Program control full-spectrum titration method for automatic multi-color change reaction

Abstract

The invention discloses a program control full-spectrum titration method for automatic multi-color change reaction, and belongs to the technical field of chemical analysis. According to the method, the full-spectrum titration color change parameter signal value is used as a mark for marking the progress of the reaction stage, and the full-spectrum titration color change parameter signal value reaching the preset titration condition change point is used for indicating different stages of the reaction and carrying out the indication mark of the titration condition needing to be changed in the next step so as to enable the reaction to be continuously carried out; the full-flow continuous detection of the chemical reaction of multi-color-change full-spectrum titration is realized, and more accurate analysis information is provided for the system change process in the chemical reaction through the application of the visible light full-spectrum titrator.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical analysis, and in particular relates to a program-controlled full-spectrum titration method for automated multi-color change reactions. Background Art

[0002] The full spectrum titration method is a new analytical technology in titration analysis, and is widely used in environmental protection, food, chemical industry and other fields. The current full spectrum titration method is only suitable for the detection of single color change titration, that is, after the full spectrum titration parameters within the preset value range appear in the titration, all titration operations are completed and the titration is terminated. Therefore, this method is only suitable for single color change titration from one color to another, but when multiple color changes occur during the titration process, it is impossible to perform automated full-program titration detection. In other words, at present, whether it is photometric titration technology or spectral titration technology that replaces it, the automated detection control and data processing methods are limited to controlling a single color change through a single titration method. At this time, the color mutation point of the titration system not only represents the change of titration conditions, but also indicates the termination of the titration operation.

[0003] However, in actual analysis and testing work, there are at least the following two titration operation modes: one is the titration operation that requires changing different titration methods or titration conditions for multiple times. In this type of titration work, the completion of the titration work requires multiple different titration methods to be performed in sequence. At this time, multiple titration condition change points will be generated; the other is the titration operation with multiple color mutation points, which is often called a titration mode with multiple titration jump points. At this time, a single color change cannot meet the overall description of the titration operation, and multiple color changes do not necessarily indicate changes in multiple titration conditions.

[0004] For example, the principle of GB / T 6730.5-2022 Determination of total iron content in iron ore by titration after reduction with titanium trichloride is that after the sample is decomposed, iron is reduced by stannous chloride and titanium trichloride, excess reducing agent is oxidized by dilute potassium dichromate solution, sodium diphenylamine sulfonate is used as an indicator, and the reduced iron is titrated with potassium dichromate standard solution. The completion of each titration stage is marked by color change, and the total iron content is calculated by the volume of potassium dichromate standard solution consumed. The color change process is "light yellow → blue → colorless → green → blue-green → purple". For example, in the "SN / T 5253-2020 Determination of Aluminum Content in Ferrosilicon by EDTA Titration", the "7.3 Determination" step is also clearly specified: ... After adding nitric acid to the sample, add hydrofluoric acid to completely dissolve it, add perchloric acid to mix well and heat to nearly dry, cool it, add hydrochloric acid solution, heat it to dissolve it and precipitate it with sodium hydroxide solution; wash the beaker and precipitate with boiled hot sodium hydroxide washing solution, add phenolphthalein indicator to the filtrate and neutralize it with hydrochloric acid solution until it is colorless and in excess; add EDTA and acetic acid-sodium acetate buffer solution in turn and boil it, add PAN indicator while it is hot, and titrate it with copper sulfate standard solution until it is stable purple-red; then add saturated sodium fluoride solution until it turns fruit green, add PAN indicator after boiling, and titrate it with copper sulfate standard solution until it turns stable purple-red. Calculate the aluminum content based on the volume of copper sulfate standard solution consumed. "That is, its color change process is "colorless→purple-red→fruit green→purple-red".

[0005] For example, Zhang Ning established a method for measuring molybdenum in molybdenum concentrate, and the color changes at different stages are "none → yellow → pink" (Zhang Ning, et al. Determination of molybdenum in molybdenum concentrate by EDTA subtraction titration [J] China Molybdenum Industry, 2010, 34(4): 28-30); Fan Lixin established a method for measuring lead content in crude tin, and the color changes at different stages are "none → purple red → yellow" (Fan Lixin, et al. Determination of lead in crude tin by EDTA titration [J] Metallurgical Analysis, 2017, 37(5): 68-69); Wang Minlei established a method for measuring lead content in molybdenum concentrate by EDTA subtraction titration [J] Metallurgical Analysis, 2017, 37(5): 68-69); The method for measuring the amount of molybdenum in molybdenum concentrate established by Zhang Jianhui, the color change at the end of different stages is "none → red-purple → blue" (Wang Minlei, et al. Determination of molybdenum content in molybdenum concentrate by lead nitrate volumetric method [J] Nonferrous Mining and Metallurgy, 2007, 23 (3) 95-96); the method for measuring the hardness of water studied by Zhang Jianhui, the color change at the end of different stages is "none → purple-red → pure blue" (Zhang Jianhui, et al. Study on the determination of hardness of domestic water by complexometric titration [J] Contemporary Chemical Research, 2017, 02: 109-110); Li Huajuan in the method for determining the content of sodium sulfonate in petroleum, the color change at different stages is "none → purple-red → pure blue" (Zhang Jianhui, et al. Study on the determination of hardness of domestic water by complexometric titration [J] Contemporary Chemical Research, 2017, 02: 109-110); The color change at the end of each stage is “none → upper layer blue-green → lower layer blue → upper layer colorless” (Li Huajuan. Determination of mass concentration of sodium petroleum sulfonate by alkaline phase titration with bromocresol green [J] Guangdong Chemical Industry, 2016, 43(320): 163-164); Zhang Hongyan analyzed the peroxide value in oil, and the color change at the end of different stages is “none → light yellow → blue → blue disappears” (Zhang Hongyan. Factors affecting the determination of peroxide value in animal and vegetable oils and their products [J] Food Safety Guide, 2017(21): 79); Li Hao measured lead, In the method established for copper, the color changes at the end points of different stages are "none → brown red → bright blue → purple red → light purple" (Li Hao, et al. Determination of lead and copper in lead concentrate by continuous titration [J]. Chemical Analysis and Metering, 2016, 25(4): 46-49); in the research method of reducing sugar by Liu Ye, the color changes at the end points of different stages are "blue → blue-black → purple-black → purple-red → orange-yellow" (Liu Ye, et al. Research on the determination of reducing sugar in wine by direct titration [J] Journal of Food Safety and Quality, 2017, 8(6): 2180-2184).

[0006] For the complex titration method with multiple color changes and multiple steps of titration condition changes mentioned above, current testers can only rely on manual vision to judge the color endpoints at different stages, or manually continue the next stage of automatic titration after a single automatic titration is completed, which cannot meet the automated titration requirements of the entire titration process.

[0007] Moreover, when the titration condition change point and the color mutation point in the titration mode are not consistent, how to effectively distinguish and identify each titration condition change point and color mutation point becomes a difficulty in data processing and automated control of titration technology.

[0008] Therefore, developing a titration method suitable for multiple titration condition change points and / or multiple color mutation points has become an urgent problem to be solved by those skilled in the art. Summary of the invention

[0009] In view of this, the purpose of the present invention is to provide a titration method suitable for multiple titration condition change points and / or multiple color mutation points in order to address the problems existing in the prior art. The method realizes full-spectrum automated detection of multiple color change titrations in complex titration reactions through user-defined titration signal response and titration condition matching.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] A program-controlled full-spectrum titration method for automated multi-color change reaction, the program-controlled full-spectrum titration method comprising a plurality of titration steps performed in sequence, titration condition change points being preset between the titration steps to mark the change of titration conditions, the total amount of reagent added in the last titration step being the reaction endpoint reagent amount of the current analytical reaction system, and the parameter value of the measured item in the sample being calculated using the reaction endpoint reagent amount.

[0012] The multi-color change reaction of the present invention comprises a plurality of titration steps performed sequentially, wherein at least two color titration steps are included, and the last titration step is color titration.

[0013] In addition, the principle of the visible light full spectrum titration method (visible spectral titration technology, VSTT) is to use a sensor to obtain the data of the change in the visible light range during the whole reaction process, establish a rectangular coordinate system with the reagent volume, and use the signal of the full spectrum titration color change parameter as the titration endpoint value of this step, which corresponds to the volume of the added reagent. The visible light full spectrum titration method can overcome the defects of using "human eyes" + "thinking judgment" + "language description" + "manual control", no clear titration endpoint parameters, great interference from external conditions, arbitrary description of results, inability to save the measurement process, poor credibility, and inability to trace the value. It meets the methodological requirements, has the advantages of clear titration endpoint signal and no interference with the reaction process, and has a very broad application prospect.

[0014] Furthermore, after completing the titration operation of all steps, the total amount of reagent added in the last titration step is used as the reaction endpoint reagent amount of the current analytical reaction system, and the parameter value of the measured item in the sample is calculated based on the reaction endpoint reagent amount. The parameter value of the measured item can be the content of the measured item or the pH value calibrated by the full pH threshold indicator.

[0015] It is worth noting that the current full-spectrum titration method is only applicable to single-color change reactions, that is, it only includes one titration step. When a titration step is completed, the amount of reagent added in the current titration step is recorded as the amount of reagent at the reaction endpoint for calculation. Therefore, when performing the titration of multiple color change reactions, not only is it necessary to manually adjust the titration conditions of each titration step, but the instrument will also automatically record the amount of reagents in each titration step and calculate it. This not only increases the manual workload, but also increases the data processing capacity of the instrument, which in turn leads to the cumbersomeness of the multi-color change reaction titration procedure and the increase of inspection time.

[0016] The present invention provides an automated program control method for multiple color change reactions, sets changes in titration conditions between multiple titration steps performed in sequence, and uses the total amount of reagents added in the last titration step as the reaction endpoint reagent amount for calculation of the current analytical reaction system, without calculating the amount of reagents added in other titration steps. While reducing the manual workload, it also effectively reduces the data processing volume of instruments and equipment, and effectively improves the work efficiency of the multiple color change reaction titration program.

[0017] Further, the titration condition change point includes a titration condition limit point or a full spectrum titration color change parameter signal value limit point;

[0018] The titration conditions include one or more of the volume of the titration reagent, the temperature of the titration system, the magnetic conditions of the titration system, the illumination conditions of the titration system, the fluid speed of the titration reagent, and the microwave assistance of the titration system;

[0019] The full spectrum titration color change parameters include chromaticity value parameters, color change peak parameters of the color change curve S and color change curve S J The color change peak parameters.

[0020] Furthermore, the chromaticity value parameter includes lightness L * Value, red-green quality index a * Value, yellow-blue index b * Value, chroma C * ab Value, hue angle h ab Value and color difference △E value;

[0021] The color change peak parameters of the color change curve S include the color change curve S s and color change curve S △s .

[0022] It is worth noting that the calculation formula of the full spectrum titration color change parameter involved in the present invention includes:

[0023] Lightness value L * Calculation formula:

[0024]

[0025] Among them, when (i.e. 0.0088565),

[0026] when (i.e. 0.0088565),

[0027] Red-green color index value a * Calculation formula:

[0028]

[0029] Among them, when (i.e. 0.0088565),

[0030] when (i.e. 0.0088565),

[0031] Among them, when (i.e. 0.0088565),

[0032] when (i.e. 0.0088565),

[0033] Yellow-blue color index value b * Calculation formula:

[0034]

[0035] Among them, when (i.e. 0.0088565),

[0036] when (i.e. 0.0088565),

[0037] Among them, when (i.e. 0.0088565),

[0038] when (i.e. 0.0088565),

[0039] Chroma value C * ab Calculation formula:

[0040]

[0041] Hue angle hab Calculation formula:

[0042]

[0043] Where:

[0044] L * ——Psychological lightness coordinate value of the sample in CIELAB color space (also called lightness value);

[0045] a * ——Psychological chromaticity coordinate value of the sample in CIELAB color space (also known as red-green color index value);

[0046] b * ——Psychological chromaticity coordinate value of the sample in the CIELAB color space (also known as the yellow-blue color index value);

[0047] C * ab ——Chroma value of the sample in CIELAB color space;

[0048] h ab ——The hue angle value of the sample in the CIELAB color space, unit

[0049] X 10 ——Color stimulus value X among CIE 1964 standard colorimetric observers;

[0050] Y 10 ——Color stimulus value Y among CIE 1964 standard colorimetric observers;

[0051] Z 10 ——Color stimulus value Z among CIE 1964 standard colorimetric observers.

[0052] Color difference △E calculation formula 1:

[0053]

[0054] Where:

[0055] △L * ——are the brightness differences of sample 1 and sample n in the CIELAB color space;

[0056] △a * ——are the red-green color index differences of sample 1 and sample n in the CIELAB color space;

[0057] △b * ——respectively are the yellow-blue index differences of sample 1 and sample n in the CIELAB color space.

[0058] Color difference △E calculation formula 2:

[0059]

[0060] Where:

[0061] △L * ——are the brightness differences of sample 1 and sample n in the CIELAB color space;

[0062] △C * ab ——are the chroma differences between sample 1 and sample n in the CIELAB color space;

[0063] △h ab ——are the hue angle differences between sample 1 and sample n in the CIELAB color space, in radians (°).

[0064] Color change curve S of full spectrum titration s Calculation formula 1:

[0065]

[0066] Where:

[0067] S s —Color change curve of full spectrum titration (when the measurement value J takes the current amount);

[0068] n—1,2,3,…;

[0069] x—1,2,3,…;

[0070] y—2,3,4,…;

[0071] M—Lightness L of the chromaticity value in CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Value and color difference △E value;

[0072] J—titration process time t parameter, pulse signal f parameter, reagent volume v parameter, reagent concentration c parameter, pH value and hydrogen ion concentration c [H+] One of the parameters.

[0073] Color change curve S of full spectrum titration △s The calculation method is:

[0074]

[0075] Where:

[0076] S △s —Color change curve of full spectrum titration (when the measured value J takes the difference of the current amount);

[0077] n—1,2,3,…;

[0078] m—1,2,3,…;

[0079] x—1,2,3,…;

[0080] y—2,3,4,…;

[0081] M—Lightness L of the chromaticity value in CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Value and color difference △E value;

[0082] J—titration process time t parameter, pulse signal f parameter, reagent volume v parameter, reagent concentration c parameter, pH value and hydrogen ion concentration c [H+] A parameter value in a parameter.

[0083] Color change curve S J The calculation method is:

[0084]

[0085] Where:

[0086] S J —Full spectrum titration endpoint curve parameter value;

[0087] S a —Lightness L of the chromaticity value in the CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Any one of the value and color difference △E value;

[0088] S b —With S a Lightness L of chromaticity values ​​in different CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b *Value and its derived parameter chroma C * ab Value, hue angle h ab Any one of the value and color difference △E value.

[0089] Further, the program-controlled full-spectrum titration method of the automated multi-color change reaction includes:

[0090] When the preset titration condition change point of the titration step is the limiting point of the titration condition, the sample to be tested is titrated, the titration condition value of each metering point is recorded, and it is determined whether the titration condition value of each metering point matches the condition value of the limiting point of the preset titration condition;

[0091] If they match, the visible light full spectrum titrator is controlled to change the titration conditions according to the preset program, enter the next titration step, and continue the operation;

[0092] If they do not match, the visible light full spectrum titrator is controlled to maintain the operating state.

[0093] Further, the program-controlled full-spectrum titration method of the automated multi-color change reaction includes:

[0094] When the preset titration condition change point of the titration step is the full spectrum titration color change parameter signal value limit point, full spectrum titration is performed on the sample to be tested, the real-time full spectrum titration color change parameters of each metering point are recorded, and it is determined whether the full spectrum titration color change parameter data of each metering point matches the full spectrum titration color change parameter signal value of the preset titration condition change point;

[0095] If they match, the visible light full spectrum titrator is controlled to stop the current operation state;

[0096] If they do not match, the visible light full spectrum titrator is controlled to maintain the operating state.

[0097] Furthermore, the program-controlled full-spectrum titration method of the automated multi-color reaction also includes:

[0098] When the visible light full spectrum titrator stops the current operation state, determining whether the full spectrum titration color change parameter data of the metering point matches the preset titration endpoint full spectrum titration color change parameter signal value;

[0099] If they match, the visible light full spectrum titrator is controlled to terminate the operation;

[0100] If they do not match, the visible light full spectrum titrator is controlled to change the titration conditions according to the preset program, enter the next titration step, and continue the operation.

[0101] Furthermore, the change of the titration conditions includes adding a reagent or changing one or more of the physical conditions.

[0102] Furthermore, the adding of the reagent includes one or more of adding the original titration reagent and adding a new titration reagent;

[0103] The physical condition changes include one or more of temperature conditions, magnetic conditions, light conditions, fluid rotation speed, and microwave assistance.

[0104] It is worth mentioning that titration data can provide information about the spectral absorption of the color-forming substance structure at different color change stages in a chemical reaction. Considering that the structure of the compound changes differently at different stages of a chemical reaction, the absorption of light of different wavelengths is different, and the overall solution presents different colors. Different colors also represent different reaction stages. By measuring different colors, the progress of the chemical reaction can be inferred, so as to determine the change in different reaction conditions to make the reaction proceed to the next stage.

[0105] The present invention uses the full-spectrum titration color change parameter signal value as a mark to identify the progress of the reaction stage. When the full-spectrum titration color change parameter signal value reaches the preset titration condition change point, it indicates the different stages of the reaction and the need to change the titration condition in the next step to allow the reaction to continue. This realizes the full-process automated detection of chemical reactions of multi-color change full-spectrum titration, and through the application of a visible light full-spectrum titrator, provides more accurate analysis information for the system change process in the chemical reaction.

[0106] Compared with the prior art, the present invention has the following advantages:

[0107] 1. The present invention adopts visible light full spectrum detection calculation, and uses real color measurement to represent the color and its change with the signal value of the digital full spectrum titration color change parameter, and identifies the titration end point of each stage by the established signal value of the full spectrum titration color change parameter.

[0108] 2. The present invention marks the titration endpoints at different stages with the signal value of the full-spectrum titration color change parameter, realizes the digital, graphical and automatic identification of the titration endpoint, and realizes the intelligent identification and control of multi-color change experiments by combining automation technology;

[0109] 3. The present invention establishes the corresponding relationship between the color parameter value measured by the visible light full spectrum titration technology and the amount of reagent added, realizing the traceability and transfer of the value.

[0110] 4. The present invention provides the minimum detection limit and quantitative limit parameters of the detection method through the visible light full spectrum titration technology, which makes up for the methodological defects of artificial sensory titration. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0112] Figure 1 The present invention is a schematic flow chart of the program-controlled full-spectrum titration method using an automated multi-color change reaction, a manual titration and a single-color change full-spectrum titration method for the two color change reactions in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention.

[0113] Figure 2 The color change curve S of the monochromatic full spectrum titration method in Comparative Example 2 of the present invention is △s =△a * / △V diagram.

[0114] Figure 3 The color change curve S of the program-controlled full-spectrum titration method for the automated multi-color change reaction in Example 1 of the present invention is △s =(△a * / △V) 3 picture.

[0115] Figure 4 This is a chromaticity curve diagram of the program-controlled full-spectrum titration method for automated multi-color change reaction in Example 1 of the present invention. DETAILED DESCRIPTION

[0116] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0117] In some of the processes described in the specification and claims of the present invention and the above-mentioned figures, multiple operations that appear in a specific order are included, but it should be clearly understood that these operations may not be executed in the order in which they appear in this article or executed in parallel. The serial numbers of the operations, such as 101, 102, etc., are only used to distinguish between different operations, and the serial numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations may be executed in sequence or in parallel. It should be noted that the descriptions of "first", "second", etc. in this article are used to distinguish different steps, messages, devices, modules, etc., and do not represent the order of precedence, nor do they limit the "first" and "second" to be different types.

[0118] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0119] The present invention discloses a program-controlled full-spectrum titration method for automated multi-color change reactions. The method establishes a visible light full-spectrum titration method suitable for chemical reactions with multiple titration condition change points and / or multiple color mutation points through user-defined titration signal response and titration condition matching, thereby realizing full-spectrum automated detection of multi-color change titrations in complex titration reactions.

[0120] Furthermore, considering that the structure of the compound has different changes at different chemical reaction stages, the degree of light absorption at different wavelengths is different, and the color of the overall solution is also different. Different colors also represent different reaction stages. By measuring different colors, the progress of the chemical reaction can be inferred, so as to determine the change of different reaction conditions to make the reaction proceed to the next stage. The present invention uses the full-spectrum titration color change parameter signal value as a mark to identify the progress of the reaction stage, and indicates the different stages of the reaction and the need to change the titration conditions in the next step to allow the reaction to continue by reaching the preset titration condition change point. The indicator mark achieves the goal of completing and measuring the chemical reaction of the multi-color change full-spectrum titration in the same reaction system, and provides more accurate analysis information for the system change process in the chemical reaction through the application of the visible light full-spectrum titrator.

[0121] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0122] Example 1

[0123] Program-controlled full-spectrum titration method for automated multicolor reaction of total hardness in water

[0124] (1) Chemical reaction principle: When chrome black T indicator is added to the water sample, chrome black T forms purple chelates with calcium and magnesium ions. The instability constants of these chelates are greater than the instability constants of ethylenediaminetetraacetic acid calcium and magnesium chelates. When pH = 10, disodium ethylenediaminetetraacetic acid first forms chelates with calcium ions and then with magnesium ions. At the titration endpoint, the solution presents the blue color of chrome black T indicator.

[0125] (2) Program control of automated multi-color reaction Full spectrum titration method setting program:

[0126] The first titration step: adding chrome black T indicator to the water sample of the reaction container, recording the real-time full-spectrum titration color change parameters of each metering point, and determining whether the full-spectrum titration color change parameter data of each metering point matches the full-spectrum titration color change parameter signal value of the preset first titration condition change point, when the full-spectrum titration color change parameter data of a certain metering point matches the full-spectrum titration color change parameter signal value of the preset first titration condition change point, stopping the dripping of chrome black T indicator, and determining whether the full-spectrum titration color change parameter data of the metering point matches the preset titration endpoint full-spectrum titration color change parameter signal value, if not matching, changing the titration reagent, and entering the EDTA titration step;

[0127] The second titration step: add EDTA to the reaction system, record the real-time full-spectrum titration color change parameters of each metering point, and determine whether the full-spectrum titration color change parameter data of each metering point matches the full-spectrum titration color change parameter signal value of the preset second titration condition change point (i.e., the full-spectrum titration color change parameter signal value of the titration endpoint). When the full-spectrum titration color change parameter data of a certain metering point matches the full-spectrum titration color change parameter signal value of the preset second titration condition change point, stop the addition of EDTA, and control the visible light full-spectrum titrator to terminate the operation. The total amount of EDTA added in the second titration step is taken as the titration reaction endpoint value of the total hardness in water, and the total hardness content in water is calculated.

[0128] (3) Calculation formula for total hardness content in water

[0129] Calculation formula:

[0130]

[0131] Where:

[0132] ρ (CaCO3) ——Total hardness content in the sample (calculated as CaCO3), in milligrams per kilogram (mg / L)

[0133] V1——The volume of EDTA-2Na standard solution consumed by the sample solution, in milliliters (mL);

[0134] V0——The volume of EDTA-2Na standard solution consumed by the blank solution, in milliliters (mL);

[0135] V——volume of water sample, in milliliters (mL);

[0136] c (EDTA-2Na) ——The molar concentration of EDTA-2Na standard solution, in moles per liter (mol / L);

[0137] 100.09——The mass of calcium carbonate equivalent to 1mL of 1mol / L EDTA-2Na standard solution, in millimoles (g / mol).

[0138] (4) Equipment, instruments and reagents used

[0139] Spectral titrator: SXZ-3, produced by Qinhuangdao Water Bear Technology Co., Ltd. Equipped with 8-bit automatic sampler, fiber optic spectrometer, 400μm fiber, AST905 interface, collimating lens, CNC stirrer, automatic signal processing system; spectral range 380nm~780nm, △λ5nm, measurement cycle 200ms, integration time 150ms, optical path 10.0mm, S 快 +S 慢 Titration mode, titration rate 0.167 mL / min, stirring speed 400 rpm. 180 mL boot-type reactor, L = 10.0 mm, produced by Qinhuangdao Water Bear Technology Co., Ltd.

[0140] (5) Reagents:

[0141] Buffer solution (pH = 10): Dissolve 67.5 g of ammonium chloride (NH4Cl) in 300 mL of distilled water, add 570 mL of ammonium hydroxide (ρ 20 =0.90 g / mL), diluted with water to 1000 mL.

[0142] Chrome black T indicator (5g / L): weigh 0.5g Chrome black T (C 20 H 12 N3NaO7S), dissolved in 100mL triethanolamine (C6H 15 NO3).

[0143] Sodium sulfide solution (50 g / L): Weigh 5.0 g of sodium sulfide (Na2S·9H2O), dissolve it in water, and dilute to 100 mL.

[0144] Hydroxylamine hydrochloride solution (10 g / L): Weigh 1.0 g of hydroxylamine hydrochloride (NH2OH·HCl), dissolve it in water, and dilute to 100 mL.

[0145] Potassium cyanide solution (100 g / L): Weigh 10.0 g of potassium cyanide (KCN), dissolve it in water, and dilute to 100 mL.

[0146] Ethylenediaminetetraacetic acid disodium standard solution (EDTA-2Na standard solution) [c(C 10 H 14 N 2O8Na2·H2O)=0.01mol / L]: Weigh 3.72g of disodium ethylenediaminetetraacetate (abbreviated as EDTA-2Na) and dissolve it in 1000mL of distilled water. Determine its accurate concentration according to GB / T 601.

[0147] (6) Automated multi-color reaction program-controlled full-spectrum titration method titration steps and preset parameters:

[0148] Step 1: Add chrome black T indicator, and set the first titration condition to change the chromaticity value to a * =4±1 and b * =6±1, stop the chrome black T reaction process and automatically enter the second step;

[0149] Step 2: Add EDTA solution and preset the titration endpoint full spectrum titration color change parameter signal value as color change curve S △s =(△a * / △V) 3 The peak value ( Figure 3 )(where S △s —Color change curve of full spectrum titration, a * — red-green color index value, v— added reagent volume value), the volume value of EDTA added in the second titration step is taken as the endpoint value of the full-spectrum multicolor titration method for the total hardness in water, and the total hardness content in water is calculated.

[0150] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the beneficial effects of the program-controlled full-spectrum titration method for automated multi-color change reaction disclosed in the present invention are further illustrated by the following comparative examples, but they should not be construed as limitations of the present invention. The method properties obtained by other experiments conducted by technicians in this field based on the above-mentioned invention content and the applications based on the above-mentioned properties are also deemed to fall within the protection scope of the present invention.

[0151] Comparative Example 1

[0152] Manual titration method of total hardness in water

[0153] Pipette 25.0mL of zinc standard solution into a 150mL conical flask, add 25mL of distilled water, add a few drops of ammonia water until there is a faint ammonia smell, then add 5mL of buffer solution and 4 drops of chrome black T indicator, and titrate with EDTA2Na standard solution under constant shaking until the blue color remains unchanged.

[0154] Three laboratories were commissioned to measure the same water sample according to the methods of Example 1 and Comparative Example 1. The results are shown in Table 1.

[0155] Table 1 Test results of the same water sample in three laboratories (n=6)

[0156]

[0157] It can be seen that the relative standard deviations of the program-controlled full-spectrum titration method for the automated multi-color change reaction disclosed in Example 1 are 1.86%, 1.13% and 0.93% respectively, and the relative standard deviations of the manual titration method disclosed in Comparative Example 1 are 2.91%, 3.42% and 3.82% respectively. The precision of the program-controlled full-spectrum titration method for the automated multi-color change reaction is better than that of the manual titration method. Therefore, the program-controlled full-spectrum titration method for the automated multi-color change reaction disclosed in the present invention realizes continuous measurement of the whole process, and there is no need to manually continue titration after manual judgment at each color change point, and can replace the manual titration method to realize continuous automated measurement.

[0158] In addition, the program-controlled full-spectrum titration method for automated multi-color change reactions disclosed in the present invention can be seamlessly connected with the titration standards specified in the national standard, and its precision is better than that of the manual titration method. While realizing continuous automated detection, it is conducive to the effective integration of full-spectrum titration technology within the original national standard framework, helps in the digital upgrade of titration detection methods, and effectively improves the working efficiency of the multi-color change reaction titration procedure.

[0159] Comparative Example 2

[0160] Monochromatic Full Spectrum Titration Method for Total Hardness in Water

[0161] Manually draw 25.0mL of zinc standard solution into a 150mL container, add 25mL of distilled water, add a few drops of ammonia water until there is a faint ammonia smell, then add 5mL of buffer solution and 4 drops of chrome black T indicator to stop the first color change process of the chrome black T reaction process;

[0162] Manually place the above reaction solution in the full spectrum titrator, start the titration step: add EDTA to the reaction system, record the real-time full spectrum titration color change parameters of each metering point, and determine whether the full spectrum titration color change parameter data of each metering point matches the full spectrum titration color change parameter signal value of the preset second titration condition change point (i.e., the full spectrum titration color change parameter signal value of the titration endpoint). When the full spectrum titration color change parameter data of a certain metering point matches the full spectrum titration color change parameter signal value of the preset second titration condition change point, stop the addition of EDTA, and control the visible light full spectrum titrator to terminate the operation. The total amount of EDTA added in the second titration step is the titration reaction endpoint value of the total hardness in the water, and the total hardness content in the water is calculated.

[0163] The total hardness of three water samples (water sample 1: Nongfu Spring brand mineral water, water sample 2: Baishanshui brand mineral water, water sample 3: tap water) was measured in parallel 6 times using the same full spectrum titrator according to the method of Example 1 and Comparative Example 2. The measurement results are shown in Table 2 and the measurement diagram is shown in Table 2. Figure 2 .

[0164] Table 2 Test results of three different water bodies (n=6)

[0165]

[0166] It can be seen that the relative standard deviations of the program-controlled full-spectrum titration method for automated multi-color change reactions disclosed in Example 1 are 1.8%, 1.0%, and 0.7%, respectively, and the relative standard deviations of the single-color change full-spectrum titration method disclosed in Comparative Example 2 are 3.8%, 1.4%, and 1.1%. The precision of the program-controlled full-spectrum titration method for automated multi-color change reactions is better than that of the single-color change full-spectrum titration method. The program-controlled full-spectrum titration method for automated multi-color change reactions realizes continuous measurement of the entire process, without the need to continue titrating after determining the endpoint separately in each step of the multi-reaction color change titration process, which makes up for the shortcomings of the existing single-color change full-spectrum titration method, and realizes the continuous automated measurement of multi-color change reactions by the same full-spectrum titrator through program settings. This is conducive to the effective integration of full-spectrum titration technology within the original national standard framework, helps in the digital upgrade of titration detection methods, and effectively improves the working efficiency of multi-color change reaction titration procedures.

[0167] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A program-controlled full-spectrum titration method for automated multi-color change reaction, characterized in that: The program-controlled full-spectrum titration method includes a plurality of titration steps performed sequentially, wherein titration condition change points are preset between the titration steps to mark the change of titration conditions, the total amount of reagent added in the last titration step is the reaction endpoint reagent amount of the current analytical reaction system, and the parameter value of the measured item in the sample is calculated based on the reaction endpoint reagent amount.

2. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 1, characterized in that: The titration condition change point includes a titration condition limit point or a full spectrum titration color change parameter signal value limit point; The titration conditions include one or more of the volume of the titration reagent, the temperature of the titration system, the magnetic conditions of the titration system, the illumination conditions of the titration system, the fluid speed of the titration reagent, and the microwave assistance of the titration system; The full spectrum titration color change parameters include chromaticity value parameters, color change peak parameters of the color change curve S and color change curve S J The color change peak parameters.

3. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 2, characterized in that: The chromaticity value parameters include lightness L * Value, red-green quality index a * Value, yellow-blue index b * Value, chroma C * ab Value, hue angle h ab Value and color difference △E value; The color change peak parameters of the color change curve S include the color change curve S s and color change curve S △s .

4. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 2, characterized in that: Methods include: When the preset titration condition change point of the titration step is the limiting point of the titration condition, the sample to be tested is titrated, the titration condition value of each metering point is recorded, and it is determined whether the titration condition value of each metering point matches the condition value of the limiting point of the preset titration condition; If they match, the visible light full spectrum titrator is controlled to change the titration conditions according to the preset program, enter the next titration step, and continue the operation; If they do not match, the visible light full spectrum titrator is controlled to maintain the operating state.

5. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 2, characterized in that: The method comprises: When the preset titration condition change point of the titration step is the full spectrum titration color change parameter signal value limit point, full spectrum titration is performed on the sample to be tested, the real-time full spectrum titration color change parameters of each metering point are recorded, and it is determined whether the full spectrum titration color change parameter data of each metering point matches the full spectrum titration color change parameter signal value of the preset titration condition change point; If they match, the visible light full spectrum titrator is controlled to stop the current operation state; If they do not match, the visible light full spectrum titrator is controlled to maintain the operating state.

6. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 4, characterized in that: Also includes: When the visible light full spectrum titrator stops the current operation state, determining whether the full spectrum titration color change parameter data of the metering point matches the full spectrum titration color change parameter signal value of the preset titration end point; If they match, the visible light full spectrum titrator is controlled to terminate the operation; If they do not match, the visible light full spectrum titrator is controlled to change the titration conditions according to the preset program, enter the next titration step, and continue the operation.

7. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 1, characterized in that: The change of the titration conditions includes adding a reagent or changing one or more of the physical conditions.

8. The program-controlled full-spectrum titration method for automated multi-color change reaction according to claim 7, characterized in that: The adding of reagents includes one or more of adding original titration reagents and adding new titration reagents; The physical condition changes include one or more of temperature conditions, magnetic conditions, light conditions, fluid rotation speed, and microwave assistance.

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