Method for detecting perfluoroalkane

Abstract

The invention discloses a method for detecting perfluoroalkane, and relates to the technical field of perfluoroalkane detection, water free radical cationic clusters are generated by ionizing water vapor in a detection device, the formed water free radical cationic clusters react with C-F bonds in perfluoroalkane to generate corresponding products, and the perfluoroalkane is detected. Finally, characteristic ion fragments capable of recognizing the perfluoroalkane are obtained through a tandem mass spectrometer, so that identification and analysis of the perfluoroalkane are achieved, and a theoretical basis is provided for development of a perfluoroalkane degradation technology.

Description

Technical Field

[0001] The present invention relates to the technical field of alkane detection, in particular to a method for detecting perfluoroalkane. Background Art

[0002] Perfluoroalkanes (PFAS) are a class of synthetic organic fluoride compounds in which hydrogen atoms are replaced by fluorine. They are extremely chemically stable (with a C-H bond energy of approximately 485 kJ / mol) and possess water and oil repellency. Consequently, they are widely used in industrial and consumer products such as non-stick cookware, waterproof coatings, firefighting foam, and food packaging. Their unique physical and chemical properties make them "permanent chemicals," difficult to degrade through natural processes and prone to long-term accumulation in the environment. Their widespread use poses persistent pollution and health risks, making the detection of PFAS particularly important.

[0003] In order to quickly detect perfluoroalkanes, relevant technicians have developed many different methods. For example, liquid chromatography (LC) is used to separate PFAS mixtures in complex samples, and then tandem mass spectrometry (MS / MS) is used for qualitative and quantitative analysis to identify different PFAS compounds based on characteristic fragment ion patterns; volatile or semi-volatile PFAS are separated by gas chromatography, and their mass-to-charge ratio (m / z) is detected by mass spectrometry for qualitative and quantitative analysis, which is suitable for small molecule PFAS with low boiling points; PFAS in the sample is enriched by solid phase extraction (SPE), and then analyzed by LC-MS / MS, which significantly improves the detection sensitivity and accuracy and is suitable for low-concentration environmental water samples.

[0004] However, these methods currently have some shortcomings. For example, in liquid chromatography-tandem mass spectrometry (LC-MS / MS), other coexisting substances in complex samples may inhibit or enhance the signal of the target PFAS, and it needs to rely on isotope internal standard correction. In addition, the high-precision mass spectrometer and maintenance costs limit its popularity in small laboratories; gas chromatography-mass spectrometry (GC-MS) can only detect PFAS with high volatility and is not sensitive enough to highly polar or non-volatile PFAS (such as sulfonic acids); solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS / MS), different SPE columns have large differences in retention efficiency for PFAS, and the adsorbent type (such as WAX, C18) needs to be optimized according to the target compound, and its versatility is low. Summary of the Invention

[0005] The present invention aims to provide a method for detecting perfluoroalkanes (PFAs). This method utilizes the interaction between water radical cations and PFAs, focusing on the localized breakage and oxidative cleavage of C-F bonds, thereby enabling the identification of PFAs. Although the reaction efficiency is relatively low, the mechanism provides a theoretical basis for the development of PFA degradation technologies.

[0006] The present invention discloses a method for detecting perfluoroalkanes. The method comprises the following steps: ionizing water vapor in a detection device to generate water radical cation clusters; the formed water radical cation clusters react with the C-F bonds in the perfluoroalkanes to generate corresponding products; and finally, a tandem mass spectrometer is used to obtain characteristic ion fragments that can identify the perfluoroalkanes, thereby realizing the identification and analysis of the perfluoroalkanes.

[0007] Preferably, the detection device comprises an ionization channel, a sample channel and a mass spectrometer, wherein the ionization channel is used to ionize water to obtain water radical cation clusters;

[0008] The sample channel is used to transport perfluoroalkane so that it can react with water radical cation clusters;

[0009] The mass spectrometer is used to detect and analyze the reaction products.

[0010] Preferably, the ionization channel comprises a discharge needle connected to a high voltage source, and a capillary is coaxially sleeved on the discharge needle.

[0011] Preferably, the sample channel includes a sample storage device and a heating device, and the heating device can heat the sample storage device.

[0012] Preferably, the method specifically includes the following steps:

[0013] Inert gas is introduced into the ionization channel to form an inert gas with water vapor. At the same time, inert gas is introduced into the sample channel and the sample storage device, and a heating device is activated to heat the sample in the sample storage device to a boiling point, so that the stored sample is introduced into the front end of the mass spectrometer inlet in the form of gas;

[0014] Applying high voltage to the tip of the discharge needle through the high voltage source to ionize water vapor through the ionization channel to generate water radical cation clusters;

[0015] The formed water radical cation clusters interact with the CF bonds of the sample molecules in the sample channel in three-dimensional space, causing the molecular electron cloud to undergo predictable changes, thereby generating detectable products;

[0016] The formed product is detected by the mass spectrometer and analyzed by the mass spectrometer to obtain ion fragments that can identify perfluoroalkane, thereby achieving identification analysis of perfluoroalkane.

[0017] Furthermore, the monitoring conditions of the mass spectrometer were as follows: the temperature in the ion transfer capillary was maintained at 150 °C, the capillary voltage was 1.0 V, the lens voltage was 30.0 V, and the pressure vacuum in the ion trap was set to 1×10 -5 torr.

[0018] Furthermore, the inert gas is argon.

[0019] Furthermore, the high voltage is 2-4 kV.

[0020] The device and method for detecting perfluoroalkanes proposed in the present invention have the following beneficial effects:

[0021] When air humidity is low, water vapor can be introduced using a carrier gas. When air humidity is high, no carrier gas is required, and the water vapor in the air can be directly ionized, making it convenient to use. By regulating the electric field strength, the ionized water vapor produces a large number of water radical cation clusters. The formed water radical cation clusters react with the C-F bonds in perfluoroalkanes to form corresponding products. Finally, characteristic ion fragments that can identify perfluoroalkanes are obtained through tandem mass spectrometry. The entire device is simple, has low modification costs, uses water as a carrier, and is green and pollution-free. The reaction time between the water radical cation clusters and perfluoroalkanes is fast, enabling high-throughput analysis, which is of great significance for the detection and degradation of perfluoroalkanes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0023] Figure 1 1 is a schematic structural diagram of a device for detecting perfluoroalkanes according to an embodiment of the present invention;

[0024] Figure 2 This is the mass spectrum of water radical cations prepared by regulating the energy-charge transfer law in Example 1 (the second carrier gas channel is closed);

[0025] Figure 3 and Figure 4 The primary and secondary mass spectra are respectively the product (m / z 435) and the addition product formed by the interaction between the water radical cation formed in the first carrier gas channel and the sample perfluorooctane in the second carrier gas channel.

[0026] Figure 5 and Figure 6 The primary and secondary mass spectra are respectively the product (m / z 385) and the addition product formed by the interaction between the water radical cation formed in the first carrier gas channel and the sample perfluoroheptane in the second carrier gas channel.

[0027] Figure 7 and Figure 8 The primary and secondary mass spectra are respectively the product (m / z 335) and the addition product formed by the interaction between the water radical cation formed in the first carrier gas channel and the sample perfluorohexane in the second carrier gas channel. DETAILED DESCRIPTION

[0028] To make the objects, features, and advantages of the present invention more readily apparent, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0029] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be an element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may also be an element centered thereon. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0030] In the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," and the like should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0031] See also Figure 1 , a detection device proposed in one embodiment of the present invention includes an ionization channel, a sample channel and a mass spectrometer 13;

[0032] The ionization channel includes a discharge needle 1 , a first pipeline 2 , a first carrier gas channel 3 , a high-voltage source, a first capillary 5 , and a water storage device 6 .

[0033] The water storage device 6 stores water, and the first carrier gas channel 3 is inserted into the water storage device 6. The first carrier gas channel 3 is used to supply an inert gas, such as argon, to the water storage device 6. The purpose of providing the inert gas in the ionization channel is to remove the water and prevent interference from other impurities when the tip of the discharge needle 1 ionizes the water.

[0034] One end of the first pipeline 2 is inserted into the water storage device 6, and the other end of the first pipeline 2 is connected to the first capillary 5 via a first two-way valve. The discharge needle 1 is disposed in the first capillary 5. The high-voltage source is connected to the discharge needle and is configured to provide a high voltage to the discharge needle 1, for example, 2.5 kV, to ionize the water vapor and generate water radical cation clusters through corona discharge. Specifically, the discharge needle 1 is a conical stainless steel discharge needle.

[0035] The first capillary 5 has two functions: (1) wrapping the discharge needle 1 to prevent the entire discharge needle 1 from being exposed to the outside; and (2) introducing a neutral water flow so that the water flow can fully contact the discharge needle 1.

[0036] The sample channel includes a second pipeline 8 , a second carrier gas channel 9 , a sample storage device 10 , and a second capillary tube 12 .

[0037] The sample storage device 10 stores the sample to be tested, and the second carrier gas channel 9 is inserted into the sample storage device 10. The second carrier gas channel 9 is used to provide inert gas to the sample storage device 10, thereby introducing the sample into the front end of the inlet of the mass spectrometer 13 in the form of neutral gas.

[0038] One end of the second pipeline 8 is inserted into the sample storage device 10, and the other end of the second pipeline 8 is connected to the second capillary tube 12 via a second two-way valve. At the same time, a heating pot 11 is required to heat the sample storage device 10.

[0039] The end of the first capillary 5 away from the first pipeline 2 and the end of the second capillary 12 away from the second pipeline 8 are both located at the front end of the inlet of the mass spectrometer 13, so that the water radical cation clusters formed in the ionization channel and the sample in the form of neutral gas can converge at the front end of the inlet of the mass spectrometer 13.

[0040] Preferably, the ionization channel further includes a first flow control valve 7 , which is provided on the first carrier gas channel 3 and is used to control the flow of gas in the ionization channel.

[0041] also, Figure 1 Where a is the distance between the ionization channel and the sample channel and the mass spectrometer; b is the distance between the ionization channel and the sample channel; α is the angle between the ionization channel and the sample channel, respectively, and the mass spectrometer; and β is the angle between the ionization channel and the sample channel. These four parameters all affect ionization efficiency and can be adjusted in practice to achieve a higher target signal.

[0042] Based on the above device, a method for detecting perfluoroalkanes includes:

[0043] Inert gas is introduced into the water storage device 6 through the first carrier gas channel 3 to form an inert gas containing water vapor. At the same time, inert gas is introduced into the sample storage device 10 through the second carrier gas channel 9 to introduce the sample stored in the sample storage device 10 into the front end of the inlet of the mass spectrometer 13 in the form of gas.

[0044] Applying a high voltage of 2-4 kV to the tip of the discharge needle 1 through the high voltage source 4, introducing moist water vapor into the tip of the discharge needle 1 through the first pipeline 2, so as to generate water radical cation clusters by ionization through corona discharge;

[0045] The formed water radical cation clusters interact with the CF bonds of the sample molecules in the sample channel in three-dimensional space, causing the molecular electron cloud to undergo predictable changes, thereby generating detectable products;

[0046] The formed product is detected by the mass spectrometer 13 and analyzed by the mass spectrometer 13 to obtain characteristic ion fragments that can identify perfluoroalkanes, thereby achieving identification analysis of perfluoroalkanes.

[0047] In the following examples, the monitoring conditions of the mass spectrometer were as follows: the temperature in the ion transfer capillary was maintained at 150°C, the capillary voltage was 1.0 V, the lens voltage was 30.0 V, and the pressure vacuum in the ion trap was set to 1×10 -5 torr.

[0048] Example 1

[0049] use Figure 1 In the device shown, when the second carrier gas channel is closed, moist water vapor is introduced into the first carrier gas channel to the tip of the discharge needle, and a high voltage of 2.5kV is applied to the discharge needle to produce a high abundance of water radical cation clusters (H2O)2 +· Ion m / z 36, specifically Figure 2 As shown. Among them, m / z 54 is (H2O)3 +· Ion, m / z 55 is (H2O)3H + ion.

[0050] Example 2

[0051] use Figure 1The device shown is used to detect perfluorooctane. Inert argon gas is introduced into the water storage device through the first carrier gas channel to form an inert gas containing water vapor. At the same time, argon gas is introduced into the sample storage device through the second carrier gas channel to introduce the sample stored in the sample storage device into the front end of the mass spectrometer inlet in the form of gas. A high voltage of 2.5kV is applied to the tip of the discharge needle 1 through a high voltage source, and moist water vapor is introduced into the tip of the discharge needle 1 through the first pipeline to generate water radical cation clusters through corona discharge ionization. The formed water radical cation clusters interact with the C-F bonds of the sample molecules in the sample channel in three-dimensional space, causing predictable changes in the molecular electron cloud and generating detectable product signals.

[0052] Figure 3 and Figure 4 The following are the primary and secondary mass spectra of the product (m / z 435) and the addition product formed by the interaction of the water radical cation formed in the first carrier gas channel with the perfluorooctane sample in the second carrier gas channel. (m / z 438 → m / z 435 → m / z 369 → m / z 319 → m / z 269 → m / z 219 → m / z 169)

[0053] Example 3

[0054] Similarly, using Figure 1 The device shown detects perfluoroheptane. Inert argon gas is introduced into the water storage device through the first carrier gas channel to form an inert gas containing water vapor. At the same time, argon gas is introduced into the sample storage device through the second carrier gas channel to introduce the sample stored in the sample storage device into the front end of the mass spectrometer inlet in the form of gas. A high voltage of 2.5kV is applied to the tip of the discharge needle 1 through a high voltage source, and moist water vapor is introduced into the tip of the discharge needle 1 through the first pipeline to generate water radical cation clusters through corona discharge ionization. The formed water radical cation clusters interact with the C-F bonds of the sample molecules in the sample channel in three-dimensional space, causing predictable changes in the molecular electron cloud and generating detectable product signals.

[0055] Figure 5 and Figure 6 The following are the primary and secondary mass spectra of the product (m / z 385) and the addition product formed by the interaction of the water radical cation formed in the first carrier gas channel with the sample perfluoroheptane in the second carrier gas channel (m / z 388→m / z385→m / z 319→m / z 269→m / z 219→m / z 169).

[0056] Example 4

[0057] Similarly, using Figure 1The device shown is used to detect perfluorohexane. Inert argon gas is introduced into the water storage device through the first carrier gas channel to form an inert gas containing water vapor. At the same time, argon gas is introduced into the sample storage device through the second carrier gas channel to introduce the sample stored in the sample storage device into the front end of the mass spectrometer inlet in the form of gas. A high voltage of 2.5 kV is applied to the tip of the discharge needle 1 through a high voltage source, and moist water vapor is introduced into the tip of the discharge needle 1 through the first pipeline to generate water radical cation clusters through corona discharge ionization. The formed water radical cation clusters interact with the CF bonds of the sample molecules in the sample channel in three-dimensional space, causing predictable changes in the molecular electron cloud and generating detectable product signals.

[0058] Figure 7 and Figure 8 The primary and secondary mass spectra show the product (m / z 335) and addition product formed by the interaction of the water radical cation formed in the first carrier gas channel with the perfluorohexane sample in the second carrier gas channel (m / z 338→m / z335→269→m / z 219→m / z 169).

[0059] In summary, the above-described device and method for detecting perfluoroalkanes allows water vapor to be introduced using a carrier gas when the air humidity is low. When the air humidity is high, no carrier gas is required, and the water vapor in the air can be directly ionized, making it convenient to use. By regulating the electric field strength, the ionized water vapor produces a large number of water radical cation clusters. The formed water radical cation clusters react with the C-F bonds in the perfluoroalkanes to produce corresponding products. Finally, characteristic ion fragments that can identify perfluoroalkanes are obtained through tandem mass spectrometry. The entire device is simple, has low modification costs, uses water as a carrier, is green and pollution-free, and the reaction time between the water radical cation clusters and the perfluoroalkanes is fast, enabling high-throughput analysis, which is of great significance for the detection and degradation of perfluoroalkanes.

[0060] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0061] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for detecting perfluoroalkanes, characterized in that: By ionizing water vapor in the detection device to generate water radical cation clusters, the formed water radical cation clusters react with the CF bonds in perfluoroalkanes to generate corresponding products. Finally, a tandem mass spectrometer is used to obtain characteristic ion fragments that can identify perfluoroalkanes, thereby realizing the identification and analysis of perfluoroalkanes.

2. A method for detecting perfluoroalkanes according to claim 1, characterized in that The monitoring conditions of the mass spectrometer were as follows: the temperature in the ion transfer capillary was maintained at 150°C, the capillary voltage was 1.0 V, the lens voltage was 30.0 V, and the pressure vacuum in the ion trap was set to 1×10 -5 torr.

3. The method for detecting perfluoroalkanes according to claim 1, wherein: The detection device includes an ionization channel, a sample channel and a mass spectrometer. The ionization channel is used to ionize water to obtain water radical cation clusters; the sample channel is used to transport perfluoroalkane so that it can react with the water radical cation clusters; and the mass spectrometer is used to detect and analyze the reaction products.

4. A method for detecting perfluoroalkanes according to claim 3, characterized in that: The ionization channel comprises a discharge needle connected to a high voltage source, wherein a capillary is coaxially sleeved with the discharge needle.

5. The method for detecting perfluoroalkanes according to claim 3, wherein: The sample channel includes a sample storage device and a heating device, and the heating device can heat the sample storage device.

6. The method for detecting perfluoroalkanes according to claim 1, wherein: The specific steps include: Inert gas is introduced into the ionization channel to form an inert gas with water vapor. At the same time, inert gas is introduced into the sample channel and the sample storage device, and a heating device is activated to heat the sample in the sample storage device to a boiling point, so that the stored sample is introduced into the front end of the mass spectrometer inlet in the form of gas; Applying high voltage to the tip of the discharge needle through the high voltage source to ionize water vapor through the ionization channel to generate water radical cation clusters; The formed water radical cation clusters interact with the CF bonds of the sample molecules in the sample channel in three-dimensional space, causing the molecular electron cloud to undergo predictable changes, thereby generating detectable products; The formed product is detected by the mass spectrometer and analyzed by the mass spectrometer to obtain ion fragments that can identify perfluoroalkane, thereby achieving identification analysis of perfluoroalkane.

7. A method for detecting perfluoroalkanes according to claim 6, characterized in that: The inert gas is argon.

8. The method for detecting perfluoroalkanes according to claim 6, wherein: The high voltage is 2-4 kV.

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