A method for detecting perfluorooctanoic acid in water

Abstract

This invention relates to the field of detection and analysis technology, and discloses a method for detecting perfluorooctanoic acid (PFOA) in water. The method includes the following steps: filtering a water sample through a filter membrane and collecting the filtrate; using a C18 reversed-phase chromatographic column, with an aqueous solution containing tetrabutylammonium bisulfate as mobile phase A and acetonitrile as mobile phase B, isocratic elution is performed at a detection wavelength of 208-215 nm, and detection is performed using a UV detector or a diode array detector; qualitative analysis is performed based on chromatographic retention time, and quantitative analysis is performed using the external standard method based on chromatographic peak area. This invention, by optimizing the detection wavelength and introducing tetrabutylammonium bisulfate as an ion-pairing reagent, effectively improves the chromatographic peak shape and resolution of PFOA, achieving a correlation coefficient R0 within a wide linear range of 0.5-200 mg / L. 2 The detection limit is >0.999, which meets the detection requirements of most water bodies; the method has good repeatability, with a spiked recovery rate of up to 98.30%-108.35% in complex matrices; it has strong anti-interference ability, and the detection results are stable in the pH range of 4-10, making it suitable for actual water samples under different acid and alkaline conditions.

Description

Technical Field

[0001] This invention relates to the field of detection and analysis technology, and in particular to a method for detecting perfluorooctanoic acid (PFOA) in water. Background Technology

[0002] Perfluorooctanoic acid (PFOA) is a typical representative of the perfluorinated and polyfluoroalkyl compounds (PFAS) family, widely used and frequently detected in the environment. In its molecular structure, the hydrogen atoms on the carbon chain are completely replaced by fluorine atoms, and the carbon-fluorine bond energy is as high as approximately 485 kJ / mol. This unique structure endows it with extremely strong chemical stability, thermal stability, hydrophobicity, and oleophobicity, making it an indispensable key material in industrial production and daily life. For a long time, PFOA and its salts have been widely used in non-stick cookware coatings, oil-resistant food packaging materials, waterproof and stain-resistant textiles, leather treatment agents, electroplating industry auxiliaries, and aqueous film-forming foam fire extinguishing agents. Long-term large-scale production and use worldwide have led to its continuous release into the environment.

[0003] Because PFOA is difficult to biodegrade, hydrolyze, photolyze, or oxidize in the natural environment, it exhibits typical environmental persistence. It is widely present in surface water, groundwater, drinking water, soil, atmosphere, and organisms. Major sources of pollution are concentrated in chemical industrial park emissions, landfill leachate, industrial wastewater treatment plant effluent, and leachate from specific contaminated sites. Furthermore, PFOA has significant bioaccumulation and biomagnification effects, accumulating through the food chain and eventually entering the human body, where it persists in tissues such as the liver and blood for extended periods. Its extremely long half-life makes it difficult to eliminate through normal metabolism. Epidemiological and toxicological studies have confirmed a significant association between long-term exposure to PFOA and hepatotoxicity, immune system suppression, and the development of certain cancers.

[0004] With the rapid development of PFOA pollution control technologies, especially the deepening research on degradation technologies such as advanced oxidation, catalytic reduction, pyrolysis, and biodegradation, the demand for rapid, efficient, and low-cost quantitative detection of high-concentration PFOA continues to rise. Currently, the mainstream detection method for PFOA is liquid chromatography-tandem mass spectrometry (LC-MS / MS). This method has high sensitivity and specificity, and is suitable for the determination of trace PFOA in environmental water samples. However, it has significant shortcomings in high-concentration sample detection scenarios: the pretreatment process is cumbersome and time-consuming, the detection cost is high, the equipment investment is large, and the technical requirements for operators are high. It is difficult to meet the needs of scenarios such as rapid screening of large batches of samples, real-time monitoring of industrial processes, and dynamic tracking of degradation reactions.

[0005] High-performance liquid chromatography (HPLC) offers advantages such as low equipment cost, ease of operation, fast analysis speed, good repeatability, and suitability for large-volume sample detection, theoretically serving as a low-cost alternative to LC-MS / MS. However, in practical applications, conventional HPLC methods face insurmountable technical bottlenecks: PFOA molecules are highly polar and extremely water-soluble, exhibiting almost no retention on conventional C18 reversed-phase columns. They readily co-elute with solvent peaks, large amounts of inorganic ions in water, organic matter, and other interfering substances, failing to form stable, identifiable, and quantifiable chromatographic peaks under UV detection. This renders conventional HPLC unsuitable for the effective separation and detection of PFOA. Furthermore, in complex matrices such as degradation reaction systems and industrial wastewater, high concentrations of inorganic salts, metal ions, organic acids, and oxidation products further exacerbate interference, causing peak distortion, baseline drift, and significant quantitative deviations. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide a method for detecting perfluorooctanoic acid (PFOA) in water.

[0007] The second objective of this invention is to provide an application of this method.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a method for detecting perfluorooctanoic acid (PFOA) in water, comprising the following steps: The water sample is filtered through a filter membrane, and the filtrate is collected. A C18 reversed-phase column was used, with an aqueous solution containing tetrabutylammonium hydrogen sulfate as mobile phase A and acetonitrile as mobile phase B. Isocratic elution was performed at a detection wavelength of 208-215 nm, and detection was performed using a UV detector or a diode array detector. Qualitative analysis was performed using chromatographic retention time, and quantitative analysis was performed using the external standard method based on chromatographic peak area.

[0009] In some embodiments of the present invention, the pore size of the filter membrane is 0.22-0.45 μm; the filtration includes discarding the first 0.5-1 mL of filtrate and collecting the subsequent filtrate.

[0010] In some preferred embodiments of the present invention, the pore size of the filter membrane is 0.22-0.24 μm; the filtration includes discarding the first 0.8-1 mL of filtrate and collecting the subsequent filtrate.

[0011] In some embodiments of the present invention, the filter membrane comprises a polyethersulfone filter membrane.

[0012] In some embodiments of the present invention, the parameters of the C18 reversed-phase chromatographic column include at least one of the following: inner diameter of 4.0-4.6 mm; length of 150-250 mm; pressure resistance of 300-500 bar; and pore size of the packing particles of 80-100 Å and particle size of 2.7-5.0 μm.

[0013] In some preferred embodiments of the present invention, the parameters of the C18 reversed-phase chromatographic column include at least one of the following: inner diameter of 4.4-4.6 mm; length of 200-250 mm; pressure resistance of 350-450 bar; and pore size of the packing particles of 80-90 Å and particle size of 4.0-5.0 μm.

[0014] In some embodiments of the present invention, the packing material of the C18 reversed-phase chromatography column is octadecylsilane-bonded silica gel.

[0015] In some embodiments of the present invention, the injection volume is 50-100 μL.

[0016] In some preferred embodiments of the present invention, the injection volume is 50-60 μL.

[0017] In some embodiments of the present invention, the mobile phase A is an ion-pair-weakly acidic buffer system, comprising 0.5-2.5 mmol / L tetrabutylammonium bisulfate, 5-8 mmol / L basicity regulator and 2.5-10 mmol / L weakly acidic buffer.

[0018] In some preferred embodiments of the present invention, the mobile phase A is an ion-pair-weakly acidic buffer system, comprising 1.5-2.5 mmol / L tetrabutylammonium bisulfate, 5-6 mmol / L basicity regulator and 2.5-10 mmol / L weakly acidic buffer.

[0019] In some embodiments of the present invention, the alkalinity regulator is selected from at least one of potassium hydroxide and sodium hydroxide.

[0020] In some preferred embodiments of the present invention, the alkalinity regulator is sodium hydroxide.

[0021] In some embodiments of the present invention, the weakly acidic buffer is selected from at least one of acetic acid, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, citric acid, and formic acid.

[0022] In some preferred embodiments of the present invention, the weakly acidic buffer is selected from acetic acid or potassium dihydrogen phosphate.

[0023] In some embodiments of the present invention, the weakly acidic buffer is acetic acid, and its content in mobile phase A is 5-10 mmol / L.

[0024] In some embodiments of the present invention, the weakly acidic buffer is potassium dihydrogen phosphate, and its content in mobile phase A is 2.5-5 mmol / L.

[0025] In some embodiments of the present invention, the total flow rate of mobile phase A and mobile phase B is 0.9-1.7 mL / min.

[0026] In some preferred embodiments of the present invention, the total flow rate of mobile phase A and mobile phase B is 0.9-1.1 mL / min.

[0027] In some embodiments of the present invention, in the isocratic elution, the ratio of mobile phase A to mobile phase B is (1-1.5):1.

[0028] In some preferred embodiments of the present invention, in the isocratic elution, the ratio of mobile phase A to mobile phase B is (1-1.2):1.

[0029] In some embodiments of the present invention, the temperature of the chromatographic column for isocratic elution is 25-35°C.

[0030] In some preferred embodiments of the present invention, the chromatographic column temperature for isocratic elution is 28-32°C.

[0031] In some embodiments of the present invention, the qualitative judgment criterion is: the retention time deviation between the sample and the standard is within ±0.5 min.

[0032] In some embodiments of the present invention, the quantification specifically includes: calculating the content of perfluorooctanoic acid (PFOA) based on the peak area of ​​the chromatographic peak in the obtained chromatogram and the linear regression equation; the vertical axis of the linear regression equation is the chromatographic peak area corresponding to PFOA, and the horizontal axis is the concentration of a water blank solution standard of PFOA at a certain concentration gradient.

[0033] In some embodiments of the present invention, the concentration of the aqueous blank standard sample of perfluorooctanoic acid ranges from 1 to 25 mg / L.

[0034] In some embodiments of the present invention, the linear range of the quantification is 0.5-200 mg / L, and the linear correlation coefficient R0 is [missing value]. 2 ≥0.999.

[0035] The second aspect of the present invention provides the application of the method described in the first aspect of the present invention in the determination of residual perfluorooctanoic acid in water after degradation reaction.

[0036] In some embodiments of the present invention, the water is selected from industrial wastewater, chemical industrial park drainage, groundwater from contaminated sites, surface water, effluent from advanced oxidation treatment systems, or water samples from catalytic degradation systems.

[0037] Compared with the prior art, the beneficial effects of the present invention are: The method for detecting perfluorooctanoic acid (PFOA) in water provided by this invention requires only simple filtration for sample pretreatment, eliminating the need for complex operations such as derivatization or solid-phase extraction, significantly simplifying the process and reducing detection costs and time. This method uses a conventional high-performance liquid chromatography (HPLC) platform, avoiding the high instrument investment and maintenance costs of liquid chromatography-tandem mass spectrometry (LC-MS / MS), making it economical and practical. Regarding detection performance, by optimizing the detection wavelength (208-215 nm) and introducing tetrabutylammonium bisulfate as an ion-pairing reagent, the chromatographic peak shape and resolution of PFOA are effectively improved, achieving a correlation coefficient R0 within a wide linear range of 0.5-200 mg / L. 2 The detection limit is >0.999, meeting the needs of most water body detection. The method has good repeatability, with a relative deviation of ≤3.26% for multiple parallel quantifications. The spiked recovery rate in complex matrices is as high as 98.30%-108.35%. It has strong anti-interference ability and can accurately quantify even in complex water samples containing high concentrations of sulfate, fluoride, iron and suspended solids. In addition, the method has stable detection results in the pH range of 4-10 and is applicable to actual water samples under different acid and alkaline conditions. It is particularly suitable for the rapid quantitative analysis of perfluorooctanoic acid in complex water bodies such as wastewater and leachate treated with transition metal oxide systems, providing a reliable technical means for pollution monitoring and degradation effect evaluation. Attached Figure Description

[0038] Figure 1 The images show the UV-Vis spectra of perfluorooctanoic acid (PFOA) samples of different concentrations on a mixed mobile phase substrate in Example 1. Figure 2 This is a superimposed graph of the absorbance-concentration standard curves of perfluorooctanoic acid within the characteristic absorption range in Example 2; Figure 3 This is a high-performance liquid chromatography (HPLC) overlay chromatogram corresponding to different amounts of tetrabutylammonium bisulfate added in Example 3; Figure 4 This is a high-performance liquid chromatography (HPLC) overlay diagram corresponding to different ratios of mobile phase A and mobile phase B in Example 4; Figure 5 This is a superimposed graph of peak area-concentration standard curves for perfluorooctanoic acid (PFOA) at concentrations of 0.5-200 mg / L in Example 5. Figure 6 The image shows the high-performance liquid chromatogram of the actual water sample in Example 6. Figure 7 This is a superimposed graph of eight parallel quantitative standard curves from Example 6; Figure 8 This is a graph showing the spiked recovery results of the samples after the two degradation reactions in Example 7; Figure 9This is a high-performance liquid chromatography overlay of samples with pH = 4-10 from Example 8. Detailed Implementation

[0039] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0040] The following information is provided regarding the instruments, equipment, and reagents used in the examples and comparative examples: instrument: Shimadzu Automated High-Performance Liquid Chromatography System: Prominence LC-20A HPLC system (parallel LC-20AD quaternary low-pressure infusion unit, DGU-20As degassing unit, SIL-20A autosampler, CTO-40A column oven), SPD-20A UV-Vis detector and LabSolutions workstation software (version 5.81 SP1).

[0041] Equipment and reagents: Acetonitrile, OceanPak chromatographic grade; Glacial acetic acid, sodium hydroxide, and tetrabutylammonium hydrogen sulfate, analytical grade, were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. The experimental water was ultrapure water, which was obtained from the Milli-Qsystems water purification system. 0.22μm polyethersulfone needle filter membrane, purchased from Shanghai Anpu Laboratory Technology Co., Ltd. Perfluorooctanoic acid (PFOA) standard (purity ≥99%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Example 1 This embodiment determines the characteristic absorption wavelength range of perfluorooctanoic acid in the mobile phase system: The mobile phase substrate of the test system was: 50% acetonitrile, 6 mmol / L NaOH, 5 mmol / L potassium dihydrogen phosphate, 2 mmol / L tetrabutylammonium hydrogen sulfate, pH=6.

[0043] Sample preparation: Accurately weigh 10.00 mg of perfluorooctanoic acid (PFOA) standard, place it in a 100 mL volumetric flask, dissolve it in ultrapure water by sonication and dilute to the mark, shake well, and prepare a 100 mg / L standard stock solution; prepare a series of PFOA standard solutions with concentrations of 0, 21.86, 44.72, 107.37, 213.45 and 427.69 mg / L in the above mobile phase substrate.

[0044] Testing instrument: UV-Vis spectrophotometer, wavelength scanning range 200-280nm.

[0045] Figure 1 The images show the UV-Vis spectra of perfluorooctanoic acid (PFOA) samples of different concentrations on a mixed mobile phase substrate in Example 1. Figure 1 It can be seen that perfluorooctanoic acid samples of different concentrations all have strong characteristic absorption in the 208-215nm range, so the 208-215nm range is determined as the characteristic absorption range.

[0046] Example 2 This embodiment examines the linear relationship between perfluorooctanoic acid concentration and absorbance at wavelengths ranging from 208 to 215 nm: The mobile phase substrate of the test system was: 50% acetonitrile, 6 mmol / L NaOH, 5 mmol / L potassium dihydrogen phosphate, 2 mmol / L tetrabutylammonium hydrogen sulfate, pH=6.

[0047] Sample preparation: Accurately weigh 10.00 mg of perfluorooctanoic acid (PFOA) standard, place it in a 100 mL volumetric flask, dissolve it in ultrapure water by sonication and dilute to the mark, shake well, and prepare a 100 mg / L standard stock solution; prepare a series of PFOA standard solutions with concentrations of 0, 21.86, 44.72, 107.37, 213.45 and 427.69 mg / L in the above mobile phase substrate.

[0048] Testing instrument: UV-Vis spectrophotometer, with detection wavelengths of 208, 209, 210, 211, 212, 213, 214 and 215 nm.

[0049] Test method: At each of the above wavelengths, the absorbance of six perfluorooctanoic acid (PFOA) samples of different concentrations was measured. Standard curves were fitted with PFOA concentration as the x-axis and absorbance as the y-axis.

[0050] Figure 2 This is a superimposed graph of absorbance-concentration standard curves of perfluorooctanoic acid within the characteristic absorption range in Example 2, from... Figure 2 It can be seen that the standard curve R is available for all wavelengths. 2 All values ​​are greater than 0.999, indicating excellent linearity.

[0051] Example 3 This example investigates the effect of tetrabutylammonium bisulfate concentration on the retention behavior and peak shape of perfluorooctanoic acid (PFOA). Chromatographic conditions: Column: Agilent ZORBAX Eclipse XDB C18, 4.6mm×250mm, 5μm, 80Å; Filler: Octadecylsilane-bonded silica gel; Mobile phase A: an aqueous solution containing 6 mmol / L sodium hydroxide, 8 mmol / L acetic acid, and different concentrations of tetrabutylammonium hydrogen sulfate (0, 0.5, 1.0, 1.5 and 2.0 mmol / L); Mobile phase B: Acetonitrile; Elution method: isocratic elution, mobile phase A: mobile phase B = 50: 50 (v / v); Total flow rate: 1.0 mL / min; Detection wavelength: 210nm; Column temperature: 30℃; Injection volume: 50 μL; Sample: 50 mg / L perfluorooctanoic acid standard solution, pH=4.

[0052] Figure 3 This is a high-performance liquid chromatography (HPLC) overlay chromatogram corresponding to different amounts of tetrabutylammonium bisulfate added in Example 3. Figure 3 It can be seen that perfluorooctanoic acid is not retained when tetrabutylammonium bisulfate is not added; the peak is normal after adding tetrabutylammonium bisulfate, and the peak is better when the amount of tetrabutylammonium bisulfate added is 1.5-2.0 mmol / L.

[0053] Example 4 This embodiment examines the optimal isocratic elution ratio of mobile phase A to mobile phase B: Chromatographic conditions: Column: Agilent ZORBAX Eclipse XDB C18, 4.6mm×250mm, 5μm, 80Å; Filler: Octadecylsilane-bonded silica gel; Mobile phase A: An aqueous solution containing 6 mmol / L sodium hydroxide, 8 mmol / L acetic acid, and 2 mmol / L tetrabutylammonium hydrogen sulfate; Mobile phase B: Acetonitrile; Elution method: isocratic elution, mobile phase A: mobile phase B ratios of 80:20, 70:30, 60:40, and 50:50 (v / v); Total flow rate: 1.0 mL / min; Detection wavelength: 210nm; Column temperature: 30℃; Injection volume: 50 μL; Sample: 50 mg / L perfluorooctanoic acid standard solution, pH=4.

[0054] Figure 4 This is a high-performance liquid chromatography (HPLC) overlay chromatogram corresponding to different ratios of mobile phase A and mobile phase B in Example 4. Figure 4It can be seen that the peak shape and resolution are better when the volume ratio of mobile phase A to mobile phase B is (50: 50)-(60: 40), that is, when the ratio of mobile phase A to mobile phase B is (1-1.2):1, and the peak shape and resolution are optimal when the volume ratio of the two is 1:1.

[0055] Example 5 This embodiment establishes a wide-range quantitative standard curve of 0.5-200 mg / L: Chromatographic conditions: Column: Agilent ZORBAX Eclipse XDB C18, 4.6mm×250mm, 5μm, 80Å; Filler: Octadecylsilane-bonded silica gel; Mobile phase A: An aqueous solution containing 6 mmol / L sodium hydroxide, 8 mmol / L acetic acid, and 2 mmol / L tetrabutylammonium hydrogen sulfate; Mobile phase B: Acetonitrile; Elution method: isocratic elution, mobile phase A: mobile phase B = 50: 50 (v / v); Total flow rate: 1.0 mL / min; Detection wavelength: 210nm; Column temperature: 30℃; Injection volume: 50 μL.

[0056] Sample preparation: Accurately weigh 10.00 mg of perfluorooctanoic acid (PFOA) standard, place it in a 100 mL volumetric flask, dissolve it in ultrapure water by sonication and dilute to the mark, shake well, and prepare a 100 mg / L standard stock solution; in the above mobile phase substrate, prepare a series of PFOA standard solutions with concentrations of 0.5, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180 and 200 mg / L.

[0057] A regression equation was fitted with concentration as the x-axis and peak area as the y-axis.

[0058] Figure 5 This is a superimposed peak area-concentration standard curve of perfluorooctanoic acid (PFOA) ranging from 0.5 to 200 mg / L in Example 5. Figure 5 We know that the linear equation is y = 2204.84x - 98.84, R0 2 =0.99998, indicating an excellent linear relationship.

[0059] Example 6 This embodiment provides a high-performance liquid chromatography (HPLC) method for the detection of perfluorooctanoic acid (PFOA) in water, as detailed below: Preparation of standard solutions: Accurately weigh 10.00 mg of perfluorooctanoic acid standard, place it in a 100 mL volumetric flask, dissolve it with ultrapure water by sonication and dilute to the mark, shake well, and prepare a 100 mg / L standard stock solution. The standard stock solution was diluted sequentially with ultrapure water to prepare standard solutions of 1, 2.5, 5, 10 and 25 mg / L, and then placed into liquid chromatography vials for testing.

[0060] Sample pretreatment: The sample to be tested is a reaction suspension resulting from the catalytic oxidation and degradation of perfluorooctanoic acid using iron-loaded biochar as a persulfate catalyst. The water sample contains a large amount of suspended solids, and the water quality parameters are: SO42- 2- Content 2g / L, F - Content 6mg / L, Fe 3+ Content 50 mg / L, water pH=4.5; Before testing, the suspension after the reaction was directly drawn with a sterile syringe, filtered through a 0.22μm polyethersulfone filter membrane, and the first 1mL of filtrate was discarded. The next 1mL of filtrate was collected into a liquid chromatography bottle for testing.

[0061] Chromatographic conditions: Column: Agilent ZORBAX Eclipse XDB C18, 4.6mm×250mm, 5μm, 80Å; Filler: Octadecylsilane-bonded silica gel; Mobile phase A: An aqueous solution containing 2.3 mmol / L tetrabutylammonium hydrogen sulfate, 6 mmol / L sodium hydroxide, and 8 mmol / L acetic acid; Mobile phase B: Acetonitrile; Elution method: isocratic elution, mobile phase A: mobile phase B = 50: 50 (v / v); Total flow rate: 1.0 mL / min; Detection wavelength: 210nm; Column temperature: 30℃; Injection volume: 50 μL; Data collection time: 11 min.

[0062] Standard curve and linear relationship: After baseline equilibration, a series of standard working solutions were sequentially injected and analyzed. The peak areas corresponding to the calibrated concentrations were obtained by integrating the peaks at retention times of 9.7–10.0 min. The peak areas of the 1, 2.5, 5, 10, and 25 mg / L standards were 1936, 5174, 9766, 20413, and 52193 μV·min, respectively. A standard curve was plotted with perfluorooctanoic acid concentration on the x-axis and peak area on the y-axis, with an intercept of 0, yielding the regression equation: y = 2076.799x, R02 =0.9998.

[0063] Sample testing: The sample was determined using the chromatographic method described above. Figure 6 The image shows the high-performance liquid chromatogram of the actual water sample in Example 6. A distinct characteristic peak appears at a retention time of approximately 9.84 min, consistent with the retention time of the standard. The peak area of ​​the perfluorooctanoic acid (PFOA) peak is calculated to be 18590 μV·min using software integration. Substituting this into the linear regression equation, the concentration of PFOA in the sample can be calculated to be 8.942 mg / L.

[0064] Following the above test method, under the same conditions, the above series of standard solutions (1, 2.5, 5, 10, and 25 mg / L) were independently and in parallel eight times. For each measurement, a standard curve was plotted with concentration on the x-axis and peak area on the y-axis. Figure 7 This is a superimposed graph of eight parallel quantitative standard curves from Example 6, generated by... Figure 7 It can be seen that the correlation coefficient R of the 8th standard curve is... 2 All values ​​were greater than 0.999, and the relative standard deviation (RSD) of the peak area at each concentration point was 1.49%-3.26%, indicating excellent method repeatability.

[0065] Example 7 This embodiment examines the anti-interference capability and accuracy of the method under high salt and high metal ion matrix conditions: Sample matrix: Sample 1: Contains 0.5 g / L SO4 2- water sample; Sample 2: Contains 2 g / L SO4 2- 15mg / LF - 20 mg / L Fe 3+ Complex water samples.

[0066] Spiked concentration: Add 10, 25, and 40 mg / L of perfluorooctanoic acid standard solution to the two types of samples, respectively.

[0067] Pre-treatment and detection: After filtering through a 0.22 μm filter membrane and discarding 1 mL of the initial filtrate, the sample was analyzed under the same chromatographic conditions as in Example 6, and the spiked recovery rate was calculated.

[0068] Figure 8 This is a graph showing the spiked recovery results of the samples after the two degradation reactions in Example 7. Figure 8 It can be seen that under the interference of high salt and high metal ion matrices, the spiked recovery rate is between 98.30% and 108.35%, indicating that the method can still accurately quantify under highly interfering matrices.

[0069] Example 8 This example examines the effect of different pH values ​​on the detection results: Prepare a 50 mg / L perfluorooctanoic acid standard solution, adjust the pH to 4, 6, 8 and 10 respectively, and perform chromatographic analysis under the same conditions as in Example 6. Record the chromatogram and peak area.

[0070] Figure 9 This is a high-performance liquid chromatography (HPLC) overlay of samples with pH values ​​of 4-10 from Example 8. Figure 9 It can be seen that integrating the peak with a retention time of 8.3 min yielded peak areas of 73846, 73254, 73285 and 73441 μV·min for pH=4, 6, 8 and 10 respectively, with a relative deviation of 0.37%, indicating that this detection method has good stability for quantitative detection of water samples between pH=4 and 10.

[0071] In summary, the use of a mobile phase system containing tetrabutylammonium bisulfate combined with high-performance liquid chromatography (HPLC) and ultraviolet detection enables good retention and separation of perfluorooctanoic acid (PFOA) on a C18 reversed-phase column. It exhibits excellent linearity in the characteristic wavelength range of 208-215 nm, with a wide linear range of 0.5-200 mg / L. The method demonstrates good repeatability, high spiked recovery, and strong resistance to matrix interference. It can be stably detected in complex water bodies with pH values ​​of 4-10. Furthermore, compared to traditional HPLC-tandem mass spectrometry (LC-MS / MS), this invention eliminates the need for isotope internal standards and solid-phase extraction pretreatment, resulting in lower equipment investment. The consumable cost per detection is only 15-20 mg / L compared to mass spectrometry. The method is a fraction of the concentration of perfluorooctanoic acid (PFOA) in water samples, with rapid and simple pretreatment, making it particularly suitable for detecting PFOA in complex, heavily interfered water samples. It has broad application prospects: i. Chemical wastewater and industrial discharge: For chemical wastewater with high salinity and high background values, this method allows direct sample injection and analysis without complex pretreatment, significantly improving detection efficiency; ii. Monitoring of advanced oxidation / catalytic degradation systems: In PFOA degradation experiments, the concentration of PFOA is generally high, and the reaction system is usually accompanied by product changes and matrix fluctuations. This invention can rapidly and in real-time monitor changes in PFOA concentration, providing reliable data support for evaluating degradation efficiency.

Claims

1. A method for detecting perfluorooctanoic acid (PFOA) in water, characterized in that, Includes the following steps: The water sample is filtered through a filter membrane, and the filtrate is collected. A C18 reversed-phase column was used, with an aqueous solution containing tetrabutylammonium hydrogen sulfate as mobile phase A and acetonitrile as mobile phase B. Isocratic elution was performed at a detection wavelength of 208-215 nm, and detection was performed using a UV detector or a diode array detector. Qualitative analysis was performed using chromatographic retention time, and quantitative analysis was performed using the external standard method based on chromatographic peak area.

2. The method for detecting perfluorooctanoic acid in water according to claim 1, characterized in that, The filter membrane has a pore size of 0.22-0.45 μm; the filtration includes discarding the first 0.5-1 mL of filtrate and collecting the subsequent filtrate.

3. The method for detecting perfluorooctanoic acid in water according to claim 1, characterized in that, The parameters of the C18 reversed-phase chromatographic column include at least one of the following: inner diameter of 4.0-4.6 mm; length of 150-250 mm; pressure resistance of 300-500 bar; and pore size of the packing particles of 80-100 Å and particle size of 2.7-5.0 μm.

4. The method for detecting perfluorooctanoic acid in water according to claim 1, characterized in that, The mobile phase A is an ion-pair-weakly acidic buffer system, containing 0.5-2.5 mmol / L tetrabutylammonium bisulfate, 5-8 mmol / L basicity regulator, and 2.5-10 mmol / L weakly acidic buffer.

5. The method for detecting perfluorooctanoic acid in water according to claim 4, characterized in that, The alkalinity regulator is selected from at least one of potassium hydroxide and sodium hydroxide; And / or, the weakly acidic buffer is selected from at least one of acetic acid, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, citric acid, and formic acid.

6. The method for detecting perfluorooctanoic acid in water according to claim 1, characterized in that, The total flow rate of mobile phase A and mobile phase B is 0.9-1.7 mL / min.

7. The method for detecting perfluorooctanoic acid in water according to claim 6, characterized in that, In the isocratic elution, the ratio of mobile phase A to mobile phase B is (1-1.5):

1.

8. The method for detecting perfluorooctanoic acid in water according to claim 7, characterized in that, The column temperature for isocratic elution is 25-35℃.

9. The application of the method according to any one of claims 1-8 in determining residual perfluorooctanoic acid in water after degradation reaction.

10. The application according to claim 9, characterized in that, The water samples are selected from industrial wastewater, chemical industrial park drainage, groundwater from contaminated sites, surface water, effluent from advanced oxidation treatment systems, or water samples from catalytic degradation systems.

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