Rapid determination method for dihydrogen phosphate in dry powder extinguishing agent

Abstract

The invention relates to the technical field of chemical analysis, and discloses a dry powder extinguishing agent dihydrogen phosphate rapid determination method which comprises the following steps: a) taking 0.5-1.0 g of a dry powder extinguishing agent sample, accurately weighing the dry powder extinguishing agent sample to 0.001 g, and placing the dry powder extinguishing agent sample in a reaction container with a magnetic stirrer and a temperature control system; b) adding 50 milliliters of ultrapure water into the reaction container, and stirring for 5 minutes at the speed of 300 revolutions per minute at room temperature to fully dissolve the sample; c) filtering the dissolved sample solution through a 0.22 micron polytetrafluoroethylene filter membrane to remove insoluble impurities so as to obtain a clear filtrate; and d) adding a color developing reagent A (formed by mixing ammonium molybdate and nitric acid and with the concentration of 0.25 M) into the filtered filtrate. By accurately weighing to 0.001 g, the accuracy of the sample amount is ensured, the error in the measurement process is reduced, and the reliability of the measurement result is improved; the measurement accuracy is improved; the dissolving efficiency is obviously improved, the dissolving time is shortened, and the sample is fully dissolved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, in particular to a method for quickly determining dihydrogen phosphate of a dry powder fire extinguishing agent. Background Art

[0002] As an important chemical substance, diammonium phosphate is widely used in agriculture, industry and firefighting. Especially in dry powder fire extinguishing agents, diammonium phosphate is the main component, and the accurate determination of its content is of great significance to the quality control of fire extinguishing agents. With the advancement of science and technology, methods for quickly and accurately determining the content of diammonium phosphate have received increasing attention.

[0003] Existing methods for determining diammonium phosphate mainly include chemical titration, ion chromatography, and ultraviolet spectrophotometry. These methods can meet the determination requirements to a certain extent, but there are often some shortcomings in actual operation. Although the chemical titration method is simple to operate, it is greatly affected by human factors, and the repeatability and accuracy of the determination results are low; the ion chromatography method has high sensitivity and selectivity, but the equipment is expensive and the operation is complicated, and it is not suitable for rapid on-site determination; the ultraviolet spectrophotometry method has certain advantages in determining the content of diammonium phosphate, but its pretreatment process is cumbersome and the determination time is long.

[0004] The problems existing in the prior art mainly include the following points: first, the weighing and dissolution during sample preparation are not accurate enough, resulting in large errors in the measurement results; second, the solution purity is not high, and impurities interfere with the color development reaction, affecting the accuracy of the measurement. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for rapid determination of dihydrogen phosphate of dry powder fire extinguishing agent, which solves the problem that the traditional method has large errors in the determination results due to inaccurate weighing and dissolution during sample preparation.

[0006] To achieve the above object, the present invention is implemented by the following technical scheme: a method for rapid determination of dihydrogen phosphate of dry powder fire extinguishing agent, comprising the following steps: a) Take 0.5-1.0g of dry powder fire extinguishing agent sample and weigh it accurately to 0.001g, and place it in a reaction container equipped with a magnetic stirrer and temperature control system; b) Add 50 ml of ultrapure water to the reaction vessel and stir at 300 rpm for 5 minutes at room temperature to fully dissolve the sample; c) filtering the dissolved sample solution through a 0.22 μm polytetrafluoroethylene filter membrane to remove insoluble impurities and obtain a clear filtrate; d) Add color reagent A (formed by mixing ammonium molybdate and nitric acid, with a concentration of 0.25M) to the filtered filtrate, and add color reagent B (ascorbic acid solution, with a concentration of 0.05M) in a volume ratio of 1:1, and react at 25-30°C for 10 minutes; e) Transfer the color reaction solution to the cuvette of a spectrophotometer and measure its absorbance at a wavelength of 700 nanometers; f) In order to correct and improve the accuracy of the determination, a standard curve was drawn by adding different concentrations of diammonium phosphate standard solutions and calibrated using the internal standard method; g) According to the measured absorbance value, calculate the content of diammonium phosphate in the sample through the standard curve, and process the data through software to obtain accurate results.

[0007] Preferably, ultrasonic wave is used to assist in the sample dissolution process, with a frequency of 40 kHz and a power of 150 W to improve the dissolution efficiency.

[0008] Preferably, the conductivity of the ultrapure water does not exceed 0.05 μS / cm to ensure the purity of the solution.

[0009] Preferably, the molar ratio of ammonium molybdate to nitric acid in the color developing reagent A is 4:1 to ensure the best color developing effect and make the color developing reaction more stable.

[0010] Preferably, the concentration range of ammonium dihydrogen phosphate of the standard curve is 0.05 mg / L to 200 mg / L to cover the concentration range actually measured and ensure the linear relationship of the measurement results.

[0011] Preferably, the color development reaction solution is quickly cooled to room temperature after the reaction is completed to stabilize the color development result, and is cooled using a cooling water bath.

[0012] Preferably, the cuvette light path of the spectrophotometer is 1 cm to ensure the accuracy of the measurement, and a high-precision quartz cuvette is used.

[0013] Preferably, an anti-interference agent EDTA-2Na is added during the color development reaction to enhance the selectivity of the color development reaction and reduce the interference of other metal ions. The sensitivity of the color development reaction is evaluated by measuring the minimum detection limit of diammonium phosphate solutions of different concentrations, and the minimum detection limit should be less than 0.05 mg / L.

[0014] Preferably, the total measurement time of the method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color development reaction and absorbance measurement, and ensures the characteristics of rapid measurement.

[0015] Preferably, the total measurement time of the method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color development reaction and absorbance measurement, and ensures the characteristics of rapid measurement.

[0016] The present invention provides a method for quickly determining dihydrogen phosphate in a dry powder fire extinguishing agent. It has the following beneficial effects: 1. The present invention ensures the accuracy of the sample amount by accurately weighing to 0.001 grams, reduces the error in the measurement process, and improves the reliability of the measurement results; uses ultrapure water with a conductivity of no more than 0.05 μS / cm to ensure the purity of the solution, avoids the interference of impurities on the color development reaction, and improves the accuracy of the measurement; uses ultrasonic assistance with a frequency of 40 kHz and a power of 150 W during the sample dissolution process, significantly improves the dissolution efficiency, shortens the dissolution time, and ensures that the sample is fully dissolved.

[0017] 2. The present invention removes insoluble impurities through a 0.22-micron polytetrafluoroethylene filter membrane to obtain a clear filtrate, which is conducive to the subsequent color development reaction and ensures the smooth progress of the measurement process; the color development reagent A formed by mixing ammonium molybdate and nitric acid and the color development reagent B formed by ascorbic acid solution are used to ensure the stability of the color development reaction and the best color development effect, thereby improving the sensitivity and selectivity of the color development reaction.

[0018] 3. The present invention can effectively correct and improve the accuracy of the measurement by drawing a standard curve and using the internal standard method for calibration, ensuring the accurate calculation of the content of ammonium dihydrogen phosphate in the sample; the total measurement time of the entire method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color reaction and absorbance measurement, which significantly improves the measurement efficiency and is suitable for rapid analysis needs; a high-precision quartz colorimetric cell with an optical path of 1 cm is used, combined with a spectrophotometer to measure the absorbance at a wavelength of 700 nanometers, ensuring the accuracy and consistency of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1: Please see attached Figure 1 The embodiment of the present invention provides a method for quickly determining dihydrogen phosphate of a dry powder fire extinguishing agent, comprising the following steps: a) Take 0.5-1.0g of dry powder fire extinguishing agent sample and weigh it accurately to 0.001g, and place it in a reaction container equipped with a magnetic stirrer and temperature control system; b) Add 50 ml of ultrapure water to the reaction vessel and stir at 300 rpm for 5 minutes at room temperature to fully dissolve the sample; c) filtering the dissolved sample solution through a 0.22 μm polytetrafluoroethylene filter membrane to remove insoluble impurities and obtain a clear filtrate; d) Add color reagent A (formed by mixing ammonium molybdate and nitric acid, with a concentration of 0.25M) to the filtered filtrate, and add color reagent B (ascorbic acid solution, with a concentration of 0.05M) in a volume ratio of 1:1, and react at 25-30°C for 10 minutes; e) Transfer the color reaction solution to the cuvette of a spectrophotometer and measure its absorbance at a wavelength of 700 nanometers; f) In order to correct and improve the accuracy of the determination, a standard curve was drawn by adding different concentrations of diammonium phosphate standard solutions and calibrated using the internal standard method; g) According to the measured absorbance value, calculate the content of diammonium phosphate in the sample through the standard curve, and process the data through software to obtain accurate results.

[0022] In one embodiment, the sample amount is accurately weighed to 0.001 grams to ensure accuracy, reduce errors in the measurement process, and improve the reliability of the measurement results; ultrapure water with a conductivity not exceeding 0.05 μS / cm is used to ensure the purity of the solution, avoid interference of impurities on the color development reaction, and improve the accuracy of the measurement; ultrasonic assistance with a frequency of 40 kHz and a power of 150 W is used during the sample dissolution process to significantly improve the dissolution efficiency, shorten the dissolution time, and ensure that the sample is fully dissolved.

[0023] Furthermore, by accurately weighing to 0.001 grams, the accuracy of the sample amount is ensured, the error in the measurement process is reduced, and the reliability of the measurement results is improved; ultrapure water with a conductivity not exceeding 0.05μS / cm is used to ensure the purity of the solution, avoid the interference of impurities on the color development reaction, and improve the accuracy of the measurement; in the process of sample dissolution, ultrasonic assistance with a frequency of 40kHz and a power of 150W is used to significantly improve the dissolution efficiency, shorten the dissolution time, and ensure that the sample is fully dissolved.

[0024] Ultrasonic assistance was used during the sample dissolution process with a frequency of 40kHz and a power of 150W to improve the dissolution efficiency; the conductivity of ultrapure water did not exceed 0.05μS / cm to ensure the purity of the solution; the molar ratio of ammonium molybdate to nitric acid in the colorimetric reagent A was 4:1 to ensure the best color development effect and make the color development reaction more stable; the concentration range of ammonium dihydrogen phosphate of the standard curve was 0.05mg / L to 200mg / L to cover the actual measured concentration range and ensure the linear relationship of the measurement results.

[0025] In one embodiment, during the sample dissolution process, ultrasound acts on the sample at a frequency of 40kHz and a power of 150W, generating cavitation effect and microjets, greatly promoting the dispersion and dissolution of the sample and improving the dissolution efficiency; the conductivity of ultrapure water is lower than 0.05μS / cm, and the extremely low conductivity ensures that the content of impurity ions in the water is extremely low, thereby avoiding interference factors that may be introduced in solution preparation and color development reaction, and ensuring the accuracy of the experimental results; the molar ratio of ammonium molybdate to nitric acid in the color development reagent A is 4:1. At this ratio, a stable color development reaction product can be formed, improving the stability and sensitivity of the color development, and making the detection results more reliable; the concentration range of ammonium dihydrogen phosphate of the standard curve is set at 0.05mg / L to 200mg / L, which can cover the sample concentration range that may be encountered in the experiment, and ensure that within this range, a good linear relationship is maintained between the detection signal and the concentration, thereby achieving accurate quantitative analysis.

[0026] Furthermore, by using ultrasonic assisted dissolution with a frequency of 40kHz and a power of 150W, the dissolution efficiency of the sample can be significantly improved, the dissolution time can be reduced, and the overall efficiency of the experiment can be improved; using ultrapure water with a conductivity not exceeding 0.05μS / cm helps to ensure the high purity of the solution, avoid impurities interfering with the color development reaction, and improve the accuracy of the test results; the molar ratio of ammonium molybdate to nitric acid in the color development reagent A is 4:1, which can ensure the best effect of the color development reaction, make the color development more stable, and provide more reliable test results.

[0027] The color reaction solution is quickly cooled to room temperature after the reaction is completed to stabilize the color development results, and a cooling water bath is used for cooling; the cuvette light path of the spectrophotometer is 1 cm to ensure the accuracy of the measurement, and a high-precision quartz cuvette is used.

[0028] In one embodiment, after the color development reaction is completed, the color development reaction solution is quickly cooled to room temperature. The cooling water bath provides a constant cooling environment, so that the color development reaction stops quickly and fixes the color development result, avoiding the influence of temperature changes on the color development product, thereby ensuring the stability and reproducibility of the color development result; the spectrophotometer uses a cuvette with a light path of 1 cm for measurement. The light path is fixed and accurate, which helps to control the consistency of the optical path and ensure the consistency of the conditions for each measurement. The use of high-precision quartz cuvettes can avoid the problems of impurities or inconsistent light transmittance that may be introduced by ordinary glass cuvettes, thereby further improving the accuracy of the measurement and the reliability of the data.

[0029] Furthermore, the color development reaction solution is quickly cooled to room temperature after the reaction is completed, which helps to stabilize the color development results and avoid color development instability or color development result errors caused by temperature changes; using a spectrophotometer with a cuvette light path of 1 cm can ensure the accuracy of the measurement, and by using a high-precision quartz cuvette, the reliability and repeatability of the measurement results can be further improved.

[0030] The anti-interference agent EDTA-2Na is added during the color development reaction to enhance the selectivity of the color development reaction and reduce the interference of other metal ions. The sensitivity of the color development reaction is evaluated by measuring the minimum detection limit of different concentrations of diammonium phosphate solution, and the minimum detection limit should be less than 0.05 mg / L. The total measurement time of the method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color development reaction and absorbance measurement, and the characteristics of rapid measurement are ensured. The total measurement time of the method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color development reaction and absorbance measurement, and the characteristics of rapid measurement are ensured.

[0031] In one embodiment, EDTA-2Na is added during the color development reaction. EDTA-2Na can form a stable chelate with metal ions in the solution, thereby reducing the interference of these metal ions on the color development reaction, enhancing the selectivity of the color development reaction, ensuring that the color development reaction is only sensitive to the target substance, and improving the accuracy of the measurement result; the sensitivity of the color development reaction is evaluated by measuring the minimum detection limit of different concentrations of diammonium phosphate solution, and the minimum detection limit should be less than 0.05 mg / L. By controlling the experimental conditions and optimizing the color development reaction, it is ensured that a low concentration of diammonium phosphate solution can be detected, thereby improving the sensitivity of the color development reaction.

[0032] Furthermore, by adding the anti-interference agent EDTA-2Na, the interference of other metal ions can be effectively reduced, the selectivity of the color development reaction can be enhanced, and the accuracy and reliability of the measurement results can be ensured; by measuring the minimum detection limit of diammonium phosphate solutions of different concentrations, the sensitivity of the color development reaction is evaluated, and the minimum detection limit should be less than 0.05 mg / L, ensuring that extremely low concentrations of target substances can be detected.

[0033] Embodiment 2: Take 0.5-1.0 gram of dry powder fire extinguishing agent sample, accurately weigh it to 0.001 gram, and place it in a reaction container equipped with a magnetic stirrer and a temperature control system; add 50 ml of ultrapure water with a conductivity not exceeding 0.05 μS / cm to the reaction container to ensure the purity of the solution, and stir at 300 rpm at room temperature for 5 minutes to fully dissolve the sample, and add ultrasonic assistance with a frequency of 40 kHz and a power of 150 W to improve the dissolution efficiency, shorten the dissolution time, and ensure that the sample is fully dissolved.

[0034] The remaining steps are consistent with those in the first embodiment.

[0035] Embodiment three: The dissolved sample solution was filtered through a 0.22-micron polytetrafluoroethylene filter membrane to remove insoluble impurities and obtain a clear filtrate; color reagent A (formed by a mixture of ammonium molybdate and nitric acid, with a concentration of 0.25 M) was added to the filtered filtrate, and color reagent B (ascorbic acid solution, with a concentration of 0.05 M) was added at a volume ratio of 1:1, and a buffer solution (pH=7.0) was added, and the reaction was carried out at 25-30°C for 10 minutes to ensure that the color development reaction was carried out under the optimal pH conditions to enhance the color development stability.

[0036] The remaining steps are consistent with those in the first embodiment.

[0037]

[0038] Table 1 In the above table, Example 1 shows a higher dissolution efficiency and stability of the color development reaction, and has a lower minimum detection limit and a shorter total determination time, indicating that it has advantages in the rapid and accurate determination of the content of diammonium dihydrogen phosphate. Since Example 2 does not use ultrasonic assistance, its dissolution efficiency is slightly lower and the total determination time is slightly longer. Although Example 3 performs well in the stability of the color development reaction, it is slightly inferior to Example 1 in dissolution efficiency and total determination time; this comparison shows that Example 1 may provide faster and more accurate test results in practical applications, especially when rapid on-site analysis is required. In this way, the advantages of Example 1 are clearly demonstrated, and the promotion of its application is supported by scientific data.

[0039] Comparative Example 1: Chemical titration Method steps: Sample preparation: Weigh a certain amount of dry powder fire extinguishing agent sample, dissolve it in an appropriate amount of distilled water, and stir evenly.

[0040] Acidification: Add an appropriate amount of hydrochloric acid to acidify the sample solution to reach a specific pH value.

[0041] Titration: Titrate the sample solution with standard silver nitrate solution until a constant white precipitate appears.

[0042] Calculation: Calculate the content of dihydrogen phosphate in the sample based on the volume of silver nitrate solution consumed.

[0043] Comparative Example 2: Ion chromatography Method steps: Sample preparation: Weigh a certain amount of dry powder fire extinguishing agent sample, dissolve it in deionized water, and ultrasonically vibrate it to make it fully dissolved.

[0044] Filtration: Filter the dissolved sample solution to remove insoluble impurities.

[0045] Chromatographic analysis: Use an ion chromatograph, select appropriate ion exchange columns and eluents, and perform analysis.

[0046] Detection: Quantitative analysis is performed based on the retention time and peak area of ​​the dihydrogen phosphate peak in the chromatogram.

[0047] Comparative Example 3: Conductivity method Method steps: Sample preparation: Weigh a certain amount of dry powder fire extinguishing agent sample, dissolve it in deionized water, and stir evenly.

[0048] Conductivity measurement: Use a conductivity meter to measure the conductivity of the sample solution.

[0049] Calibration curve: Prepare a calibration curve of conductivity and concentration based on a dihydrogen phosphate standard solution of known concentration.

[0050] Calculation: Use the calibration curve to convert the conductivity value of the sample solution to obtain the content of aluminum dihydrogen phosphate.

[0051]

[0052] Table 2 The total measurement time of Example 1 does not exceed 20 minutes, which is significantly shorter than other methods; the minimum detection limit is 0.03 mg / L, which is lower than other methods, ensuring that low concentrations of target substances can be detected; the measurement accuracy is as high as 99.8%, with extremely small errors, which is significantly better than other methods; the relative standard deviation (RSD) is only 1.2%, indicating that the measurement results are highly consistent.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent, characterized in that: The following steps are involved: a) Take 0.5-1.0g of dry powder fire extinguishing agent sample and weigh it accurately to 0.001g, and place it in a reaction container equipped with a magnetic stirrer and temperature control system; b) Add 50 ml of ultrapure water to the reaction vessel and stir at 300 rpm for 5 minutes at room temperature to fully dissolve the sample; c) filtering the dissolved sample solution through a 0.22 μm polytetrafluoroethylene filter membrane to remove insoluble impurities and obtain a clear filtrate; d) Add color reagent A (formed by mixing ammonium molybdate and nitric acid, with a concentration of 0.25M) to the filtered filtrate, and add color reagent B (ascorbic acid solution, with a concentration of 0.05M) in a volume ratio of 1:1, and react at 25-30°C for 10 minutes; e) Transfer the color reaction solution to the cuvette of a spectrophotometer and measure its absorbance at a wavelength of 700 nanometers; f) In order to correct and improve the accuracy of the determination, a standard curve was drawn by adding different concentrations of diammonium phosphate standard solutions and calibrated using the internal standard method; g) According to the measured absorbance value, calculate the content of diammonium phosphate in the sample through the standard curve, and process the data through software to obtain accurate results.

2. A method for rapid determination of dihydrogen phosphate in a dry powder fire extinguishing agent according to claim 1, characterized in that: Ultrasonic waves were used to assist in the sample dissolution process, with a frequency of 40 kHz and a power of 150 W to improve the dissolution efficiency.

3. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The conductivity of the ultrapure water does not exceed 0.05 μS / cm to ensure the purity of the solution.

4. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The molar ratio of ammonium molybdate to nitric acid in the color developing reagent A is 4:1 to ensure the best color developing effect and make the color developing reaction more stable.

5. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The concentration range of diammonium phosphate of the standard curve is 0.05 mg / L to 200 mg / L to cover the concentration range actually measured and ensure the linear relationship of the measurement results.

6. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The color development reaction solution is quickly cooled to room temperature after the reaction is completed to stabilize the color development result, and is cooled using a cooling water bath.

7. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The cuvette light path of the spectrophotometer is 1 cm to ensure the accuracy of the measurement, and a high-precision quartz cuvette is used.

8. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The anti-interference agent EDTA-2Na is added during the color development reaction to enhance the selectivity of the color development reaction and reduce the interference of other metal ions. The sensitivity of the color development reaction is evaluated by measuring the minimum detection limit of diammonium phosphate solutions of different concentrations, and the minimum detection limit should be less than 0.05 mg / L.

9. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The total measurement time of the method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color development reaction and absorbance measurement, and ensures the characteristics of rapid measurement.

10. A method for rapid determination of dihydrogen phosphate in dry powder fire extinguishing agent according to claim 1, characterized in that: The total measurement time of the method does not exceed 20 minutes, including sample preparation, dissolution, filtration, color development reaction and absorbance measurement, and ensures the characteristics of rapid measurement.

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