A dynamic titration method applied to a coulometric Karl Fischer moisture titrator

Abstract

The application discloses a dynamic titration method applied to a coulometric Karl Fischer moisture titrator, and comprises two parts of drift determination and titration, wherein the titration part comprises a starting stage, a high-speed stage, a transition stage, a speed reduction stage and an ending stage in sequence, and the titration specifically comprises the following steps: when being in the starting stage, collecting a current real-time potential E, and judging whether E is greater than the sum of CE and EP; when E is greater than the sum of CE and EP, the high-speed stage is carried out; when E is less than the sum of CE and EP, the transition stage is carried out; when E is less than the sum of CE and EP and E is greater than EP, the speed reduction stage is carried out; and the ending stage is that after the potential is lower than the endpoint potential EP, a titration delay is selected to terminate the whole titration process. According to the application, the titration time is greatly shortened, the accuracy of the titration is improved, and the accuracy of the drift determination is improved.

Description

Technical Field

[0001] This invention relates to the technical field of electrolytic potentiometric titration, and particularly to a dynamic titration method applied to a coulometric Karl von Moisture Titrator. Background Technology

[0002] Moisture content detection is one of the most common indicators in analytical testing. Various industries have relevant regulations and standards, and there is a large demand for moisture content determination in all walks of life.

[0003] There are many methods for determining the moisture content of substances, with common methods including drying, spectroscopic chromatography, and Karl Fischer method. The Karl Fischer method is not only low-cost and fast, but also highly accurate, making it a recognized classic method for highly accurate moisture determination.

[0004] Currently, most domestic moisture analyzers lag significantly behind imported instruments, exhibiting slower titration speeds and poorer repeatability. This difference in titration speed is particularly noticeable when using coulometric methods to test high-moisture samples. For certain samples, a Karl Fischer furnace is required for sample introduction, and the long furnace injection time further contributes to the poor repeatability of coulometric moisture analyzers when used in conjunction with a Karl Fischer furnace.

[0005] Technical terms: CE is the control potential, EP is the endpoint potential, and K is 0.0066*CE-4. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a dynamic titration method for a coulometric Karl Fischer moisture titrator. To achieve the above-mentioned objective and other advantages of the present invention, a dynamic titration method for a coulometric Karl Fischer moisture titrator is provided, comprising:

[0007] The drift determination and titration are divided into two parts. The titration part includes an initial stage, a high-speed stage, a transition stage, a decreasing stage, and an ending stage. Specifically, the titration involves: during the initial stage, acquiring the current real-time potential E and determining if E is greater than the sum of CE + EP; if E is greater than the sum of CE + EP, proceeding to the high-speed stage; if E is less than the sum of CE + EP, and... Then a transition phase will be implemented; when When that happens, a deceleration phase will begin;

[0008] The final stage is when the potential drops below the endpoint potential EP, at which point the titration delay is selected to terminate the entire titration process.

[0009] Preferably, when the potential in the titration portion reaches the endpoint potential EP, the drift measurement begins. The drift measurement is performed for 1-2 minutes, and the drift measurement ends when the difference between two adjacent drift values ​​is less than 2ug / min. The drift value is then saved for calculation.

[0010] Preferably, when the real-time potential E falls in the high-speed stage, the electrolysis cycle is 1000ms, the electrolysis current duty cycle Dr is 0.8, and the titration enters the transition stage as the potential decreases.

[0011] Preferably, when the real-time potential E falls into the transition phase, the electrolysis cycle becomes 500ms, the electrolysis current duty cycle Dr is 0.5, and the titration proceeds to the deceleration phase as the potential decreases.

[0012] Preferably, when the real-time potential E falls within the deceleration phase, the electrolysis cycle becomes 500 ms, and the electrolysis current duty cycle Dr begins to change according to a regular pattern, which conforms to the following formula:

[0013]

[0014] As the potential decreases, the titration reaches its final stage.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: Under this model, the titration speed is greatly improved, significantly reducing the gap between domestic and imported instruments. The drift algorithm is optimized, resulting in better measurement repeatability. When used in conjunction with a cassette furnace, the moisture titrator employing this model remains highly accurate in measuring samples with low moisture content, with blank value repeatability within 5 μg. When measuring high moisture content samples, the testing time is significantly shortened, and the measurement accuracy is significantly improved without affecting its overall precision. Attached Figure Description

[0016] Figure 1 This is a flowchart of the dynamic titration method applied to a coulometric Karl von Meadows water titrator according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Reference Figure 1A dynamic titration method for a coulometric Karl Fischer moisture titrator is disclosed, comprising two parts: drift determination and titration. The titration part includes, sequentially, an initial stage, a high-speed stage, a transition stage, a decreasing stage, and an ending stage. The entire titration process uses a maximum electrolytic current of 400 mA, thereby significantly shortening the titration time and improving titration accuracy. A control potential is set; outside the control potential, full-speed electrolysis titration is performed; within the control potential, electrolysis is performed slowly. Based on the potential changes, the titration follows different electrolysis patterns. Furthermore, according to the set potential range, the electrolysis time at the titration endpoint is adjusted according to different patterns, slowly approaching the titration endpoint potential to ensure titration accuracy.

[0019] Drift measurement begins after the titration potential reaches the endpoint and lasts for 1 minute. 且 The drift value is calculated within 1 minute. The drift measurement ends when the difference between two consecutive drift values ​​is less than 2 μg / min, and the drift value is saved for further calculation. To reduce the impact of drift, the drift test time can be increased, which is especially important when injecting samples into a Karl flask. Using a drift comparison method and extending the drift measurement time before drift measurement improves the accuracy of the drift measurement.

[0020] The titration process includes:

[0021] Step S101: In the initial stage, acquire the current real-time potential E. Determine which process the titration should begin from. The specific determination criteria are as follows:

[0022]

[0023] Step S102: When the potential falls within the high-speed stage, the electrolysis cycle is 1000 ms, and the electrolysis current duty cycle Dr is 0.8. As the potential decreases, the titration proceeds to the next stage. The electrolysis current is used to electrolyze iodine, and can be selected from 400 mA, 300 mA, 200 mA, and 100 mA.

[0024] Step S103: When the potential falls into the transition phase, the electrolysis cycle becomes 500 ms, and the electrolysis current duty cycle Dr is 0.5. As the potential decreases, the titration proceeds to the next stage.

[0025] Step S104: When the potential falls within the decreasing phase, the electrolysis period becomes 500 ms, and the electrolysis current duty cycle Dr begins to change according to a pattern. This duty cycle change follows the formula below. As the potential decreases, the titration enters the next stage.

[0026]

[0027] Step S105: When the potential is lower than the endpoint potential EP, select the titration delay to terminate the entire titration process. At this time, the delay termination time is 30 seconds, that is, the titration is judged to end only when the potential is lower than the endpoint potential and can be maintained for 30 seconds.

[0028] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be apparent to those skilled in the art.

[0029] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A dynamic titration method applied to a coulometric Karl Fischer moisture titrator, characterized in that, include: The drift determination and titration are divided into two parts. The titration part includes an initial stage, a high-speed stage, a transition stage, a decreasing stage, and an ending stage. Specifically, the titration includes: in the initial stage, the current real-time potential E is collected, and it is determined whether E is greater than the sum of CE + EP; if E is greater than the sum of CE + EP, the high-speed stage is performed; if E is less than the sum of CE + EP and CE + EP > E > EP - +5, then proceed to the transition phase; when E < EP - When +5, the deceleration phase begins, where CE is the control potential, EP is the endpoint, and K is a variable calculated from the control potential CE: K = 0.0066 * CE - 4. The final stage involves terminating the titration process by selecting a titration delay once the potential drops below the endpoint potential EP. Once the potential in the titration section reaches the endpoint potential EP, the drift measurement begins. This drift measurement involves testing the drift value for 1-2 minutes. The drift measurement ends when the difference between two consecutive drift values ​​is less than 2ug / min, and the drift value is saved for calculation.

2. The dynamic titration method applied to a coulometric Karl Fischer moisture titrator as described in claim 1, characterized in that, When the real-time potential E falls into the high-speed stage, the electrolysis cycle is 1000ms and the electrolysis current duty cycle Dr is 0.

8. As the potential decreases, the titration enters the transition stage.

3. The dynamic titration method applied to a coulometric Karl Fischer moisture titrator as described in claim 2, characterized in that, When the real-time potential E falls into the transition phase, the electrolysis cycle becomes 500ms, the electrolysis current duty cycle Dr is 0.5, and the titration proceeds to the deceleration phase as the potential decreases.

4. The dynamic titration method applied to a coulometric Karl Fischer moisture titrator as described in claim 3, characterized in that, When the real-time potential E falls within the deceleration phase, the electrolysis cycle becomes 500 ms, and the electrolysis current duty cycle Dr begins to change according to a certain pattern. This change in duty cycle conforms to the following formula: ； As the potential decreases, the titration reaches its final stage.

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