Method and system for quickly and accurately determining automatic titration end point

Abstract

The invention relates to the technical field of titration analysis, and provides a method and a system for quickly and accurately determining an automatic titration end point. The method for quickly and accurately determining the automatic titration end point comprises the following steps: S1, rinsing a titration system; s2, starting circulation; s3, circulation is carried out; s4, re-determining the volume value range of the required titrant; s5, continuously dropwise adding; s6, repeated iteration is carried out; s7, circulating termination; and S8, data fitting. According to the method for rapidly and accurately determining the automatic titration end point, the problems that an existing automatic titration technology is low in efficiency, poor in adaptive capacity to samples with unknown concentrations, low in verification iteration efficiency and low in precision influenced by solution diffusion can be solved, and the requirements of accurate and rapid titration, adaptation to the samples with the unknown concentrations and multi-batch verification are met. In addition, the invention also provides a system for quickly and accurately determining the automatic titration end point.

Description

Technical Field

[0001] This application relates to the technical field of titration analysis, and in particular to a method and system for rapidly and accurately determining the endpoint of an automated titration. Background Technology

[0002] In the field of titration analysis in analytical chemistry, automated titration technology is a commonly used method for determining sample concentration. Related technologies mainly revolve around automated titrators, with the core objective of replacing manual titration with automated operation, thereby improving the convenience of the titration process. Currently, existing automated titration technologies are applied in laboratory analysis and some industrial testing scenarios. They primarily use automated components to control the addition of titrant and sample, and monitor the reaction, to achieve the determination of sample concentration.

[0003] In practical applications, existing automated titration technologies typically employ fixed step sizes or preset addition patterns. Specifically, the titration system is first rinsed, then the titrant is added to the reaction vessel using a titration pump at preset fixed volumes or step sizes. Simultaneously, sensors monitor the reaction system's response signal, and changes in the response signal determine whether the titration endpoint is approaching. Some technologies employ a "fast-then-slow" addition strategy, rapidly adding the titrant initially to shorten the overall time, and then slowing the addition rate near the endpoint to avoid over-titering. After completing one titration, some systems prepare for the next operation by simply rinsing the tubing or reaction vessel, relying on manual intervention or a preset program to determine whether a repeat verification is needed to confirm the titration endpoint.

[0004] From a practical application perspective, existing automated titration technologies have several problems. First, fixed step sizes and preset addition modes result in low efficiency. Because a pre-titration step is needed to roughly determine the titrant dosage range, or a fixed "fast then slow" rhythm is relied upon, the overall titration process is time-consuming and cannot flexibly adjust the addition strategy according to the actual concentration of the sample. Second, the adaptability to samples with unknown concentrations is poor. Due to the fixed addition mode, the range of sample concentrations that can be accurately measured is limited. When dealing with samples with concentrations exceeding the preset range, it is easy to have excessive or insufficient titrant, requiring multiple adjustments and re-titrations. Third, titration accuracy is easily affected. On the one hand, existing technologies do not adequately treat the titration pump inlet and tubing; titrant or sample residue at the inlet can easily cause solution diffusion, interfering with reaction signal monitoring. On the other hand, some technologies only determine the titration endpoint based on a single or a few data points, failing to form multi-data verification around the true endpoint, leading to large concentration calculation errors. Summary of the Invention

[0005] In view of this, this application aims to propose a method and system for rapidly and accurately determining the endpoint of automatic titration, in order to solve the problems of low efficiency, poor adaptability to samples of unknown concentration, accuracy affected by solution diffusion, and low efficiency of verification iteration in existing automatic titration technologies, and to meet the needs of accurate and rapid titration, adaptability to samples of unknown concentration, and multiple batch verification.

[0006] To achieve the above objectives, the technical solution of this application is implemented as follows: In a first aspect, this application proposes a method for rapidly and accurately determining the endpoint of an automated titration, comprising the following steps: S1, the rinsing titration system, during which the response signals before and after the reaction endpoint are measured and recorded, establishing the range for judging the reaction endpoint response signal [V]. min V max Draw n0 volumes of sample and m0 volumes of titrant into the reaction vessel, and set the cycle termination conditions; S2, loop start, estimate the initial range of titrant volume required for n0 volume sample [a] 0min a 0max After the reaction is complete, measure and record the reaction signal V0. S3, repeat the process, and determine the range [V] based on the reaction signal V0 and the reaction endpoint response signal. min V max The relationship between these parameters determines whether over-titration has occurred. S4, redetermine the required volume range of the titrant. If titration is not completed, redetermine the initial volume range of the required titrant to [a]. i+1 a imax If over-titration occurs, the initial range for the required titrant volume should be redefined as [a]. imin a i+1 ], where a i+1 =(a imin +a imax ) / 2; S5, if titration is not completed, continue adding m to the reaction system. i Record the total volume S of titrant added. m If the titration is excessive, continue adding n to the reaction system. i For a sample of a certain volume, record the total sample volume S that has been added. n ; S6, repeat the forward-reverse titration process from step S2 to step S5 to obtain a series of data pairs (a) around the true titration endpoint. i+1 V i ); S7, Cycle terminates when the difference a between the endpoints of the required titrant volume range is reached.imax -a imin The loop terminates when the volume is less than the set loop termination condition volume. S8, Data fitting, using the data pairs (a) collected in step S6. i+1 V i The sample concentration is accurately calculated by fitting the data using mathematical algorithms.

[0007] Furthermore, in step S5: The amounts of sample and total volume, as well as the amounts of titrant and total volume, satisfy the following relationships: n i =(a i+1 +a imax ) / 2 / n0×S n –S m m i =n0 / [(a i+1 +a imax ) / 2]×S m -S n .

[0008] Furthermore, in step S3: If the reaction signal V0 is less than V min If the titration has not been completed, it is considered that the reaction has not been completed; if the reaction signal V0 is greater than V... max This is considered over-titration.

[0009] Furthermore, in step S8: The mathematical algorithm used for fitting is at least one of linear fitting, polynomial fitting, nonlinear fitting, exponential fitting, or S-curve fitting.

[0010] Furthermore, it also includes step S9: Rinse the titration system and repeat steps S1 to S8 to verify the results; if multiple verification results are set, record the titration endpoint to speed up the iteration process.

[0011] Furthermore, the range of values ​​for the loop termination condition is set to 0.15%-0.5% of the container range.

[0012] Compared with existing technologies, the method for rapidly and accurately determining the endpoint of automated titration proposed in this application has the following advantages: (1) This application establishes the response signal judgment range through the rinsing system, cyclically adjusts the titrant volume range, obtains data pairs through forward and reverse titration and fits them, thereby achieving the effect of rapidly and accurately determining the titration endpoint and improving efficiency while ensuring titration accuracy.

[0013] (2) This application achieves precise control of the amount added under non-titration or over-titration conditions through the calculation formula of sample and titrant addition, which helps to promote the efficient advancement of the cyclic over-titration process.

[0014] (3) This application achieves objective and unified judgment of the reaction stage by judging the standard of over-titration based on the relationship between the reaction signal and the judgment range, thereby reducing the impact of human error on the titration process.

[0015] (4) This application uses various mathematical algorithms such as linear fitting and polynomial fitting to fit the data pairs, thereby eliminating random errors in single data measurement and improving the accuracy of sample concentration calculation.

[0016] (5) This application uses a rinsing system to repeatedly titrate and verify the results and record historical endpoints to accelerate the iteration process, thereby improving the reliability of the results and shortening the time for subsequent verification experiments.

[0017] (6) By setting the range of values ​​for the loop termination condition, this application achieves the effect of avoiding excessive iteration while meeting the titration accuracy requirements, thereby improving titration accuracy and efficiency.

[0018] Secondly, this application proposes a system for realizing the above-described method for rapidly and accurately determining the endpoint of an automated titration, including a reactor assembly for a reaction vessel for a sample and a titrant; A titrant assembly, including a first titration pump and a titrant container, is used to quantitatively add a titrant to the reactor assembly; The sample assembly includes a second titration pump and a sample container for quantitatively adding a sample to the reactor assembly; An indicator assembly includes a first micropump and an indicator container for adding an indicator to the reactor assembly; The buffer assembly includes a second micropump and a buffer container for adding buffer to the reactor assembly.

[0019] Furthermore, the reactor assembly includes: Reaction vessel; A stirrer, installed inside the reaction vessel, is used to stir the reactants, accelerate the reaction rate, and improve the degree of reaction completion. A sensor, mounted on the reaction vessel, is used to convert reaction progress information into a measurable electrical signal.

[0020] Furthermore, this also includes multi-way directional valves; The multi-way reversing valve is connected to the reaction vessel, the outlet of the first titration pump, and the outlet of the second titration pump, respectively.

[0021] Furthermore, it also includes waste liquid tanks.

[0022] Compared to existing technologies, the system proposed in this application for the above-mentioned method of rapidly and accurately determining the endpoint of automatic titration has the following advantages: (1) This application achieves hardware support for the repeated titration method through the coordinated work of various components such as reactor components, titrant components, and sample components, ensuring the quantitative addition of each substance and the stable reaction during the titration process.

[0023] (2) This application promotes the mixing of reactants by using a stirrer in the reaction vessel and a sensor to convert the degree of reaction into an electrical signal in real time, thereby improving the sufficiency of the reaction and the authenticity of the signal, and providing a reliable basis for titration judgment.

[0024] (3) This application connects the reaction vessel with the titration pump and the sample pump through a multi-way reversing valve, which simplifies the pipeline structure, reduces solution residue and diffusion, and improves the accuracy of the added volume.

[0025] (4) This application collects the titration waste liquid in a waste liquid tank, which realizes the environmental protection of centralized treatment of waste liquid, while ensuring the cleanliness of the reaction vessel and avoiding the effect of residues interfering with subsequent experiments. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the method for rapidly and accurately determining the automatic titration endpoint as described in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the system for rapidly and accurately determining the endpoint of automatic titration as described in Embodiment 2 of this application.

[0027] Explanation of reference numerals in the attached figures: 1. Reactor assembly; 101. Reaction vessel; 102. Stirrer; 103. Sensor; 2. Titrant assembly; 201. First titration pump; 202. Titrant container; 3. Sample assembly; 301. Second titration pump; 302. Sample container; 4. Indicator assembly; 401. First micropump; 402. Indicator container; 5. Buffer assembly; 501. Second micropump; 502. Buffer container; 6. Multi-way directional valve; 7. Waste tank. Detailed Implementation

[0028] To make the technical solution and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0030] Furthermore, it should be noted that in the description of this application, if terms such as "upper," "lower," "inner," or "outer" appear, indicating orientation or positional relationship, these are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, if terms such as "first" or "second" appear, they are also used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] Furthermore, in the description of this application, unless otherwise expressly defined, the terms "installation," "connection," "joining," and "connector" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application in light of the specific circumstances.

[0032] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0033] The present application will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0034] Example 1 This application provides a method for rapidly and accurately determining the endpoint of an automated titration. It is applied to the field of titration analysis to solve the problems of low efficiency, poor adaptability to samples of unknown concentration, accuracy affected by solution diffusion, and low efficiency of verification iteration in existing automated titration technologies. It meets the needs of accurate and rapid titration, adaptability to samples of unknown concentration, and multiple batch verification.

[0035] Existing technologies typically employ fixed step sizes or preset addition patterns for titration operations. Specifically, the titration system is first rinsed, then the titrant is added to the reaction vessel using a titration pump at a preset fixed volume or step size. Simultaneously, sensors monitor the response signal of the reaction system, and changes in the response signal determine whether the titration endpoint is approaching. Some technologies use a "fast-then-slow" addition strategy, rapidly adding the titrant initially to shorten the overall time, and slowing the addition rate as the endpoint approaches to avoid over-titering. After completing one titration, some systems prepare for the next operation by simply rinsing the tubing or reaction vessel, relying on manual or preset program judgment to determine whether re-verification is needed to confirm the titration endpoint. From a practical application perspective, existing automated titration technologies have several problems. First, fixed step sizes and preset addition patterns result in low efficiency. Because a pre-titering step is needed to roughly determine the titrant dosage range, or relying on a fixed "fast-then-slow" rhythm, the overall titration process is time-consuming and cannot flexibly adjust the addition strategy according to the actual concentration of the sample. Secondly, it has poor adaptability to samples with unknown concentrations. Due to the fixed addition mode, the range of sample concentrations that can be accurately measured is limited. When faced with samples with concentrations exceeding the preset range, it is easy to have excessive or insufficient titrant, requiring multiple adjustments and re-titrations. Thirdly, titration accuracy is easily affected. On the one hand, existing technologies do not adequately treat the titration pump inlet and tubing. Residue of titrant or sample at the inlet can easily cause solution diffusion, interfering with reaction signal monitoring. On the other hand, some technologies determine the titration endpoint only through a single or a few data points, without forming multiple data validations around the true endpoint, resulting in large concentration calculation errors.

[0036] In view of this, in order to overcome the shortcomings of the prior art, the method for rapidly and accurately determining the automatic titration endpoint in this embodiment includes the following steps: S1, the rinsing titration system, during which the response signals before and after the reaction endpoint are measured and recorded, establishing the range for judging the reaction endpoint response signal [V]. min V max Draw n0 volumes of sample and m0 volumes of titrant into the reaction vessel, and set the cycle termination conditions; S2, loop start, estimate the initial range of titrant volume required for n0 volume sample [a] 0min a 0max After the reaction is complete, measure and record the reaction signal V0. S3, repeat the process, and determine the range [V] based on the reaction signal V0 and the reaction endpoint response signal. min V max The relationship between these parameters determines whether over-titration has occurred. S4, redetermine the required volume range of the titrant. If titration is not completed, redetermine the initial volume range of the required titrant to [a]. i+1a imax If over-titration occurs, the initial range for the required titrant volume should be redefined as [a]. imin a i+1 ], where a i+1 =(a imin +a imax ) / 2; S5, if titration is not completed, continue adding m to the reaction system. i Record the total volume S of titrant added. m If the titration is excessive, continue adding n to the reaction system. i For a sample of a certain volume, record the total sample volume S that has been added. n ; S6, repeat the forward-reverse titration process from step S2 to step S5 to obtain a series of data pairs (a) around the true titration endpoint. i+1 V i ); S7, Cycle terminates when the difference a between the endpoints of the required titrant volume range is reached. imax -a imin The loop terminates when the volume is less than the set loop termination condition volume. S8, Data fitting, using the data pairs (a) collected in step S6. i+1 V i The sample concentration is accurately calculated by fitting the data using mathematical algorithms.

[0037] In step S1, the rinsing of the titration system can be achieved by repeatedly rinsing the titration tubing and reaction vessel with the titrant or sample to remove any residual substances from the previous experiment and avoid interference with the current titration reaction. When measuring and recording the response signals before and after the reaction endpoint, the response signals can specifically be physical quantities that reflect the reaction progress, such as pH, potential, photometric value, or current value. These signals are collected and stored in real time by sensors, establishing a range for judging the reaction endpoint response signal [V]. min V max This provides a clear basis for subsequent judgment on whether over-titration has occurred, avoiding errors caused by subjective judgment; the operation of extracting samples and titrants into the reaction vessel can be achieved through a metering pump, ensuring the accuracy of the extraction volume; when setting the cycle termination condition, it is necessary to combine it with the actual titration accuracy requirements to ensure that subsequent cycles can meet the accuracy requirements without reducing efficiency due to excessive iteration.

[0038] In step S2, the initial range of the volume of titrant required for the sample can be estimated based on historical titration data of similar samples or preliminary pre-titering results. Precise calculation is not required; only an approximate range needs to be given. After the reaction is complete, the reaction signal V0 is measured. It is necessary to wait for the sample and titrant in the reaction system to be mixed evenly and for the reaction to reach a stable state to avoid signal deviation due to incomplete reaction and to ensure that the recorded V0 can truly reflect the current degree of reaction.

[0039] In step S3, based on the reaction signal V0 and the judgment range [V min V max The relationship between the titration and the reaction is determined by the fact that if the reaction has not reached its endpoint, the sample is still in excess in the system, and the response signal will be lower than V. min However, when the reaction exceeds the endpoint, the titrant is in excess, and the response signal will be higher than V. max This judgment method can intuitively and quickly determine the current stage of the reaction, providing direction for subsequent adjustments.

[0040] In step S4, through a i+1 =(a imin +a imax The range of titrant volume values ​​is redefined by using a dichotomy method to narrow down the range. If the titration is not completed, it means that the current titrant is still insufficient and the lower limit needs to be increased to increase the amount of titrant. If the titration is completed, it means that the titrant is excessive and the upper limit needs to be reduced to decrease the amount of titrant. This method can quickly approximate the titrant volume corresponding to the true endpoint and reduce the number of cycles.

[0041] In step S5, the addition of titrant or sample to the reaction system can be achieved using a quantitative titration pump to ensure the accuracy of the added volume; record the total volume S of the titrant. m and total sample volume S n This provides basic data for subsequent calculations of the amount to be added, avoiding errors in subsequent range adjustments due to volume recording deviations.

[0042] In step S6, the forward-reverse titration process is repeated iteratively. Forward titration involves adding titrant to advance the reaction, while reverse titration involves adding sample to bring the reaction back. Through this back-and-forth approximation method, multiple sets of data pairs (a) around the true endpoint can be obtained. i+1 V i These data can comprehensively reflect the law of reaction signal change with titrant volume, providing sufficient data support for subsequent accurate fitting.

[0043] The determination of the cycle termination condition in step S7 is based on the titration accuracy requirements and the container range setting. When the difference between the endpoints of the titrant volume range is less than the set value, it indicates that the current range can meet the accuracy requirements of concentration calculation. Continuing the cycle will increase the operation time but it is difficult to significantly improve the accuracy. Therefore, terminating the cycle can improve efficiency while ensuring titration accuracy.

[0044] In step S8, the data pairs are fitted using mathematical algorithms. A suitable algorithm can be selected based on the changing patterns of the reaction signal and the titrant volume. The fitting process can eliminate random errors in single data measurements. The sample concentration is calculated based on the overall trend of the data, which significantly improves the accuracy of concentration calculation compared to judging the endpoint from a single data point.

[0045] Reference Figure 1 The specific meaning and technical logic of the formulas relating sample addition amount to total amount and titrant addition amount to total amount mentioned in step S5 are as follows: In formula n i =(a i+1 +a imax ) / 2 / n0×S n –S m In the middle, (a i+1 +a imax ) / 2 represents the median value of the titrant volume range redefined during titration, reflecting the estimated titrant volume at the current stage; dividing by n0 is to establish the proportional relationship between the estimated titrant volume and the initial sample volume, and then multiplying by S n The theoretical titrant requirement can be obtained based on the total amount of sample added, and finally, the total volume S of titrant added is subtracted. m This will give you the sample volume n that needs to be supplemented this time. i This calculation method ensures that the added titrant volume is just enough to drive the reaction closer to the endpoint, avoiding deviations in range adjustment caused by adding too much or too little.

[0046] Formula m i =n0 / [(a i+1 +a imax ) / 2]×S m -S n In, n0 / [(a i+1 +a imax [) / 2] represents the ratio of the initial sample volume to the estimated titrant volume, multiplied by S m The theoretical sample requirement can be obtained based on the total amount of titrant added, minus the total sample volume S. n The volume of titrant m to be added can then be obtained. i This calculation method can be used to bring the reaction back from the titration state to the endpoint by adding a titrant, ensuring that subsequent range adjustments can still be made around the true endpoint.

[0047] By calculating the amount added using the two formulas above, precise control of the amount of titrant and sample added can be achieved, avoiding errors caused by manual estimation of the amount added. This provides data support for the efficient advancement of the cyclic titration process, thereby improving the accuracy of titration endpoint determination.

[0048] The criteria for judging over-titration in step S3, and the range of the reaction endpoint response signal [V] min V max The determination of [ ] is based on the response signals recorded before and after the endpoint during the rinsing process. V min The corresponding reaction reaches its stable response signal value just before the endpoint, at which point the sample in the system has not yet completely reacted, and the amount of titrant used is insufficient; V max The corresponding reaction just exceeds the stable response signal value after the endpoint. At this point, the titrant in the system is in excess, and the sample has reacted completely.

[0049] When the reaction signal V0 is less than V min When the reaction signal V0 is greater than V, it indicates that the sample in the current system is still in excess, and the titrant has not yet met the reaction requirements, i.e., the titration has not been completed; when the reaction signal V0 is greater than V, it indicates that the reaction signal is greater than V. max When the titrant in the system exceeds the reaction requirement, the sample has completely reacted, and there is an excess of titrant, i.e., over-titering. This judgment criterion divides the reaction stage by clearly defined signal value ranges, avoiding the subjectivity of relying on operator experience, ensuring consistent judgment results for different operators and different experimental batches, reducing the impact of human error on the titration process, and providing a unified and reliable basis for subsequent range adjustments and addition calculations.

[0050] Regarding the mathematical fitting algorithms in step S8, linear fitting is suitable for scenarios where the response signal and titrant volume change linearly during the reaction process. For example, in some acid-base titrations, the pH value increases or decreases linearly with the increase of titrant volume. Linear fitting can quickly determine the titrant volume corresponding to the signal abrupt change point, i.e., the titration endpoint. Polynomial fitting is suitable for scenarios where the response signal and titrant volume change nonlinearly but with a gradual trend. For example, in some complexometric titrations, polynomial fitting can smooth data fluctuations and accurately capture the inflection point of signal change. Nonlinear fitting is suitable for scenarios where the response signal and titrant volume have a complex nonlinear relationship. For example, in some redox titrations, a custom nonlinear model can be used to fit the data trend. Exponential fitting is suitable for scenarios where the response signal changes exponentially with the titrant volume. For example, in some photometric titrations, the absorbance decreases exponentially with the increase of titrant volume. S-curve fitting is suitable for scenarios where the response signal changes abruptly near the endpoint and changes in an S-shape overall. For example, in most potentiometric titrations, it can accurately locate the endpoint volume corresponding to the signal abrupt change.

[0051] By selecting a suitable fitting algorithm based on the signal change characteristics of different titration reactions, the multiple sets of data collected in step S6 can be fully utilized to eliminate the random errors of single data measurement. The sample concentration can be calculated by the overall trend of the data. Compared with relying on a single data point to determine the endpoint, the accuracy of concentration calculation is greatly improved, ensuring that even if there are slight deviations in some data, reliable concentration results can still be obtained.

[0052] The operation of rinsing the titration system in step S9 can be done in the same way as in step S1, that is, rinsing the tubing and reaction vessel with titrant or sample to ensure that there is no residual waste liquid in the tubing and to avoid interference with the repeated titration reaction. Repeating the process from S1 to S8 allows for verification of the consistency of the first titration result through multiple parallel experiments. If the deviation of the multiple verification results is within the allowable range, it indicates that the first result is reliable. If multiple verifications are required, after recording the titration endpoint, subsequent verification experiments can be based on this endpoint to narrow down the initial value range of the titrant volume in step S2, without having to re-estimate the broad initial range and reducing the number of iterations.

[0053] This step verifies the results through repeated experiments, effectively eliminating the influence of accidental factors such as brief fluctuations in the sensor and slight deviations in dosage on the results in a single experiment, thus improving the reliability of sample concentration determination. At the same time, by narrowing the initial range of subsequent experiments based on historical titration endpoints, the number of cycles can be reduced, the overall titration time can be shortened, and the technical effect of verifying reliability and improving efficiency can be achieved.

[0054] In step S1, the range of values ​​for the cycle termination condition needs to be determined based on the actual titration accuracy requirements. If the value is too large, the difference between the endpoints of the titrant volume range will be large, and the sample concentration error calculated based on this range will exceed the allowable range, failing to meet the accuracy requirements. If the value is too small, it will result in too many cycle iterations, prolonging the overall titration time and reducing experimental efficiency.

[0055] Setting this range of values ​​can improve efficiency while ensuring titration accuracy. It ensures that the range of titrant volume is small enough to meet the accuracy requirements of routine titration analysis when the cycle ends, while avoiding time waste caused by excessive iteration. This makes the method highly efficient while ensuring accuracy, and it is suitable for various scenarios such as routine laboratory analysis and industrial online detection.

[0056] Example 2 This application provides a system for implementing the above-described method for rapidly and accurately determining the endpoint of an automatic titration, referring to... Figure 2 This includes reactor assembly 1, titrant assembly 2, sample assembly 3, indicator assembly 4, and buffer assembly 5.

[0057] Reactor assembly 1 serves as the reaction site for the sample and titrant. Its reaction vessel 101 can be made of corrosion-resistant materials such as glass or polytetrafluoroethylene, suitable for various acid-base and redox titration reactions, avoiding chemical reactions between the vessel material and the reactants that could affect the results. The first titration pump 201 in titrant assembly 2 can be either a syringe pump or a metering pump. These pumps have precise volume control capabilities, enabling quantitative addition of the titrant and ensuring that the volume of titrant added each time meets the calculation requirements. The titrant container 202 can be made of light-proof or corrosion-resistant material depending on the properties of the titrant to prevent deterioration. The second titration pump 301 in sample assembly 3 is related to the first titration pump 201. Similar in structure to the first micropump 401, it also possesses quantitative titration capability, allowing precise control of the sample addition volume. Sample container 302 stores the sample to be measured, ensuring its stability during titration. The first micropump 401 in indicator assembly 4 can be a micro-injection pump, enabling precise addition of trace amounts of indicator, preventing excessive indicator from affecting reaction equilibrium. Indicator container 402 stores the indicator, ensuring its availability. The second micropump 501 in buffer assembly 5 has a similar structure to the first micropump 401, allowing precise addition of buffer solution to maintain pH or ionic strength stability in the reaction system. Buffer container 502 stores the buffer solution. Both the first and second micropumps 401 automatically flush the nozzles after each addition, reducing diffusion effects.

[0058] All components work collaboratively and are electrically connected to a computer or controller with built-in control programs, enabling online, multi-batch, automated control and providing hardware support for the implementation of the method. The quantitative dosing capabilities of the first titration pump 201 and the second titration pump 301 ensure the quantitative dosing of n in step S5. i m i The precise addition of reagents; the micro-addition capabilities of the first micropump 401 and the second micropump 501 ensure that the amounts of indicator and buffer solution are appropriate; reactor component 1 provides a stable environment for the reaction, and the precise control of each component together ensures the smooth progress of the cyclic titration process, ensuring that the method can achieve rapid and accurate determination of the titration endpoint; the use of the first titration pump 201 realizes intelligent and optimized control of the titrant dosage, saving reagent consumption.

[0059] Reference Figure 2The reaction vessel 101 serves as the reaction site for the reactants and can be selected with different volumes depending on the scale of the titration reaction. Its smooth inner wall reduces the residue of reactants. The stirrer 102 can be either a magnetic stirrer or a mechanical stirrer. A magnetic stirrer achieves stirring by driving the stir bar to rotate through a magnetic field, while a mechanical stirrer achieves stirring by driving the stirring paddle to rotate through a motor. Both stirring methods ensure thorough mixing of the sample, titrant, indicator, and buffer solution within the reaction system, avoiding incomplete reactions caused by uneven local concentrations and ensuring that the reaction signal accurately reflects the overall reaction extent. The sensor 103 can be selected based on the type of response signal, such as a pH electrode, a potential electrode, or a photometric sensor. The pH electrode detects changes in the pH value of the system, the potential electrode detects changes in the potential of the system, and the photometric sensor detects changes in the absorbance or color of the system. These sensors convert the reaction extent into a measurable electrical signal, which is transmitted to the data processing unit in real time, providing a basis for signal recording and judgment in steps S2 and S3.

[0060] The thorough stirring action of stirrer 102 avoids signal deviation caused by local concentration differences, ensuring that the signal collected by sensor 103 can represent the state of the entire reaction system. Sensor 103 converts the degree of reaction into an electrical signal, realizing real-time monitoring of the reaction process. The combination of the two provides a reliable guarantee for signal judgment during the cyclic titration process, further improving the accuracy of titration endpoint determination.

[0061] Reference Figure 2 The multi-way reversing valve 6 can be a common structure such as a three-way valve or a four-way valve. Its valve body material can be selected based on the properties of the reactants to prevent corrosion by the titrant or sample. This valve is connected to the reaction vessel 101, the outlet of the first titration pump 201, and the outlet of the second titration pump 301, respectively. The connection status between the first titration pump 201 or the second titration pump 301 and the reaction vessel 101 can be controlled by switching the valve. When titrant needs to be added, the valve is switched to connect the first titration pump 201 to the reaction vessel 101, and the titrant enters the reaction vessel 101 through the valve. When sample needs to be added, the valve is switched to connect the second titration pump 301 to the reaction vessel 101, and the sample enters the reaction vessel 101 through the valve.

[0062] This connection method simplifies the system's piping structure, avoiding the complexity caused by setting up separate inlet lines for the first titration pump 201 and the second titration pump 301. Simultaneously, it reduces solution residue in the piping during valve switching, preventing mixing and diffusion of different solutions during the switching process. This ensures the accuracy of the titrant or sample volume added to the reaction vessel 101, further reducing the impact of solution diffusion on the titration results and guaranteeing the accuracy of cyclic titration. Compared to valve heads also used for diffusion prevention, the multi-way directional valve 6 does not require frequent replacement.

[0063] Waste liquid tank 7 can be a corrosion-resistant and well-sealed container used to collect waste liquid in reaction vessel 101 after titration experiments. After each titration experiment, the waste liquid in reaction vessel 101 can be discharged into waste liquid tank 7 through pipeline to avoid direct discharge of waste liquid causing environmental pollution or residue in reaction vessel 101 affecting the next experiment.

[0064] Reference Figure 2 The waste liquid tank 7 enables centralized collection and treatment of titration waste liquid, improving the standardization and environmental friendliness of system operation. At the same time, timely emptying of the waste liquid in the reaction vessel 101 ensures that the reaction vessel 101 is clean before the next experiment, avoiding interference from waste liquid residue on subsequent titration reactions and ensuring the reliability of experimental results.

[0065] The above descriptions are merely some embodiments of this application and are not intended to limit this application. The technical features or structures in the foregoing different embodiments can be arbitrarily combined to form other specific technical solutions as needed. For those skilled in the art, this application can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of the claims of this application.

Claims

1. A method for rapidly and accurately determining the endpoint of an automated titration, characterized in that, Includes the following steps: S1, the rinsing titration system, during which the response signals before and after the reaction endpoint are measured and recorded, establishing the range for judging the reaction endpoint response signal [V]. min V max Draw n0 volumes of sample and m0 volumes of titrant into the reaction vessel, and set the cycle termination conditions; S2, loop start, estimate the initial range of titrant volume required for n0 volume sample [a] 0min a 0max After the reaction is complete, measure and record the reaction signal V0. S3, repeat the process, and determine the range [V] based on the reaction signal V0 and the reaction endpoint response signal. min V max The relationship between these parameters determines whether over-titration has occurred. S4, redetermine the required volume range of the titrant. If titration is not completed, redetermine the initial volume range of the required titrant to [a]. i+1 a imax ]; If over-titration occurs, the initial range of the required titrant volume should be redefined as [a]. imin a i+1 ], where a i+1 =(a imin +a imax ) / 2; S5, if titration is not completed, continue adding m to the reaction system. i Record the total volume S of titrant added. m If the titration is excessive, continue adding n to the reaction system. i For a sample of a certain volume, record the total sample volume S that has been added. n ; S6, repeat the forward-reverse titration process from step S2 to step S5 to obtain a series of data pairs (a) around the true titration endpoint. i+1 V i ); S7, Cycle terminates when the difference a between the endpoints of the required titrant volume range is reached. imax -a imin The loop terminates when the volume is less than the set loop termination condition volume. S8, Data fitting, using the data pairs (a) collected in step S6. i+1 V i The sample concentration is accurately calculated by fitting the data using mathematical algorithms.

2. The method for rapidly and accurately determining the endpoint of an automatic titration according to claim 1, characterized in that, In step S5: The amounts of sample and total volume, as well as the amounts of titrant and total volume, satisfy the following relationships: n i =(a i+1 +a imax ) / 2 / n0×S n –S m m i =n0 / [(a i+1 +a imax ) / 2]×S m -S n 。 3. The method for rapidly and accurately determining the endpoint of an automatic titration according to claim 1, characterized in that, In step S3: If the reaction signal V0 is less than V min If the titration has not been completed, it is considered that the reaction has not been completed; if the reaction signal V0 is greater than V... max This is considered over-titration.

4. The method for rapidly and accurately determining the endpoint of an automatic titration according to claim 1, characterized in that, In step S8: The mathematical algorithm used for fitting is at least one of linear fitting, polynomial fitting, nonlinear fitting, exponential fitting, or S-curve fitting.

5. The method for rapidly and accurately determining the endpoint of an automatic titration according to claim 1, characterized in that, It also includes step S9: Rinse the titration system and repeat steps S1 to S8 to verify the results; if multiple verification results are set, record the titration endpoint to speed up the iteration process.

6. The method for rapidly and accurately determining the endpoint of an automatic titration according to claim 1, characterized in that, The range of values ​​for the loop termination condition is set to 0.15%-0.5% of the container's capacity.

7. A system for rapidly and accurately determining the endpoint of an automatic titration, used to implement the method for rapidly and accurately determining the endpoint of an automatic titration as described in any one of claims 1 to 6, characterized in that, include: Reactor assembly (1), a reaction vessel for the sample and titrant; The titrant assembly (2) includes a first titration pump (201) and a titrant container (202) for quantitatively adding titrant to the reactor assembly (1); The sample assembly (3) includes a second titration pump (301) and a sample container (302) for quantitatively adding a sample to the reactor assembly (1); The indicator assembly (4) includes a first micropump (401) and an indicator container (402) for adding an indicator to the reactor assembly (1); The buffer assembly (5) includes a second micropump (501) and a buffer container (502) for adding buffer to the reactor assembly (1).

8. The system for rapidly and accurately determining the endpoint of an automatic titration according to claim 7, characterized in that, The reactor assembly (1) includes: Reaction vessel (101); A stirrer (102) is installed inside the reaction vessel (101) to stir the reactants, accelerate the reaction rate, and improve the degree of reaction completion. A sensor (103), disposed on the reaction vessel (101), is used to convert reaction degree information into a measurable electrical signal.

9. The system for rapidly and accurately determining the endpoint of an automatic titration according to claim 8, characterized in that, It also includes a multi-way directional valve (6); The multi-way reversing valve (6) is connected to the reaction vessel (101), the liquid outlet of the first titration pump (201), and the liquid outlet of the second titration pump (301), respectively.

10. The system for rapidly and accurately determining the endpoint of an automatic titration according to claim 7, characterized in that, It also includes waste liquid tanks (7).

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