CN114942299A - Titration end point analysis method and system based on permanganate index automatic analyzer - Google Patents
Titration end point analysis method and system based on permanganate index automatic analyzer Download PDFInfo
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- 238000004448 titration Methods 0.000 title claims abstract description 188
- 238000004458 analytical method Methods 0.000 title claims abstract description 28
- 230000029087 digestion Effects 0.000 claims abstract description 78
- 239000012286 potassium permanganate Substances 0.000 claims abstract description 71
- 238000006243 chemical reaction Methods 0.000 claims abstract description 36
- 238000000034 method Methods 0.000 claims abstract description 29
- 238000000954 titration curve Methods 0.000 claims abstract description 28
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 25
- 230000008569 process Effects 0.000 claims abstract description 22
- 230000004044 response Effects 0.000 claims abstract description 15
- 238000003756 stirring Methods 0.000 claims abstract description 15
- 239000000243 solution Substances 0.000 claims description 68
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 16
- 239000007788 liquid Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 230000003647 oxidation Effects 0.000 claims description 8
- 238000007254 oxidation reaction Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000003366 endpoint assay Methods 0.000 claims 2
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 230000001590 oxidative effect Effects 0.000 description 4
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 description 4
- 229940039790 sodium oxalate Drugs 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 239000007800 oxidant agent Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000003918 potentiometric titration Methods 0.000 description 2
- 238000003908 quality control method Methods 0.000 description 2
- 238000002798 spectrophotometry method Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000035772 mutation Effects 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000002943 spectrophotometric absorbance Methods 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/40—Concentrating samples
- G01N1/4044—Concentrating samples by chemical techniques; Digestion; Chemical decomposition
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/44—Sample treatment involving radiation, e.g. heat
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N35/00—Automatic analysis not limited to methods or materials provided for in any single one of groups G01N1/00 - G01N33/00; Handling materials therefor
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Abstract
The invention relates to a titration end point analysis method and a system based on a permanganate index automatic analyzer, wherein the method comprises the following steps: s1, starting titration; s2, a first titration stage, wherein the potential of the digestion solution after each drop of potassium permanganate in the titration process is collected, and whether the potential is larger than a potential threshold value is judged; if yes, go to step S3; s3, reducing the amount of each drop of potassium permanganate in the titration process, and performing potassium permanganate titration in a second titration stage; s4, collecting the potential of the digestion solution after each drop of potassium permanganate in the titration process in the second titration stage, and establishing a dynamic titration curve corresponding to the potential of the digestion solution, the response time of an electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of a reducing agent and the dropping volume of the potassium permanganate after the titration is started; and S5, judging the titration end point based on the dynamic titration curve. The dynamic titration curve established by the invention cooperatively considers the influence of titration environmental factors, and further improves the judgment precision of the titration end point.
Description
Technical Field
The invention belongs to the technical field of analysis and detection, and particularly relates to a titration end point analysis method and system based on a permanganate index automatic analyzer.
Background
Permanganate index is one of the important indicators for automatic monitoring of surface water. According to GB 11892-.
Currently, the measuring methods adopted by automatic permanganate index analyzers include spectrophotometry and titration. The titration method is further classified into an absorbance titration method and a potentiometric titration method. The potentiometric titration method carries out end point judgment through solution oxidation-reduction potential, can well avoid the defect that spectrophotometric methods and absorbance titration methods are easily influenced by water turbidity and chromaticity, and is widely applied. However, no matter which measurement method is adopted, the permanganate index automatic analyzer has the defect of low quality control qualified rate in practical application, and in practical use, the quality control requires standard substance check to disallow the modification of key parameters, the recalibration of the instrument and the like.
Because the permanganate index is a relative index, the oxidation rate of potassium permanganate can be influenced by the change of any factors such as digestion reaction temperature, digestion time, standard sample components (mostly adopting sodium oxalate) and the like, and the accuracy of a detection result is further influenced. At present, the technological design of digestion reaction temperature, digestion time and the like of a permanganate index automatic analyzer in the market and the adopted standard sample components are not completely consistent with those of GB 11892-.
Disclosure of Invention
Based on the above-mentioned shortcomings and drawbacks of the prior art, it is an object of the present invention to at least solve one or more of the above-mentioned problems of the prior art, in other words, to provide a permanganate index autoanalyzer-based titration endpoint analysis method and system which meets one or more of the above-mentioned needs.
In order to achieve the purpose, the invention adopts the following technical scheme:
a titration end point analysis method based on a permanganate index automatic analyzer comprises the following steps:
s1, starting titration, and carrying out potassium permanganate titration at a first titration stage on digestion liquid in the digestion pool; wherein the digestion solution contains a water sample to be tested and a reducing agent, and is continuously stirred in the titration process;
s2, a first titration stage, wherein the potential of the digestion solution after each drop of potassium permanganate in the titration process is collected, and whether the potential is larger than a potential threshold value is judged; if yes, go to step S3;
s3, reducing the amount of each drop of potassium permanganate in the titration process, and performing potassium permanganate titration in a second titration stage;
s4, collecting the potential of the digestion solution after each drop of potassium permanganate in the titration process in the second titration stage, and establishing a dynamic titration curve corresponding to the potential of the digestion solution, the response time of an electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of a reducing agent and the dropping volume of the potassium permanganate after the titration is started;
and S5, judging the point with the maximum slope as the titration end point based on the dynamic titration curve.
Preferably, the dynamic titration curve is:
wherein P is the potential of the digestion solution, V 0 The volume of potassium permanganate added before the start of the titration, V 1 Volume of reducing agent, V 2 The dropwise adding volume of the potassium permanganate after the start of titration, T is the response time of an electrode, v is the stirring speed of a digestion solution, T is the titration reaction temperature, and T is 0 To counteract the reaction temperature, k 0 、k 1 、k 2 、k 3 、k 4 And c are constants.
Preferably, the titration frequency of the second titration phase is less than the titration frequency of the first titration phase.
Preferably, in step S1, the sample preparation process of the digestion solution in the digestion tank includes the following steps:
s01, measuring and quantifying a water sample to be detected, sulfuric acid and a part of potassium permanganate solution, feeding the water sample, the sulfuric acid and the part of potassium permanganate solution into a digestion pool, heating, and timing after the temperature reaches the digestion reaction temperature;
s02, collecting the potential of the mixed liquid in the digestion tank every other preset period to judge whether the mixed liquid is in an oxidation state at present; if so, when the constant temperature time reaches a preset time, cooling to the titration reaction temperature, and adding the residual potassium permanganate solution at one time;
and S03, adding a reducing agent to obtain a digestion solution.
Preferably, in step S02, the potassium permanganate solution is added in portions before the potential of the mixed solution is in an oxidized state.
Preferably, the digestion reaction temperature is 90-100 ℃.
Preferably, the titration reaction temperature is 70-80 ℃.
Preferably, the predetermined time is 10-20 min.
The invention also provides a titration end point analysis system based on the permanganate index automatic analyzer, which applies the titration end point analysis method in the scheme above, and the titration end point analysis system comprises:
the potential acquisition module is used for acquiring the potential of the digestion solution;
the potential judgment module is used for judging whether the potential of the digestion solution is greater than a potential threshold value;
the titration control module is used for controlling the amount of each drop of potassium permanganate in the titration process;
the dynamic titration curve module is used for carrying out dynamic titration according to a dynamic titration curve corresponding to the response time of the potential of the digestion solution and the electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of the reducing agent and the dropping volume of the potassium permanganate after titration is started;
and the titration end point judging module is used for judging the point with the maximum slope based on the dynamic titration curve, namely the titration end point.
Preferably, the dynamic titration curve is:
wherein P is the potential of the digestion solution, V 0 The volume of potassium permanganate added before the start of the titration, V 1 Volume of reducing agent, V 2 The dropwise adding volume of the potassium permanganate after the start of titration, T is the response time of an electrode, v is the stirring speed of the digestion solution, T is the titration reaction temperature, and T is 0 To counteract the reaction temperature, k 0 、k 1 、k 2 、k 3 、k 4 And c are constants.
Compared with the prior art, the invention has the beneficial effects that:
according to the titration end point analysis method and system, the titration end point is early warned in real time through the potential of the electrode, and when titration is close to the end point, the titration speed is controlled in advance, so that titration is fully reacted, namely the purpose of accurate titration is achieved, and the purpose of rapid measurement is also achieved. Particularly, the dynamic titration curve established by the invention cooperatively considers the influence of titration environmental factors (including temperature, response time of an electrode, stirring speed and the like), and further improves the judgment precision of the titration end point.
Drawings
FIG. 1 is a flow chart of a titration endpoint analysis method based on a permanganate index autoanalyzer in example 1 of the present invention;
FIG. 2 is a graph of the change in potential versus titration volume for the titration process of example 1 of the present invention;
FIG. 3 is a block diagram of a titration endpoint analysis system based on an automatic permanganate index analyzer of example 1 of the present invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention, the following description will explain the embodiments of the present invention with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, without inventive effort, other drawings and embodiments can be derived from them.
Example 1:
as shown in fig. 1, the titration endpoint analysis method based on the permanganate index automatic analyzer of the present embodiment specifically includes the following steps:
s1, beginning titration, and carrying out potassium permanganate titration at a first titration stage on the digestion solution in the digestion pool; wherein the digestion solution contains a water sample to be tested and a reducing agent, and is continuously stirred in the titration process;
in the step S1, the sample preparation process of the digestion solution in the digestion tank includes the following steps:
s01, measuring and quantifying a water sample to be detected, sulfuric acid and a part of potassium permanganate solution, feeding the water sample, the sulfuric acid and the part of potassium permanganate solution into a digestion pool, heating, and timing after the temperature reaches the digestion reaction temperature; wherein the digestion reaction temperature is 90-100 ℃, and can be determined according to the actual application requirements.
S02, collecting the potential of the mixed liquid in the digestion tank every other preset period to judge whether the mixed liquid is in an oxidation state at present; if so, when the constant temperature time reaches a preset time, cooling to the titration reaction temperature, and adding the residual potassium permanganate solution at one time; wherein the titration reaction temperature can be specifically determined between 70 ℃ and 80 ℃ according to the actual application requirement; the preset time can be determined within 10-20 min according to the actual application requirement.
In addition, before the potential of the mixed solution is in an oxidation state, the potassium permanganate solution is added in batches, so that the self-adaptive adjustment of the volume of the added potassium permanganate is realized, and the residual volume of the added sodium oxalate due to self-heating decomposition of a large amount of excess potassium permanganate is avoided, so that the volume consumed by titration of the potassium permanganate standard solution is influenced, and the accuracy of a measured value is finally influenced.
And S03, adding a reducing agent to obtain a digestion solution.
S2, a first titration stage, wherein the potential of the digestion solution after each drop of potassium permanganate in the titration process is collected, and whether the potential is larger than a potential threshold value is judged; if yes, go to step S3;
s3, reducing the amount (for example, half-drop amount) of each drop of potassium permanganate in the titration process, and performing potassium permanganate titration in a second titration stage; in addition, the titration frequency of the second titration phase is less than the titration frequency of the first titration phase.
S4, collecting the potential of the digestion solution after each drop of potassium permanganate in the titration process in the second titration stage, and establishing a dynamic titration curve corresponding to the potential of the digestion solution, the response time of an electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of a reducing agent and the dropping volume of the potassium permanganate after the titration is started;
wherein the dynamic titration curve is:
wherein P is the potential of the digestion solution, V 0 The volume of potassium permanganate added before the start of the titration, V 1 Volume of reducing agent, V 2 The dropwise adding volume of the potassium permanganate after the start of titration, T is the response time of an electrode, v is the stirring speed of a digestion solution, T is the titration reaction temperature, and T is 0 To counteract the reaction temperature, k 0 、k 1 、k 2 、k 3 、k 4 And c are constants. In addition, due to the termination of titrationThe potential value of the point is related to the initial potential value during titration, and the initial potential value needs to be deducted, so that the judgment precision of the titration end point is further improved; wherein the initial potential value is related to the total volume of potassium permanganate added in the solution before titration and the digestion reaction temperature.
And S5, judging the point with the maximum slope as the titration end point based on the dynamic titration curve.
Specifically, the process of determining the titration endpoint in this embodiment is as follows:
1. the potential value P of the digestion solution in the titration process is measured in real time by an electrode, and the volume V of the dropped potassium permanganate is controlled 2 And the speed of titration;
2. as shown in fig. 2, the change in potential is divided into three stages: the phase A-rapid titration, the residual reducing agent in the solution is excessive, so the dropping amount of the potassium permanganate is small, and the titration speed and the unit dropping volume of the potassium permanganate can be accelerated; the potential value of the stage is basically unchanged and is at a low level, because the potential value of the reducing agent is presented; b-stage-slow titration, wherein the amount of the residual reducing agent is less and less along with the more and more dropping volume of the potassium permanganate, the titration speed and the unit dropping volume of the potassium permanganate are slowed down before the end point is approached, and because the potential value mutation point is sought, the slower the titration speed is, the better the dropping volume is, the better the titration speed is; the potential value will gradually increase in this stage; c stage-excess titration stage, after the residual reducing agent is completely reacted, the dropped potassium permanganate is excess, and the potential value is stabilized at high level again, so that the titration reaction is completed, and the titration is suspended.
3. According to the three stages of the titration process, a dynamic titration curve is drawn as shown in fig. 2, and in the stage B, the potential is related to the response time of the electrode, the reaction temperature of the solution, the stirring speed of the solution, the volume of the reducing agent and the dropping volume of the potassium permanganate, and the dynamic titration curve is fitted according to experimental data and empirical values.
4. And (4) finding out the point with the maximum slope according to the derivation of a dynamic titration curve relational expression of the B-stage potential and the dripping volume of the potassium permanganate, namely the titration end point.
The permanganate index automatic analyzer of the embodiment uses a variable speed and variable volume titration method, which is superior to the method for controlling the titration speed by titration volume in the market; and the titration end point is pre-warned in real time through the potential of the electrode, and when the titration is close to the end point, the titration speed is controlled in advance, so that the titration is fully reacted, the purpose of accurate titration is achieved, and the purpose of rapid measurement is also achieved.
The embodiment also provides a titration end point analysis system based on the permanganate index automatic analyzer, and the titration end point analysis method of the embodiment is applied. Specifically, as shown in fig. 3, the titration endpoint analysis system includes: the device comprises a potential acquisition module, a potential judgment module, a titration control module, a dynamic titration curve module and a titration end point judgment module.
The potential acquisition module of the embodiment is used for acquiring the potential of the digestion solution; the method is particularly used for collecting the potential of the mixed liquid and the digestion liquid in the digestion pool at each stage.
The potential judgment module of this embodiment is used for judging whether the potential of the digestion solution is greater than the potential threshold.
The titration control module of the embodiment is used for controlling the amount of each drop of potassium permanganate and the titration frequency in the titration process.
The dynamic titration curve module of the embodiment is used for generating a dynamic titration curve corresponding to the dropping volume of the potassium permanganate after titration according to the response time of the electric potential of the digestion solution and the electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of the reducing agent and the dropping volume of the potassium permanganate after titration;
wherein the dynamic titration curve is:
wherein P is the potential of the digestion solution, V 0 The volume of potassium permanganate added before the start of the titration, V 1 Volume of reducing agent, V 2 The dropwise adding volume of the potassium permanganate after the start of titration, T is the response time of an electrode, v is the stirring speed of a digestion solution, T is the titration reaction temperature, and T is 0 To counteract the reaction temperature, k 0 、k 1 、k 2 、k 3 、k 4 And c are constants.
The titration end point determining module of this embodiment is configured to determine a point with a maximum slope based on the dynamic titration curve, that is, a titration end point.
More specifically, the application examples of the titration endpoint analysis method based on the permanganate index automatic analyzer of this embodiment are as follows:
(1) a permanganate index automatic analyzer measures a quantitative water sample, sulfuric acid and a part of potassium permanganate solution, heating is carried out, and timing is carried out after the temperature reaches the specified temperature of 95 ℃; the above-mentioned quantitative volumes refer to: 25mL of water sample, 1.25mL of 25% sulfuric acid solution and 0.25mL of potassium permanganate solution are digested at the constant temperature of 95 ℃ and are continuously stirred in a magnetic stirring mode.
(2) The ORP electrode is judged once every 30s, if the ORP electrode is judged to be in an oxidation state at present, when the constant temperature time reaches 15min, the residual potassium permanganate solution is added at one time after the temperature is reduced to 80 ℃.
And if the current state is judged to be a reduction state by ORP, continuously dripping 0.25mL of oxidant, continuously detecting after 30 seconds, and repeating the action until the dripping is finished or the oxidation state is reached, wherein the total volume of the oxidant is kept unchanged at 5 mL.
(3) After the temperature is reduced to 80 ℃, the reducing agent (such as sodium oxalate) is added, and the potential of the current electrode is measured.
(4) Recording the current electrode potential, starting titration, namely A stage, and measuring the current electrode potential in real time.
(5) When the electrode potential changes suddenly, the titration speed is changed, namely the B stage, and the current electrode potential P is:
(6) and continuously dripping the oxidant potassium permanganate solution, wherein the electrode potential value of the instrument is in a stable state, namely a C stage, and the current liquid to be detected is in an oxidizing state, which indicates that the titration end point is reached before.
(7) According toB-stage potential P and titration volume V 2 The point with the maximum slope is found out as the titration end point.
(8) Calibrating by using a sodium oxalate standard sample, and obtaining the permanganate index concentration according to a least square method;
(9) and checking the result to be qualified by using glucose standard substances with different concentrations.
The foregoing has outlined rather broadly the preferred embodiments and principles of the present invention and it will be appreciated that those skilled in the art may devise variations of the present invention that are within the spirit and scope of the appended claims.
Claims (10)
1. A titration end point analysis method based on a permanganate index automatic analyzer is characterized by comprising the following steps:
s1, starting titration, and carrying out potassium permanganate titration at a first titration stage on digestion liquid in the digestion pool; wherein the digestion solution contains a water sample to be tested and a reducing agent, and is continuously stirred in the titration process;
s2, a first titration stage, wherein the potential of the digestion solution after each drop of potassium permanganate in the titration process is collected, and whether the potential is larger than a potential threshold value is judged; if yes, go to step S3;
s3, reducing the amount of each drop of potassium permanganate in the titration process, and entering the potassium permanganate titration of a second titration stage;
s4, collecting the potential of the digestion solution after each drop of potassium permanganate in the titration process in the second titration stage, and establishing a dynamic titration curve corresponding to the potential of the digestion solution, the response time of an electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of a reducing agent and the dropping volume of the potassium permanganate after the titration is started;
and S5, judging the point with the maximum slope as the titration end point based on the dynamic titration curve.
2. The titration endpoint assay of claim 1, wherein the dynamic titration curve is:
wherein P is the potential of the digestion solution, V 0 The volume of potassium permanganate added before the start of the titration, V 1 Volume of reducing agent, V 2 The dropwise adding volume of the potassium permanganate after the start of titration, T is the response time of an electrode, v is the stirring speed of a digestion solution, T is the titration reaction temperature, and T is 0 To counteract the reaction temperature, k 0 、k 1 、k 2 、k 3 、k 4 And c are constants.
3. The titration endpoint analysis method of claim 2, wherein the titration frequency of the second titration phase is less than the titration frequency of the first titration phase.
4. The titration endpoint analysis method according to any one of claims 1 to 3, wherein in step S1, the sample preparation process of the digestion solution in the digestion tank comprises the following steps:
s01, measuring and quantifying a water sample to be detected, sulfuric acid and a part of potassium permanganate solution, feeding the water sample, the sulfuric acid and the part of potassium permanganate solution into a digestion pool, heating, and timing after the temperature reaches the digestion reaction temperature;
s02, collecting the potential of the mixed liquid in the digestion tank every other preset period to judge whether the mixed liquid is in an oxidation state at present; if so, when the constant temperature time reaches a preset time, cooling to the titration reaction temperature, and adding the residual potassium permanganate solution at one time;
and S03, adding a reducing agent to obtain a digestion solution.
5. The titration endpoint analysis method according to claim 4, wherein in step S02, the potassium permanganate solution is added in portions before the potential of the mixed solution is in an oxidation state.
6. The titration end-point analysis method according to claim 4, wherein the digestion reaction temperature is 90 to 100 ℃.
7. The titration end-point assay according to claim 4, wherein the titration reaction temperature is 70 to 80 ℃.
8. The titration endpoint analysis method according to claim 4, wherein the predetermined time period is 10-20 min.
9. The titration end-point analysis system based on an automatic permanganate index analyzer, which applies the titration end-point analysis method according to claim 1, wherein the titration end-point analysis system comprises:
the potential acquisition module is used for acquiring the potential of the digestion solution;
the potential judgment module is used for judging whether the potential of the digestion liquid is greater than a potential threshold value;
the titration control module is used for controlling the amount of each drop of potassium permanganate in the titration process;
the dynamic titration curve module is used for carrying out dynamic titration on a curve corresponding to the response time of the potential of the digestion solution and the electrode, the titration reaction temperature, the stirring speed of the digestion solution, the volume of the reducing agent and the dropping volume of the potassium permanganate after titration is started;
and the titration end point judging module is used for judging the point with the maximum slope based on the dynamic titration curve, namely the titration end point.
10. The titration endpoint analysis system of claim 9, wherein the dynamic titration curve is:
wherein P is the potential of the digestion solution, V 0 The volume of potassium permanganate added before the start of the titration, V 1 Volume of reducing agent, V 2 The dropwise addition volume of the potassium permanganate after the start of titration, t is the response time of the electrode, vThe stirring speed of the digestion solution is T, the titration reaction temperature is T 0 To counteract the reaction temperature, k 0 、k 1 、k 2 、k 3 、k 4 And c are constants.
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| CN202210505428.6A CN114942299B (en) | 2022-05-10 | 2022-05-10 | Titration endpoint analysis method and system based on permanganate index automatic analyzer |
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