A method for measuring indicator characterisation in the full ph domain with visible light full spectrum technology

Abstract

The present application belongs to the technical field of titration analysis, and particularly relates to a method for measuring indicator characterization in a full pH domain by using visible light full spectrum technology. The method for measuring indicator characterization in a full pH domain by using visible light full spectrum technology provided by the present application comprises the following steps: in the titration of the indicator in a full pH domain, a spectral-potential-temperature three-dimensional form analyzer is used to continuously determine the characteristic spectral signal and the pH signal formed after the structural change of the indicator in the solution absorbs visible light during the titration process, the characteristic spectral signal is expressed by the chromaticity value parameter value of the CIE 1976 (L * a * b * ) color uniformity space, the chromaticity value parameter value is calculated as a visible light full spectrum parameter, the visible light full spectrum parameter and the pH signal are used to establish a full pH threshold coordinate curve of the indicator, and the full pH domain characterization result of the indicator measured by the visible light full spectrum titration method is obtained. The characterization method provided by the present application realizes the digitization and graphization of the indicator addition amount and the corresponding color change of each measurement period of the titration process, and can trace and analyze the structural change of the indicator in each measurement period.

Description

Technical Field

[0001] This invention belongs to the field of indicator technology, specifically relating to a method for measuring indicator characterization using visible light full-spectrum technology across the entire pH range. Background Technology

[0002] Advances and requirements in modern testing technology have highlighted the inherent limitations of sensory titration techniques, which rely on visual observation, cognitive judgment, and verbal description. These limitations have hindered the application of titration analysis. The main obstacles are: inconsistent color evaluation conditions, with few standards specifying the required conditions for color observation, leading to different experiments being conducted under unsuitable conditions; inherent evolutionary defects in the human eye resulting in varying and inconsistent observation thresholds among individuals; inconsistent and unreliable verbal descriptions of color changes; and reliance on subjective evaluation during observation, making traceability of measurement values ​​impossible.

[0003] In 2019, Wang Fei published his independent work, *Spectroscopic Titration Technology in Chemical Analysis*, which defined the meaning of full-spectrum titration technology (Visible Spectral Titration Technology, VSTT), established the theoretical framework of full-spectrum titration, set rules for determining the validity of full-spectrum titration data, and formulated a method for establishing full-spectrum titration. This laid the theoretical foundation for spectroscopic titration, providing the main support for VSTT technology from theory to practical application.

[0004] However, there is currently no existing technology that can measure the full visible spectrum of an indicator across the entire pH range. Summary of the Invention

[0005] The purpose of this invention is to provide a method for characterizing indicators using visible light full-spectrum technology across the entire pH range. The characterization method provided by this invention digitizes and graphically represents the amount of indicator added and its corresponding color change for each measurement cycle in a sensory titration process. Simultaneously, it allows for tracing and analyzing the structural transformation of the indicator in each measurement cycle.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for characterizing indicators using visible light full-spectrum technology across the entire pH range, comprising the following steps:

[0008] In the titration of an indicator across the entire pH range, a three-dimensional spectrophotometer-potential-temperature spectrophotometer was used to continuously measure the characteristic spectral signal and pH signal formed by the absorption of visible light after structural changes of the indicator in the solution during the titration process. The characteristic spectral signal was defined according to CIE 1976(L). * a * b *The chromaticity parameter value in the uniform color space is represented, and the chromaticity parameter value is calculated as a visible light full spectrum parameter. The visible light full spectrum parameter is used to establish a full pH threshold coordinate curve of the indicator with the pH signal, and the full pH range characterization result of the indicator measured by visible light full spectrum titration is obtained; the full pH range is 0 to 13.5.

[0009] The characterization results include:

[0010] CIE 1976 (L) indicator for the entire pH range * a * b * ) chromaticity value L * value, a * value and b * Colorimetric value curves under different pH conditions;

[0011] Chroma C of the indicator across the entire pH range * ab Hue angle h ab The curves showing the variation of color difference ΔE under different pH conditions;

[0012] CIE 1976 (L) indicator for the entire pH range * a * b * ) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * Relationship representation results;

[0013] CIE 1976 (L) indicator for the entire pH range * a * b * The color change parameter curve S) Ja*-b* S Jb*-hab S Jb*-△E and S JC*ab-△E Characterization results of the relationship under different pH conditions;

[0014] CIE 1976 (L) indicator for the entire pH range * a * b * The titration color change trajectory of )

[0015] The correlation between wavelength and absorbance of the indicator across the entire pH range.

[0016] Preferably, the indicator is a CIE 1976 (L) standard across the entire pH range. * a * b *) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * The relationship characterization results include: CIE 1976 (L) for the indicator across the entire pH range. * a * b * (equal brightness L) * The value of a * -b * Chromaticity index chart, CIE 1976 (L) indicator for the entire pH range * a * b * The yellow-blue magenta index b) * The value of a * -L * CIE 1976 (L) color index chart and indicator for the entire pH range * a * b * The red-green product index a) * value b * -L * Color index chart.

[0017] Preferably, the indicator is a CIE 1976 (L) standard across the entire pH range. * a * b * The titration color change trajectory of the indicator is L across the entire pH range. * -a * -b * The 3D visual model titration curve.

[0018] Preferably, the correlation between wavelength and absorbance of the indicator across the entire pH range includes: wavelength-absorbance curves, absorbance at the maximum absorption wavelength under different pH conditions, and a 3D visual model titration curve of A-λ-pH for the entire pH range titration curve.

[0019] Preferably, the pH resolution of the spectro-potential-temperature three-dimensional spectrophotometer is 0.1 pH.

[0020] Preferably, the measurement conditions include: a spectral range of 380nm to 780nm, Δλ = 5nm, a measurement period of 200ms, and an optical path of 10.0mm.

[0021] Preferably, during the continuous measurement, the spectral blank of the three-dimensional spectrophotometer-potential-temperature morphology analyzer is calibrated with water to a value of L. * =100.0, a * =0.0, b* =0.0.

[0022] Preferably, the titration process of the indicator includes the following steps:

[0023] Add the indicator solution dropwise to the solution, adjust the pH to 0.1 with acid solution, and titrate the pH to 13.5 with alkaline solution.

[0024] Preferably, the titration is performed at room temperature.

[0025] Preferably, the indicator includes phenolphthalein, bromocresol purple, or methyl orange.

[0026] This invention provides a method for characterizing indicators across the entire pH range using visible light full-spectrum technology. The method includes the following steps: during the titration of the indicator across the entire pH range, a three-dimensional spectrophotometer (spectro-potential-temperature) is used to continuously measure the characteristic spectral signal and pH signal formed after the indicator absorbs visible light during the titration process, reflecting structural changes in the indicator. The characteristic spectral signal is defined using CIE 1976(L... * a * b * The chromaticity parameter value in a uniform color space is used to represent the indicator. This chromaticity parameter value is then calculated as a full-spectrum visible light parameter. A full-pH threshold coordinate curve of the indicator is established by comparing the full-spectrum visible light parameter with the pH signal, yielding the full-pH range characterization results of the indicator measured by the full-spectrum visible light titration method. The full-pH range is 0–13.5. The characterization results include: the CIE 1976 (L) standard for the indicator's full-pH range. * a * b * ) chromaticity value L * value, a * value and b * Colorimetric curves under different pH conditions; chroma C of the indicator across the entire pH range. * ab Hue angle h ab The curves showing the variation of color difference ΔE under different pH conditions; CIE 1976 (L) for indicators across the entire pH range. * a * b * ) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * Relationship characterization results; CIE 1976 (L) for indicators across the entire pH range * a * b * The color change parameter curve S) Ja*-b* SJb*-hab S Jb*-△E and S JC*ab-△E Characterization results of the relationship under different pH conditions; CIE 1976 (L) for indicators across the entire pH range. * a * b * The titration color change trajectory of the indicator; the correlation between wavelength and absorbance across the entire pH range. The characterization method provided by this invention has the following advantages:

[0027] This invention establishes for the first time a continuous measurement method for the full pH range of indicators, and measures the color change value of the indicators.

[0028] This invention establishes for the first time the parameters of a full-spectrum titration color change curve for S Ja*-b* S Jb*-hab S Jb*-△E and S JC*ab-△E The three types of curves enable visualization and peaking of the measurement process.

[0029] This invention establishes for the first time an indicator with isoluminance a across the entire pH range. * -b chart, yellow-blue product index a * -L * The chart and the red-green product index b * -L * The graph shows three chromaticity indexes, which visually analyze the mathematical relationship between color change and pH.

[0030] This invention is the first to measure the color change values ​​of three indicators, and verifies and discovers the monochromatic and multicolor color change values ​​of various indicators.

[0031] This invention establishes for the first time a 3D visual model titration curve of A-λ-pH across the entire pH range of an indicator and an L-pH model of the indicator across the entire pH range. * -a * -b * The 3D visual model of the titration curve intuitively describes the spectral variation of the indicator.

[0032] This invention uses VSTT to continuously measure the pH range of the indicator from 0 to 13.5, obtaining a color change curve for the pH range. The color change point is identified by the signal peak on the curve, realizing the digitization and graphical representation of the amount of reagent added and the corresponding color change for each measurement cycle in the sensory titration process. This allows for the traceability and analysis of the structural transformation in each measurement cycle. Attached Figure Description

[0033] Figure 1 CIE 1976(L) for phenolphthalein * a * b * L *value, a * value, b * pH plane coordinate graph;

[0034] Figure 2 For bromocresol purple, CIE 1976(L) * a * b * L * value, a * value, b * pH plane coordinate graph;

[0035] Figure 3 CIE 1976 (L) for methyl orange * a * b * L * value, a * value, b * pH plane coordinate graph;

[0036] Figure 4 The graph shows the relationship between the chroma of phenolphthalein, bromocresol purple, and methyl orange indicators and pH.

[0037] Figure 5 A graph showing the relationship between the hue angles of phenolphthalein, bromocresol purple, and methyl orange indicators and pH.

[0038] Figure 6 The graph shows the relationship between the color difference and pH of phenolphthalein, bromocresol purple, and methyl orange indicators.

[0039] Figure 7 Phenolphthalein CIE 1976 (L) * a * b * ) of L * Value (brightness) of a * -b * Color index chart;

[0040] Figure 8 Phenolphthalein CIE 1976 (L) * a * b * ) of b * Value (yellow-blue magenta index) a * -L * Color index chart;

[0041] Figure 9 Phenolphthalein CIE 1976 (L) * a * b * ) of a * value (red-green index) b * -L *Color index chart;

[0042] Figure 10 Bromocresol purple (CIE 1976) * a * b * ) of L * Value (brightness) of a * -b * Color index chart;

[0043] Figure 11 Bromocresol purple (CIE 1976) * a * b * ) of b * Value (yellow-blue magenta index) a * -L * Color index chart;

[0044] Figure 12 Bromocresol purple (CIE 1976) * a * b * ) of a * value (red-green index) b * -L * Color index chart;

[0045] Figure 13 Methyl orange (CIE 1976) * a * b * ) of L * Value (brightness) of a * -b * Color index chart;

[0046] Figure 14 Methyl orange (CIE 1976) * a * b * ) of b * Value (yellow-blue magenta index) a * -L * Color index chart;

[0047] Figure 15 Methyl orange (CIE 1976) * a * b * ) of a * value (red-green index) b * -L * Color index chart;

[0048] Figure 16 Color change curves of three indicators at pH threshold (SJa*-b* ) and color change point;

[0049] Figure 17 Color change curves of three indicators at pH threshold (S Ja*-b* ) and magnified image of the color-changing point;

[0050] Figure 18 Color change curves of three indicators at pH threshold (S Jb*-hab ) and color change point;

[0051] Figure 19 Color change curves of three indicators at pH threshold (S Jb*-hab ) and magnified image of the color-changing point;

[0052] Figure 20 Color change curves of three indicators at pH threshold (S Jb*-△E ) and color change;

[0053] Figure 21 Color change curves of three indicators at pH threshold (S Jb*-△E ) and magnified image of the color-changing point;

[0054] Figure 22 Color change curves of three indicators at pH threshold (S JC*ab-△E ) and color change point;

[0055] Figure 23 Color change curves of three indicators at pH threshold (S JC*ab-△E ) and magnified image of the color-changing point;

[0056] Figure 24 This is a wavelength-absorbance curve of phenolphthalein across the entire pH range.

[0057] Figure 25 L for the entire pH range of phenolphthalein * -a * -b * 3D visual model of titration curve;

[0058] Figure 26 A 3D visual model titration curve of phenolphthalein across the entire pH range (A-λ-pH).

[0059] Figure 27 This is a wavelength-absorbance curve of bromocresol purple across the entire pH range.

[0060] Figure 28 L for the entire pH range of bromocresol purple * -a * -b * 3D visual model of titration curve;

[0061] Figure 29A 3D visual model titration curve of bromocresol violet across the entire pH range (A-λ-pH).

[0062] Figure 30 The wavelength-absorbance curves of methyl orange under different pH conditions are shown.

[0063] Figure 31 L for methyl orange across the entire pH range * -a * -b * 3D visual model of titration curve;

[0064] Figure 32 The figure shows a 3D visual model titration curve of methyl orange across the entire pH range (A-λ-pH). Detailed Implementation

[0065] This invention provides a method for characterizing indicators using visible light full-spectrum technology across the entire pH range, comprising the following steps:

[0066] In the titration of an indicator across the entire pH range, a three-dimensional spectrophotometer-potential-temperature spectrophotometer was used to continuously measure the characteristic spectral signal and pH signal formed by the absorption of visible light after structural changes of the indicator in the solution during the titration process. The characteristic spectral signal was defined according to CIE 1976(L). * a * b * The chromaticity parameter value in the uniform color space is represented, and the chromaticity parameter value is calculated as a visible light full spectrum parameter. The visible light full spectrum parameter is used to establish a full pH threshold coordinate curve of the indicator with the pH signal, and the full pH range characterization result of the indicator measured by visible light full spectrum titration is obtained; the full pH range is 0 to 13.5.

[0067] The characterization results include:

[0068] CIE 1976 (L) indicator for the entire pH range * a * b * ) chromaticity value L * value, a * value and b * Colorimetric value curves under different pH conditions;

[0069] Chroma C of the indicator across the entire pH range * ab Hue angle h ab The curves showing the variation of color difference ΔE under different pH conditions;

[0070] CIE 1976 (L) indicator for the entire pH range * a * b * ) Chromaticity index diagram of chromaticity values ​​a* -b * Color index chart a * -L * Color index chart b * -L * Relationship representation results;

[0071] CIE 1976 (L) indicator for the entire pH range * a * b * The color change parameter curve S) Ja*-b* S Jb*-hab S Jb*-△E and S JC*ab-△E Characterization results of the relationship under different pH conditions;

[0072] CIE 1976 (L) indicator for the entire pH range * a * b * The titration color change trajectory of )

[0073] The correlation between wavelength and absorbance of the indicator across the entire pH range.

[0074] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0075] In this invention, the indicator preferably includes phenolphthalein, bromocresol purple, or methyl orange.

[0076] In this invention, the titration process of the indicator preferably includes the following steps:

[0077] The indicator solution is added dropwise to the solution, and the pH is adjusted to ~0.1 by adding acid solution. The pH is then titrated to ~13.5 with alkaline solution. The titration is performed at room temperature. This invention does not have special requirements for the preparation method of the indicator solution; conventional methods well-known to those skilled in the art can be used.

[0078] In this invention, the indicator solution is preferably added dropwise to the solution used in the solution preparation, specifically water. The acid solution is preferably a sulfuric acid solution. The alkaline solution is preferably a sodium hydroxide solution.

[0079] In this invention, the pH resolution of the spectro-potential-temperature three-dimensional spectrophotometer is 0.1 pH. The spectro-potential-temperature three-dimensional spectrophotometer is preferably the GDW2304-11X3 (basic model) originally developed by Qinhuangdao Water Bear Technology Co., Ltd. The measurement conditions include: a spectral range of 380 nm to 780 nm, Δλ = 5 nm, a measurement period of 200 ms, and an optical path of 10.0 mm. During continuous measurement, the spectral blank of the water-corrected full-spectrum titrator is L. *=100.0, a * =0.0, b * =0.0.

[0080] In this invention, the indicator is CIE 1976 (L) across the entire pH range. * a * b * ) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * The preferred characterization results of the relationship include: CIE 1976 (L) indicators across the entire pH range. * a * b * (equal brightness L) * The value of a * -b * Chromaticity index chart, CIE 1976 (L) indicator for the entire pH range * a * b * The yellow-blue magenta index b) * The value of a * -L * CIE 1976 (L) color index chart and indicator for the entire pH range * a * b * The red-green product index a) * value b * -L * Color index chart.

[0081] In this invention, the indicator is CIE 1976 (L) across the entire pH range. * a * b * The titration color change trajectory characterization of the indicator is preferably based on the L-axis across the entire pH range. * -a * -b * The 3D visual model titration curve.

[0082] In this invention, the correlation between wavelength and absorbance of the indicator across the entire pH range preferably includes: a wavelength-absorbance curve, absorbance at the maximum absorption wavelength under different pH conditions, and a 3D visual model titration curve of A-λ-pH for the entire pH range titration curve.

[0083] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0084] Example 1

[0085] This embodiment uses three commonly used acid-base titration indicators: phenolphthalein, bromocresol purple, and methyl orange.

[0086] The method for preparing sodium hydroxide solution is as follows: Weigh analytical grade sodium hydroxide and prepare sodium hydroxide titration solutions of different concentrations from approximately 0.01% to 20%.

[0087] The method for preparing sulfuric acid solution is as follows: Analytical pure sulfuric acid is prepared into an approximately 1% sulfuric acid solution using primary water.

[0088] The preparation method of the indicator solution is shown in Table 1.

[0089] Table 13 Preparation Methods for Indicator Solutions

[0090]

[0091] VSTT measurement method for indicators

[0092] Titration process

[0093] Add 100 μL of indicator solution to 100 mL of water, adjust the pH to approximately 0.1 with sulfuric acid solution, and titrate the pH to approximately 14 with sodium hydroxide solution.

[0094] VSTT measurement conditions for indicators

[0095] Instrument and parameter settings: GDW2304-11X3 (basic model) spectro-potential-temperature three-dimensional spectrophotometer, pH resolution 0.1 pH; spectral range 380 nm~780 nm, Δλ=5 nm, measurement period 200 ms, optical path 10.0 mm, stirring speed approximately 450 rpm. Water was used as the blank for correction to L. * =100.0, a * =0.0, b * =0.0, reaction vessel volume 180mL, measured at room temperature.

[0096] Measurement Principles and Algorithms

[0097] Visible Spectral Titration Technology (VSTT) is a technique that uses a stable visible light source to pass through a chemical reaction solution. The characteristic spectrum formed by the absorption of visible light by the analyte in the solution due to structural changes is measured using CIE 1976 (L...). * a * b * Uniform Color Space (CIE 1976) * a * b* The calculated colorimetric value parameter is represented by the colorimetric value parameter and the reagent environment quantity, which are then used to calculate the VSTT parameter. The VSTT parameter and the reagent environment quantity are used to establish the VSTT curve coordinates, and the VSTT curve and the reagent environment have a mathematical correspondence.

[0098] 1. CIE 1976(L) * a * b * Calculation method of parameter values

[0099] Brightness L * Formula for calculating the value:

[0100]

[0101] Red-Green Product Index a * Formula for calculating the value:

[0102]

[0103] Yellow-blue magenta index b * Formula for calculating the value:

[0104]

[0105] Chroma C * ab Formula for calculating the value:

[0106] Hue angle h ab Formula for calculating the value:

[0107] Formula for calculating color difference ΔE:

[0108] 2. VSTT parameters

[0109]

[0110]

[0111]

[0112]

[0113] 3. CIE 1976(L) * a * b * The chromaticity curve and VSTT curve

[0114] 1. CIE 1976(L) * a * b *) chromaticity value L * value, a * value and b * value;

[0115] 2. CIE 1976(L) * a * b * ) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * ;

[0116] 3. CIE 1976(L) * a * b * The color difference parameter ΔE;

[0117] VSTT method for measuring the CIE 1976(L) standard for three indicators * a * b * Results and Data Analysis

[0118] (1) The color change threshold and color change point of the three indicators are shown in Table 2.

[0119] Table 2. Color change threshold and color change point of indicators

[0120]

[0121] (2) Analysis of the VSTT color change curve and color change parameters of the indicator

[0122] Three indicators were measured, and color change curves of VSTT were obtained for all three indicators over the entire pH range. The CIE 1976(L) standard for VSTT of the three indicators was also obtained. * a * b * ) Figure, wavelength-absorbance curve, A-λ-pH 3D visual model of the full pH threshold titration curve, L-pH titration curve of the full pH threshold * -a * -b * A 3D visual model of the titration curve was generated. The color change curve reveals the color parameters and corresponding volume values ​​or pH values ​​for each measurement cycle, thus achieving a color description of the measurement cycle. The established CIE 1976(L) standard... * a * b * ) Figure, wavelength-absorbance curve, A-λ-pH 3D visual model of the full pH threshold titration curve, L-pH titration curve of the full pH threshold * -a* -b * The 3D visual model titration curve is shown. The three indicators—phenolphthalein, bromocresol purple, and methyl orange—were characterized using visible light full-spectrum technology across the entire pH range. Figures 1 to 32 .

[0123] (1) Analysis of phenolphthalein characterization results:

[0124] Figure 1 The experimental pH range of 0.1–13.5 was described, and the phenolphthalein colorimetric curve showed significant fluctuations within the pH range of 8.0–13.5. * and b * The values ​​showed a decreasing trend around pH 8.0–10.5 and an increasing trend around pH 12.0–13.5. * The value shows an increasing trend around pH 8.0–10.5 and a decreasing trend around pH 12.0–13.5, indicating that the structure of phenolphthalein changes within these two pH ranges, affecting the absorption spectrum. The CIE 1976(L) values ​​of phenolphthalein under different pH conditions are shown. * a * b * ) of L * Value (brightness) of a * -b * Color index chart ( Figure 7 The trajectory indicates that, at equal brightness L * Under the given conditions, phenolphthalein solution is colorless from pH 0.1 to pH 7.0. From pH 7.0 to pH 10.5, the color changes from colorless to purplish-red, reaching its deepest color at pH 10.3. From pH 10.5 to pH 13.5, the color changes from purplish-red back to colorless. The color change trajectory is basically within the range specified in CIE 1976(L). * a * b * The first, second, and fourth quadrants of the chromaticity index (CIE1976) graph are shown. This indicates that phenolphthalein undergoes structural changes during the pH transitions from 7.0 to 10.5 and from 10.5 to 13.5. The CIE1976 (L) chromaticity index of phenolphthalein under different pH conditions is also shown. * a * b * ) of b * Value (yellow-blue magenta index) a * -L * Color index chart ( Figure 8 The trajectory indicates that, in the yellow-blue index b * Under the given conditions, the phenolphthalein solution showed no color change from pH 0.1 to pH 7.0; and its brightness (L) increased at pH 10.3 from pH 7.0 to pH 10.5.* The lowest value, red-green index a * The value is highest, and the solution changes from clear and colorless to red; the brightness (L) increases from pH 10.5 to pH 13.5. * The value has rebounded somewhat, a * As the pH value decreases, the solution changes from red to clear and colorless. This indicates that the phenolphthalein solution undergoes structural changes at two points: between pH 7.0 and pH 10.5, and between pH 10.5 and pH 13.5. Phenolphthalein CIE 1976 (L) * a * b * ) of a * value (red-green index) b * -L * Color index chart ( Figure 9 The trajectory of the red-green product index (a) indicates that... * Under the given conditions, the phenolphthalein solution showed no color change from pH 0.1 to pH 7.0; and its brightness (L) increased at pH 10.3 from pH 7.0 to pH 10.5. * The lowest value, yellow-blue magenta index b * At its lowest value, the solution changes from clear and colorless to blue; the brightness (L) changes from pH 10.5 to pH 13.5. * The value has rebounded somewhat, b * As the pH value increases, the solution changes from blue to clear and colorless. This indicates that the phenolphthalein solution undergoes structural changes at two points: between pH 7.0 and pH 10.5, and between pH 10.5 and pH 13.5. Figure 24 It can be seen that at pH 1.0, pH 2.0, pH 3.0, pH 4.0, pH 5.0, pH 6.0, pH 7.0, and pH 8.0, phenolphthalein has no absorption peak in the 380nm–780nm range and is colorless; at pH 9.0, it has an absorption peak in the 500nm–600nm range, with a maximum absorption peak around 550nm, and is red; at pH 10.0, it has an absorption peak in the 460nm–600nm range, with a maximum absorption peak around 550nm, and is red; at pH 11.0, it has an absorption peak in the 480nm–600nm range, with a maximum absorption peak around 550nm, and is red. At pH 12.0, there is an absorption peak in the range of 460 nm to 600 nm, with the maximum absorption peak around 550 nm, and the color is red; at pH 13.0, there is an absorption peak in the range of 480 nm to 600 nm, with the maximum absorption peak around 550 nm, and the color is red. Figure 25 In order to more clearly show the trend of change, L * The axis was chosen to be in the coordinate range of 91 to 100. In this three-dimensional coordinate system, L is located at pH 0.1. *Value 99.63, a * Values ​​0.324 and b * Value 0.857, colorless and transparent; L at pH 7.0 * Value 98.94, a * Values ​​0.328 and b * Value 0.962, colorless and transparent; L at pH 8.4 * Value 98.56, a * Values ​​0.883 and b * Value 0.828, color pink; L at pH 10.3 * Value 91.87, a * Values ​​14.66 and b * Value -9.063, color dark red; L at pH 13.5 * Value 97.28, a * Values ​​-0.299 and b * Value 0.216, color is colorless and transparent. Figure 25 The total pH threshold of phenolphthalein (L) * -a * -b * The 3D visual model titration curve is the first to comprehensively record and display the relationship between color changes and different pH conditions. Figure 26 The A-λ-pH 3D visual model of the phenolphthalein full-pH threshold titration curve shows that the maximum absorption peak is around 550 nm. From pH 8 onwards, peaks gradually appear, reaching their maximum value in the pH 10.0–12.0 range, and then decreasing sharply near pH 12.0. The solution is purplish-red in color.

[0125] (2) Analysis of bromocresol purple characterization results:

[0126] Figure 2 The chromaticity curves of bromocresol violet from pH 0.1 to pH 13.5 show two notable fluctuations, near pH 5.9 and pH 13.5. From pH 0.1 to pH 4, the chromaticity curves show no notable fluctuations. * value, a * value and b * The values ​​were all very stable, indicating that the solution did not undergo structural changes altering its spectral composition. From pH 4 to pH 8, there were two noteworthy fluctuations in the chromaticity curve. * The value shows a decreasing trend in the pH range of 5 to 7. * value and b *The values ​​show a distinct broken-line change around pH 5 and pH 7, intersecting near pH 6. This indicates that the structure of bromocresol violet changes within the pH 5–pH 7 range, affecting the absorption spectrum. From pH 8 to pH 13.5, there is one noteworthy fluctuation in the chromaticity curve within this range. * The value tends to decrease after pH 11.0–12. * value and b * The similarity in values ​​around pH 9.0–13.5 indicates that the structure of bromocresol violet may have changed in this pH range, affecting the absorption spectrum. The CIE 1976 (L) values ​​of bromocresol violet under different pH conditions are shown in the figure. * a * b * ) color index chart ( Figure 10 The trajectory indicates that, at equal brightness L * Under the given conditions, bromocresol purple solution changes color from yellowish-green to nearly colorless during the pH range from 0.1 to 5.9, and the color change trajectory follows the CIE 1976(L) standard. * a * b * The second quadrant of the chromaticity index graph; during the pH range of 5.9 to 13.5, the solution color changes from nearly colorless to reddish-blue, reaching its maximum near pH 8.3, and then gradually changes from reddish-blue to light reddish-blue. There is no significant change between pH 13.0 and pH 13.5. The color change trajectory is shown in CIE 1976 (L... * a * b * The fourth quadrant of the CIE 1976 (L) color index graph. Bromocresol violet under different pH conditions. * a * b * ) of b * Value (yellow-blue magenta index) a * -L * Color index chart ( Figure 11 The trajectory indicates that, in the yellow-blue index b * Under the given conditions, the color of bromocresol purple solution changes from a lighter green to nearly transparent and colorless during the pH range of 0.1 to 5.9, with a decrease in lightness value. During the pH range of 5.9 to 13.5, the solution color changes from nearly transparent and colorless to red, reaching its maximum near pH 8.3, then gradually changes from red to light red, with the lightness value also decreasing to its lowest value. No significant change is observed during the pH range of 13.0 to 13.5. The CIE 1976 (L) standard for bromocresol purple under different pH conditions is presented. * a * b* ) of a * value (red-green index) b * -L * Color index chart ( Figure 12 The trajectory of the red-green product index (a) indicates that... * Under the given conditions, the color of bromocresol purple solution changes from yellow to nearly colorless and transparent during the pH range of 0.1 to 5.9, with a decrease in lightness value; during the pH range of 5.9 to 13.5, the color of the solution changes from nearly colorless and transparent to blue, reaching its maximum value near pH 8.3, and then gradually changes from blue to light blue, with the lightness value also reaching its extreme value; there is no significant change during the pH range of 13.0 to 13.5. Figure 27In pH 1.0, the maximum absorption peak is at 420 nm, and the color is yellow. At pH 2.0, there is an absorption peak in the range of 380 nm to 520 nm, the same range as at pH 1.0, with a maximum absorption peak at 430 nm, and the color is deep yellow. At pH 3.0, there is an absorption peak in the range of 380 nm to 520 nm, similar to at pH 2.0, with a maximum absorption peak at 440 nm, and the color is yellow-orange. At pH 4.0, there are absorption peaks in the first range of 380 nm to 520 nm and the second range of 560 nm to 620 nm, with the maximum absorption peaks at 425 nm (first at 425 nm) and 585 nm (second at 585 nm), and the color is a deep yellow mixed with a very pale purplish-red. At pH 5.0, absorption peaks are observed at two locations: 380 nm to 520 nm (first location) and 560 nm to 620 nm (second location). The maximum absorption peaks are at 440 nm (first location) and 585 nm (second location). The absorption peak at the second location is significantly stronger than that at pH 4.0, and the color is a mixture of a deep yellow and a pale purplish-red. At pH 6.0, absorption peaks are observed at two locations: 420 nm to 470 nm (first location) and 520 nm to 640 nm (second location). The maximum absorption peaks are at 430 nm (first location) and 585 nm (second location). The absorption peak at the second location is significantly stronger than that at pH 5.0, and the color is a pale purplish-red mixture of a very pale yellow and a deep purplish-red. At pH 7.0, absorption peaks are observed at 440 nm to 630 nm, with a maximum absorption peak at 585 nm. The absorption peak is significantly stronger than the second absorption peak at pH 6.0, and the color is a more concentrated purplish-red. At pH 8.0, an absorption peak is observed in the range of 440 nm to 640 nm, with a maximum absorption peak at 590 nm. The absorption peak is slightly increased compared to pH 7.0, and the color is deep purplish-red. At pH 9.0, an absorption peak is observed in the range of 440 nm to 640 nm, with a maximum absorption peak at 590 nm. The absorption peak is slightly decreased compared to pH 8.0, and the color is purplish-red. At pH 10.0, an absorption peak is observed in the range of 440 nm to 640 nm, with a maximum absorption peak at 590 nm. The absorption peak is slightly decreased compared to pH 9.0, and the color is purplish-red. At pH 11.0, an absorption peak is observed in the range of 460 nm to 640 nm, with a maximum absorption peak at 590 nm. The absorption peak is essentially the same as that at pH 10.0, and the color is purplish-red. At pH 12.0, an absorption peak is observed in the range of 470 nm to 640 nm, with a maximum absorption peak at 590 nm. The absorption peak is slightly increased compared to pH 11.0, and the color is deep purplish-red. At pH 13.0, there is an absorption peak in the range of 470 nm to 640 nm, with the maximum absorption peak at 590 nm. The absorption peaks are basically the same as those at pH 12.0, and the color is deep purple-red. Figure 28 To more clearly show the trend of change, L * The axis was chosen to be in the range of 40–65. In this three-dimensional coordinate system, the starting point is L at pH 0.1.* Value 65.5, a * Values ​​-1.66 and b * Value 20.03, color a pale greenish-yellow; L at pH 5.2 * Value 62.6, a * Values ​​-1.38 and b * The value is 12.58, and the color is a pale greenish-yellow, lighter than at pH 0.1; the L at pH 5.9... * Value 58.0, a * Values ​​0.13 and b * Value 0.56, color a near-colorless mixture of red and yellow; L at pH 6.8 * Value 52.9, a * Values ​​4.31 and b * Value -14.50, color is a pale reddish blue, which can be considered a pale purple; L at pH 7.0 * Value 52.1, a * Values ​​5.39 and b * Value -17.27, color a reddish blue, which can be considered a slightly darker purple; L at pH 7.2 * Value 50.7, a * Values ​​7.45 and b * Value -21.92, color is a reddish blue, which can be considered purple; L at pH 8.3 * Value 50.8, a * Values ​​8.09 and b * Value -22.36, color is a reddish blue, which can be considered a deep purple; L at pH 13.0 * Value 40.5, a * Values ​​1.36 and b * Value -11.08, color is a pale reddish-blue, which can be considered blue; L at pH 13.5 * Value 41.5, a * Values ​​1.55 and b * The value is -10.48, and the color is a bluish-purple with a hint of red, which can be considered as blue. Figure 29The A-λ-pH 3D visual model of the full pH threshold titration curve of bromocresol purple shows that the maximum absorption peak is around 590 nm. Before pH 6.0, the absorption peak is predominant at 430 nm, and after pH 6.0, it generally shows a downward trend; after pH 6.0, the absorption peak is predominant at 590 nm, especially maintaining high absorbance from pH 7.0 to pH 8.0. Before pH 6.0, the absorbed wavelength is predominantly 430 nm, resulting in a lack of purple-blue in the solution; under D65 illuminant conditions, the solution exhibits a yellowish-green color after the loss of purple-blue. After pH 6.0, the absorbed wavelength is predominantly 590 nm, resulting in a lack of yellow in the solution; under D65 illuminant conditions, the solution exhibits a reddish-purple-red color after the loss of yellow.

[0127] (3) Analysis of methyl orange characterization results:

[0128] Figure 3 The experiment was conducted in the pH range of 0.4 to 13.5, and a noteworthy fluctuation was observed in the chromaticity curve near pH 3.5 to 4.5. Figure 3 This indicates that there is one noteworthy fluctuation in the chromaticity curve within the pH range of 0.4 to 7.0. (Lightness L) * The value tends to increase around pH 3.0, and the red-green index a... * Value and Yellow-Blue Magenta Index b * The values ​​show an intersecting trend around pH 4.3, indicating that the structure of methyl orange changes near pH 4.3, affecting the absorption spectrum. From pH 7.0 to pH 13.5, the chromaticity curve shows no noteworthy fluctuations. (Lightness L) * Value, Red-Green Product Index a * Value and Yellow-Blue Magenta Index b * The absorption curve for methyl orange is flat, almost a straight line, between pH 7.0 and pH 13.5. In measurements of methyl orange at different pH values, the focus is primarily on the pH range of 4.3, where structural changes alter the absorbance spectrum. CIE 1976(L) values ​​of methyl orange under different pH conditions are presented. * a * b * ) of a * -b * Color index chart as follows Figure 13 The trajectory indicates that, at equal brightness L * Under the given conditions, methyl orange solution changes color from red to yellow relatively quickly between pH 0.4 and pH 7.0; however, it remains yellow with a very small change between pH 7.0 and pH 13.5. Methyl orange (CIE 1976)* a * b * ) of b * Value (yellow-blue magenta index) a * -L * Color index chart ( Figure 14 The trajectory indicates that, in the yellow-blue index b * Under the given conditions, the red-green index a of methyl orange solution during the pH range from 0.4 to 3.0... * Value and brightness L * The values ​​did not change significantly; during the pH period from 3.0 to 3.3, the red-green index a of the solution... * The value did not change significantly, and the brightness L... * The value showed an upward trend, and the solution color changed from a darker red to a slightly lighter red; during the pH period from 3.3 to 7.0, the red-green index a... * The value shows a decreasing trend, and the solution brightness L * As the value slowly increases, the solution color changes from a slightly lighter red to nearly colorless; the red-green index a of the solution changes during the pH period from 7.0 to 13.5. * Value and brightness L * The value did not change significantly, and the solution color and brightness remained essentially unchanged, remaining nearly colorless. Methyl orange (CIE 1976) * a * b * ) of a * value (red-green index) b * -L * Color index chart ( Figure 15 The trajectory of the red-green product index (a) indicates that... * Under the given conditions, the yellow-blue index b of methyl orange solution during the pH range from 0.4 to 3.0... * Value and brightness L * The value showed an upward trend, albeit a small increase, with the solution color changing from nearly colorless to pale yellow and the brightness slightly increasing; during the pH range of 3.0 to 3.3, the solution color remained essentially unchanged, and the brightness (L) remained relatively stable. * The value increased significantly; during the pH range from 3.3 to 7.0, the yellow-blue index b... * Value and brightness L * The pH value of the solution showed an upward trend, and the color changed from light yellow to a deeper yellow. During the period from pH 7.0 to pH 13.5, the yellow-blue index b... * Value and brightness L * The value did not change significantly, and the color and brightness of the solution remained largely unchanged, remaining a deep yellow. Figure 30At pH 1.0, an absorption peak is observed in the range of 420 nm to 580 nm, with a maximum absorption peak at 510 nm; at pH 2.0, an absorption peak is observed in the range of 380 nm to 580 nm, with a maximum absorption peak at 510 nm; at pH 3.0, an absorption peak is observed in the range of 440 nm to 580 nm, with a maximum absorption peak at 510 nm; at pH 4.0, an absorption peak is observed in the range of 420 nm to 570 nm, with a maximum absorption peak at 510 nm; at pH 5.0, an absorption peak is observed in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 6.0, an absorption peak is observed in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 7.0, an absorption peak is observed in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm. At pH 8.0, there is an absorption peak in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 9.0, there is an absorption peak in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 10.0, there is an absorption peak in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 11.0, there is an absorption peak in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 12.0, there is an absorption peak in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm; at pH 13.0, there is an absorption peak in the range of 380 nm to 560 nm, with a maximum absorption peak at 465 nm. Figure 31 To more clearly show the trend of change, L * The coordinates chosen for the axes are 76–82. In this three-dimensional coordinate system, the L-axis represents the color curve of methyl orange at pH 0.4. * Value 94.9, a * Value 7.34 and b * A value of 0.36 indicates a color that is a deep red with a near-colorless pale yellow hue, which can be considered red. At pH 3.0, the solution color corresponds to the L-axis of the curve. * Value 95.2, a * Values ​​6.92 and b * The value is 1.21, and the color is a deep red with a pale yellow tint; at pH 3.3, the solution color corresponds to the L curve. * Value 97.1, a * Values ​​6.71 and b * The pH value is 1.54, and the color is a deep red with a pale yellow tint; at pH 4.3, the solution color corresponds to the L curve. * Value 98.2, a * Values ​​3.44 and b * A pH of 3.82 indicates a color that is a mixture of yellow and red, which can be considered orange-yellow. At pH 4.4, the solution color corresponds to the L-axis of the curve. * Value 98.4, a *Values ​​2.46 and b * The pH value is 4.88, and the color is a light reddish-yellow; at pH 7.0, the solution color corresponds to the L curve. * Value 98.5, a * Values ​​0.70 and b * The pH value is 6.27, and the color is a pale reddish-yellow with a near-colorless hue, which can be considered yellow. At pH 13.5, the solution color corresponds to the L curve. * Value 98.5, a * Values ​​0.69 and b * The value is 6.32, and the color is a pale reddish-yellow with a near-colorless hue, which can be considered yellow. The L of methyl orange across the entire pH threshold... * -a * -b * The 3D visual model titration curve is the first to comprehensively record and display the relationship between color changes and different pH conditions. Figure 32 The A-λ-pH 3D visual model of the titration curve of methyl orange across the entire pH threshold shows that, between pH 1.0 and pH 4.0, the maximum absorption peak is clearly around 510 nm, and the spectrum shows red. After pH 4.0, the maximum absorption wavelength is 465 nm, and the spectrum shows yellow, which is consistent with the actual solution color.

[0129] (4) Comparison results of the three indicators

[0130] Figure 16 and Figure 17 In China: Traditional literature defines the color change threshold range of phenolphthalein indicator as pH 8.0–pH 10.0 (colorless → reddish-purple), while VSTT's S... Ja*-b* The color change points are pH 8.4 and pH 13.3. The first color change point, pH 8.4, is within the color change threshold range of traditional literature, while the second color change point, pH 13.3, is not recorded. The traditional literature color change threshold range for bromocresol purple indicators is pH 5.2–pH 6.8 (yellow → purplish-red). VSTT's SJ... a*-b* The color change point is pH 6.3, within the color change threshold range; the traditional literature color change threshold range for methyl orange indicators is pH 3.0–pH 4.4 (red → yellow), and the S of VSTT… Ja*-b* The color change point is pH 4.2, which is within the color change threshold range.

[0131] Figure 18 Color change curves of three indicators at pH threshold (S Jb*-hab ) and color change point; Figure 19 Color change curves of three indicators at pH threshold (S Jb*-hab (and a magnified image of the color-changing point.) Figure 18 and Figure 19It can be seen that the color change curve S of phenolphthalein Jb*-hab The color change points of bromocresol purple are at pH = 8.3 and pH = 13.2, and the color change curve S of bromocresol purple is shown. Jb*-hab The color change point of methyl orange is at pH 6.3, and the color change curve S of methyl orange is shown. Jb*-hab The pH value at which the color changes is 0.5.

[0132] Figure 20 Color change curves of three indicators at pH threshold (S Jb*-△E ) and color change; Figure 21 Color change curves of three indicators at pH threshold (S Jb*-△E (and a magnified image of the color-changing point.) Figure 20 and Figure 21 It can be seen that the color change curve S of phenolphthalein Jb*-△E The color change points of bromocresol purple are at pH = 9 and pH = 13.1, and the color change curve S... Jb*-△E The pH value of the color change point of methyl orange is 6.1, and the color change curve S of methyl orange is... Jb*-△E The pH value at which the color changes is 0.7.

[0133] Figure 22 Color change curves of three indicators at pH threshold (S JC*ab-△E ) and color change point; Figure 23 Color change curves of three indicators at pH threshold (S JC*ab-△E (and a magnified image of the color-changing point.) Figure 22 and Figure 23 It can be seen that the color change curve S of phenolphthalein JC*ab-△E The color change points of bromocresol purple are at pH = 8.4 and pH = 13.3, and the color change curve S of bromocresol purple is shown. JC*ab-△E The color change curve S of methyl orange at pH = 6.2 (the pH point of the color change). JC*ab-△E The colorless point.

[0134] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for characterizing indicators using visible light full-spectrum technology across the entire pH range, characterized in that, Includes the following steps: In the titration of an indicator across the entire pH range, a three-dimensional spectrophotometer-potential-temperature spectrophotometer was used to continuously measure the characteristic spectral signal and pH signal formed by the absorption of visible light after structural changes of the indicator in the solution during the titration process. The characteristic spectral signal was defined according to CIE 1976(L). * a * b * The chromaticity parameter value in the uniform color space is represented, and the chromaticity parameter value is calculated as a visible light full spectrum parameter. The visible light full spectrum parameter is used to establish a full pH threshold coordinate curve of the indicator with the pH signal, and the full pH range characterization result of the indicator measured by visible light full spectrum titration is obtained; the full pH range is 0 to 13.

5. The characterization results include: CIE 1976 (L) indicator for the entire pH range * a * b * ) chromaticity value L * value, a * value and b * Colorimetric value curves under different pH conditions; Chroma C of the indicator across the entire pH range * ab Hue angle h ab The curves showing the variation of color difference ΔE under different pH conditions; CIE 1976 (L) indicator for the entire pH range * a * b * ) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * Relationship representation results; CIE 1976 (L) indicator for the entire pH range * a * b * The color change parameter curve S) Ja*-b* S Jb*-hab S Jb*-△E and S JC*ab-△E Characterization results of the relationship under different pH conditions; CIE 1976 (L) indicator for the entire pH range * a * b * The titration color change trajectory of ) The correlation between wavelength and absorbance of the indicator across the entire pH range.

2. The characterization method according to claim 1, characterized in that, The indicator is CIE 1976 (L) across the entire pH range. * a * b * ) Chromaticity index diagram of chromaticity values ​​a * -b * Color index chart a * -L * Color index chart b * -L * The relationship characterization results include: CIE 1976 (L) for the indicator across the entire pH range. * a * b * (equal brightness L) * The value of a * -b * Color index chart, CIE 1976 (L) indicator for the entire pH range * a * b * The yellow-blue magenta index b) * The value of a * -L * CIE 1976 (L) color index chart and indicator for the entire pH range * a * b * The red-green product index a) * value b * -L * Color index chart.

3. The characterization method according to claim 1, characterized in that, The indicator is CIE 1976 (L) across the entire pH range. * a * b * The titration color change trajectory of the indicator is L across the entire pH range. * -a * -b * The 3D visual model titration curve.

4. The characterization method according to claim 1, characterized in that, The correlation between wavelength and absorbance of the indicator across the entire pH range includes: wavelength-absorbance curves, absorbance at the maximum absorption wavelength under different pH conditions, and a 3D visual model of the A-λ-pH titration curve of the titration curve across the entire pH range.

5. The characterization method according to claim 1, characterized in that, The pH resolution of the spectro-potential-temperature three-dimensional spectrophotometer is 0.1 pH.

6. The characterization method according to claim 1 or 5, characterized in that, The measurement conditions include: a spectral range of 380 nm to 780 nm, Δλ = 5 nm, a measurement period of 200 ms, and an optical path of 10.0 mm.

7. The characterization method according to claim 1, characterized in that, During the continuous measurement, the spectral blank of the three-dimensional spectrophotometer-potential-temperature morphology analyzer was calibrated with water to a value of L. * =100.0, a * =0.0, b * =0.

0.

8. The characterization method according to claim 1, characterized in that, The titration process of the indicator includes the following steps: Add the indicator solution dropwise to the solution, adjust the pH to 0.1 with acid solution, and titrate the pH to 13.5 with alkaline solution.

9. The characterization method according to claim 8, characterized in that, The titration was performed at room temperature.

10. The characterization method according to claim 1, characterized in that, The indicator includes phenolphthalein, bromocresol purple, or methyl orange.

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