CN112129751A - A high accuracy titration outfit for chemical oxygen demand is surveyd - Google Patents
A high accuracy titration outfit for chemical oxygen demand is surveyd Download PDFInfo
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- CN112129751A CN112129751A CN202011021371.XA CN202011021371A CN112129751A CN 112129751 A CN112129751 A CN 112129751A CN 202011021371 A CN202011021371 A CN 202011021371A CN 112129751 A CN112129751 A CN 112129751A
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- G—PHYSICS
- 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
- G01N31/162—Determining the equivalent point by means of a discontinuity
Abstract
The invention provides a high-precision titration device for measuring chemical oxygen demand, which comprises a titration cell, a color sensor, a light source, an automatic camera recording component, a titration reagent pipeline, a pure water pipeline, a color developing agent pipeline, a liquid transfer pipeline and a temperature sensor. The invention adopts the principle of relative change to judge the end point color instead of the absolute color value, cancels the prior color correction process, saves the recording time, and can also avoid the influence of background interference colors such as the color, the turbidity and the like of the water body on the end point color judgment, thereby greatly improving the resolution efficiency. In addition, the invention is provided with three titration reagent composite pipelines with high, medium and low concentrations to realize sample introduction with different concentrations, and is combined with a temperature sensor and a mechanical stirring device to ensure that the reaction can be rapidly carried out at the optimal reaction temperature. And the titration reagent pipeline, the pure water pipeline, the color developing agent pipeline and the liquid transfer pipeline are designed integrally.
Description
Technical Field
The invention relates to a measuring instrument component in the field of environmental protection detection, in particular to a component of a titration analysis pool in a measuring instrument for measuring Chemical Oxygen Demand (COD), and belongs to the field of analytical chemistry detection.
Background
Chemical-Oxygen-Demand (COD), which is abbreviated as COD, refers to the mass concentration of Oxygen in mg/L corresponding to the dissolved substances in water and the potassium dichromate which is a strong oxidant consumed by suspended substances under certain conditions. It is a comprehensive index for representing the reductive substances in the water body. The COD in the water body is too high, which indicates that the organic pollution is serious, and the balance of the environment and the biological community is damaged, so that the water body is deteriorated. Therefore, COD is an important parameter of sewage treatment plants and an important index for environmental monitoring.
At present, 3 kinds of dichromate method titration methods (HJ828-2017, instead of GB11914-1989), acid potassium permanganate method (GB11892-1989) and chromium method rapid digestion spectrophotometry (HJ/T399-2007) are mainly applied in domestic standard methods for determining chemical oxygen demand in water. Wherein the analysis and determination process relates to the application requirement based on color end point judgment according to the requirement of determination standard in the dichromate method for determining chemical oxygen demand of water quality HJ 828-2017.
There are various factors that affect the judgment of the color end point, mainly including confirmation of the color of the titration end point, which is the end point of the reaction, the exact volume of the titrant to be added, the homogeneity of the reaction solution (e.g., the influence of particles, bubbles in the reaction solution), and the like.
For the color confirmation of the titration end point, the traditional method needs to wait until the digested and leached sample is cooled to room temperature, then a color developing agent (ferron indicator) is manually added, then titration operation is carried out, the judgment of the titration end point needs human eye identification, the titration is immediately stopped when color change occurs, and titration mention is recorded, so that the result is calculated.
For example, chinese patent application CN201710357472.6 entitled "an analytical method for detecting chemical oxygen demand in water" discloses an analytical method for detecting chemical oxygen demand in water, wherein in the titration step, ferron indicator is added to the diluted sample, the titration is performed with ferrous sulfate standard solution until the color of the sample solution suddenly changes to reddish brown, and the number of milliliters used by the ferrous sulfate standard solution is recorded. In addition, the chinese patent application CN201810095274.1 entitled "a rapid COD detection method for high chloride domestic sewage suitable for oil production platform" discloses an analysis method for detecting chemical oxygen demand of domestic sewage, wherein the liquid in the pipe to be digested is digested at 165 ℃ for 15min, then taken out and cooled to room temperature, the liquid in the digestion pipe is transferred to a conical flask and added with a drizzle indicator, the solution is titrated with a standard solution of ferrous ammonium sulfate, the usage amount of the standard solution of ferrous ammonium sulfate is recorded, and a blank experiment is performed at the same time to measure the COD concentration of a water sample. Similar invention applications can also be seen in CN201811405123.8 and the invention name of "organic wastewater COD on-line detection method", CN201910927558.7 and the invention name of "a wastewater COD rapid semi-quantitative detection method", CN201710357472.6 and the invention name of "an analysis method for detecting chemical oxygen demand in water".
However, in the prior art, in the first aspect, for the above conventional method for visually determining the titration endpoint, since the color mutation at the timing of the final titration is a transient change, the user operation needs to be carefully performed, the titration speed is very slow, or else, the titration is excessive. Considering that the titration process involves color change, the final data is the result calculation through the volume recorded by the user, if the final titration data lacks validity and reliability, the data tracing basis is lacked after system errors occur, and therefore the traditional visual measurement method cannot adapt to the titration display reaction of the chemical oxygen demand.
In recent years, a technology of automatically detecting color mutation of a titration end point by using a color sensor instead of a visual method has appeared, for example, chinese patent application CN201710445840.2, entitled "a seawater COD measuring device and method" discloses a measuring device for detecting chemical oxygen demand in seawater, which comprises a sample introduction unit, a digestion unit, a condensation unit, and a titration unit, and further comprises a color judgment device, wherein the color judgment device comprises a surface light source and a color sensor which are arranged at two sides of a titration tank of the titration unit, and light emitted by the surface light source passes through liquid in a container and is received by the color sensor.
The invention of Chinese patent application CN202010197092.2, entitled "full-automatic chemical oxygen demand analyzer and its working process" discloses a full-automatic chemical oxygen demand analyzer, which automatically inputs reagents, automatically resolves, automatically cools, automatically titrates, identifies color change in a machine vision mode, and automatically judges a terminal point. Therefore, the effects of reducing errors and obtaining real data are achieved.
Although the combination color sensor replaces a visual method to judge the titration detection end point, the artificial error can be effectively avoided, and the reading error can be prevented, the method ignores the inevitable system error of the self environment of the instrument. For example, zhanxiamin (development of portable water quality analyzer based on color sensing, university of tianjin, university of master's academic thesis, 2013) reports that the stability of the measurement result of the apparatus depends on the stability of the light source, the stability of the RGB color sensor and the stability of the measurement environment, and it is difficult to guarantee that the test is performed under the same condition due to the application limitation of the portable detection apparatus, thereby causing systematic errors in the measurement result (see section 5.2).
Furthermore, wu liang (auto titrator development based on colorimetric analysis, university of changan university, university of university, academic thesis, 2018) reported that for COD meters, accuracy (bias) was mainly a measure of the effect of systematic errors, expressed as a deviation of systematic test results from true values (see section 5.1). In the case of a titration instrument, systematic errors are mainly caused by illumination conditions, operating means, working condition environment and geometric errors of the instrument. The correct measurement (i.e. high accuracy) of the instrument can minimize the systematic error and ensure the accurate measurement of the result (see section 5.2.1).
Regarding the determination of the color development endpoint by using a color sensor, daoxiang (review and prospect of the development and application of the color recognition auto-titration method, popular science, vol.18, No. 202, 2016) reports that this color detection method is to achieve color detection by measuring three primary colors constituting the color of an object, or to detect the color difference between the object to be detected and a standard color (see page 36). However, in the method of measuring the three primary colors constituting the color of the object to detect the color, which is based on the known standard color, when the chromaticity of the standard color is adjusted according to actual needs, there is a possibility that the actual color endpoint is different from the original color endpoint, which may cause systematic error in determining the endpoint, for example, the original detected endpoint color is blue, and the actual detected endpoint color is deep blue or light blue. For the method for detecting the color difference between the measured object and the standard color, if the numerical range of the manually preset color difference has an error, the actual color end point is different from the original color end point, and the system error exists in the end point judgment. Therefore, although there is a high accuracy in replacing the visual method with the color sensor, there is still an inevitable systematic error.
In order to avoid the above system errors, the conventional processing method is to calibrate the instrument before the test, for example, wu brightness reports that different samples to be tested are selected to be put into the instrument for measurement, and each sample also needs to be repeatedly measured by the instrument for multiple times. And recording the result of each measurement, calculating the average value of multiple tests of the same sample, making a difference with the corresponding standard value, and calculating the relationship between the RGB tristimulus values and the titration result values through a formula so as to determine the accuracy threshold (see section 5.1.2). For example, juyongfeng (automatic titrator system design and implementation based on colorimetric analysis, volume 27, No. 7, 2019) reports that a uniform colorimetric standard needs to be established before colorimetric measurement of colorimetric sensor to ensure the measurement accuracy, so that white balance correction needs to be completed before color acquisition, and the sensor is calibrated to be in a state to be detected (see section 2.3).
However, this pre-calibration method requires a long time and is disadvantageous in the field or the need for rapid determination of chemical oxygen demand in water samples, particularly in the rapid detection of reaction solutions containing particulate impurities and bubbles, and thus further improvement is required.
In a second aspect, the exact volume of titrant added is influenced by how precisely the titration volume and titration rate added is controlled. The traditional manual titration method is carried out by adopting a burette, and artificial reading errors exist during the final titration volume reading; and the minimum amount of the traditional titration is 1 drop (about 50ul), which cannot be compared with the minimum volume of the automatic titration (with the precision of 1ul), so that more accurate quantification is realized, taking a standard sample with the chemical oxygen demand of 50mg/L as an example, 1 drop is titrated more or less by adopting the traditional manual method, and a relative error of 4 percent is introduced to the error of the result.
Although titration pump or metering pump technology has been developed to date, where the precise volume to be added can be controlled by auto-titration, the problem of how to control the titration rate is not addressed. If a large dose (e.g., 50ul) of auto-titration is used, overdetermination is likely to occur, resulting in inaccurate results; if the automatic titration is carried out with a microdose (e.g., accuracy of 1 to 5ul), the titration rate tends to be too slow, the process tends to be too long, and side-effect reactions (e.g., oxidation or reduction reactions) of the reaction solution tend to occur, and further improvement is desired.
In the third aspect, the homogeneity of the reaction solution that affects the titration result depends mainly on the constancy of the reaction temperature and the rapid homogenization of the reaction solution. Wherein, for the former, whole titration process temperature also plays comparatively crucial effect to the colour development of colour development agent, and the temperature is too low, and the colour is unobvious also can influence the titration result, and it also has very important meaning to data traceability, but traditional method still needs user's manual record, needs extra thermometer, and has the risk of forgetting, consequently needs through real-time supervision temperature to confirm the optimum temperature of colour development reaction.
For the latter, the titration process of the traditional method needs to shake the titration flask by hand continuously, so that the titration liquid is fully mixed and reacted, the operation workload is large, and the method is not friendly to users who titrate in large quantities. Improvements are therefore needed.
In a fourth aspect, a conventional titration apparatus is generally provided with a washing solution line, a color reagent line, a titration reagent line, and a post-reaction liquid transfer line. Although the pipeline can process different solutions respectively to obtain good effect, the structure of the titration apparatus is complicated due to the design of excessive pipelines, so the simplification of the titration sample-adding apparatus is also the key point of the urgent need for improvement.
Therefore, there is a need for a high precision titration apparatus for chemical oxygen demand determination, which has the advantages of high accuracy, system error prevention and no need of pre-calibration, and has a simple structure, which is convenient for modular production and assembly, and reduces the cost of production, assembly and maintenance, so as to replace the existing high precision titration apparatus or the detector directly used for producing and determining Chemical Oxygen Demand (COD).
Disclosure of Invention
The first invention principle is to design a color sensor combined synchronous automatic camera recording component, which can replace a visual method, improve the detection accuracy of a titration end point, prevent manual error, record color change in a titration process in real time, provide basis for data tracing and ensure the effectiveness and reliability of titration data. Wherein, this automatic record part of making a video recording receives computer automatic control, can whole recording as required, also can estimate the time quantum range around the colour change terminal point according to software, especially the time quantum around the colour change terminal point that the colour sensor sent, and compare RGB's relative colour change value and judge the colour, because adopt the principle of relative change to carry out terminal point colour judgement, rather than adopt absolute color value to judge, consequently, can cancel the colour correction process in advance, and save recording time, can also stop the influence of background interference colours such as water body colour itself, turbidity to terminal point colour judgement, thereby improve resolution efficiency greatly. Before titration begins, when the chemical state and color in the titration cell are relatively stable, the RGB value at the moment is taken as a reference, potassium permanganate titration is carried out, when the potassium permanganate titration is close to a terminal point, the color of a water body changes, the RGB value at the moment is detected to change correspondingly, the system exceeds a preset change amplitude through the RGB change amplitude as a basis, and the titration terminal point is considered to be reached. Therefore, the absolute color of the water body before and after titration does not need to be corrected in the whole process, and the method is fast and efficient.
According to the second invention principle, on the basis of the first principle, three titration reagent composite pipelines with high, medium and low concentrations are arranged, and sample injection with different concentrations is realized under the driving of a titration pump or a metering pump, wherein the high concentration titration reagent is injected in the initial stage of reaction, the medium concentration titration reagent is injected in the middle stage of reaction, and the low concentration titration reagent is injected in the final stage of reaction, so that the titration rate is greatly accelerated, and the sample injection accuracy in the final stage is guaranteed.
The third invention principle of the invention is that on the basis of the second and third principles, a temperature sensor and a mechanical stirring device are jointly introduced to ensure that the reaction is rapidly carried out at the optimal reaction temperature.
Alternatively, the fourth invention principle of the present invention is that based on the above principle, the titration reagent pipeline, the pure water pipeline, the color reagent pipeline and the liquid transfer pipeline are designed into an integrated structure, and the sample adding sequence is strictly limited, so that the mutual pollution between the reagents is prevented, and the sample adding device is simplified.
Therefore, the invention provides a high-precision titration device for measuring chemical oxygen demand, which comprises a titration cell, a color sensor, a light source, an automatic camera recording component, a titration reagent pipeline, a pure water pipeline, a color developing agent pipeline, a liquid transfer pipeline and a temperature sensor, wherein,
the titration cell is made of a light-transmitting material, a light source is arranged on the outer edge of one side of the titration cell, and a color sensor capable of receiving a forward emission light path of the light source is arranged on the outer edge of the other opposite side of the titration cell;
an automatic camera recording component is arranged on the outer edge of the titration cell perpendicular to the light path direction, and a temperature sensor for monitoring the temperature change of the liquid in the titration cell is arranged on the outer edge of the other opposite side;
wherein, the color sensor and the automatic camera recording component are synchronously connected with the computer host or the automatic controller, the computer host or the automatic controller can synchronously set the recording time sections of the color sensor and the automatic camera recording component and synchronously start, close and manage the data recorded by the color sensor and the automatic camera recording component, the system chemical reaction state and color are made relatively stable by the addition of the color-developing agent/other reagent before the titration begins, continuously titrating and adding a titration solution according to the RGB data of the current color sensor as a reference standard, comparing and analyzing the real-time RGB data of the color sensor and the reference standard by software, when obvious RGB value change is found and a change threshold value exceeds the system setting, the titration end point can be judged, relative comparison analysis is adopted in the whole process, so that the prior color correction process is cancelled, and the recording time is saved.
The temperature sensor is connected with the computer host or the automatic controller and can send the real-time temperature of the cooling conductor to the computer host or the automatic controller so that the computer host or the automatic controller can automatically control the start time of sample adding and camera shooting recording.
In one embodiment, the light-transmissive material of the titration cell comprises plastic, glass, quartz, polymer material, the light source comprises low-heat-generation LED (white, green, etc.), laser light source, etc., the color sensor comprises RGB color sensing chip, CCD chip, color sensor, silicon photodiode, and the temperature sensor comprises infrared temperature sensor, resistance temperature sensor (such as PT100 platinum resistor), thermocouple, IC temperature sensor, thermistor, etc.
In another embodiment, a magnetic stirring part is arranged below the titration cell, and a magnetic stirring bar is arranged at the bottom of the titration cell and can rapidly stir and uniformly mix the solution in the titration cell under the driving of the magnetic stirring part. In a specific embodiment, the magnetic stirring component is driven by a motor or coils to form a rotating alternating magnetic field to drive the magnetic stirrer in the titration cell to rotate, and the component can be a motor to drive a magnetic head to rotate or a rotating alternating magnetic field formed by a plurality of groups of coils.
In another embodiment, a mechanical stirring component is arranged at the bottom of the titration cell, and the mechanical stirring component can rapidly stir and mix the solution in the titration cell. In one embodiment, the mechanical stirring part comprises a vertically downward stirring shaft and a terminal stirrer, wherein the stirring shaft vertically extends upwards out of the titration cell and is connected with the power device, or a rotary stirring part directly installed at the bottom of the titration cell and provides driving force through a power line which penetrates downwards out of the bottom of the titration cell and is connected with the power device.
In one embodiment, the titration reagent pipeline, the pure water pipeline, the color reagent pipeline and the liquid transfer pipeline are respectively and independently connected with an automatic metering pump controlled by a computer host or an automatic controller, so that various reagents are accurately added into a titration cell, wherein the titration reagent pipeline is used for adding a titration reagent into the titration cell in a titration process; the pure water pipeline is used for adding pure water and cleaning the titration cell to prevent cross contamination; the color developing agent pipeline is used for adding the color developing agent; the liquid transfer pipeline is used for transferring the titrating liquid to the titration cell, transferring the titrated sample out of the titration cell, and transferring the waste liquid in the cleaning process out of the titration cell.
In a specific embodiment, the titration reagent pipelines are 2-3 pipelines, and 3 pipelines with high concentration, medium concentration and low concentration or 2 pipelines with high concentration and low concentration can be set according to different types of titration reagents and sample loading amount ranges predicted by a computer, so as to be respectively used for adding different titration reagents of high-concentration and low-concentration samples.
In any of the above-mentioned embodiments, can with titration reagent pipeline, pure water pipeline, colour development agent pipeline, liquid transfer pipeline integration set up to 1 pipeline to simplify the setting of application of sample pipeline greatly, wherein when using, this integration pipeline need add in proper order and wait to titrate sample solution, colour development solution, titrate solution, then transfer the waste liquid of titrating the completion to the waste liquid pond through the integration pipeline after titrating, and add pure water solution and wash the titration cell, the waste liquid that has washd is transferred to the waste liquid pond by the integration pipeline again. In one embodiment, when the titration reagent line, the pure water line, the color reagent line and the liquid transfer line are configured as separate lines, the liquid transfer line can be connected to the titration liquid through the upper or lower portion of the titration cell.
In any of the above embodiments, the titration cell is a closed container, and one or more access holes are provided on the upper end surface for introducing an integrated pipeline or a titration reagent pipeline, a pure water pipeline, a color reagent pipeline, and a liquid transfer pipeline. In a preferred embodiment, the upper end surface of the titration cell is further provided with an air pressure balancing port for keeping the titration cell in communication with the outside air, so that the sample addition, the transfer and the reagent addition can be carried out smoothly.
In any of the above embodiments, the color sensor, the automatic camera recording component, the temperature sensor, the light source, the titration reagent pipeline, the magnetic stirring component or the mechanical stirring component are all connected to a computer host or an automatic controller, and the computer host or the automatic controller can implement sending instructions according to the received information, and perform synchronous control on the above components, so as to accurately adjust and record the color change end point, accurately control the added titration volume and titration rate, and accurately control the homogeneity of the reaction solution, thereby realizing the correction of blank color cancellation and the rapid titration determination.
The second objective of the present invention is to provide a method for accurately titrating a solution to be measured by using the above high-precision titration apparatus, which comprises the following steps:
(1) transferring the titrated sample to a titration cell through a liquid transfer pipeline;
(2) adding a color developing agent (such as a ferron solution) according to the titration requirement, and waiting for chemical reaction balance;
(3) in the step (2), the stirring component starts to stir the sample, the light source, the color sensor, the temperature sensor and the automatic camera recording component start to operate, and the RGB value of the solution to be detected which is recovered to be natural color or colorless is recorded;
(4) 3 drops of color developing agent is added into the color developing agent pipeline;
(5) titrating a reagent (such as ammonium ferrous sulfate) into the titration cell through a titration reagent pipeline, monitoring the color change in real time by a color sensor, and recording the RGB value when the color changes from yellow to reddish brown through blue-green;
(6) by analyzing the RGB change values of the step (3) and the step (5), if a preset RGB change threshold value is exceeded, the titration end point is judged to be reached, and if the preset RGB change threshold value is not exceeded, the step (5) is continuously repeated;
(7) and transferring the waste liquid after titration away through a liquid transfer pipeline, adding pure water through a pure water pipeline to clean the titration tank, and transferring the cleaned waste liquid away through the liquid transfer pipeline again.
In one embodiment, the above steps are precisely controlled by a computer host or an automatic controller, so that the steps of transferring, titrating, stirring, measuring temperature, recording images, recording RGB values, comparing and analyzing the RGB values, cleaning and the like of various reagents are completed.
In another embodiment, if the RGB variation value of step (6) far exceeds the predetermined RGB variation threshold, the time period before and after the end of the color variation transmitted by the color sensor recorded by the automatic image-pickup recording means is corrected to a titration value corresponding to a time close to the RGB variation threshold.
In other embodiments, in step (5), when the computer predicts that the concentration of the sample to be titrated is too high, the titrating reagent line with high concentration is instructed to drop titrating reagent, the amount of titrating reagent added and the color change are monitored, and the titrating reagent line (or the integrated line) adjusted to low concentration is dropped titrating reagent according to the predicted titration time and titration amount.
In other embodiments, the titration reagent line, the pure water line, the color reagent line, and the liquid transfer line in steps (1) to (7) are integrated to be set to 1 line.
In other embodiments, the liquid may be added and transferred through a liquid transfer line connected above or below the titration cell.
Technical effects
1. The invention can replace a visual method, improve the detection accuracy of the titration end point, prevent manual error, record the color change in the titration process in real time, provide basis for tracing the source of data and ensure the effectiveness and reliability of titration data.
2. The composite pipeline of the invention can realize sample injection with different concentrations, thereby greatly accelerating the titration rate and ensuring the sample injection accuracy at the final stage.
3. The present invention combines the introduction of a temperature sensor and a mechanical stirring device to ensure that the reaction proceeds rapidly at the optimum reaction temperature.
4. The device integrates the titration reagent pipeline, the pure water pipeline, the color reagent pipeline and the liquid transfer pipeline, has smaller volume compared with the prior device, can realize modular design, can be flexibly connected into or replaced in the prior chemical oxygen demand analyzer or determinator, can save a large amount of expenses, and avoids the cost brought by purchasing a new instrument again.
5. The invention can automatically send instructions according to a preset program through the operation of a computer host or a controller, saves the operation and monitoring steps of manpower, can flexibly monitor the time periods before and after the color change end point sent by the color sensor, and can provide the basis of tracing to the source so as to save the recording time, thereby greatly improving the distinguishing efficiency. (ii) a
6. Compared with the detection principle that whether the absolute value of the color change accords with the preset value or not needs to be judged by the existing color sensor, but the system error needs to be avoided by color correction in advance.
Drawings
FIG. 1: front view of the titration cell containing a magnetic stirring member.
FIG. 2: side view of a titration cell containing a magnetically stirred component.
FIG. 3: front view of the titration cell containing a mechanical agitation means.
FIG. 4: side view of the titration cell and integrated design piping containing mechanical agitation components.
FIG. 5: the invention is a work flow chart.
FIG. 6: the invention comprises a product object diagram of a split type pipeline.
FIG. 7: the invention also provides a product object diagram containing the integrated pipeline.
Reference numerals:
1: a titration cell; 2: a color sensor; 3: an LED light source; 4: an automatic camera recording component (i.e., a camera); 5: a temperature sensor; 6: a titration reagent line; 7: a pure water line; 8: a color-developing agent pipeline; 9: a liquid transfer line; 10: a stirring member; 11: an air pressure balancing port; 12: magnetic stirring seeds; 13: integrated pipeline
Detailed Description
In order to make the technical means, the characteristics, the purposes and the functions of the invention easy to understand, the invention is further described with reference to the specific drawings.
As shown in fig. 1-2, the titration apparatus includes a titration cell 1, a color sensor 2, a light source 3, an automatic image recording unit 4, a temperature sensor 5, a titration reagent line 6, a pure water line 7, a color developing agent line 8, a liquid transfer line 9, a stirring unit 10 (magnetic stirring unit), an air pressure balance port 11, a magnetic stirrer 12, and the like.
Wherein, the titration cell 1 is a transparent cylinder with closed upper and lower end surfaces. Be equipped with LED lamp light source 3 at titration cell outside edge one side, this light source 3 generates heat for a short time, can effectively avoid its self to generate heat and arouse analysis pool temperature variation, can effectively reduce the influence of ambient light to color sensor 2. And a color sensor 2 is arranged on the outer edge of the titration cell on the other side opposite to the light source and used for receiving the light path emitted by the light source in the forward direction. An automatic camera recording component 4 is arranged on the outer edge of the titration cell vertical to the light path direction, and a temperature sensor 5 selected from an IC temperature sensor or an infrared temperature sensor is arranged on the inner side of the titration cell opposite to the automatic camera recording component 4.
The magnetic stirring component 10 is arranged on the outer side of the bottom of the titration cell 1 and can generate a rotary alternating magnetic field to drive the magneton 12 in the titration cell to rotate.
Titration cell upper end surface is equipped with atmospheric pressure balance mouth 11, titration reagent pipeline 6 (can additionally set up the titration reagent pipeline of high concentration, not shown), pure water pipeline 7, colour-developing agent pipeline 8, liquid transfer pipeline 9 along the diametric line at center in proper order, and wherein the liquid transfer pipeline 9 opening is established in the position that is close to titration cell 1 lower extreme surface to fully shift the liquid after all reactions.
As shown in fig. 3, the titration apparatus includes a titration cell 1, a color sensor 2, a light source 3, an automatic image recording unit 4, a temperature sensor 5, a titration reagent line 6, a pure water line 7, a color developing agent line 8, a liquid transfer line 9, a stirring unit 10 (mechanical stirrer), an air pressure balance port 11, and the like. The titration cell 1, the color sensor 2, the LED light source 3, the temperature sensor 5, the air pressure balance port 11, the titration reagent line 6 (a high-concentration titration reagent line, not shown, may be additionally provided), the pure water line 7, the color reagent line 8, and the liquid transfer line 9 are provided in the same manner as in fig. 1-2. However, a mechanical stirring member 10 which is vertically downward and extends into the liquid is arranged along the central axis above the titration cell, and the mechanical stirring member comprises a stirring shaft and a stirring rod at the tail end, wherein the stirring shaft vertically extends upward out of the titration cell and is connected with a power device.
As shown in fig. 4, the titration apparatus is basically the same as that shown in fig. 3, but the titration reagent line 6, the deionized water line 7, the color developing agent line 8, and the liquid transfer line 9 are integrated into an integrated line 13. In addition, a high concentration titration reagent line (not shown) may be additionally provided.
All the color sensors and the automatic camera recording component, the temperature sensor, the light source, the titration reagent pipeline, the magnetic stirring component or the mechanical stirring component in the attached drawing are connected with a computer host or an automatic controller, the computer host or the automatic controller can implement sending instructions according to received information, and the components are synchronously controlled, so that how to accurately adjust and record the color change end point, accurately control the added titration volume and the titration rate, and accurately control the homogeneity of the reaction solution, thereby realizing the correction of blank color cancellation and the rapid titration determination.
The workflow of the present invention consists in (see fig. 5): treat that titrated sample passes through the liquid transfer pipeline and gets into the titration cell, lay the magnon in the titration cell, magnetic stirring part 10 (mechanical stirring spare) operation, drive magnon 12 (stirring) rotation in the titration cell, begin to stir the sample, LED light source 3, color sensor 2, temperature sensor 5, camera 4 begins to operate, add the colour-developing agent through colour-developing agent pipeline 8, then through 6 titration reagents toward titration cell 1 in titration cell of titration reagent pipeline, color sensor 2 real-time supervision colour changes, become reddish brown through blue and green when the colour, record RGB value this moment. And (3) analyzing the RGB change values before and after titration, if the RGB change values exceed a preset RGB change threshold value, judging that a titration end point is reached, and if the RGB change values do not exceed the preset RGB change threshold value, continuously repeating titration until titration is completed. The waste liquid after bottom fixing is transferred away through a liquid transfer pipeline 9, pure water is added through a pure water pipeline 7 to clean the titration tank, and the cleaned waste liquid is transferred away through the liquid transfer pipeline 9 again. If the titration reagent pipeline, the pure water pipeline, the color reagent pipeline and the liquid transfer pipeline are integrated to be set to be 1 pipeline, the solution is added and transferred through the integrated pipeline.
In the above working process, when the computer predicts that the concentration of the sample to be titrated is too high, the titrating reagent pipeline with high concentration is instructed to drop titrating reagent, the amount of the titrating reagent added and the color change are monitored, and the titrating reagent pipeline (or the integrated pipeline) with low concentration is adjusted to drop titrating reagent according to the predicted titrating time and the titrating amount.
The specific product object diagram is shown in FIGS. 6-7.
Specific embodiments of the invention have been described above. It is to be understood that the invention is not limited to the particular embodiments described above, and that equipment and structures not described in detail are to be understood as being practiced in a manner common in the art; various changes or modifications may be made by one skilled in the art within the scope of the claims without departing from the spirit of the invention, and without affecting the spirit of the invention.
Claims (10)
1. A high-precision titration apparatus for measuring chemical oxygen demand comprises a titration cell, a color sensor, a light source, an automatic camera recording component, a titration reagent pipeline, a pure water pipeline, a color developing agent pipeline, a liquid transfer pipeline and a temperature sensor,
the titration cell is made of a light-transmitting material, a light source is arranged on the outer edge of one side of the titration cell, and a color sensor capable of receiving a forward emission light path of the light source is arranged on the outer edge of the other opposite side of the titration cell;
an automatic camera recording component is arranged on the outer edge of the titration cell perpendicular to the light path direction, and a temperature sensor for monitoring the temperature change of the liquid in the titration cell is arranged on the outer edge of the other opposite side;
the temperature sensor is connected with the computer host or the automatic controller and can send the real-time temperature of the cooling conductor to the computer host or the automatic controller so that the computer host or the automatic controller can automatically control the start time of sample adding and camera shooting recording.
The color sensor and the automatic camera recording component are synchronously connected with the computer host or the automatic controller, the computer host or the automatic controller can synchronously set the recording time sections of the color sensor and the automatic camera recording component and synchronously start, close and manage the data recorded by the color sensor and the automatic camera recording component, the system chemical reaction state and color are made relatively stable by the addition of the color-developing agent/other reagent before the titration begins, continuously titrating and adding a titration solution according to the RGB data of the current color sensor as a reference standard, comparing and analyzing the real-time RGB data of the color sensor and the reference standard by software, when obvious RGB value change is found and a change threshold value exceeds the system setting, the titration end point can be judged, relative comparison analysis is adopted in the whole process, so that the prior color correction process is cancelled, and the recording time is saved.
2. The high-precision titration apparatus according to claim 1, wherein a magnetic stirring component is disposed below the titration cell, and a magnetic stirrer is disposed at the bottom of the titration cell, and the magnetic stirrer is driven by the magnetic stirring component to rapidly stir and mix the solution in the titration cell, preferably the magnetic stirring component is driven by a motor or a coil to form a rotating alternating magnetic field, and the magnetic stirrer in the titration cell is driven to rotate, wherein the component can be a motor driving a magnetic head to rotate or a rotating alternating magnetic field formed by a plurality of coils; alternatively, the first and second electrodes may be,
wherein be equipped with mechanical stirring part bottom the titration tank, solution in this part ability rapid mixing blending titration cell, preferred mechanical stirring part includes perpendicular decurrent (mixing) shaft and terminal stirring, and the (mixing) shaft upwards stretches out the titration tank perpendicularly and is connected with power device, or the rotation type stirring part of direct mount in the titration tank bottom, and it provides drive power through wearing out the titration tank bottom downwards and being connected with power device's power cord.
3. A high precision titration apparatus as claimed in any one of claims 1-2, wherein the titration reagent line, the pure water line, the color reagent line, and the liquid transfer line are independently connected to an automatic metering pump controlled by a computer host or an automatic controller, respectively, so that each reagent is accurately added into the titration cell, wherein the titration reagent line is used for adding the titration reagent into the titration cell during titration; the pure water pipeline is used for adding pure water and cleaning the titration cell to prevent cross contamination; the color developing agent pipeline is used for adding the color developing agent; the liquid transfer pipeline is used for transferring the titrating liquid to the titration cell, transferring the titrated sample out of the titration cell, and transferring the waste liquid in the cleaning process out of the titration cell.
4. The high precision titration apparatus according to claim 3, wherein the titration reagent pipeline has 2-3 pipelines, and 3 pipelines with high concentration, medium concentration and low concentration or 2 pipelines with high concentration and low concentration can be set according to different types of titration reagents and the sample loading amount range predicted by the computer, so as to be respectively used for adding different titration reagents of high and low concentration samples.
5. The high precision titration apparatus according to any one of claims 1 to 4, wherein the titration reagent pipeline, the pure water pipeline, the color reagent pipeline, and the liquid transfer pipeline are integrally arranged as 1 pipeline to greatly simplify the arrangement of the sample adding pipeline, wherein the integrated pipeline is required to sequentially add the sample solution to be titrated, the color solution, and the titration solution when in use, and then the titrated waste liquid is transferred to the waste liquid pool through the integrated pipeline after the titration is finished, and the pure water solution is added to clean the titration pool, and the cleaned waste liquid is transferred to the waste liquid pool by the integrated pipeline.
6. The high precision titration apparatus according to claim 5, wherein when the titration reagent line, the pure water line, the color reagent line, and the liquid transfer line are provided as separate lines, the liquid transfer line can be connected to the titration liquid through the upper or lower portion of the titration cell.
7. A high precision titration apparatus as claimed in any one of claims 1 to 6, wherein the titration cell is a closed container, and one or more access holes are provided on the upper surface thereof for accessing the integrated pipeline or titration reagent pipeline, pure water pipeline, color reagent pipeline, and liquid transfer pipeline, preferably wherein the upper surface of the titration cell is further provided with an air pressure balancing port for keeping the titration cell in communication with the external air, thereby facilitating the addition and transfer of the sample and the smooth addition of the reagent.
8. The high precision titration apparatus according to claim 7, wherein the color sensor and the automatic recording component, the temperature sensor, the light source, the titration reagent line, the magnetic stirring component or the mechanical stirring component are connected to a computer host or an automatic controller, and the computer host or the automatic controller can perform a command transmission according to the received information, perform a synchronous control on the components, and perform a correction and a fast titration for canceling the blank color and a fast titration for precisely adjusting and recording the color change endpoint, precisely controlling the titration volume and the titration rate to be added, and precisely controlling the homogeneity of the reaction solution.
9. A method for accurately titrating a solution to be measured by using the high-precision titration apparatus according to claims 1 to 8, comprising the steps of:
(1) transferring the titrated sample to a titration cell through a liquid transfer pipeline;
(2) adding a color developing agent according to the titration requirement, and waiting for chemical reaction balance;
(3) in the step (2), the stirring component starts to stir the sample, the light source, the color sensor, the temperature sensor and the automatic camera recording component start to operate, and the RGB value of the solution to be detected which is recovered to be natural color or colorless is recorded;
(4) 3 drops of color developing agent is added into the color developing agent pipeline;
(5) titrating the reagent into a titration cell through a titration reagent pipeline, monitoring the color change in real time by a color sensor, and recording the RGB value when the color is changed from yellow to reddish brown through blue-green;
(6) by analyzing the RGB change values of the step (3) and the step (5), if a preset RGB change threshold value is exceeded, the titration end point is judged to be reached, and if the preset RGB change threshold value is not exceeded, the step (5) is continuously repeated;
(7) transferring the waste liquid after titration away through a liquid transfer pipeline, adding pure water through a pure water pipeline to clean the titration tank, and transferring the cleaned waste liquid away through the liquid transfer pipeline again;
the steps are accurately controlled by a computer host or an automatic controller, so that the steps of transferring, titrating, stirring, measuring temperature, recording a video, recording RGB values, comparing and analyzing the RGB values, cleaning and the like of various reagents are completed.
10. The method of claim 9, wherein when the RGB variation value of step (6) is far beyond the predetermined RGB variation threshold, the time period before and after the end of the color variation transmitted by the color sensor recorded by the automatic image-recording means is corrected to a titration value corresponding to a time close to the RGB variation threshold; and/or the presence of a gas in the gas,
in the step (5), when the computer predicts that the concentration of the sample to be titrated is too high, the titration reagent pipeline with high concentration is instructed to drip the titration reagent, the amount of the added titration reagent and the color change are monitored, and the titration reagent pipeline (or the integrated pipeline) with low concentration is adjusted to drip the titration reagent according to the predicted titration time and titration amount.
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