the concentration of each component. It is obtained in advance by an analysis method.

  FIG. 8 shows a sampling unit for in-line measurement combined with the diluting device 80. This sampling unit is used for a sample having a large ultraviolet absorption such as a sterilizing detergent. A sample solution is introduced by bypassing a part from a sample circulation line 82 from a bath (not shown) of a sterilizing detergent aqueous solution to a bypass line 84, and then pure water is mixed into the sample solution by a diluting device 80. Dilute to 1/10. Then, the diluted sample is introduced into the flow cell 14 of the ultraviolet spectrometer. The sample after the measurement is returned to the above-mentioned dredger and recycled or drained. Since the measurement sample is not contaminated with impurities, it can be recycled. When the sample is returned to the tank and reused, the stock solution of each component constituting the sterilizing detergent is added in an amount calculated so that the concentration of the sterilizing detergent in the tank does not become thin. That is, even when the concentration is reduced for measurement, it can be corrected when returning to the original state.

  Absorbance was measured in the far ultraviolet region using the above-described measuring apparatus. FIG. 9 shows (a) 0.02 wt% aqueous hydrogen peroxide solution, (b) diluted mixed acid (0.01 wt% peracetic acid, 0.02 wt% hydrogen peroxide, 0.05 wt% The absorbance at a wavelength of 180 to 200 nm is shown. This figure shows that peracetic acid in the sterilizing detergent exhibits a larger absorption than hydrogen peroxide in a short wavelength region of 190 nm or less. This corresponds to the above prediction based on FIG. 1 and FIG.

  10 and 11 show a flow of density calculation processing by the CPU 66. FIG. First, when measurement of a sample having a known concentration is started (S10), light intensity data at a plurality of wavelengths is input from the A / D converter 62 (S12). Then, the absorbance is calculated from the light intensity data and stored (S14). If there is a sample of the next known concentration (YES in S16), the above process is repeated. If there is no sample of the next known concentration (NO in S16), a calibration curve formula between the absorbance and the concentration is calculated (S18) and stored in the RAM 50 (S20).

  Next, when measurement of a sample having an unknown concentration is started (S22), light intensity data at a plurality of wavelengths is input from the A / D converter 62 (S24). Then, the absorbance is calculated from the light intensity data (S26). Then, the concentration is calculated from the absorbance and the calibration curve (S28) and stored in the RAM 70 (S30). Here, it is determined whether or not the measurement is finished (S32). If not finished, the process returns to step 24 and the density measurement is continued.

  The method of processing the light intensity data in the processing of the CPU 66 shown in FIG. 10 is the same as that described in Japanese Patent Laid-Open No. 6-265471 by the present applicant, which was used for the spectroscopic measurement in the near infrared wavelength region. is there. Specific contents of the data processing will be described below.

この式において、ｉは、分光される複数の紫外線波長の順番ないし番号（たとえば、１〜７）であり、Ｒ_ｉは、測定対象である酸溶液のｉ番目の波長の紫外線の透過強度値（または反射強度値）であり、Ｂ_ｉは、フローセル１４内に導入された基準濃度の酸溶液の、ｉ番目の波長の紫外線の透過強度値（または反射強度値）であり、Ｄ_ｉは、フローセル１４を遮光したときのｉ番目の波長の紫外線の透過強度値（または反射強度値）である。なお、Ｂ_ｉおよびＤ_ｉは、あらかじめ測定されているデータであり、データ処理装置のＲＡＭ５０に格納されている。 First, a calculation process according to the following equation (1) is performed on the input digital signal of light intensity to calculate the absorbance A _i .

In this equation, i is the order or number (for example, 1 to 7) of a plurality of ultraviolet wavelengths to be spectrally separated, and R _i is the transmission intensity value of ultraviolet rays of the i-th wavelength of the acid solution to be measured ( or a reflection intensity value), B _i is the acid solutions of reference density introduced into the flow cell 14, i-th transmission intensity value of ultraviolet rays having a wavelength (or reflection intensity value), D _i is the flow cell 14 is the transmission intensity value (or reflection intensity value) of the ultraviolet light of the i-th wavelength when 14 is shielded. B _i and D _i are data measured in advance, and are stored in the RAM 50 of the data processing apparatus.

Next, the following equation (2) is converted into the absorbance A _i obtained by the arithmetic processing according to equation (1).

The reason for performing the conversion of equation (2) is as follows. The absorbance A _i calculated by the equation (1) changes due to fluctuations in the light emission intensity of the ultraviolet lamp 10, fluctuations in sensitivity of the light receiving element 28, distortion of the optical system, and the like. However, this change is not very wavelength-dependent, and is superimposed in the same phase and at the same level on each absorbance data for each wavelength of ultraviolet light. Therefore, this change can be offset by taking the difference between the wavelengths as shown in Equation (2).

Incidentally, with variation and degradation in absorbance A _i due to temperature variations of the acid solution itself, but also occurs such fluctuations due to an increase in color change and turbidity, these variations are well known methods (e.g. Japanese Patent Laid-Open 3-209149 The description thereof will be omitted.

Next, based on _Si obtained by equation (2), the following equations (3) to (5) are calculated for the three components (peracetic acid, acetic acid and hydrogen peroxide) in the peracetic acid-containing chemical solution. Then, the content (concentration) C _{1 of} peracetic acid, the content (concentration) C _{2 of} acetic acid, and the content (concentration) C ₃ of hydrogen peroxide are calculated.

式（６）において、Ｓ_ｉとＳ_ｉ＋１は式（１）と式（２）により得られたデータであり、α、βおよびγは検量線式の係数であり、Ｚ_０は定数項である。式（６）に含まれる各データは、過酢酸、酢酸および過酸化水素の濃度が既知の酸溶液の標準サンプルを用いて濃度測定部６４による測定によりあらかじめ求められたものであり、濃度演算部６４のＲＡＭ７０に格納されている。 In the formula (3), F (S i ) is a calibration curve equation peracetic acid, with including first-order terms and higher order terms for S _i, S _i and S _{i + 1} or cross section is the product of the higher order terms And a constant term, for example, represented by the following formula (6).

In Equation (6), S _i and S _{i + 1} are data obtained by Equation (1) and Equation (2), α, β, and γ are coefficients of the calibration curve equation, and Z ₀ is a constant term. . Each data included in the equation (6) is obtained in advance by measurement by the concentration measuring unit 64 using a standard sample of an acid solution with known concentrations of peracetic acid, acetic acid, and hydrogen peroxide. 64 RAMs 70.

In the formulas (4) and (5), G (S _i ) and H (S _i ) are an acetic acid calibration curve formula and a hydrogen peroxide calibration curve formula, respectively. It is an expression of the same form. Similar to the calibration curve formula for peracetic acid, these calibration curve formulas are obtained in advance using a standard sample of an acid solution with known concentrations of peracetic acid, acetic acid and hydrogen peroxide. Stored in the RAM 70.

  That is, in the measurement of the concentration of peracetic acid, acetic acid, and hydrogen peroxide in the acid solution, the flow cell 14 into which the acid solution is introduced is irradiated with ultraviolet light having a wavelength of 180 to 220 nm and transmitted through the flow cell 14 ( Or, reflected ultraviolet light is incident on the light receiving element 28, and the amounts of absorbed ultraviolet light having a plurality of wavelengths are respectively calculated based on signals corresponding to the transmitted light quantity (or reflected light quantity) of the ultraviolet light output from the light receiving element 28. The case of obtaining the concentration of the three components has been described above, but the same processing can be performed for the case of the two components, the four components, and the like.

  Next, the measurement of the concentration of a plurality of components in a multi-component aqueous solution containing peracetic acid will be described. In one example, such an aqueous solution is a peracetic acid-containing chemical solution used for sterilization, washing, and the like. A drug (active 90) manufactured by Ecolab Co., Ltd. was diluted with pure water, hydrogen peroxide solution or peracetic acid to prepare 19 test solutions having known concentrations. Active 90 is composed of 8.6% by weight peracetic acid, 23% by weight acetic acid, 22% by weight hydrogen peroxide and pure water. The resulting test solution contains 0.15 to 0.40 wt% peracetic acid, 0.20 to 1.50 wt% hydrogen peroxide and 0.20 to 1.50 wt% acetic acid. Their concentration (true value) was determined by titration.

Table 1 Composition of test solution

  In the above-described ultraviolet spectrometer, first, pure water was passed through the flow cell 14 to measure the background spectrum. Next, the test solution was diluted 10 times with pure water by the diluting device 80, and flowed through the flow cell 14 at a rate of 5 ml / min, and the far ultraviolet spectrum was measured. Here, each sample was flowed for about 1 minute to replace the previous sample, and the measurement was performed. Note that the temperature of the sample was kept at 25 ° C.

  FIG. 12 shows an ultraviolet spectrum in the wavelength range of 180 to 220 nm of the 19 test solutions described above. As can be seen from FIG. 12, the wavelength dependence of the ultraviolet spectra of these test solutions is clearly different from each other. This is because the spectra of the three components, that is, peracetic acid, acetic acid, and hydrogen peroxide water are different. That is, as shown in FIG. 9, the absorption maximum of the ultraviolet absorption spectrum of peracetic acid is at a wavelength lower than 180 nm, and the absorbance rapidly increases as the wavelength becomes shorter. In addition, as shown in FIG. 1, the ultraviolet absorption spectrum of acetic acid has an absorption peak at about 205 nm, and the absorption spectrum of hydrogen peroxide water has a peak at 180 nm or less like peracetic acid. Absorption increases slowly.

  In the analysis of the three-component ultraviolet spectrum data, the above-described multiple linear regression method was employed. Seven wavelengths (182, 185, 187.5, 190, 200, 205, 210 nm) were selected in the far ultraviolet region, and a calibration model (calibration curve) for predicting the concentration of the three components was created.

  FIG. 13a is a graph showing the correspondence between the true value and the predicted value for peracetic acid at a concentration of 0-0.02 wt%, and FIG. 13b is the true value for 0-0.15 wt% hydrogen peroxide. And FIG. 13c is a graph showing the correspondence between the true value and the predicted value for 0 to 0.15% by weight of acetic acid. In both cases, very good agreement was observed. The correlation coefficients and standard prediction errors are 0.969 and 0.002 wt% for peracetic acid, 0.997 and 0.003% wt for hydrogen peroxide, and 0.967 and 0 for acetic acid. 0.01% by weight. This shows that peracetic acid can be measured with an accuracy of 0.002% by weight. In this spectroscopic measurement method, the quantitative accuracy of hydrogen peroxide and peracetic acid has been greatly improved. The absorption spectrum depending on the concentration of peracetic acid increases rapidly in the short wavelength region of 190 nm or less. This is because it can be used.

  In addition, in the wavelength range of 200 nm or less, there is a concern about an adverse effect due to spectral interference of many inorganic and organic compounds contained in the acid solution during use. Moreover, although the oxygen dissolved in the aqueous solution shows an absorption band below 200 nm, the influence is considered to be negligible because it is small at about 8 ppm under atmospheric pressure, but it is necessary to confirm whether this assumption is correct. Therefore, as shown in FIG. 14, (a) the absorbance of the newly diluted sterilizing solution and (b) the absorbance of the used sterilizing waste solution at 170 to 300 nm were measured. The measurement was performed with a resolution of 0.1 nm in order not to miss a sharp peak. From the data in FIG. 14, it was found that there was no peak derived from contaminants in this wavelength region. The difference in spectrum between the two cases (a) and (b) is due to the increase in broad absorption below 250 nm by hydrogen peroxide. This is because, in the sterilizing solution that is actually in use, a thick sterilizing solution is added to compensate for the decrease in peracetic acid that occurs over time, so the concentration of peracetic acid is kept constant. This is because the concentration of hydrogen oxide increases.

  Table 2 shows data obtained by determining the concentrations of peracetic acid, hydrogen peroxide and acetic acid in the sterilizing solution by the far ultraviolet spectroscopic measurement method and the titration method according to the present embodiment. When the results of the two measurement methods are compared, they are in good agreement, indicating that the far ultraviolet spectroscopy method is very useful.

Table 2 Concentration measurement results in newly diluted sterilization liquid and sterilization waste liquid after use

  In addition, since the decomposition of peracetic acid and hydrogen peroxide occurs in an aqueous solution when irradiated with ultraviolet rays, the following experiment was conducted to confirm the influence of ultraviolet irradiation on spectroscopic analysis. First, zero calibration was performed by filling the cuvette cell with pure water. Next, an aqueous solution containing 0.02% by weight of peracetic acid, 0.11% by weight of hydrogen peroxide and 0.06% by weight of acetic acid was placed in the cell and irradiated with UV light for 3 minutes using a 50 W deuterium lamp. Irradiated. Here, the concentrations of peracetic acid and hydrogen peroxide were measured every 5 seconds. FIG. 15 shows the measurement results. First, the absorbance was measured for 3 minutes at 5 second intervals at a measurement wavelength of 182 nm. Furthermore, the measurement was performed by replacing the sample in the cell at the other six wavelengths in the same manner. This data indicates that the decomposition begins after 30 seconds. Therefore, at the flow rate of 5 ml / min used in the above-mentioned measurement, the time of exposure to ultraviolet rays when passing through the flow cell is shorter than 15 seconds, so that it was found that the sample decomposition due to ultraviolet irradiation is almost negligible in in-line measurement.

  In the above-described example, measurement is performed on a three-component mixed aqueous solution of peracetic acid, hydrogen peroxide solution, and acetic acid. However, the above-described ultraviolet spectroscopic measurement apparatus and method generally uses a concentration of an aqueous solution containing a plurality of components containing peracetic acid. Needless to say, it can be used for measurement. The reason why high-accuracy measurement is possible is that the characteristic that the absorption spectrum depending on the concentration of peracetic acid increases rapidly in a short wavelength region of 190 nm or less can be used, and components other than peracetic acid are limited. It is not a thing.

  As explained above, in the far ultraviolet optical measurement of an aqueous solution containing peracetic acid, the concentration of a plurality of components in the aqueous solution could be quantitatively measured simultaneously. This method is very simple and allows rapid spectroscopic measurement and analysis. For example, the detection limit of peracetic acid was 0.002% by weight, the detection limit of hydrogen peroxide was 0.003% by weight, and the detection limit of acetic acid was 0.01% by weight. The concentration of hydrogen peroxide was required to be 0.2% by weight or less for dilution, but the measurement could be automatically performed using a diluter. In addition, the measuring device could be downsized and used for in-line measurement.

Graph of absorbance in ultraviolet region of (a) 1.7 wt% aqueous acetic acid solution, (b) 0.2 wt% aqueous hydrogen peroxide solution, and (c) diluted peracetic acid-based disinfectant cleaner Graph of the second derivative of absorbance in FIG. The figure which shows an example of a structure of a density | concentration measurement part Flow cell diagram Diagram explaining the operation of the bandpass mirror Diagram showing the configuration of a bandpass mirror Block diagram of concentration calculator Diagram of an in-line measuring device combined with a dilution device Graph of absorbance of (a) 0.02% hydrogen peroxide and (b) diluted disinfectant solution Microprocessor data processing flowchart Microprocessor data processing flowchart Spectral graphs in the ultraviolet region for several peracetic acid samples. Graph showing correspondence between true value and predicted value for 0-0.02% by weight of peracetic acid Graph showing correspondence between true value and predicted value for 0 to 0.15 wt% hydrogen peroxide Graph showing the correspondence between true value and predicted value for 0-0.15% by weight acetic acid (A) graph of absorbance of newly diluted sterilization solution and (b) absorbance of sterilization waste solution Graph of decomposition of peracetic acid and hydrogen peroxide in samples during UV irradiation

Explanation of symbols

10 UV light source, 14 flow cell, 18 monochromatic grating spectroscope, 26 light receiving element, 64 density calculation unit, 66 CPU, 68 ROM, 70 RAM, 80 dilution device.

Claims (9)

An optical concentration measurement method for an aqueous solution containing peracetic acid,
Samples of multi-component aqueous solutions containing known concentrations of peracetic acid are introduced into the cell, and light of different wavelengths in the ultraviolet region including wavelengths of 190 nm or less are transmitted to the sample in the cell, and the intensity value of the transmitted light is measured Repeat this measurement for multiple samples,
Calculate the absorbance from the intensity values of the plurality of samples, find a calibration curve formula between the concentration and absorbance of multiple components containing peracetic acid,
An aqueous solution containing peracetic acid to be measured is introduced into the cell, light of the different wavelengths is transmitted through the aqueous solution in the cell, and the intensity value of the transmitted light is measured.
An optical concentration measurement method that calculates an absorbance from an intensity value and determines a concentration of a plurality of components including peracetic acid in the aqueous solution using the absorbance and the calibration curve equation.   The concentration measuring method according to claim 1, wherein the plurality of components are peracetic acid, hydrogen peroxide, and acetic acid.   The concentration measurement method according to claim 1, wherein the ultraviolet wavelength region is 180 to 210 nm. A cell for introducing a multi-component aqueous solution containing peracetic acid;
A light source that irradiates the cell with light in an ultraviolet wavelength region including a wavelength of 190 nm or less;
A light receiving element for detecting the light intensity of transmitted light from the cell with a wavelength resolution of 5 nm or less and greater than 0.2 nm;
A concentration measuring device comprising: a spectroscopic element that splits light into different wavelengths including a wavelength of 190 nm or less in an optical path from a light source to a light receiving element.   5. The concentration measuring apparatus according to claim 4, wherein the light receiving element is a diamond thin film sensor.   The spectroscopic element is composed of a plurality of filters that reflect shorter wavelengths than different design wavelengths and transmit longer wavelengths than the design wavelengths, and arrange these filters in the optical path in the order of the design wavelengths. 6. The concentration measuring apparatus according to claim 4, wherein light having a specific wavelength reflected from the filter is selected and emitted.   The concentration measuring apparatus according to claim 4, wherein the spectroscopic element splits light in a wavelength region of 180 to 210 nm. further,
Storage means for storing a calibration curve equation indicating the relationship between the concentration and absorbance of a plurality of components containing the peracetic acid;
A concentration calculating means for calculating an absorbance from a light intensity signal output from the light receiving element, and determining a concentration of a plurality of components including peracetic acid based on the calibration curve formula from the absorbance; The concentration measuring device according to any one of claims 4 to 7. 9. The cell according to claim 4, wherein the cell is a flow cell into which a sample is continuously introduced, and further includes a diluting device for diluting the sample introduced into the flow cell with water. Concentration measuring device.

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