First, Karl Fischer moisture analyzer instrument features:
1. The burette nozzle of the burette has a reverse osmosis structure.
2. Glass burette with protective cover.
3. Easy to replace KF reagents.
4. Standard accessories with solvent replacement pump.
5. It can automatically control the moisture evaporator (ADP-511S).
6. Comply with GLP/GMP specifications.
Second, safety protection Karl Fischer reagent mainly consists of iodine, sulfur dioxide, pyridine and methanol solution. Among them, sulfur dioxide and pyridine are highly volatile and harmful to the human body. They should be handled under good ventilation conditions. Especially when changing reagents, pay attention to exhaust air to prevent harmful gases from inhaling the body. Wear protective glasses and latex gloves to avoid spilling harmful agents on your eyes and hands. In the event that reagents are spilled, your eyes and hands should be immediately flushed with running water. In severe cases, they should be taken to hospital for treatment.
However, the actual situation is that some operators lack knowledge of the hazards of the reagents. Without any protective measures, the reagents are randomly poured into and poured out, and the house smells are completely ignored. The problem of self-protection awareness needs to be strengthened.
Third, the application of reagents Karl Fischer reagent for the high degree of freshness, the purchase of Karl Fischer reagents should pay attention to the date of production, according to the amount used to buy it. And to avoid light preservation in order to extend the shelf life.
At present, there is a pyridine-free Karl Fischer reagent available to solve the problem of pungent odor pyridine reagents, but the determination of the pyridine-containing Karl Fischer reagent endpoint mutation is more obvious, the color of the reagent to the end point is The light brown color, based on experience, can be predicted by the naked eye to the end of the imminent, while the pyridine-free Karl Fischer reagent endpoint mutation is not obvious, the reagent to the end of the color is dark brown.
The choice of the two can be based on the sample's moisture content and the accuracy of the sample detection requirements. For samples with low water content and high test accuracy, the pyridine-containing Karl Fischer reagent is recommended. In contrast, the Karl Fischer reagent without pyridine was used.
Anhydrous methanol is used as a dissolving agent for the sample and it has a wide range of application. General organic compounds, saturated or unsaturated hydrocarbons, and general inorganic compounds, acidic oxides, partially organic and inorganic salts can be suitably used. However, some ketone and aldehyde samples cannot be reacted with methanol. If it is found that the reaction cannot be interrupted, there is no end point, and when the reaction is carried out continuously, the question of whether or not there is a side reaction should be considered. When a side reaction occurs, it only takes a few minutes for the reaction to proceed. In this case, ethylene glycol methyl ether can be used instead of methanol to obtain a more constant titration volume, and the moisture of certain ketone and aldehyde chemical products can be determined without using any special technology.
PH value is too high, the sample is too alkaline, can also cause side reactions, that is, continuous reaction, and no end. At this point, the PH value is too high can be used to adjust the pH value of the buffer solution, too high alkaline toluidine, salicylic enzyme, can ease the alkaline solution, but can not use acetic acid.
When carrying out the methanol water titration (commonly known as blank titration), if the color in the reaction vessel gradually changes from colorless to dark brown, the instrument still has no end point, and it should be considered that the Karl-Fischer reagent has failed and the reagent should be replaced.
IV. Electrode contamination and maintenance The electrode is a key component of the moisture analyzer. Contamination of the electrode surface can directly lead to reduced sensitivity. Some electrodes are used for long-term analysis of oil samples. After the electrode surface is contaminated with oil, the sensitivity is reduced, making the electrode pair. The endpoint was judged to be dull, resulting in an excess of Karl Fischer reagents and a darker solution at the end of the reaction. At this point the electrodes must be cleaned. Although the contaminants on the electrode were invisible to the naked eye, a slow response was observed and directly affected the measurement accuracy. Therefore, the electrode must be cleaned after a period of use, but a considerable number of operators did not consider this problem.
When the sensitivity is reduced, the electrode is seriously polluted. The paper can be wiped with a piece of acetone to wipe the electrode, but it must be careful, but also must wait until the acetone has evaporated completely. Or immerse the electrodes in a dilute solution for 24 hours, remove them, rinse with water, and wipe them with filter paper. It can also be cleaned with potassium dichromate solution for 1 minute to activate the electrode. In special circumstances, such as the sample waiting to be analyzed, the electrode cleaning time is not allowed, then an emergency solution can be used to solve the electrode contamination event. Wipe the two ends of the electrode gently with very fine sandpaper. After the filter paper is wiped, it can be effective.
If the instrument is not used for a period of time, the Karl Fischer reagents in the pump tube and in the fluid path should be completely drained to avoid clogging of the tube due to crystallization due to volatilization of the reagents; the Karl Fischer reagent in the same reaction flask should also be After finishing, the electrode wipes. In the detection of the instrument, it can often be found that the measurement of the sample by the operator is completed and that the power supply is turned off. The maintenance of the instrument and the accuracy of the measurement should be closely related to the problem.
Fifth, Karl Fischer reagent titer (commonly known as water equivalent) Calibrate the calibration of the Karl Fischer reagent titration accuracy is directly related to the accuracy of the sample determination, the different test conditions, the entire device seal device How well the performance of the Karl Fischer reagent titers changes, especially for samples that require high measurement accuracy.
The calibration of the titer should in principle be performed before the daily sample test. The titer can be calibrated using a standard substance with a certain moisture content. Some standard materials are liquid and encapsulated in ampoules. Each time it is consumed, the accuracy is high and the cost is high: Some of the standard materials are solid, with high accuracy, and require high preservation of reference materials. Once you get wet, you're in trouble.
The simplest and most practical is pure water calibration. With a micro-syringe to accurately remove the water, generally take 10 to 30 microliters of water for calibration, repeated several times in succession, averaged to determine the Karl Fischer reagent titers. However, some laboratory inspectors do not fully understand the meaning of Karl Fischer's reagent titer calibration, or are irresponsible for inertness. Even if a bottle of reagent is used for one titer calibration from start to use, it will be used After a few months, the sample test always uses a titer calibration value, obviously there is a large error.
The titer of the Karl Fischer reagent gradually changes with the extension of the use time, and the error of the titer relative to the first day also increases. From this it can be seen that the initial titre has been used to calculate the measured value for several months, and the error to the measured value is large. Therefore, the Karl Fischer reagent should be frequently calibrated for titration. The time interval for calibration of Karl Fischer reagent titers should be reasonably determined based on the laboratory ambient temperature, humidity and the instrument's sealing performance, as well as the test requirements. To ensure the accuracy of the measurement. The accuracy of sample measurement is related to the quality of the product.
According to the Karl Fischer determination of moisture content, in the presence of methanol and alkali, water reacts chemically with iodine and sulfur dioxide in accordance with the following chemical equation: H2OI2SO2CH30H3RN→[RHN]SO4CH32[RHN]I for volumetric titration Iodine is added as a titrant.
1. The burette nozzle of the burette has a reverse osmosis structure.
2. Glass burette with protective cover.
3. Easy to replace KF reagents.
4. Standard accessories with solvent replacement pump.
5. It can automatically control the moisture evaporator (ADP-511S).
6. Comply with GLP/GMP specifications.
Second, safety protection Karl Fischer reagent mainly consists of iodine, sulfur dioxide, pyridine and methanol solution. Among them, sulfur dioxide and pyridine are highly volatile and harmful to the human body. They should be handled under good ventilation conditions. Especially when changing reagents, pay attention to exhaust air to prevent harmful gases from inhaling the body. Wear protective glasses and latex gloves to avoid spilling harmful agents on your eyes and hands. In the event that reagents are spilled, your eyes and hands should be immediately flushed with running water. In severe cases, they should be taken to hospital for treatment.
However, the actual situation is that some operators lack knowledge of the hazards of the reagents. Without any protective measures, the reagents are randomly poured into and poured out, and the house smells are completely ignored. The problem of self-protection awareness needs to be strengthened.
Third, the application of reagents Karl Fischer reagent for the high degree of freshness, the purchase of Karl Fischer reagents should pay attention to the date of production, according to the amount used to buy it. And to avoid light preservation in order to extend the shelf life.
At present, there is a pyridine-free Karl Fischer reagent available to solve the problem of pungent odor pyridine reagents, but the determination of the pyridine-containing Karl Fischer reagent endpoint mutation is more obvious, the color of the reagent to the end point is The light brown color, based on experience, can be predicted by the naked eye to the end of the imminent, while the pyridine-free Karl Fischer reagent endpoint mutation is not obvious, the reagent to the end of the color is dark brown.
The choice of the two can be based on the sample's moisture content and the accuracy of the sample detection requirements. For samples with low water content and high test accuracy, the pyridine-containing Karl Fischer reagent is recommended. In contrast, the Karl Fischer reagent without pyridine was used.
Anhydrous methanol is used as a dissolving agent for the sample and it has a wide range of application. General organic compounds, saturated or unsaturated hydrocarbons, and general inorganic compounds, acidic oxides, partially organic and inorganic salts can be suitably used. However, some ketone and aldehyde samples cannot be reacted with methanol. If it is found that the reaction cannot be interrupted, there is no end point, and when the reaction is carried out continuously, the question of whether or not there is a side reaction should be considered. When a side reaction occurs, it only takes a few minutes for the reaction to proceed. In this case, ethylene glycol methyl ether can be used instead of methanol to obtain a more constant titration volume, and the moisture of certain ketone and aldehyde chemical products can be determined without using any special technology.
PH value is too high, the sample is too alkaline, can also cause side reactions, that is, continuous reaction, and no end. At this point, the PH value is too high can be used to adjust the pH value of the buffer solution, too high alkaline toluidine, salicylic enzyme, can ease the alkaline solution, but can not use acetic acid.
When carrying out the methanol water titration (commonly known as blank titration), if the color in the reaction vessel gradually changes from colorless to dark brown, the instrument still has no end point, and it should be considered that the Karl-Fischer reagent has failed and the reagent should be replaced.
IV. Electrode contamination and maintenance The electrode is a key component of the moisture analyzer. Contamination of the electrode surface can directly lead to reduced sensitivity. Some electrodes are used for long-term analysis of oil samples. After the electrode surface is contaminated with oil, the sensitivity is reduced, making the electrode pair. The endpoint was judged to be dull, resulting in an excess of Karl Fischer reagents and a darker solution at the end of the reaction. At this point the electrodes must be cleaned. Although the contaminants on the electrode were invisible to the naked eye, a slow response was observed and directly affected the measurement accuracy. Therefore, the electrode must be cleaned after a period of use, but a considerable number of operators did not consider this problem.
When the sensitivity is reduced, the electrode is seriously polluted. The paper can be wiped with a piece of acetone to wipe the electrode, but it must be careful, but also must wait until the acetone has evaporated completely. Or immerse the electrodes in a dilute solution for 24 hours, remove them, rinse with water, and wipe them with filter paper. It can also be cleaned with potassium dichromate solution for 1 minute to activate the electrode. In special circumstances, such as the sample waiting to be analyzed, the electrode cleaning time is not allowed, then an emergency solution can be used to solve the electrode contamination event. Wipe the two ends of the electrode gently with very fine sandpaper. After the filter paper is wiped, it can be effective.
If the instrument is not used for a period of time, the Karl Fischer reagents in the pump tube and in the fluid path should be completely drained to avoid clogging of the tube due to crystallization due to volatilization of the reagents; the Karl Fischer reagent in the same reaction flask should also be After finishing, the electrode wipes. In the detection of the instrument, it can often be found that the measurement of the sample by the operator is completed and that the power supply is turned off. The maintenance of the instrument and the accuracy of the measurement should be closely related to the problem.
Fifth, Karl Fischer reagent titer (commonly known as water equivalent) Calibrate the calibration of the Karl Fischer reagent titration accuracy is directly related to the accuracy of the sample determination, the different test conditions, the entire device seal device How well the performance of the Karl Fischer reagent titers changes, especially for samples that require high measurement accuracy.
The calibration of the titer should in principle be performed before the daily sample test. The titer can be calibrated using a standard substance with a certain moisture content. Some standard materials are liquid and encapsulated in ampoules. Each time it is consumed, the accuracy is high and the cost is high: Some of the standard materials are solid, with high accuracy, and require high preservation of reference materials. Once you get wet, you're in trouble.
The simplest and most practical is pure water calibration. With a micro-syringe to accurately remove the water, generally take 10 to 30 microliters of water for calibration, repeated several times in succession, averaged to determine the Karl Fischer reagent titers. However, some laboratory inspectors do not fully understand the meaning of Karl Fischer's reagent titer calibration, or are irresponsible for inertness. Even if a bottle of reagent is used for one titer calibration from start to use, it will be used After a few months, the sample test always uses a titer calibration value, obviously there is a large error.
The titer of the Karl Fischer reagent gradually changes with the extension of the use time, and the error of the titer relative to the first day also increases. From this it can be seen that the initial titre has been used to calculate the measured value for several months, and the error to the measured value is large. Therefore, the Karl Fischer reagent should be frequently calibrated for titration. The time interval for calibration of Karl Fischer reagent titers should be reasonably determined based on the laboratory ambient temperature, humidity and the instrument's sealing performance, as well as the test requirements. To ensure the accuracy of the measurement. The accuracy of sample measurement is related to the quality of the product.
According to the Karl Fischer determination of moisture content, in the presence of methanol and alkali, water reacts chemically with iodine and sulfur dioxide in accordance with the following chemical equation: H2OI2SO2CH30H3RN→[RHN]SO4CH32[RHN]I for volumetric titration Iodine is added as a titrant.
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