Method for detecting perfluorinated compounds in water

Abstract

The invention relates to a method for detecting perfluorinated compounds in water, which comprises the following steps: carrying out solid-liquid separation on a water sample to prepare a liquid to be detected; carrying out on-line solid phase extraction-liquid chromatography-mass spectrometry detection on the to-be-detected liquid, and calculating the content of the perfluorinated compounds in the to-be-detected liquid by an internal standard method. The detection method is high in automation degree, simple and rapid to operate and capable of accurately detecting the perfluorinated compounds in the water.

Description

Technical Field

[0001] This application relates to the technical field of chemical analysis, and particularly to a method for detecting perfluorinated compounds in water. Background Art

[0002] Per- and polyfluoroalkyl substances (PFASs) are a class of synthetic fluorinated organic compounds. Due to their good chemical stability and high surface activity, they are widely used in fields such as electroplating, papermaking, textiles, foam fire extinguishers, and food packaging materials. With the production, use, and improper disposal of PFASs-related products, a large amount of PFASs has entered the ecological environment. Currently, PFASs have been detected in various environmental matrices (water bodies, sediments, soils, atmospheres, dusts) globally. Research shows that PFASs have environmental persistence, bioaccumulation, as well as developmental toxicity, immunotoxicity, endocrine disrupting effects, and potential carcinogenicity, posing a potential threat to the ecological environment and human health.

[0003] Currently, PFASs pollution has attracted wide attention from the international community. Many countries and organizations around the world have gradually restricted the production and use of PFASs. Related compounds such as perfluorooctane sulfonic acid (PFOS) have been listed as persistent organic pollutants in the "Stockholm Convention", and China has also included PFASs in the "List of New Pollutants under Key Control (2023)". Therefore, monitoring the pollution level of PFASs in water environment is of great significance for PFASs ecological risk assessment and improving relevant environmental legislation. Currently, for the detection of PFASs, the solid-phase extraction (SPE) method is mostly used to enrich and purify PFASs in the water environment first, and then LC-MS / MS is used for detection and analysis. However, the SPE method requires manual steps such as activation, sample loading, elution, nitrogen blowing, reconstitution, and filtration. The operation is cumbersome and time-consuming, requires a large amount of sample, and is prone to introducing human errors, affecting the accuracy and precision of the measurement results. In addition, the liquid chromatography equilibrium time and separation time of these methods are long, while the effective target acquisition time of the mass spectrometry is short, and the instrument spends part of the time on ineffective acquisition. Summary of the Invention

[0004] Based on this, this application provides a detection method with high automation, simple and rapid operation, and capable of accurately detecting perfluorinated compounds in water.

[0005] The specific technical solution is as follows:

[0006] A method for detecting perfluorinated compounds in water, comprising the following steps:

[0007] Perform solid-liquid separation on the water sample to prepare a test solution;

[0008] Perform on-line solid phase extraction - liquid chromatography - mass spectrometry detection on the test solution, and calculate the content of perfluorinated compounds in the test solution by the internal standard method;

[0009] Among them, the conditions for the on-line solid phase extraction include:

[0010] The mobile phase includes mobile phase A, mobile phase B, mobile phase C and mobile phase D. The mobile phase A is an aqueous ammonium acetate solution with a concentration of 1 mM to 5 mM, the mobile phase B is methanol, the mobile phase C is acetonitrile, and the mobile phase D is methanol and acetonitrile with a volume ratio of 1:(0.5 - 1.5);

[0011] Gradient elution is adopted, and the program includes:

[0012] From 0 min to 2.5 min, keep the flow rate at 2 mL / min, the volume percentage of mobile phase A remains 95%, the volume percentage of mobile phase B remains 0%, the volume percentage of mobile phase C remains 5%, and the volume percentage of mobile phase D remains 0%;

[0013] From 2.5 min to 2.8 min, the flow rate changes from 2 mL / min to 0.01 mL / min, the volume percentage of mobile phase A remains 95%, the volume percentage of mobile phase B remains 0%, the volume percentage of mobile phase C remains 5%, and the volume percentage of mobile phase D remains 0%;

[0014] From 2.8 min to 2.81 min, the flow rate changes from 0.01 mL / min to 1 mL / min, the volume percentage of mobile phase A changes from 95% to 0%, the volume percentage of mobile phase B changes from 0% to 95%, the volume percentage of mobile phase C changes from 5% to 0%, and the volume percentage of mobile phase D changes from 0% to 5%;

[0015] From 2.81 min to 5 min, keep the flow rate at 1 mL / min, the volume percentage of mobile phase A remains 0%, the volume percentage of mobile phase B changes from 95% to 0%, the volume percentage of mobile phase C remains 0%, and the volume percentage of mobile phase D changes from 5% to 100%;

[0016] From 5 min to 9 min, keep the flow rate at 1 mL / min, the volume percentage of mobile phase A remains 0%, the volume percentage of mobile phase B remains 0%, the volume percentage of mobile phase C remains 0%, and the volume percentage of mobile phase D remains 100%;

[0017] From 9 min to 9.01 min, the flow rate is maintained at 1 mL / min. The volume percentage of mobile phase A changes from 0% to 95%, the volume percentage of mobile phase B remains 0%, the volume percentage of mobile phase C changes from 0% to 5%, and the volume percentage of mobile phase D changes from 100% to 0%.

[0018] From 9.01 min to 10 min, the flow rate is maintained at 1 mL / min. The volume percentage of mobile phase A remains 95%, the volume percentage of mobile phase B remains 0%, the volume percentage of mobile phase C remains 5%, and the volume percentage of mobile phase D remains 0%.

[0019] The conditions of the liquid chromatography include:

[0020] The mobile phase includes mobile phase E and mobile phase F. Mobile phase E includes an aqueous solution of ammonium formate with a concentration of 5 mM to 25 mM and ammonia water accounting for 0.1% to 1% by mass of the ammonium formate aqueous solution. Mobile phase F is acetonitrile.

[0021] Gradient elution is adopted, and the program includes:

[0022] From 0 min to 10 min, the volume percentage of mobile phase E changes from 95% to 5%, and the volume percentage of mobile phase F changes from 5% to 95%.

[0023] From 10 min to 13 min, the volume percentage of mobile phase E changes from 5% to 95%, and the volume percentage of mobile phase F changes from 95% to 5%.

[0024] From 13 min to 13.01 min, the volume percentage of mobile phase E changes from 95% to 5%, and the volume percentage of mobile phase F changes from 5% to 95%.

[0025] From 13.01 min to 14 min, the volume percentage of mobile phase E remains 5%, and the volume percentage of mobile phase F remains 95%.

[0026] The conditions of the mass spectrometry include:

[0027] The ionization mode is ESI+ mode, the ion source temperature is 300 °C to 400 °C, and the spray voltage is 4000 V to 5000 V.

[0028] In one of the embodiments, the solid phase extraction column used for the online solid phase extraction is WAX online chromatographic column or its equivalent solid phase extraction column.

[0029] In one embodiment, at least two solid-phase extraction columns are used for the online solid-phase extraction. While one solid-phase extraction column is performing the online solid-phase extraction, the other is being regenerated and balanced. The two perform online solid-phase extraction alternately and deliver the sample to the liquid chromatography.

[0030] In one embodiment, the chromatographic column used in the liquid chromatography is a C18 column.

[0031] In one embodiment, the conditions of the liquid chromatography further include one or more of the following:

[0032] (1) The chromatographic column used is an ACQUITY UPLC BEH C18 column or its equivalent chromatographic column;

[0033] (2) The column temperature is 35°C to 45°C;

[0034] (3) The flow rate is 0.2 mL / min to 0.6 mL / min.

[0035] In one embodiment, the conditions of the mass spectrometry further include one or more of the following:

[0036] (1) The pressure of the first ion source gas is 40 psi to 60 psi;

[0037] (2) The pressure of the second ion source gas is 40 psi to 60 psi;

[0038] (3) The pressure of the curtain gas is 20 psi to 40 psi;

[0039] (4) The collision gas is nitrogen, and the pressure is 5 psi to 15 psi;

[0040] (5) The scanning mode is multiple reaction monitoring.

[0041] In one embodiment, calculating the content of perfluorinated compounds in the test solution by the internal standard method includes:

[0042] Adding the isotope internal standard of the perfluorinated compound to the test solution, performing online solid-phase extraction-liquid chromatography-mass spectrometry combined detection on the obtained mixed solution, collecting the peak areas of the perfluorinated compound and its isotope internal standard in the test solution, and calculating the content of the perfluorinated compound in the test solution.

[0043] In one embodiment, the perfluorinated compounds include one or more of perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluorooctylsulfonamide, perfluorobutanesulfonic acid, perfluoropentanesulfonic acid, perfluorohexanesulfonic acid, perfluoroheptanesulfonic acid, perfluorooctanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, N-methylperfluorooctylsulfonamidoglycine, N-ethyl-perfluorooctanesulfonamidoglycine, 4:2 fluorotelomer sulfonic acid, 6:2 fluorotelomer sulfonic acid, 8:2 fluorotelomer sulfonic acid, hexafluoropropylene oxide dimer acid, hexafluoropropylene oxide trimer acid, 6:2 chlorinated polyfluoroether sulfonic acid, and 8:2 chlorinated polyfluoroether sulfonic acid.

[0044] In one embodiment, the solid-liquid separation includes centrifugation and / or filtration.

[0045] In one embodiment, the filtration includes a first filtration using a 0.4 μm to 0.5 μm polyethersulfone membrane and a second filtration using a 0.2 μm to 0.3 μm polyethersulfone membrane.

[0046] The detection method for perfluorinated compounds in water provided by this application uses a fully automated online solid-phase extraction platform, combined with liquid chromatography and mass spectrometry, and reasonably designs the parameters of each step, providing a complete solution from sample pretreatment and purification to data acquisition and analysis, truly realizing the automation of the entire process of PFASs detection in the water environment. The operation is simple and fast, and the detection method has good selectivity, accuracy, and repeatability, and can be used for the accurate determination of PFASs in the water environment, providing technical support for the realization of high-throughput automatic detection of PFASs in the water environment.

[0047] Without limitation, the detection method for perfluorinated compounds in water has the following advantages:

[0048] (1) The pretreatment method is simple and the operation is easy: subsequent fully automated online SPE-LC-MS / MS determination can be carried out through simple steps such as filtration.

[0049] (2) High sensitivity: Only a small sample injection volume is required, trace substances can be enriched to increase the concentration of the analyte, and a lower environmental detection concentration can be obtained by injecting a larger sample volume through multiple sample injections.

[0050] (3) High recovery rate: The recovery rate of the target substance is high, meeting the detection requirements of PFASs in the water environment.

[0051] (4) High working efficiency: It can achieve an uninterrupted 24-hour operation sequence, superimposing the time for sample pretreatment and online solid-phase extraction with the LC-MS / MS running time. Automatically completing the pretreatment and analysis process for a single sample only takes 14 minutes, saving time and increasing the sample throughput;

[0052] (5) Low usage cost: The online SPE column can be reused more than 300 times, and the solvent amount required for each sample is reduced, reducing the environmental pollution caused by waste liquid;

[0053] (6) Small system error: The sample can be well separated from interfering impurities through the online SPE system, and the residue amount is low, avoiding cross-contamination between samples and having good reproducibility;

[0054] (7) High automation level: The online SPE system, liquid chromatography, and mass spectrometry system can be controlled by the same control software, and the flow path switching valve can be coordinated through the software; the flow path corresponding to the sample to be analyzed is switched to the mass spectrometry for data acquisition in sequence, improving the sample analysis efficiency. Description of the Drawings

[0055] Figure 1 It is a schematic flow diagram of the analysis procedure of online SPE in an example of this application;

[0056] Figure 2 It is the total ion chromatogram of the quantitative and qualitative ions of 29 PFASs and their internal standards in an example of this application. Detailed Embodiments

[0057] The following further elaborates on the detection method of perfluorinated compounds in water of this application in combination with specific embodiments. This application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of this application more thorough and comprehensive.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0059] The optional scope of the terms "and / or", "or / and", and "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items.

[0060] Herein, "one or more" refers to any one, any two, or any two or more of the listed items.

[0061] In this application, terms such as "first" and "second" are only for non-exhaustive listing and description purposes and should be understood not to constitute a closed limitation on quantity.

[0062] In this application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open-ended technical solutions containing the listed features.

[0063] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0064] In this application, for the percentage content involved, unless otherwise specified, for solid-liquid mixtures and solid-solid mixtures, it refers to the mass percentage, and for liquid-liquid mixtures, it refers to the volume percentage.

[0065] In this application, for the percentage concentration involved, unless otherwise specified, it all refers to the final concentration. The final concentration refers to the proportion of the added component in the system after adding this component.

[0066] In this application, for the temperature parameter, unless otherwise specifically limited, it allows both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0067] In this application, room temperature generally refers to 4°C to 30°C, and preferably refers to 20 ± 5°C.

[0068] In some examples of this application, a method for detecting perfluorinated compounds in water is provided, including the following steps:

[0069] Perform solid-liquid separation on the water sample to prepare a test solution;

[0070] Perform on-line solid-phase extraction-high performance liquid chromatography-mass spectrometry (SPE-HPLC-MS) detection on the test solution, and calculate the content of perfluorinated compounds in the test solution by the internal standard method;

[0071] Among them, the conditions for the on-line solid-phase extraction include:

[0072] The mobile phase includes mobile phase A, mobile phase B, mobile phase C and mobile phase D. Mobile phase A is an aqueous solution of ammonium acetate with a concentration of 1 mM to 5 mM. Mobile phase B is methanol. Mobile phase C is acetonitrile. Mobile phase D is a mixture of methanol and acetonitrile with a volume ratio of 1:(0.5 - 1.5);

[0073] Gradient elution is adopted, and the program includes:

[0074] From 0 min to 2.5 min, the flow rate is maintained at 2 mL / min. The volume percentage of mobile phase A is maintained at 95%, the volume percentage of mobile phase B is maintained at 0%, the volume percentage of mobile phase C is maintained at 5%, and the volume percentage of mobile phase D is maintained at 0%;

[0075] From 2.5 min to 2.8 min, the flow rate changes from 2 mL / min to 0.01 mL / min. The volume percentage of mobile phase A is maintained at 95%, the volume percentage of mobile phase B is maintained at 0%, the volume percentage of mobile phase C is maintained at 5%, and the volume percentage of mobile phase D is maintained at 0%;

[0076] From 2.8 min to 2.81 min, the flow rate changes from 0.01 mL / min to 1 mL / min. The volume percentage of mobile phase A changes from 95% to 0%, the volume percentage of mobile phase B changes from 0% to 95%, the volume percentage of mobile phase C changes from 5% to 0%, and the volume percentage of mobile phase D changes from 0% to 5%;

[0077] From 2.81 min to 5 min, the flow rate is maintained at 1 mL / min. The volume percentage of mobile phase A is maintained at 0%, the volume percentage of mobile phase B changes from 95% to 0%, the volume percentage of mobile phase C is maintained at 0%, and the volume percentage of mobile phase D changes from 5% to 100%;

[0078] From 5 min to 9 min, the flow rate is maintained at 1 mL / min. The volume percentage of mobile phase A is maintained at 0%, the volume percentage of mobile phase B is maintained at 0%, the volume percentage of mobile phase C is maintained at 0%, and the volume percentage of mobile phase D is maintained at 100%;

[0079] From 9 min to 9.01 min, the flow rate is maintained at 1 mL / min. The volume percentage of mobile phase A changes from 0% to 95%, the volume percentage of mobile phase B is maintained at 0%, the volume percentage of mobile phase C changes from 0% to 5%, and the volume percentage of mobile phase D changes from 100% to 0%;

[0080] From 9.01 min to 10 min, the flow rate is maintained at 1 mL / min, the volume percentage of mobile phase A is maintained at 95%, the volume percentage of mobile phase B is maintained at 0%, the volume percentage of mobile phase C is maintained at 5%, and the volume percentage of mobile phase D is maintained at 0%.

[0081] The conditions of the liquid chromatography include:

[0082] The mobile phase includes mobile phase E and mobile phase F. Mobile phase E includes an aqueous solution of ammonium formate with a concentration of 5 mM to 25 mM, and ammonia water accounting for 0.1% to 1% by mass of the aqueous ammonium formate solution. Mobile phase F is acetonitrile;

[0083] Gradient elution is adopted, and the program includes:

[0084] From 0 min to 10 min, the volume percentage of mobile phase E changes from 95% to 5%, and the volume percentage of mobile phase F changes from 5% to 95%;

[0085] From 10 min to 13 min, the volume percentage of mobile phase E changes from 5% to 95%, and the volume percentage of mobile phase F changes from 95% to 5%;

[0086] From 13 min to 13.01 min, the volume percentage of mobile phase E changes from 95% to 5%, and the volume percentage of mobile phase F changes from 5% to 95%;

[0087] From 13.01 min to 14 min, the volume percentage of mobile phase E is maintained at 5%, and the volume percentage of mobile phase F is maintained at 95%;

[0088] The conditions of the mass spectrometry include:

[0089] The ionization mode is ESI+ mode, the ion source temperature is 300 °C to 400 °C, and the spray voltage is 4000 V to 5000 V.

[0090] Specifically, the concentration of the aqueous ammonium acetate solution in mobile phase A includes but is not limited to: 1 mM, 1.5 mM, 2 mM, 2.5 mM, 3 mM, 3.5 mM, 4 mM, 4.5 mM, 5 mM, or the range between any two of the foregoing.

[0091] Specifically, the concentration of the aqueous ammonium formate solution in mobile phase E includes but is not limited to: 5 mM, 8 mM, 10 mM, 12 mM, 15 mM, 18 mM, 20 mM, 22 mM, 25 mM, or the range between any two of the foregoing.

[0092] Specifically, the mass percentage of ammonia water in mobile phase E includes but is not limited to: 0.1%, 0.3%, 0.5%, 0.8%, 1%, or the range between any two of the foregoing.

[0093] Specifically, the ion source temperature in the conditions of the mass spectrometry includes but is not limited to: 300 °C, 330 °C, 350 °C, 370 °C, 400 °C, or the range between any two of the foregoing.

[0094] Specifically, the spray voltage in the conditions of the mass spectrometry includes but is not limited to: 4000 V, 4300 V, 4500 V, 4700 V, 5000 V, or the range between any two of the foregoing.

[0095] In some of the examples, the solid phase extraction column used for the online solid phase extraction is a WAX online chromatographic column or its equivalent solid phase extraction column.

[0096] In some of the examples, the online solid phase extraction uses at least two solid phase extraction columns. During the process of online solid phase extraction of one solid phase extraction column, the other is regenerated and balanced, and the two alternate for online solid phase extraction and deliver the sample to the liquid chromatography.

[0097] Without limitation, the analysis procedure of the online SPE is completed through the following three steps, as Figure 1 shown:

[0098] (1) The sampling needle injects the test solution into the quantitative loop, the six-way valve switches positions, and the quaternary low-pressure pump brings the mixed working solution in the quantitative loop into the online SPE column, and the online SPE column enriches and purifies the mixed working solution;

[0099] (2) After the sample completely passes through the online SPE column, the ten-way valve switches positions to connect the binary high-pressure pump and the online SPE column. The binary high-pressure pump back-flushes the target compound on the online SPE column into the analytical column and then into the mass spectrometry for detection. At the same time, the quaternary low-pressure pump is connected to the other online SPE column and regenerates and balances it;

[0100] (3) Subsequently, the two online SPE columns alternate for sample loading, elution, regeneration, and balance.

[0101] Without limitation, the liquid chromatography and the mass spectrometry are performed using a triple quadrupole liquid chromatography-mass spectrometry instrument.

[0102] In some of the examples, the chromatographic column used for the liquid chromatography is a C18 column. Further, the chromatographic column used is an ACQUITY UPLC BEH C18 column or its equivalent chromatographic column.

[0103] In some of the examples, the column temperature used for the liquid chromatography is 35 °C to 45 °C. Specifically, the column temperature includes but is not limited to: 35 °C, 37 °C, 40 °C, 42 °C, 45 °C, or the range between any two of the foregoing.

[0104] In some of these examples, the flow rate used in the liquid chromatography is 0.2 mL / min to 0.6 mL / min. The flow rate includes but is not limited to: 0.2 mL / min, 0.3 mL / min, 0.4 mL / min, 0.5 mL / min, 0.6 mL / min, or the range between any two of the foregoing.

[0105] In some of these examples, the pressure of the first ion source gas used in the mass spectrometry is 40 psi to 60 psi. Specifically, the pressure of the first ion source gas includes but is not limited to: 40 psi, 45 psi, 50 psi, 55 psi, 60 psi, or the range between any two of the foregoing.

[0106] In some of these examples, the pressure of the second ion source gas used in the mass spectrometry is 40 psi to 60 psi. Specifically, the pressure of the second ion source gas includes but is not limited to: 40 psi, 45 psi, 50 psi, 55 psi, 60 psi, or the range between any two of the foregoing.

[0107] In some of these examples, the pressure of the curtain gas used in the mass spectrometry is 20 psi to 40 psi. Specifically, the pressure of the curtain gas includes but is not limited to: 20 psi, 25 psi, 30 psi, 35 psi, 40 psi, or the range between any two of the foregoing.

[0108] In some of these examples, the collision gas used in the mass spectrometry is nitrogen, and the pressure is 5 psi to 15 psi. Specifically, the pressure includes but is not limited to: 5 psi, 7 psi, 9 psi, 10 psi, 11 psi, 13 psi, 15 psi, or the range between any two of the foregoing.

[0109] In some of these examples, the scanning mode used in the mass spectrometry is multiple reaction monitoring.

[0110] In some of these examples, calculating the content of perfluorinated compounds in the test solution by the internal standard method includes:

[0111] Adding an isotope internal standard of the perfluorinated compound to the test solution, performing on-line solid phase extraction-liquid chromatography-mass spectrometry combined detection on the obtained mixed solution, collecting the peak areas of the perfluorinated compound and its isotope internal standard in the test solution, and calculating the content of the perfluorinated compound in the test solution.

[0112] In some of these examples, the perfluorinated compounds include one or more of perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluorooctanesulfonamide, perfluorobutanesulfonic acid, perfluoropentanesulfonic acid, perfluorohexanesulfonic acid, perfluoroheptanesulfonic acid, perfluorooctanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, N-methylperfluorooctanesulfonamido glycine, N-ethyl-perfluorooctanesulfonamido glycine, 4:2 fluorotelomer sulfonic acid, 6:2 fluorotelomer sulfonic acid, 8:2 fluorotelomer sulfonic acid, hexafluoropropylene oxide dimer acid, hexafluoropropylene oxide trimer acid, 6:2 chlorinated polyfluoroether sulfonic acid, and 8:2 chlorinated polyfluoroether sulfonic acid.

[0113] In some of these examples, the solid-liquid separation includes centrifugation and / or filtration.

[0114] In some of these examples, the filtration includes a first filtration using a 0.4 μm - 0.5 μm polyethersulfone membrane and a second filtration using a 0.2 μm - 0.3 μm polyethersulfone membrane.

[0115] For the experimental parameters not specified in the following specific examples, priority should be given to the guidance provided in this application document. It is also possible to refer to the experimental manuals in this field or other experimental methods known in this field, or to the experimental conditions recommended by the manufacturers.

[0116] The raw materials and reagents involved in the following specific examples can be obtained commercially, or those skilled in the art can prepare them according to known means. Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0117] For the quantitative tests in the following specific examples, three repeated experiments are set up, and the results are averaged.

[0118] Example 1

[0119] This example is for the determination of the contents of 29 perfluorinated compounds in surface water.

[0120] 1. Sample pretreatment:

[0121] First, a sample of actual surface water collected from a specific monitoring site is pretreated to obtain a pretreated sample. The pretreatment process is as follows: The surface water sample is shaken well at room temperature, filtered using a 0.45 μm polyethersulfone membrane, the filtrate is collected and transferred to a 50 mL capped centrifuge tube, and then secondary filtration is carried out using a 0.22 μm polyethersulfone membrane. The filtrate is collected and 20 mL is transferred to a 20 mL injection vial. Two parallel samples are taken for each sample.

[0122] Then, prepare a mixed working solution containing 29 perfluorinated compounds and their stable isotope internal standards (containing 29 standard substances at 50 ng / L and a mixed internal standard at 100 ng / L) for purification, separation, and detection by online SPE-LC-MS / MS.

[0123] 2. Process of online SPE extraction:

[0124] The online SPE extraction process is based on the ZD InLab OnlineSPE device. The SPE column is preferably WAX Online Column (2.1 mm * 20 mm, 30 μm), purchased from Waters. The selected injection needle volume is 10000 μL, the quantitative loop volume is 5000 μL, and the sample loading volume is 5000 μL. The elution mode of online SPE is gradient elution, and the mobile phase consists of four-component mobile phases A, B, C, and D, namely A: 2 mM ammonium acetate aqueous solution, B: methanol, C: acetonitrile, D: methanol: acetonitrile (1:1, v:v), as shown in Table 1.

[0125] Table 1 Online SPE mobile phase gradient

[0126]

[0127] Meanwhile, the analysis program of online SPE is completed through the following three steps, as Figure 1 shown:

[0128] (1) The injection needle injects 5 mL of the mixed working solution into the quantitative loop. The six-port valve switches positions, and the four-component low-pressure pump transports the mixed working solution in the quantitative loop into the online SPE column, and the online SPE column enriches and purifies the mixed working solution.

[0129] (2) After the water sample completely passes through the online SPE column, the ten-port valve switches positions to connect the binary high-pressure pump to the online SPE column. The binary high-pressure pump back-flushes the target compounds on the online SPE column into the analytical column and then into the mass spectrometer for detection. At the same time, the four-component low-pressure pump is connected to another online SPE column and regenerates and equilibrates it.

[0130] (3) Subsequently, the two online SPE columns alternate for sample loading, elution, regeneration, and equilibration.

[0131] 4. Process of LC-MS / MS separation and analysis:

[0132] The LC separation process is based on the Shimadzu LC-40D XS analytical liquid chromatography, and other equivalent liquid chromatographs can be substituted. The analytical column is an ACQUITY UPLC BEH C18 column (2.1 mm × 100 mm, 2.5 μm), purchased from Waters. The elution mode of LC is gradient elution. The mobile phase consists of E: 20 mM ammonium formate aqueous solution + 1% ammonia water, and F: acetonitrile. The gradient conditions are shown in Table 2, and the column temperature is set at 40 °C.

[0133] Table 2 Mobile Phase Gradient of Analytical Liquid Chromatography

[0134]

[0135] Meanwhile, the MS analysis and detection process is based on the AB SCIEX 5500+ (equipped with ESI source) mass spectrometer, and other equivalent mass spectrometers can be substituted. The specific mass spectrometry conditions are as follows: ionization mode: ESI+ mode; nebulizing gas (Gas1) of ion source: 50 psi; auxiliary heating gas (Gas2) of ion source: 50 psi; curtain gas: 30 psi; collision gas (nitrogen): 9 psi; source temperature: 350 °C; spray voltage: 4500 V; scanning mode: multiple reaction monitoring (MRM).

[0136] Prepare standard products of 29 perfluorinated compounds and their isotope internal standards at a concentration of 10 μg / L to determine their parent ions and daughter ions, and select the ion pairs with relatively higher responses as quantitative ions. Since the cone voltage (DP) is related to the sensitivity of the parent ion, and the collision energy (CE) is related to the abundance of the parent ion fragmenting into daughter ions, the corresponding DP and CE need to be optimized. The MRM parameters of the 29 perfluorinated compounds and their isotope internal standards after optimization are shown in Table 3, and their total ion chromatogram is as Figure 2 shown.

[0137] Table 3 MRM Method of 29 PFASs and Their Internal Standards

[0138]

[0139]

[0140]

[0141]

[0142]

[0143] Note: PFASs-1 is the quantitative ion, and PFASs-2 is the qualitative ion.

[0144] 4. Examine the methodological parameters of the detection method

[0145] Prepare a series of standard solutions with gradient concentrations of 0.5, 1, 5, 10, 50, and 100 μg / L respectively, add an equal amount of 50 μg / L isotope internal standard to each, and perform the detection according to the steps. The results show that the ratio of the peak areas of 29 perfluorinated compounds to their corresponding internal standards and the sample concentrations show a good linear relationship, and the correlation coefficients (R 2 ) are all above 0.99. The linear equations are shown in Table 4.

[0146] Table 4 Standard curves of 29 PFASs

[0147]

[0148]

[0149] As shown in Table 5, for the spiked recoveries of pure water samples (n = 6), the recoveries at 5 ng / L and 50 ng / L are in the range of 65% - 120%, the precisions are all less than 20%, the detection limits are 0.001 - 0.165 ng / L, and the quantification limits are 0.03 - 0.549 ng / L; as shown in Table 6, for the spiked recoveries of actual surface water samples (n = 6), the recoveries at 5 ng / L and 50 ng / L are in the range of 70% - 120%, the precisions are all less than 15%, the detection limits are 0.017 - 0.159 ng / L, and the quantification limits are 0.085 - 0.779 ng / L. The samples have high recoveries, low detection limits, accurate detection results, and at the same time save time costs, and can be used to monitor the situation of PFASs in actual water samples.

[0150] Table 5 Detection limits, quantification limits, recoveries, and precisions of 29 PFASs in pure water

[0151]

[0152]

[0153] Note: The recoveries and precisions are calculated by detecting 6 parallel samples at 5 ng / L and 50 ng / L respectively.

[0154] Table 6 Detection limits, quantification limits, recoveries, and precisions of 29 PFASs in surface water

[0155]

[0156]

[0157]

[0158] Note: The recoveries and precisions are calculated by detecting 6 parallel samples at 5 ng / L and 50 ng / L respectively. 5. The detection results of actual surface water samples are shown in Table 7:

[0159] Table 7 Detected Concentrations of Perfluorinated Compounds in Surface Water

[0160]

[0161]

[0162] Note: X1 to X6 are 6 actual samples of surface water randomly selected for inspection. When the target compound is not detected or the detected concentration is lower than the detection limit, it is shown as "<LOD>".

[0163] In summary, when using the method of the embodiment to detect PFASs in water, it has a high degree of automation, saving the pretreatment and analysis time; at the same time, the cost of using the online solid-phase extraction column is relatively low and it can be reused; in addition, it also has the advantages of high experimental accuracy and precision, and low detection limit, etc., and can realize the rapid analysis and determination of PFASs in environmental water samples.

[0164] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0165] The above-described embodiments only represent several implementation manners of the present application, which are convenient for understanding the technical solutions of the present application specifically and in detail, but should not be construed as limiting the scope of patent protection of the application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided by the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A detection method for perfluorinated compounds in water, characterized in that, It includes the following steps: Perform solid-liquid separation on the water sample to prepare a test solution; Perform on-line solid-phase extraction-high performance liquid chromatography-mass spectrometry (SPE-HPLC-MS) detection on the test solution, and calculate the content of perfluorinated compounds in the test solution by the internal standard method; Among them, the conditions for the on-line solid-phase extraction include: The mobile phase includes mobile phase A, mobile phase B, mobile phase C, and mobile phase D. Mobile phase A is an aqueous ammonium acetate solution with a concentration of 1 mM to 5 mM, mobile phase B is methanol, mobile phase C is acetonitrile, and mobile phase D is a mixture of methanol and acetonitrile with a volume ratio of 1:(0.5 to 1.5); Gradient elution is adopted, and the program includes: From 0 min to 2.5 min, keep the flow rate at 2 mL / min, the volume percentage of mobile phase A remains at 95%, the volume percentage of mobile phase B remains at 0%, the volume percentage of mobile phase C remains at 5%, and the volume percentage of mobile phase D remains at 0%; From 2.5 min to 2.8 min, the flow rate changes from 2 mL / min to 0.01 mL / min, the volume percentage of mobile phase A remains at 95%, the volume percentage of mobile phase B remains at 0%, the volume percentage of mobile phase C remains at 5%, and the volume percentage of mobile phase D remains at 0%; From 2.8 min to 2.81 min, the flow rate changes from 0.01 mL / min to 1 mL / min, the volume percentage of mobile phase A changes from 95% to 0%, the volume percentage of mobile phase B changes from 0% to 95%, the volume percentage of mobile phase C changes from 5% to 0%, and the volume percentage of mobile phase D changes from 0% to 5%; From 2.81 min to 5 min, keep the flow rate at 1 mL / min, the volume percentage of mobile phase A remains at 0%, the volume percentage of mobile phase B changes from 95% to 0%, the volume percentage of mobile phase C remains at 0%, and the volume percentage of mobile phase D changes from 5% to 100%; From 5 min to 9 min, keep the flow rate at 1 mL / min, the volume percentage of mobile phase A remains at 0%, the volume percentage of mobile phase B remains at 0%, the volume percentage of mobile phase C remains at 0%, and the volume percentage of mobile phase D remains at 100%; From 9 min to 9.01 min, keep the flow rate at 1 mL / min, the volume percentage of mobile phase A changes from 0% to 95%, the volume percentage of mobile phase B remains at 0%, the volume percentage of mobile phase C changes from 0% to 5%, and the volume percentage of mobile phase D changes from 100% to 0%; From 9.01 min to 10 min, keep the flow rate at 1 mL / min, the volume percentage of mobile phase A remains at 95%, the volume percentage of mobile phase B remains at 0%, the volume percentage of mobile phase C remains at 5%, and the volume percentage of mobile phase D remains at 0%; The conditions for the high performance liquid chromatography include: The mobile phase includes mobile phase E and mobile phase F. Mobile phase E includes an aqueous ammonium formate solution with a concentration of 5 mM to 25 mM and ammonia water accounting for 0.1% to 1% of the mass of the aqueous ammonium formate solution, and mobile phase F is acetonitrile; Gradient elution is adopted, and the program includes: From 0 min to 10 min, the volume percentage of mobile phase E changes from 95% to 5%, and the volume percentage of mobile phase F changes from 5% to 95%. From 10 min to 13 min, the volume percentage of mobile phase E changes from 5% to 95%, and the volume percentage of mobile phase F changes from 95% to 5%. From 13 min to 13.01 min, the volume percentage of mobile phase E changes from 95% to 5%, and the volume percentage of mobile phase F changes from 5% to 95%. From 13.01 min to 14 min, the volume percentage of mobile phase E remains 5%, and the volume percentage of mobile phase F remains 95%. The conditions of the mass spectrometry include: The ionization mode is ESI+ mode, the ion source temperature is 300 °C to 400 °C, and the spray voltage is 4000 V to 5000 V.

2. The detection method of perfluorinated compounds in water according to claim 1, wherein The solid-phase extraction column used in the on-line solid-phase extraction is a WAX on-line chromatographic column or its equivalent solid-phase extraction column.

3. The detection method of perfluorinated compounds in water according to claim 1, wherein The online solid-phase extraction uses at least two solid-phase extraction columns. During the online solid-phase extraction process of one solid-phase extraction column, the other is regenerated and balanced, and the two alternate for online solid-phase extraction and deliver the sample to the liquid chromatography.

4. The detection method of perfluorinated compounds in water according to claim 1, wherein, The chromatographic column used in the liquid chromatography is a C18 column.

5. The detection method of perfluorinated compounds in water according to claim 1, wherein The conditions of the liquid chromatography further include one or more of the following: (1) The chromatographic column used is an ACQUITY UPLC BEH C18 column or its equivalent chromatographic column; (2) The column temperature is 35 °C to 45 °C; (3) The flow rate is 0.2 mL / min to 0.6 mL / min.

6. The detection method of perfluorinated compounds in water according to claim 1, wherein The conditions of the mass spectrometry further include one or more of the following: (1) The pressure of the first ion source gas is 40 psi to 60 psi; (2) The pressure of the second ion source gas is 40 psi to 60 psi; (3) The pressure of the curtain gas is 20 psi to 40 psi; (4) The collision gas is nitrogen, and the pressure is 5 psi to 15 psi; (5) The scanning mode is multiple reaction monitoring.

7. The detection method of perfluorinated compounds in water according to any one of claims 1 to 6, characterized in that, Calculating the content of perfluorinated compounds in the test solution by the internal standard method includes: Adding the isotope internal standard of the perfluorinated compound to the test solution, performing online solid-phase extraction-liquid chromatography-mass spectrometry combined detection on the obtained mixed solution, collecting the peak areas of the perfluorinated compound and its isotope internal standard in the test solution, and calculating the content of the perfluorinated compound in the test solution.

8. The detection method of perfluorinated compounds in water according to any one of claims 1 to 6, characterized in that The perfluorinated compounds include one or more of perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluorooctyl sulfonamide, perfluorobutane sulfonic acid, perfluoropentane sulfonic acid, perfluorohexane sulfonic acid, perfluoroheptane sulfonic acid, perfluorooctane sulfonic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, perfluorododecane sulfonic acid, N-methyl perfluorooctyl sulfonamido glycine, N-ethyl-perfluorooctane sulfonamido glycine, 4:2 fluorotelomer sulfonic acid, 6:2 fluorotelomer sulfonic acid, 8:2 fluorotelomer sulfonic acid, hexafluoropropylene oxide dimer acid, hexafluoropropylene oxide trimer acid, 6:2 chlorinated polyfluoroether sulfonic acid, and 8:2 chlorinated polyfluoroether sulfonic acid.

9. The detection method of perfluorinated compounds in water according to any one of claims 1 to 6, characterized in that, Solid-liquid separation includes centrifugation and / or filtration.

10. The detection method of perfluorinated compounds in water according to claim 9, wherein The filtration includes a first filtration using a 0.4 μm to 0.5 μm polyethersulfone filter membrane and a second filtration using a 0.2 μm to 0.3 μm polyethersulfone filter membrane.

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