CN112595711A - Titration end point determination device - Google Patents
Titration end point determination device Download PDFInfo
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- 238000005070 sampling Methods 0.000 claims description 11
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 22
- 238000000034 method Methods 0.000 description 19
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 12
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 12
- 229910001424 calcium ion Inorganic materials 0.000 description 12
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 12
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
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- 229940010514 ammonium ferrous sulfate Drugs 0.000 description 3
- IMBKASBLAKCLEM-UHFFFAOYSA-L ferrous ammonium sulfate (anhydrous) Chemical compound [NH4+].[NH4+].[Fe+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O IMBKASBLAKCLEM-UHFFFAOYSA-L 0.000 description 3
- SWGJCIMEBVHMTA-UHFFFAOYSA-K trisodium;6-oxido-4-sulfo-5-[(4-sulfonatonaphthalen-1-yl)diazenyl]naphthalene-2-sulfonate Chemical compound [Na+].[Na+].[Na+].C1=CC=C2C(N=NC3=C4C(=CC(=CC4=CC=C3O)S([O-])(=O)=O)S([O-])(=O)=O)=CC=C(S([O-])(=O)=O)C2=C1 SWGJCIMEBVHMTA-UHFFFAOYSA-K 0.000 description 3
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- 238000009835 boiling Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
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- GGCZERPQGJTIQP-UHFFFAOYSA-N sodium;9,10-dioxoanthracene-2-sulfonic acid Chemical compound [Na+].C1=CC=C2C(=O)C3=CC(S(=O)(=O)O)=CC=C3C(=O)C2=C1 GGCZERPQGJTIQP-UHFFFAOYSA-N 0.000 description 1
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
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Abstract
The invention discloses a titration end point determination device, which comprises: the device comprises a titration cell, a light source, a color sensor and a judgment module; the titration cell is used for containing a titrated liquid; the light source is used for providing light rays for the color sensor; the color sensor is used for continuously acquiring color parameter information or image information of the titrated liquid at a certain time interval and sending the color parameter information or the image information to the judging module; and the judging module is used for analyzing the received color parameter information or image information and judging whether the titration end point is reached according to the change of the color parameter information or the image information. The device can reduce the personnel operation error in titration analysis and the measurement error caused by the visual deviation of the operator, and can realize the unmanned operation of titration analysis.
Description
Technical Field
The invention relates to the field of assay analysis, in particular to a titration end point determination device.
Background
Titration is a means of quantitative analysis, and is also a chemical experimental operation. It determines the content of a certain solute by quantitative reaction of two solutions. It is to indicate the end point of titration according to the color change of the indicator, then to visually measure the consumption volume of the standard solution and calculate the analysis result.
In the field of assay analysis, the determination of the titration end point by using the abrupt change of the liquid color is a key operation step in the titration analysis process, and the determination method of the titration end point adopted in the current general laboratory titration analysis is a method for manually determining the titration end point, namely, an assay operator determines whether the titration end point is reached according to the color change of an indicator. When the titration end point is reached, an assay operator visually observes the consumption volume of the standard solution in the burette, and then an analysis result is calculated.
In industrial production, some on-line analyzers automatically determine the titration end point by potentiometric titration to improve the automation level of detection, but the potentiometric titration cannot be applied to all titration analysis, and most titration analysis methods must determine the titration end point by using color mutation.
The titration analysis method for determining the titration endpoint by using the color change includes not only titration methods that do not require a pretreatment of the liquid to be measured, such as: measurement of alkalinity of water (appendix E of GB/T1756 "measurement of alkalinity (acid-base titration)"), etc.; titration methods requiring prior treatment of the liquid being tested are also included, such as: a potassium dichromate method for measuring the chemical oxygen demand of water (HJ 828-.
The titration end point is judged manually according to the change of the color, and the phenomenon of large deviation of an analysis result exists. The main reasons are: the perception of color is biased between different people, resulting in different operators' bias in the determination of the titration endpoint for the same titration analysis.
How to automatically determine the end point of titration based on the color change of the indicator or the titrated liquid is a problem to be solved.
Disclosure of Invention
The invention aims to overcome the technical defects and provides a titration end point judgment device, which comprises: the device comprises a titration cell, a light source, a color sensor and a judgment module;
the titration cell is used for containing a titrated liquid;
the light source is used for providing light rays for the color sensor;
the color sensor is used for continuously acquiring color parameter information or image information of the titrated liquid at a certain time interval and sending the color parameter information or the image information to the judging module;
and the judging module is used for analyzing the received color parameter information or image information and judging whether the titration end point is reached according to the change of the color parameter information or the image information.
As an improvement of the above apparatus, the color sensor is a machine vision device, a camera, or a camera.
As a modification of the above device, the sampling time interval of the color sensor is T, and this value can be adjusted according to the titration speed of the titrated liquid.
As an improvement of the above device, the light source is a natural light, a transmission type light source or a reflection type light source; the transmission type light source is an LED lamp, a fluorescent lamp, an electric lamp, an incandescent lamp or a halogen lamp; the reflective light source is an LED lamp, a fluorescent lamp, an electric lamp, an incandescent lamp or a halogen lamp.
As an improvement of the device, when the light source is natural light, the device also comprises a titration platform bracket used for arranging the color sensor at the bottom of the titration cell.
As an improvement of the above device, when the light source is a transmission type light source, the light source and the color sensor are respectively arranged at two sides of the titration cell, and two light-passing holes are respectively arranged at two sides of the titration cell for light to pass through; the light of the light source penetrates through the titration cell and then irradiates the color sensor.
As an improvement of the device, when the light source is a reflective light source, the light source and the color sensor are both positioned at the same side of the titration cell, and light of the light source is reflected by liquid in the titration cell and then irradiates the color sensor.
As an improvement of the above apparatus, the specific implementation process of the determination module is as follows:
extracting color data reflecting the color change of the titrated liquid from the received color parameter information or image information, wherein the color data comprises: RGB value, hue, color temperature, brightness and color saturation of the color of the titrated liquid;
comparing the extracted color data with a preset titration end point judgment condition, if the color data of the titrated liquid meets the titration end point judgment condition, judging that the titration end point is reached, and sending a message of stopping dripping the standard solution; and if the color data of the titrated liquid does not meet the judgment condition of the titration end point, sending a message of 'continuously dripping the standard solution'.
As an improvement of the device, the color sensor needs to be tested by white light before the first operation, so as to obtain the color parameter when no liquid exists in the titration cell or the liquid in the titration cell is colorless transparent liquid.
The invention has the advantages that:
the device can reduce the personnel operation error in titration analysis and the measurement error caused by the visual deviation of the operator, and can realize the unmanned operation of titration analysis.
Drawings
FIG. 1 is a schematic view of an apparatus according to embodiment 1 of the present invention;
FIG. 2 is a schematic view of an apparatus according to embodiment 3 of the present invention;
FIG. 3 is a schematic view of an apparatus according to embodiment 4 of the present invention.
Reference numerals:
1. light source 2, light source side light through hole 3, sensor side light through hole 4 and color sensor
5. Conical flask 6 and titration platform support
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
In the titration process, along with the continuous dropwise addition of the standard solution, the color of the titrated liquid can be gradually changed, and in the titration process, the color information of the titrated liquid is collected in real time by the color information collecting device, so that the titration end point can be judged according to the change of the color information of the titrated liquid. The invention collects the color parameters (such as RGB value, CMYK value, chroma, brightness, hue, gray level and other parameter values of the color of the titrated liquid) of the titrated liquid through the color information collecting device, and automatically judges the titration end point through the change of the color parameter value of the titrated liquid.
The invention provides a titration end point judgment device which is used for collecting color parameters of a titrated liquid and automatically judging a titration end point according to the change of the color parameter values of the titrated liquid.
The device includes: the device comprises a titration cell, a color sensor, a light source and a judgment module;
the titration cell is a container for holding a titrated liquid. The titration cell may be a conventional assay instrument such as a beaker, a conical flask, or any shape container specially manufactured for holding the titrated liquid and allowing the color change of the titrated liquid to be observed.
The color information acquisition device includes: color sensors, machine vision equipment, cameras, or other facility equipment. The color information acquisition device continuously acquires color parameter information or image information of the titrated liquid at certain time intervals,
for convenience of description, color information or image information acquisition devices such as color sensors, machine vision equipment, cameras, etc. are collectively referred to as color sensors.
The sampling time interval of the color sensor is T, the size of the sampling time interval T can be adjusted according to the titration speed of the titration liquid, and the sampling time interval T can be set to be several seconds or minutes. The color sensor samples once every time T, or takes an average value after sampling for many times. The color sensor transmits the collected information data of the color of the liquid in the titration cell to the judgment module.
The light source can be natural light, or light emitted by artificial light sources such as LED lamps, fluorescent lamps, electric lamps, incandescent lamps, halogen lamps and the like, or light reflected by a reflector. According to the different light paths, the light emitted by the light source enters the color sensor in a transmission mode and a reflection mode.
Light-transmissive entering color sensor: the light source and the color sensor are respectively arranged at two sides of the titration cell, and light rays of the light source penetrate through the titration cell and then irradiate on the color sensor. At this time, two light-passing holes are needed to be respectively arranged on two sides of the titration cell for light to pass through.
Light reflection enters the color sensor: the light source and the color sensor are respectively positioned at the same side of the titration cell, and after the light of the light source is reflected by the liquid in the titration cell, the light irradiates the color sensor.
The light entering the color sensor can be light transmitted through liquid in the titration cell, light reflected by liquid in the titration cell, and light transmitted through liquid in the titration cell and light reflected by liquid in the titration cell. When the color of the titrated liquid in the titration cell changes, the numerical value of the data collected by the color sensor changes along with the change of the color of the titrated liquid.
And the judging module is used for analyzing or calculating the collected color parameter information or image information each time through professional software, hardware and a specific algorithm, and finally judging whether the titration end point is reached or not according to the change of the color parameter information or the image information, particularly the change of parameters related to colors.
The method specifically comprises the following steps: extracting color data which correctly reflects the color change of the titrated liquid and can be RGB values of the color of the titrated liquid; or color parameters such as hue, color temperature, brightness, color saturation and the like of the color of the titrated liquid; or the intensity value of monochromatic light irradiated into the color information acquisition equipment after the color of the titrated liquid is filtered by a monochromatic filter such as red, green or blue.
Comparing color data which correctly reflects the color change of the titrated liquid with preset titration end point judgment conditions, judging that the titration end point is reached if the color data of the titrated liquid meets the titration end point judgment conditions, and stopping dripping the standard solution; and if the color data of the titrated liquid does not meet the judgment condition of the titration end point, continuing to dropwise add the standard solution, and performing the second time of the color information acquisition of the titrated liquid and the judgment of the titration end point.
In order to clearly illustrate the technical features of the present solution, the present solution is explained below by way of specific embodiments.
Detailed description of the preferred embodiment 1
Automatic determination of titration end point for calcium ion measurement (meeting GB/T15452) in industrial circulating water
Principle of calcium ion determination (GB/T15452) method: and in the calcium ion determination, calcium-hydroxy acid is used as an indicator when the pH value is 12-13, and the calcium ion content in the water sample is determined by using EDTA standard titration solution. During titration, EDTA and free calcium ion in the solution form complex, and the end point is the color change from purple red to bright blue.
And a light transmission type color sensor sampling mode is adopted. The schematic diagram of the light path is shown in fig. 1. Where 1 is a light source, 2 is a light source side clear hole, 3 is a sensor side clear hole, and 4 is a color sensor.
The color sensor adopts a TCS3472 chip module.
The color sensor is tested for white light before first operation or when necessary. The purpose of the white light test is to obtain a color parameter when there is no liquid in the titration cell or when the liquid in the titration cell is a colorless transparent liquid. During white light testing, the color sensor acquires the following values: RGB values RGB r0 when a red filter is used; RGB values RGB g0 when green filters are used; the RGB values RGB b0 when using a blue filter.
In the titration process, the color sensor measures the color parameter of the titrated liquid in the titration cell. The color sensor collects the color parameter values of the titrated liquid as follows: RGB value RGB [ r ] when red light filter is adopted; RGB value RGB [ g ] when green light filter is adopted; RGB value RGB [ b ] when blue light filter is used.
And the judgment module calculates the RGB color parameters of the titrated liquid in the titration cell. The RGB color parameter R value of the titrated liquid is (RGB [ R ]/RGB [ R0]) 255; the RGB color parameter G value of the titrated liquid is (RGB [ G ]/RGB [ G0]) 255; the RGB color parameter B of the titrated liquid is (RGB [ B ]/RGB [ B0]) 255.
When the color of the solution is purple red, the RGB color parameter R value of the solution is greater than the RGB color parameter B value of the solution; when the color of the solution is bright blue, the RGB color parameter R value of the solution < the RGB color parameter B value of the solution.
And comparing the RGB color parameter R value of the solution with the RGB color parameter B value of the solution to judge whether the titration end point is reached.
For further clarity of the description of the titration endpoint determination method described above, experimental data for a particular titration analysis run is set forth in detail below.
Table 1 is a record of RGB data during one calcium ion concentration measurement:
TABLE 1
| Number of drops | R | G | B |
| 0 | 120 | 56 | 84 |
| 15 | 119 | 57 | 86 |
| 20 | 103 | 50 | 76 |
| 23 | 97 | 53 | 78 |
| 24 | 89 | 54 | 82 |
| 25 | 85 | 54 | 80 |
| 26 | 70 | 56 | 84 |
In the above table, "the number of drops" refers to the number of drops of the EDTA standard solution during the titration; "R", "G" and "B" are the RGB values of the color of the titrated liquid, respectively.
When the number of the EDTA standard solution added dropwise is 25 drops, the RGB values of the color of the titration liquid are 85, 54 and 80, respectively, and at this time, the RGB color parameter R value of the solution > the RGB color parameter B value of the solution.
When the number of the EDTA standard solution added dropwise is 26 drops, the RGB values of the color of the titration liquid are 70, 56, and 84, respectively, and at this time, the RGB color parameter R value of the solution < the RGB color parameter B value of the solution.
So, it is judged that: in this titration analysis, the titration end point was reached when the amount of the EDTA standard solution added dropwise was 26 drops.
Detailed description of the preferred embodiment 2
Automatic determination of titration end point for calcium ion measurement (meeting GB/T15452) in industrial circulating water
Principle of calcium ion determination (GB/T15452) method: and in the calcium ion determination, calcium-hydroxy acid is used as an indicator when the pH value is 12-13, and the calcium ion content in the water sample is determined by using EDTA standard titration solution. During titration, EDTA and free calcium ion in the solution form complex, and the end point is the color change from purple red to bright blue.
And a light transmission type color sensor sampling mode is adopted. The schematic diagram of the light path is shown in fig. 1.
The color sensor adopts a GY-33 color sensor module.
The GY-33 color sensor module comprises a TCS3472 chip module and an MCU module. The GY-33 color sensor module can output parameters such as RGB value, brightness, color temperature, original RGBC value and the like of the color of the measured object.
In this embodiment, the GY-33 color sensor module outputs RGB values of the color of the liquid.
The GY-33 color sensor module is calibrated for white light balance before first operation or when necessary.
In the titration process, the color sensor measures the RGB value of the color of the titrated liquid in the titration cell and outputs the RGB value of the color of the liquid.
The RGB values of the color of the liquid are converted into hue values of the liquid color.
The judgment module can judge whether the titration end point is reached according to the change of the hue value of the liquid color.
For further clarity of the description of the titration endpoint determination method described above, experimental data for a particular titration analysis run is set forth in detail below.
Table 2 is the RGB data record during the primary calcium ion concentration detection:
TABLE 2
| Number of drops | R | G | B | Color phase |
| 0 | 121 | 56 | 84 | 334 |
| 20 | 120 | 57 | 86 | 332 |
| 22 | 115 | 52 | 76 | 337 |
| 25 | 93 | 53 | 78 | 323 |
| 26 | 89 | 54 | 83 | 310 |
| 27 | 85 | 54 | 81 | 308 |
| 28 | 66 | 54 | 84 | 264 |
In the above table, "the number of drops" refers to the number of drops of the EDTA standard solution during the titration; "R", "G" and "B" are RGB values of the color of the liquid to be titrated, and "hue" is the number of degrees of the hue index of the color.
The degree of hue is calculated as follows:
(1) when max (R, G, B) ═ R, that is, when R of RGB values is the largest, the hue is (G-B) × 60/(max (R, G, B) -min (R, G, B)).
(2) When max (R, G, B) ═ G, that is, when the G value among the RGB values is the maximum, the hue is 120+ (B-R) × 60/(max (R, G, B) -min (R, G, B)).
(3) When max (R, G, B) ═ B, that is, when the value of B among the RGB values is the maximum, the hue is 240+ (R-G) × 60/(max (R, G, B) -min (R, G, B)).
In the above formula, max (R, G, B) refers to the maximum value among R, G, B values, and min (R, G, B) refers to the minimum value among R, G, B values.
In the hue circle, the degree of hue corresponding to blue is approximately between 180 and 270. Therefore, the hue value less than 270 is used as the basis for determining the titration end point.
As can be seen from the test records in the table above, at the start of titration, the R value of the color of the titrated liquid was 121, the G value was 56, the B value was 84, and the calculated hue value was 334 degrees, corresponding to the red region in the hue ring.
When the number of EDTA standard solutions added dropwise was 27 drops, the RGB values of the color of the titration liquid were 85, 54, and 81, respectively, and the calculated hue value was 308 degrees, corresponding to the red region in the hue ring.
When the number of the EDTA standard solution added dropwise was 28 drops, the RGB values of the color of the titration liquid were 66, 54, and 84, respectively, and the hue value was calculated to be 364 degrees, corresponding to the blue region in the hue ring.
So, it is judged that: in this titration analysis, the titration end point was reached when 28 drops of the standard EDTA solution were added.
Detailed description of the preferred embodiment 3
Titration end point automatic determination (using GY-33 color sensor Module) for determination of Total alkalinity (GB/T1576)
According to the titration operation about the full alkalinity in the appendix E 'alkalinity determination (acid-base titration method)' of GB/T1756, the automatic determination of the titration end point is realized by using a color sensor.
The alkalinity of water means the amount of hydrogen ion-accepting substances contained in water, for example, hydroxide, carbonate, bicarbonate, phosphate, hydrogen phosphate, silicate, hydrogen silicate, sulfite, humate, ammonia, etc., which are alkaline substances commonly found in water, and they are capable of reacting with an acid. Therefore, the alkalinity content of water can be determined by titrating them with a standard solution of acid using a suitable indicator.
The alkalinity is divided into phenolphthalein alkalinity and full alkalinity. The full alkalinity was the alkalinity value measured when methyl orange was used as the indicator, and the pH at the titration end point was 4.2.
And a light transmission type color sensor sampling mode is adopted.
The schematic diagram of the light path is shown in fig. 2. Wherein 5 is a conical flask, 6 is a titration platform support, and 4 is a color sensor.
The color sensor adopts a GY-33 color sensor module.
The light source is natural light or lamplight in the laboratory analysis room.
The GY-33 color sensor module comprises a TCS3472 chip module and an MCU module. The GY-33 color sensor module can output parameters such as RGB value, brightness, color temperature, original RGBC value and the like of the color of the measured object.
In this embodiment, the GY-33 color sensor module outputs RGB values of the color of the liquid.
The GY-33 color sensor module is calibrated for white light balance before first operation or when necessary.
100mL of water sample to be detected is placed in the conical flask, and then 2 drops of methyl orange indicator are added. At this time, the color of the liquid was yellow. Titrating with a sulfuric acid standard solution, and automatically measuring the RGB value or other color parameters of the color of the liquid by a color sensor once every one drop of the sulfuric acid standard solution is added.
The judging module calculates the hue value of the color at the moment according to the parameter data of the color transmitted by the color sensor; then, whether the titration end point is reached can be judged according to the change of the hue value of the liquid color.
Detailed description of the preferred embodiment 4
Titration end point automatic judgment (adopting image information acquisition equipment) for full alkalinity determination (GB/T1576)
According to the titration operation about the full alkalinity in the appendix E 'alkalinity determination (acid-base titration method)' of GB/T1756, the automatic determination of the titration end point is realized by using a color sensor.
The alkalinity of water means the amount of hydrogen ion-accepting substances contained in water, for example, hydroxide, carbonate, bicarbonate, phosphate, hydrogen phosphate, silicate, hydrogen silicate, sulfite, humate, ammonia, etc., which are alkaline substances commonly found in water, and they are capable of reacting with an acid. Therefore, the alkalinity content of water can be determined by titrating them with a standard solution of acid using a suitable indicator.
The alkalinity is divided into phenolphthalein alkalinity and full alkalinity. The full alkalinity was the alkalinity value measured when methyl orange was used as the indicator, and the pH at the titration end point was 4.2.
And a light reflection type color sensor sampling mode is adopted. The schematic diagram of the light path is shown in fig. 3. Wherein 5 is a conical flask and 4 is a color sensor. The color sensor employs a machine vision module. The machine vision module includes an image sensor and a processor.
The model of the machine vision module adopted in the present embodiment is an OpenMV 4R 3 embedded machine vision module. The processor of the OpenMV 4R 3 embedded machine vision module is an STM32H743VIT6 processor, and the image sensor of the OpenMV 4R 3 embedded machine vision module is a hawaiv OV7725 photosensitive chip.
The light source is natural light or lamplight, etc.
In this embodiment, the RGB values of the color collected by the machine vision module are used as the color parameters for titration endpoint determination.
100mL of water sample to be detected is placed in the conical flask, and then 2 drops of methyl orange indicator are added. At this time, the color of the liquid was yellow. Titrating with a sulfuric acid standard solution, and automatically measuring the RGB value or other color parameters of the color of the liquid once by a machine vision module after adding one drop of the sulfuric acid standard solution.
The judgment module calculates the hue value of the color at the moment according to the parameter data of the color transmitted by the color sensor, and then can judge whether the titration end point is reached according to the change of the hue value of the liquid color.
In this embodiment, an image capture device such as a digital camera may be used instead of the machine vision module. And then extracting the color parameter data of the liquid from the image information data output by the image acquisition equipment for being used as a basis for determining a titration end point.
Detailed description of the preferred embodiments 5
Automatic determination of titration end point of potassium dichromate method (HJ 828-2017) for determining chemical oxygen demand of water quality
In order to obtain accurate analysis results, some titration assays require prior treatment of the titrated liquid prior to the titration operation.
For example, in the "potassium dichromate method for determining chemical oxygen demand of water" (HJ 828-.
The principle of the method is as follows: adding a known amount of potassium dichromate solution into a water sample, taking silver salt as a catalyst under a strong acid medium, boiling and refluxing, taking resorufin as an indicator, titrating unreduced potassium dichromate in the water sample by ammonium ferrous sulfate, and calculating the mass concentration of consumed oxygen according to the amount of the consumed potassium dichromate.
When the ammonium ferrous sulfate is used for titrating a water sample by using the ferrosoferrin as an indicator, the titration end point is obtained when the color of the solution is changed from yellow to reddish brown from blue-green.
In the embodiment, a water sample subjected to boiling reflux pretreatment is poured into a titration cell, and a ferroxyl indicator is added. And a light transmission type color sensor sampling mode is adopted. The schematic diagram of the light path is shown in fig. 1.
The color sensor adopts a GY-33 color sensor module, and the GY-33 color sensor module outputs RGB values of the color of the liquid. And converting the RGB value of the color of the liquid into a hue value of the color of the tested liquid.
Yellow hue ranges from about 30 degrees to about 120 degrees, cyan hue ranges from about 120 degrees to about 270 degrees, and russet hue ranges from about 270 degrees to about 360 degrees and from about 0 degrees to about 30 degrees.
The hue value of the color of the titrated liquid gradually increases with the increase of the titration amount of the ammonium ferrous sulfate titration liquid, and gradually increases from 0 degree if the hue value reaches 360 degrees.
The judgment module can judge whether the titration end point is reached according to the change of the hue value of the liquid color.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. An end-point titration determination device, comprising: the device comprises a titration cell, a light source, a color sensor and a judgment module;
the titration cell is used for containing a titrated liquid;
the light source is used for providing light rays for the color sensor;
the color sensor is used for continuously acquiring color parameter information or image information of the titrated liquid at a certain time interval and sending the color parameter information or the image information to the judging module;
and the judging module is used for analyzing the received color parameter information or image information and judging whether the titration end point is reached according to the change of the color parameter information or the image information.
2. The titration endpoint determination apparatus according to claim 1, wherein the color sensor is a machine vision device, a camera, or a camera.
3. The titration endpoint determination apparatus according to claim 2, wherein the sampling time interval of the color sensor is T, and the value is adjustable according to a titration speed of the titrated liquid.
4. The titration endpoint determination device according to claim 1, wherein the light source is a natural light, a transmissive light source, or a reflective light source; the transmission type light source is an LED lamp, a fluorescent lamp, an electric lamp, an incandescent lamp or a halogen lamp; the reflective light source is an LED lamp, a fluorescent lamp, an electric lamp, an incandescent lamp or a halogen lamp.
5. The titration endpoint determination device according to claim 4, wherein when the light source is natural light, the device further comprises a titration platform support for positioning the color sensor at the bottom of the titration cell.
6. The titration endpoint determination apparatus according to claim 4, wherein when the light source is a transmission type light source, the light source and the color sensor are respectively disposed on both sides of the titration cell, and a light-passing hole is disposed on each of both sides of the titration cell for light to pass through; the light of the light source penetrates through the titration cell and then irradiates the color sensor.
7. The titration endpoint determination apparatus according to claim 4, wherein when the light source is a reflective light source, the light source and the color sensor are both located on the same side of the titration cell, and light from the light source is reflected by the liquid in the titration cell and then irradiated onto the color sensor.
8. The titration endpoint determination device according to claim 1, wherein the determination module is implemented by:
extracting color data reflecting the color change of the titrated liquid from the received color parameter information or image information, wherein the color data comprises: RGB value, hue, color temperature, brightness and color saturation of the color of the titrated liquid;
comparing the extracted color data with a preset titration end point judgment condition, if the color data of the titrated liquid meets the titration end point judgment condition, judging that the titration end point is reached, and sending a message of stopping dripping the standard solution; and if the color data of the titrated liquid does not meet the judgment condition of the titration end point, sending a message of 'continuously dripping the standard solution'.
9. The titration endpoint determination apparatus according to claim 7, wherein the color sensor requires a white light test before first operation to obtain a color parameter when there is no liquid in the titration flask or when the liquid in the titration flask is a colorless transparent liquid.
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