Method for detecting content of ammonium sulfate in ABC dry powder extinguishing agent

Abstract

The invention discloses a method for detecting the content of ammonium sulfate in an ABC dry powder extinguishing agent. The method comprises the following steps: firstly, qualitatively judging whether a sample contains ammonium sulfate or not through X-ray diffraction; determining the total ammonia nitrogen content by adopting a Nessler's reagent spectrophotometric method, determining the ammonium dihydrogen phosphate content by adopting a gravimetric method, and determining the interference component ammonia nitrogen content by adopting an ion chromatography method; and finally calculating the ammonium sulfate content according to nitrogen conservation. According to the method, impurity interference can be effectively eliminated, the detection result is accurate and reliable, the precision is high (RSD is smaller than or equal to 2%), the adding standard recovery rate ranges from 98.50% to 102.44%, the blank of an ammonium sulfate detection method in the national standard is filled, and the method is suitable for quality control and market supervision of the ABC dry powder extinguishing agent.

Description

Technical Field

[0001] This invention belongs to the field of fire protection testing technology, specifically relating to a method for detecting the ammonium sulfate content in ABC dry powder fire extinguishing agents. Background Technology

[0002] ABC dry powder fire extinguishing agents are widely used in various fire prevention and control scenarios, including buildings and industrial sites, due to their advantages such as wide applicability to different fire types, high extinguishing efficiency, and good storage stability. Their extinguishing effectiveness depends primarily on the content ratio of their main components. Currently, the mainstream formula is 75% ammonium dihydrogen phosphate (NH4H2PO4) and 15% ammonium sulfate ((NH4)2SO4). Ammonium sulfate significantly improves the extinguishing efficiency for Class B and C fires and also improves the pulverization performance of ammonium phosphate salts, making it a key component for ensuring the quality of the extinguishing agent. The national standard GB 4066-2017 "Dry Powder Fire Extinguishing Agents" clearly specifies the detection method for ammonium dihydrogen phosphate in ABC dry powder fire extinguishing agents, but it does not specify any requirements for the detection of ammonium sulfate content. This lack of a unified and accurate testing standard for ammonium sulfate content in such products on the market presents difficulties for product quality supervision. Some companies may adulterate their products with cheap impurities containing ammonia nitrogen and sulfate to reduce costs. Using a single detection method can easily lead to interference, causing the test results to deviate from the true value and making it impossible to accurately assess the quality of the extinguishing agent. Therefore, establishing a precise and reliable method for detecting ammonium sulfate content that can eliminate interference from impurities would fill a gap in national standards and have significant theoretical and practical implications for regulating market order and ensuring fire safety. Summary of the Invention

[0003] To address the problems existing in the prior art, the purpose of this invention is to provide a method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agents. This method proposes a combined detection approach of XRD qualitative screening, Nessler's reagent spectrophotometry for total ammonia nitrogen determination, and ion chromatography to eliminate interference. Specifically, this is achieved through the following technical solution: A method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agent, the method comprising the following steps: 1) Qualitative analysis of ABC dry powder fire extinguishing agent samples was performed using X-ray diffraction to determine whether they contained ammonium sulfate and other ammonium salts; 2) The total ammonia nitrogen content of the ABC dry powder fire extinguishing agent sample was determined by Nessler's reagent spectrophotometry and denoted as X1; 3) The content of ammonium dihydrogen phosphate in the ABC dry powder fire extinguishing agent sample was determined by gravimetric method and recorded as X2; 4) The ammonia nitrogen content of interfering components in the ABC dry powder fire extinguishing agent sample was determined by ion chromatography and denoted as X3; 5) Calculate the ammonium sulfate content based on the law of conservation of nitrogen, and record it as X4.

[0004] Furthermore, in step 1), if the sample X-ray diffraction pattern shows characteristic diffraction peaks that perfectly match the ammonium sulfate standard card, and the relative intensity ratios of the characteristic peaks are consistent, then subsequent quantitative detection will be performed.

[0005] Furthermore, the total ammonia nitrogen content in step 2) The calculation formula is:

[0006] Where c1 is the concentration of ammonia nitrogen in the test solution (mg / L) and m0 is the sample mass (g).

[0007] Furthermore, the content of ammonium dihydrogen phosphate in step 3) The calculation formula is:

[0008] Where m1 is the mass of quinoline phosphomolybdate precipitate (g), m0 is the mass of the sample (g), and 1.0396 is the conversion factor for quinoline phosphomolybdate to ammonium dihydrogen phosphate.

[0009] Furthermore, the ammonia nitrogen content of the interfering component in step 4). The calculation formula is:

[0010] Where c2 is the concentration (mg / L) of the interfering component anion in the test solution, m0 is the sample mass (g), and ω1 is the ratio of the atomic mass of ammonia nitrogen in the interfering component to the relative molecular mass of the anion in the interfering component.

[0011] Furthermore, the formula for calculating the ammonium sulfate content in step 5) is: .

[0012] The method of this invention uses XRD technology to initially identify the types of impurities containing ammonia nitrogen and sulfate in the sample, and then uses Nessler's reagent spectrophotometry to determine the total ammonia nitrogen content of the sample. Combined with ion chromatography, it achieves an indirect and accurate conversion of ammonium sulfate content. This combined method can effectively eliminate impurity interference, and the detection results are accurate and reliable. It is suitable for the accurate detection of ammonium sulfate content in ABC dry powder fire extinguishing agents, and provides technical support for the quality supervision of fire protection products. Attached Figure Description

[0013] Figure 1 The XRD diffraction pattern of the sample in Example 1 is compared with the standard PDF card; Figure 2 This is the standard working curve for ammonia nitrogen content in Example 2. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments in order to better understand the present technical solution.

[0015] Experimental reagents: ammonium dihydrogen phosphate (analytical grade), ammonium sulfate (analytical grade), quinomolybdate-limonene reagent (prepared according to Appendix B of GB 4066-2017), Nessler's reagent (mercuric iodide-potassium iodide-sodium hydroxide system), potassium sodium tartrate (analytical grade), ammonium chloride (analytical grade), sodium carbonate (analytical grade), sodium bicarbonate (analytical grade), potassium dihydrogen phosphate (analytical grade), sodium chloride (analytical grade), anhydrous sodium sulfate (analytical grade); the experimental water was ultrapure water.

[0016] Experimental instruments: X-ray diffractometer (D2 PHASER, Bruker, Germany, Cu target Kα rays, 1.54184 Å); UV-Vis spectrophotometer (TU-1900, Beijing Purkinje General, China, wavelength range 190nm-900nm); ion chromatograph (AQ-1100, Thermo Fisher Scientific, USA, chromatographic column: analytical column (Dionex IonPac AS23, 4×250 mm), guard column (Dionex IonPac RFIC, 4×50 mm)); electronic analytical balance (ME204E, Mettler Toledo, graduation value 0.1 mg); electric thermostatic drying oven (DHG-9143BS-Ⅲ, Shanghai Xinmiao, accuracy ±2 ℃).

[0017] Example 1: Qualitative Analysis of Ammonium Sulfate Qualitative analysis of ammonium sulfate was performed using X-ray diffraction (XRD). 5 g of ABC dry powder fire extinguishing agent sample was weighed and ground in an agate mortar until the particle size was less than or equal to 50 μm. The sample was then taken out using a sampling spoon and spread evenly in the groove of the sample stage until it was full. The sample surface was gently pressed to scrape off excess powder, and the sample surface was repeatedly smoothed to ensure it was compacted and did not protrude above the sample stage surface. Visual inspection revealed no obvious indentations or light / dark zones on the sample surface. Any remaining powder on the sample stage was wiped clean. Experimental parameters: tube voltage 30 kV, tube current 10 mA, scanning range 2θ = 5°–65°, step size 0.02°.

[0018] XRD qualitative analysis results: Three ABC dry powder samples (S1, S2, and S3) from different manufacturers were selected for XRD analysis. The results showed that the positions and relative intensities of the diffraction peaks in the XRD diffraction patterns of samples S1 and S2 matched the standard PDF card #01-076-0579 for ammonium sulfate and #01-085-0815 for ammonium dihydrogen phosphate, indicating the presence of ammonium dihydrogen phosphate and ammonium sulfate. Sample S3 showed the presence of ammonium dihydrogen phosphate but no characteristic peaks of ammonium sulfate, indicating the absence of ammonium sulfate. Comparison of the XRD diffraction patterns of samples S1, S2, and S3 with the XRD diffraction pattern database revealed no characteristic diffraction peaks of other ammonium salts. See [link to XRD pattern comparison with standard PDF cards] for details. Figure 1 .

[0019] Qualitative determination: The measured XRD diffraction pattern is compared with the standard XRD pattern of ammonium sulfate (PDF card number 01-076-0579). If the sample pattern shows characteristic diffraction peaks that perfectly match the standard ammonium sulfate pattern (such as characteristic peaks at 2θ positions of 20.208°, 20.467°, 22.836°, etc.), and the relative intensity ratio of the characteristic peaks is consistent, then the sample is determined to contain ammonium sulfate. The sample is then compared with the database to determine whether other ammonium salts are present.

[0020] Example 2: Determination of total ammonia nitrogen content in samples The total ammonia nitrogen content of the sample was determined by Nessler's reagent spectrophotometry. First, an ammonia nitrogen standard stock solution (1000 mg / L) was prepared: 3.8190 g of ammonium chloride (analytical grade) dried at 105℃ for 2 h was accurately weighed, dissolved in ultrapure water, and diluted to 1000 mL. The solution was shaken well and stored at 4℃ for one month. Before use, it was diluted to a 10 mg / L standard working solution. 0.0 mL, 0.5 mL, 1.0 mL, 2.0 mL, 3.0 mL, 4.0 mL, and 5.0 mL of the ammonia nitrogen standard working solution were respectively placed in 50 mL colorimetric tubes, and diluted to 50 mL with water to obtain a series of ammonia nitrogen standard solutions with concentrations of 0.1 mg / L, 0.2 mg / L, 0.4 mg / L, 0.6 mg / L, 0.8 mg / L, and 1.0 mg / L. Then add 1.0 mL of potassium sodium tartrate solution, shake well, add 1.5 mL of Nessler's reagent, shake well, let stand for 10 min, and measure the absorbance at 420 nm using a 10 mm cuvette with water as a reference to obtain a standard curve, as shown below. Figure 2 As shown.

[0021] Weigh 1 g of sample, accurate to 0.0002 g, and place it in a 100 mL beaker. Add 2 mL of acetone and stir continuously. After the acetone evaporates, dissolve and filter the solution with ultrapure water at 60-70°C. Dilute the filtrate to 500 mL to obtain solution A. Transfer 0.1 mL of solution A to a 50 mL colorimetric tube and dilute with water to the mark to obtain solution B. Repeat the above steps to measure the absorbance. Measure the concentration of ammonia nitrogen in solution B by referring to the standard curve. Calculate the total ammonia nitrogen content of the extinguishing agent sample according to formula (1-1), where x1 is the mass fraction (%) of total ammonia nitrogen in the extinguishing agent sample, c1 is the concentration (mg / L) of ammonia nitrogen in solution B, and m0 is the sample mass (g). The test results are shown in Table 1.

[0022] (1-1).

[0023] Table 1: Detection results of total ammonia nitrogen content in samples S1 and S2

[0024] Example 3: Determination of ammonium dihydrogen phosphate content in samples The content of ammonium dihydrogen phosphate in the sample was determined by gravimetric method according to Appendix B of the national standard GB 4066-2017. 25 mL of the above solution A was transferred to a 400 mL beaker, diluted to 100 mL with 10 mL of nitric acid solution (1+1), preheated to near boiling, and then 40 mL of quinoline phosphomolybdate reagent was added. After gentle boiling for 1 min, the mixture was cooled to room temperature. The precipitate was filtered through a No. 4 crucible filter pre-dried to constant weight, dried at 180°C for 45 min, and then weighed. Three parallel determinations were performed, and the average value was taken (absolute deviation ≤ 0.5%). The content of ammonium dihydrogen phosphate was calculated according to formula (1-2), where x2 is the mass fraction of ammonium dihydrogen phosphate (%), m1 is the mass of quinoline phosphomolybdate precipitate (g), m0 is the sample mass (g), and 1.0396 is the conversion factor from quinoline phosphomolybdate to ammonium dihydrogen phosphate.

[0025] (1-2) Results of ammonium dihydrogen phosphate content determination: The ammonium dihydrogen phosphate content of samples S1, S2 and S3 was determined in parallel three times, and the results are shown in Table 2.

[0026] Table 2: Detection results of ammonium dihydrogen phosphate content in samples S1, S2, and S3

[0027] As shown in Table 2, the ammonium dihydrogen phosphate content of the three samples all meet the requirements of 75% ± 2.6% in GB 4066-2017, with RSD ≤ 0.28%, indicating that the national standard method has good accuracy and provides reliable data for subsequent nitrogen content correction.

[0028] Example 4: Determination of ammonia nitrogen content as an interfering component in a sample The ammonia nitrogen content of interfering components in the sample was determined by ion chromatography. The eluent was selected as 4.5 mM sodium carbonate / 0.8 mM sodium bicarbonate. The experimental parameters were: flow rate 1.0 mL / min, column temperature 30°C, injection volume 25 μL, and a conductivity detector. A series of mixed standard solutions with concentrations of 0.0–10.0 mg / L sulfate ions, 0.0–10.0 mg / L chloride ions, and 0.0–50.0 mg / L phosphate ions were prepared. 1.0 mL of the test solution A from Example 2 was transferred to a 50 mL volumetric flask and diluted to 50 mL with water to obtain test solution C. Under the same conditions as above, solution C was measured, and its anion concentration was calculated based on the standard working curve. The content of interfering components in the sample is calculated according to formula (1-3), where x3 is the mass fraction (%) of ammonia nitrogen in the interfering component in the fire extinguishing agent sample, c2 is the concentration (mg / L) of the anion of the interfering component in the test solution C, m0 is the sample mass (g), and ω1 is the ratio of the atomic mass of ammonia nitrogen in the interfering component to the relative molecular mass of the interfering component.

[0029] (1-3) As can be seen from Example 1, no other ammonium salt interference was found in samples S1 and S2, therefore X3 is 0.

[0030] Example 5: Determination of Ammonium Sulfate Content in Samples The ammonium sulfate content was determined according to formula (1-4) based on the conservation of nitrogen, where x4 is the mass fraction (%) of ammonium sulfate in the extinguishing agent sample.

[0031] (1-4) Quantitative detection results of ammonium sulfate: The ammonium sulfate-containing samples S1 and S2 were measured three times in parallel, and the results are shown in Table 3.

[0032] Table 3: Ammonium sulfate detection results for samples S1 and S2

[0033] Table 3 shows that the RSDs of samples S1 and S2 were 0.69% and 0.63%, respectively, both ≤2%. The final results indicate that the ammonium sulfate content of both S1 and S2 was within the reasonable range of 13.9% to 16.1%, matching the nominal values ​​of the samples. Sample S3 was not quantitatively analyzed because ammonium sulfate was not detected by XRD, and it was determined that it did not contain ammonium sulfate.

[0034] Example 6: Method Reliability Verification Method accuracy: Using sample S1 as the matrix, spike recovery experiments were conducted according to the steps of Examples 1-5, with low, medium and high levels of ammonium sulfate standards added. The results are shown in Table 4.

[0035] Table 4: Results of Ammonium Sulfate Spiking Recovery Test of Samples

[0036] As shown in Table 4, the spiked recovery rate ranged from 98.50% to 102.44%, which fully meets the 95%-105% recovery rate requirement specified in GB / T 27417-2017 "Guideline for Conformity Assessment and Validation of Chemical Analysis Methods", indicating that the method is of good accuracy.

[0037] Method precision: Using S1 and S2 samples as matrices, each sample was measured 7 times in parallel according to the steps of Examples 1-5. The results are shown in Table 5.

[0038] Table 5: Mass fraction of ammonium sulfate in sample S1

[0039] As can be seen from Table 5, the detection results of samples S1 and S2 both show small standard deviations, with RSD ≤ 2.0%, indicating that the dispersion of the relevant experimental data is small and that the detection method has good reproducibility.

[0040] The method described in this invention constructs an ammonium sulfate detection system for ABC dry powder fire extinguishing agents. This system achieves accurate qualitative analysis of ammonium sulfate using XRD technology, effectively avoiding ineffective quantitative operations. Ion chromatography significantly eliminates the influence of interfering components on the detection process, ensuring quantitative accuracy. Combined with Nessler's reagent spectrophotometry to determine the total ammonia nitrogen content of the sample, and after deducting the contribution of ammonia nitrogen from ammonium dihydrogen phosphate and interfering components, the ammonium sulfate content is accurately calculated. This detection system possesses the technical advantages of high spiked recovery rate and excellent data reproducibility, demonstrating significant practical application value.

Claims

1. A method for detecting the ammonium sulfate content in ABC dry powder fire extinguishing agent, characterized in that, The method includes the following steps: 1) Qualitative analysis of ABC dry powder fire extinguishing agent samples was performed using X-ray diffraction to determine whether they contained ammonium sulfate and other ammonium salts; 2) The total ammonia nitrogen content of the ABC dry powder fire extinguishing agent sample was determined by Nessler's reagent spectrophotometry and denoted as X1; 3) The content of ammonium dihydrogen phosphate in the ABC dry powder fire extinguishing agent sample was determined by gravimetric method and recorded as X2; 4) The ammonia nitrogen content of interfering components in the ABC dry powder fire extinguishing agent sample was determined by ion chromatography and denoted as X3; 5) Calculate the ammonium sulfate content based on the law of conservation of nitrogen, and record it as X4.

2. The method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agent as described in claim 1, characterized in that, If, in step 1), a characteristic diffraction peak that perfectly matches the ammonium sulfate standard card appears in the X-ray diffraction pattern of the sample, and the relative intensity ratio of the characteristic peaks is consistent, then subsequent quantitative detection will be performed.

3. The method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agent as described in claim 1, characterized in that, Total ammonia nitrogen content in step 2) The calculation formula is: ； Where c1 is the concentration of ammonia nitrogen in the test solution (mg / L) and m0 is the sample mass (g).

4. The method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agent as described in claim 1, characterized in that, Step 3) Ammonium dihydrogen phosphate content The calculation formula is: ； Where m1 is the mass of quinoline phosphomolybdate precipitate (g), m0 is the mass of the sample (g), and 1.0396 is the conversion factor for quinoline phosphomolybdate to ammonium dihydrogen phosphate.

5. The method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agent as described in claim 1, characterized in that, ammonia nitrogen content of interfering components in step 4) The calculation formula is: ； Where c2 is the concentration (mg / L) of the interfering component anion in the test solution, m0 is the sample mass (g), and ω1 is the ratio of the atomic mass of ammonia nitrogen in the interfering component to the relative molecular mass of the anion in the interfering component.

6. The method for detecting ammonium sulfate content in ABC dry powder fire extinguishing agent as described in claim 1, characterized in that, The formula for calculating the ammonium sulfate content in step 5) is: 。

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