Method for qualitative or quantitative determination of perfluoroalkyl sulfonate compounds in fire extinguishing agents

Abstract

The application discloses a method for qualitatively or quantitatively determining perfluoroalkyl sulfonate compounds in fire extinguishing agents. 19 The method is based on nuclear magnetic resonance spectroscopy technology, adopts perfluoroalkyl potassium sulfonate with known structure and purity as an internal standard substance, adds the internal standard substance into a mixed solution prepared by mixing the fire extinguishing agent, sets optimized nuclear magnetic test parameters, measures F integral areas of the to-be-measured substance and the internal standard substance at -CF3, and calculates the content of the perfluoroalkyl sulfonate according to the sample weight and the molecular weight of the perfluoroalkyl potassium sulfonate and the perfluoroalkyl sulfonate in the fire extinguishing agent. Finally, the perfluoroalkyl sulfonate compound detection step of the application is used to complete the quantitative nuclear magnetic resonance spectroscopy rapid detection of the perfluoroalkyl sulfonate compounds in the fire extinguishing agent and obtain accurate conclusions. The method provides a method for rapidly, accurately, greenly and simply detecting the perfluoroalkyl sulfonate compounds in the fire extinguishing agent on site.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry methods, specifically relating to a quantitative nuclear magnetic resonance spectroscopy method for determining perfluoroalkyl sulfonate compounds in fire extinguishing agents. Background Technology

[0002] Perfluorooctane sulfonate (PFOS) refers to perfluorooctane sulfonic acid, perfluorooctane sulfonate, and their derivatives, with the general molecular formula C8F. 17 SO2Y, where Y can be a hydroxyl group, a metal, a halogen, an amino group, or other derivatives, including polymers.

[0003] PFOS is primarily used as a surfactant in aqueous film-forming foam (AFCF) fire extinguishing agents in the fire protection industry. Fluorocarbon surfactants, represented by PFOS, can reduce the surface tension of aqueous solutions to a level where they can spread and form a film on oil surfaces. AFCF agents with added PFOS are recognized worldwide as the best-performing foam extinguishing agents for extinguishing liquid fuel fires due to their rapid extinguishing speed, sealing properties, and strong resistance to reignition. However, due to its persistence, bioaccumulation, long-distance environmental migration, and biotoxicity, the application of PFOS has also caused serious environmental impacts. In December 2002, at the 34th Joint Meeting of the Chemicals Committee of the OECD, PFOS was defined as a persistent organic pollutant. On December 5, 2005, the European Commission proposed a draft recommendation and directive on restricting the sale and use of perfluorooctane sulfonyl compounds, and assessed the costs, benefits, balance, and legality of implementing the recommendation. On October 24, 2006, the European Parliament formally passed a resolution stipulating that the content of PFOS in manufactured goods on the EU market must not exceed 0.005% of the product's mass. This marked the EU's formal and comprehensive ban on the use of PFOS in commodities. In 2009, PFOS was formally included in the Stockholm Convention on Persistent Organic Pollutants, and governments of more than 160 countries worldwide reached a consensus to restrict the use of PFOS-related compounds. China is also a signatory to the convention. With current scientific capabilities, it is difficult to achieve fire extinguishing foam (AFFF) without fluorocarbon surfactants. Considering the impact of banning PFOS on fire safety and the need for time to find suitable alternatives, the Stockholm Convention Annex temporarily listed fire extinguishing foam as an acceptable use. In 2019, the Stockholm Convention was revised, and through the efforts of relevant experts, the exemption period for the use of PFOS in the fire protection field was extended again.

[0004] As the largest user of PFOS, the production of foam fire extinguishing agents in China has received continuous and widespread attention from environmental organizations both domestically and internationally. With the maturation of alternative technologies, the control and reduction of PFOS will be an inevitable trend. Researching and establishing detection methods for PFOS in fire extinguishing agents is of great significance for scientifically understanding the use of PFOS in my country's fire protection industry, strengthening PFOS control, and reducing trade frictions.

[0005] High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS) is a commonly used method for trace analysis of complex matrices and is currently the preferred method for analyzing substances such as PFOS and PFOA in environmental, industrial, and food products. However, it is limited by complex sample preparation, the need for professional operators, long analysis time, and its inability to be applied to on-site detection. Therefore, it is particularly urgent to develop a rapid, accurate, environmentally friendly, and simple method for the rapid on-site detection of perfluoroalkyl sulfonate compounds in fire extinguishing agents.

[0006] Nuclear magnetic resonance (NMR) spectroscopy is an indispensable method for identifying the structure of substances. With the development of NMR technology, its quantitative advantages have become increasingly prominent. In NMR, the chemical shift of a proton depends on its chemical environment, and the integral area is proportional to the number of atoms. Fluorine has a natural abundance comparable to hydrogen (100%), and fluorine NMR technology... 19 Fluorinated NMR (FNMR) is used for the determination of fluorinated drugs, photosensitive materials, and surfactants. Among these, fluorinated surfactants are diverse and added in small quantities, which poses a significant challenge to the quantification of fluorinated surfactants. However, due to… 19 The F NMR method has advantages such as simple sample pretreatment, accurate results, fast detection speed, and applicability to on-site detection. 19 It is feasible to quantify perfluoroalkyl sulfonate compounds in fire extinguishing agents using the F NMR method.

[0007] This invention is based on nuclear magnetic resonance spectroscopy technology and employs... 19 The F-NMR quantitative method uses potassium perfluoroalkyl sulfonate with known structure and purity as an internal standard, which is added to the foam extinguishing agent to prepare a mixed solution. By setting and optimizing the NMR test parameters, the F-integral area of ​​the analyte and the internal standard in -CF3 is measured. Based on the sample weight and molecular weight of potassium perfluoroalkyl sulfonate and perfluoroalkyl sulfonate in the foam extinguishing agent, the content of perfluoroalkyl sulfonate is calculated. Finally, using the perfluoroalkyl sulfonate compound detection steps of this invention, rapid quantitative NMR spectroscopy detection of perfluoroalkyl sulfonate compounds in the extinguishing agent is completed, and accurate conclusions are obtained.

[0008] The present invention solves the problems existing in the prior art and provides a fast, accurate, green and environmentally friendly method that is simple to operate and can be used for rapid on-site detection of perfluoroalkyl sulfonate compounds in fire extinguishing agents. Summary of the Invention

[0009] This invention is based on nuclear magnetic resonance spectroscopy technology and employs... 19 The F-NMR quantitative method uses perfluoroalkyl sulfonates with known structure and purity as internal standards. These are added to foam fire extinguishing agents to prepare a mixed solution. By optimizing NMR testing parameters, the F-integral areas of the analyte and the internal standard in -CF3 are measured. Based on the sample weight and molecular weight of the perfluoroalkyl sulfonate internal standard and the perfluoroalkyl sulfonate in the foam fire extinguishing agent, the content of perfluoroalkyl sulfonate is calculated. Finally, using the perfluoroalkyl sulfonate compound detection steps of this invention, rapid quantitative NMR spectroscopy detection of perfluoroalkyl sulfonate compounds in fire extinguishing agents is completed, and accurate conclusions are obtained. Specific details include:

[0010] The quantitative nuclear magnetic resonance spectroscopy method for determining perfluoroalkyl sulfonate compounds in fire extinguishing agents includes the following steps:

[0011] 1) Sample preparation steps: Prepare the test sample solution. Accurately weigh a certain amount of the foam extinguishing agent sample and add it directly to the NMR tube, then add deuterated water. Select high-purity perfluoroalkyl sulfonate, accurately weigh it, and add it to the NMR tube as an internal standard.

[0012] 2) Qualitative detection steps: The test sample was detected using a nuclear magnetic resonance spectroscopy instrument. The chemical shift (δ = -81.6 ppm) of the internal standard perfluoroalkyl sulfonate-CF3 peak did not interfere with other resonance peaks, and was completely separated from the chemical shift (δ = -82.0 to -84.0 ppm) of the test sample perfluorooctyl sulfonate-CF3, without interference.

[0013] 3) Quantitative detection steps: The test sample is detected using a nuclear magnetic resonance spectroscopy instrument. The sample to be tested is selected in... 19 The triplet peak with a chemical shift of -82.0 to -84.0 ppm in the F NMR spectrum was selected as the quantitative peak, and the F integral area of ​​-CF3 was calculated for it. Similarly, the triplet peak of the internal standard perfluoroalkyl sulfonate at a chemical shift of -81.6 ppm was selected as the quantitative peak, and the F integral area of ​​-CF3 for it was calculated. Using the known mass, molecular weight, and F integral area ratio of the sample and internal standard, the content of perfluorooctyl sulfonate in the sample was calculated.

[0014] 4) Internal standards can be selected from perfluoroalkyl sulfonates with known structures, such as potassium perfluorobutyl sulfonate.

[0015] 5) The quantitative nuclear magnetic resonance spectroscopy method for determining perfluoroalkyl sulfonate compounds in fire extinguishing agents has a sampling time of 0.5–600 s.

[0016] This method solves the problems existing in the prior art and provides a fast, accurate, environmentally friendly, and simple method that can be used for rapid on-site detection of perfluoroalkyl sulfonate compounds in fire extinguishing agents. Attached Figure Description

[0017] Figure 1 A quantitative nuclear magnetic resonance spectroscopic method for determining perfluoroalkyl sulfonate compounds in fire extinguishing agents;

[0018] Figure 2 Example 2: A mixture of potassium perfluorobutyl sulfonate (internal standard) and perfluoroalkyl sulfonate (sample) 19 F NMR quantitative spectrum. Detailed Implementation

[0019] Example 1

[0020] The foam extinguishing agent sample to be tested was thoroughly shaken. 0.5 mg (accurate to 1 mg) of the sample was directly added to the NMR tube, followed by 0.5 mL of deuterated water. The mixture was sonicated until the sample was completely dissolved. NMR experimental conditions: experimental temperature 25℃, 5 mm PABBO BB probe, pulse sequence number zgflqn, pulse width (P1) 13.9 µs, sampling time (AQ) 0.73 s, relaxation time (D1) 1 s. The test was performed using an NMR instrument. If the sample... 19 The presence of a triplet at δ = -82.0 to -84.0 ppm in the F NMR spectrum indicates that the foam extinguishing agent sample contains perfluoroalkyl sulfonate compounds, which is used for qualitative analysis.

[0021] Example 2

[0022] The foam extinguishing agent sample to be tested was thoroughly shaken. 0.6 g (accurate to 1 mg) of the sample was weighed and added directly to the NMR tube. 0.5 mL of deuterated water was added, and 2.5 g (accurate to 1 mg) of high-purity perfluorobutyl sulfonate was weighed and added to the NMR tube as an internal standard. The tube was then sonicated until the sample and internal standard were completely dissolved. NMR experimental conditions: experimental temperature 25℃, 5 mm PABBO BB probe, pulse sequence number zgflqn, pulse width (P1) 13.9 µsec, sampling time (AQ) 0.73 s, relaxation time (D1) 1 s. The sample to be tested was selected in… 19The triplet peak with chemical shifts at δ = -82.0 to -84.0 ppm in the F NMR spectrum was selected as the quantitative peak, and the F integral area of ​​-CF3 was calculated for it. The triplet peak with chemical shift (δ = -81.6 ppm) of potassium perfluorobutyl sulfonate, the internal standard, was selected as the quantitative peak, and the F integral area of ​​-CF3 was calculated for it. Given the mass m of the sample to be tested... s = 0.6g and molecular weight M s =538.22, the mass m of the internal standard i =2.5g and molecular weight M i =338.19, the F-integral area ratio of the test sample and the internal standard -CF3. s / F i =1 / 5, and the content of perfluorooctyl sulfonate in the sample was calculated to be 1.33% using the following formula.

[0023]

[0024] In the formula:

[0025] wt – Content of perfluoroalkyl sulfonyl compounds in foam fire extinguishing agent samples

[0026] F s —F-integral area of ​​sample-CF3

[0027] F i —The area of ​​the F-integral of the internal standard -CF3

[0028] m s —Sample mass, in g

[0029] m i —Internal standard mass, in grams

[0030] M s —Sample molecular weight (here expressed as potassium perfluorooctyl sulfonate)

[0031] M i —Molecular weight of internal standard.

Claims

1. A method for qualitative or quantitative determination of perfluoroalkyl sulfonate compounds in fire extinguishing agents, characterized in that: Based on nuclear magnetic resonance spectroscopy, using 19 The F-NMR quantitative method uses a known perfluoroalkyl sulfonate as an internal standard, which is added to the foam extinguishing agent to prepare a mixed solution. The F-integral area of ​​the foam extinguishing agent and the internal standard in -CF3 is measured to qualitatively identify the perfluoroalkyl sulfonate compounds in the extinguishing agent. Alternatively, based on the sample weight and molecular weight of the perfluoroalkyl sulfonate internal standard and the perfluoroalkyl sulfonate in the foam extinguishing agent, the content of perfluoroalkyl sulfonate in the foam extinguishing agent is calculated to quantitatively determine the perfluoroalkyl sulfonate compounds in the extinguishing agent. The determination method includes the following steps: Sample preparation steps: Prepare the test sample liquid as the test sample: Weigh the foam fire extinguishing agent sample and add it to the nuclear magnetic resonance tube of the nuclear magnetic resonance spectrometer, and then add deuterated water; Perfluoroalkyl sulfonate was selected, weighed, and added to an NMR tube as an internal standard; The qualitative detection procedure uses nuclear magnetic resonance spectroscopy to detect the test sample: the chemical shift (δ=-81.6 ppm) of the internal standard perfluoroalkyl sulfonate-CF3 peak does not interfere with other resonance peaks, and is completely separated from the chemical shift (δ=-82.0 ~ -84.0 ppm) of the test sample perfluorooctyl sulfonate-CF3 peak, without interference; this allows for the qualitative detection of perfluoroalkyl sulfonate compounds in fire extinguishing agents. Quantitative detection steps: The test sample is analyzed using nuclear magnetic resonance spectroscopy (NMR). In step 1), deuterated water is added to the foam extinguishing agent sample in the NMR tube. Then, perfluoroalkyl sulfonate is selected, weighed, and added to the NMR tube as an internal standard. The test sample is then selected... 19 The triplet peak with chemical shift at δ = -82.0 ~ -84.0 ppm in the F NMR spectrum was selected as the quantitative peak, and the F integral area of ​​-CF3 was calculated for it. The triplet peak of the internal standard perfluoroalkyl sulfonate at chemical shift (δ = -81.6 ppm) was selected as the quantitative peak, and the F integral area of ​​-CF3 was calculated for it. With the known mass, molecular weight, and F integral area ratio of the sample and internal standard, the content of perfluorooctyl sulfonate in the sample was calculated.

2. The determination method according to claim 1, characterized in that: The internal standard can be a perfluoroalkyl sulfonate with a known structure.

3. The determination method according to claim 2, characterized in that: The internal standard may be selected from one or more of the following: potassium perfluorobutyl sulfonate, sodium perfluorobutyl sulfonate, or potassium perfluoropropyl sulfonate.

4. The determination method according to claim 1, characterized in that: The sampling time is 0.5 ~ 300s.

5. The determination method according to claim 1, characterized in that: Shake the foam extinguishing agent sample to be tested thoroughly, weigh 0.1 to 1.0 g of the sample and add it directly to the NMR tube, add 0.1 to 2 mL of deuterated water, and then add 0.5 to 5 g of perfluoroalkyl sulfonate.

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