A mass spectrometry method for perfluoroalkyl ether carboxylic acids and its application

Abstract

The present invention relates to a mass spectrometry method for perfluoroalkyl ether carboxylic acid and its application. The present invention selects [CF3(CF2) n O] or [M‑H‑CO2] as precursor ions and other fluorinated alkoxy and alkyl fragments as product ions to construct new ion pairs, and ultrasensitive detection of PFECA in various samples was achieved by optimizing the cone voltage and collision energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of mass spectrometry detection, and specifically relates to a method for ultra-sensitive detection of perfluoroalkyl ether carboxylic acids based on ultra-performance liquid chromatography-tandem mass spectrometry and an application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Liquid chromatography-tandem mass spectrometry (LC-MS / MS) is the main technology for analyzing PFASs (perfluorinated and polyfluorinated compounds). The existing technology for detecting PFECA (perfluoroalkyl ether carboxylic acid) is usually based on [MH] - As the parent ion, other characteristic ion fragments are daughter ions to form multiple reaction monitoring (MRM) ion pairs. However, for the detection of some PFECAs, the detection limit of this method is high and cannot meet the needs of actual detection. Generally, PFASs produce [MH] in the negative mode of electrospray ionization (ESI). - The parent ion will then fragment in the collision cell and the product ion will be detected in MRM mode. However, PFECA (perfluoroalkyl ether carboxylic acid) may undergo source fragmentation and CO2 neutral loss during ESI source ionization, which is manifested as the breakage of the ether oxygen bond and the loss of the carboxyl group in the PFECA skeleton. For the above reasons, conventional [MH] - The abundance of the parent ion is not high, and it will produce some source ions and [MH-CO2] fragment ions with the same retention time as the target analyte, which affects the ultrasensitive detection of PFECA and makes the mass spectrometry response of PFECA far inferior to that of traditional PFASs. Summary of the invention

[0004] In the negative ESI mode, the [MH] - To solve the problem of low abundance, the present invention provides a mass spectrometry method for PFECA and its application, selecting [CF3(CF2) n O] or [MH-CO2] as the parent ions and other fluorinated alkoxy and alkyl fragments as product ions to construct new ion pairs, and ultrasensitive detection of PFECA in various samples was achieved by optimizing the cone voltage and collision energy.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] In a first aspect, the present application provides a mass spectrometry method for ultrasensitive detection of PFECA, the steps of which include: (1) preparing a product into a sample to be tested; (2) subjecting the sample to be tested to UPLC-MS / MS detection; in the ESI negative ion mode, performing a full scan on PFECA to obtain [MH-CO2] or [CF3(CF2) n O] fragment; secondly, select the appropriate [MH-CO2] or [CF3(CF2) n O] fragment as the parent ion, and scan the daughter ions to obtain daughter ion information; (3) obtain the content of perfluoroalkyl ether carboxylic acid in the product.

[0007] In some embodiments, ultrasensitive detection of two PFECAs is performed. The chemical structures of the two PFECAs are as follows:

[0008] (Perfluoro-2-propoxypropionic acid, GenX)

[0009] (perfluoro-3,6-dioxaheptanoic acid, PFO2HpA).

[0010] Furthermore, the specific steps of mass spectrometry detection of GenX are to perform a full secondary mass spectrometry scan on GenX to obtain the parent ion of [MH-CO2] m / z 285 generated by the neutral loss of CO2. Perform a daughter ion scan on m / z 285 to obtain the characteristic daughter ions of m / z 185, 169, and 119 formed by the ether oxygen bond breakage and further loss of CF2 fragments at m / z 285. The three ion pairs of GenX are established as 285 / 185, 285 / 169, and 285 / 119.

[0011] Furthermore, the specific steps of mass spectrometry detection of PFO2HpA are to perform a full secondary mass spectrometry scan on PFO2HpA to obtain [M-CF2COOH] generated by the cleavage of the ether oxygen bond. - The parent ion was m / z 201. The daughter ion scan of m / z 201 was performed to obtain the characteristic daughter ion m / z 85 formed by the cleavage of the ether oxygen bond. The ion pair of PFO2HpA was established as 201 / 85.

[0012] In some embodiments, step (1) specifically comprises: grinding or crushing the sample to be tested, adding an organic solvent, extracting and purifying the analyte using the QuEChERS method, and performing ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) detection.

[0013] In some embodiments, the organic solvent is acetonitrile, ethyl acetate, or dichloromethane. In some embodiments, when the sample to be tested is a biological sample, it is necessary to add acid to precipitate the protein of the biological sample or to obtain the sample to be tested after high-speed centrifugation.

[0014] In some embodiments, the chromatographic detection conditions are as follows: chromatographic column: Waters Acquity BEH C18 column (1.7 μm, 2.1×50 mm); mobile phase: 2.5 mmol / L ammonium acetate aqueous solution / methanol = 95 / 5 (A), methanol / 2.5 mmol / L ammonium acetate aqueous solution = 95 / 5 (B); flow rate is 0.3 mL / min; gradient elution program: 0-0.2 min, 95%-5% A; 0.2-3 min, 5% A; 3-5 min, 5%-95% A; injection volume: 1 μL.

[0015] In some embodiments, mass spectrometry detection conditions are as follows: monitoring mode: multiple reaction monitoring; ion source: ESI; scanning mode: negative ion scanning; source temperature: 150°C; cone voltage: 10V; capillary voltage: 2.5kV; desolvation gas temperature: 450°C; desolvation gas flow rate: 1000L / hr; cone gas flow rate: 150L / hr; nebulizer pressure: 7.0bar.

[0016] In a second aspect, the present invention provides the use of the above mass spectrometry method to detect PFECA in products.

[0017] In some embodiments, the products include environmental water samples, food, food contact materials and aquatic products. Preferably, environmental water samples include drinking water, surface water, groundwater, seawater and industrial wastewater. Food includes fruits and vegetables, meat, eggs, milk and dairy products, among which fruits and vegetables include apples, watermelons, grapes, blueberries, kiwis, lettuce, radishes, Chinese cabbage cucumbers, tomatoes, cabbages and beans; meat mainly includes chicken, beef, pork and mutton; eggs mainly include eggs, duck eggs and some egg products; milk and dairy products mainly include fresh milk, milk powder and human breast milk. Food contact materials mainly include plastic bags, food packaging bags and plastic wrap. Aquatic products mainly include various edible freshwater fish, marine fish, shellfish, kelp and the like.

[0018] In some embodiments, PFASs include carboxylic acids, sulfonic acids, phosphoric acid perfluorinated compounds of different carbon chain lengths, and fluorinated compounds with chlorine substitution or hydrogen substitution, or oxygen atoms inserted into the carbon chain, such as PFOA, perfluorooctadecanoic acid, perfluorohexadecanoic acid, PFOS, perfluorobutanesulfonic acid, perfluoropentylphosphonic acid, perfluorohexylphosphonic acid, sodium dodecafluoro-3H-4,8-dioxonanoate, 1-chloropolyfluoroalkyl ether sulfonic acid, GenX, and PFO2HpA, etc. Further, PFASs is GenX or PFO2HpA.

[0019] Beneficial effects of the present invention:

[0020] The present invention discloses an ultra-sensitive detection method for PFECA. The method uses UPLC-MS / MS technology and adopts electrospray ionization tandem mass spectrometry detection mode (ESI - -MRM), [CF3(CF2) n O] or [MH-CO2] as the parent ion, and other secondary fluorinated alkoxy and alkyl fragments as the daughter ions to form a series of characteristic MRM ion pairs, which improves the mass spectrometric sensitivity of PFECA and increases the mass spectrometric response to it by 4 to 5 orders of magnitude.

[0021] The ultra-sensitive PFECA detection method of the present invention has high sensitivity and low detection limit, and is significantly superior to methods reported in literature. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 a and b are the secondary mass spectrum and daughter ion scanning diagram of GenX in negative ion mode of Example 1;

[0024] Figure 2 a and b are the secondary mass spectrum and daughter ion scanning diagram of PFO2HpA in negative ion mode of Example 2;

[0025] Figure 3 a and b are UPLC-MS / MS graphs of PFECA (1 ng / mL) in Example 3 under the conditions of Table 2 and Table 1, respectively;

[0026] Figure 4 UPLC-MS / MS graph of GenX and PFO2HpA in rapeseed in Example 4;

[0027] Figure 5 This is the UPLC-MS / MS graph of GenX and PFO2HpA in industrial wastewater in Example 6. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] As introduced in the background art, some PFECA in the prior art are [MH] - The MRM quantitative method for the parent ion has a low mass spectrometric response and cannot meet the needs of actual detection. In order to solve the above technical problems, this application proposes a new mass spectrometry method based on ion pair optimization, using [CF3(CF2) n O] or [MH-CO2] as the parent ion and other secondary fluorinated alkoxy and alkyl fragments as product ions to form a series of characteristic MRM ion pairs, thus realizing the trace detection of PFECA in various real samples.

[0031] The present invention is further described below in conjunction with embodiments.

[0032] Example 1: GenX was subjected to a full secondary mass spectrometry scan to obtain a parent ion of [MH-CO2] m / z 285 generated by neutral loss of CO2. A daughter ion scan of m / z 285 was performed to obtain characteristic daughter ions of m / z 185, 169, and 119 formed by further ether oxygen bond breakage and further loss of CF2 fragments of the parent ion. Three ion pairs of GenX were established as 285 / 185, 285 / 169, and 285 / 119 (Table 1). Figure 1 a is the secondary mass spectrum of GenX in negative ion mode, Figure 1 b is the daughter ion scan of GenX.

[0033] Example 2: By performing a full secondary mass spectrometry scan on PFO2HpA, [M-CF2COOH] generated by the cleavage of the ether oxygen bond is obtained. - The parent ion was m / z 201. A daughter ion scan was performed on m / z 201 to obtain a characteristic daughter ion m / z 85 formed by further ether oxygen bond cleavage of the parent ion. The ion pair of PFO2HpA was established as 201 / 85 (Table 1). Figure 2 a is the secondary mass spectrum of PFO2HpA in negative ion mode, Figure 2 b is the daughter ion scan of PFO2HpA.

[0034] Example 3, combined with the MRM mass spectrometry conditions of GenX and PFO2HpA in the literature (Table 2), UPLC-MS / MS comparative detection was performed on 1 ng / mL PFECA. - The conventional MRM of the parent ion [CF3(CF2) n O], [MH-CO2] and other MRM conditions can increase the mass spectrometry response of PFECA by 4 to 5 orders of magnitude, indicating that the invention is more conducive to the trace detection of PFECA. Figure 3 a is the UPLC-MS / MS graph of PFECA (1 ng / mL) under the conditions in Table 2, Figure 3 b is the UPLC-MS / MS graph of PFECA (1 ng / mL) under the conditions in Table 1.

[0035] Table 1 Optimized MRM detection conditions of PFECA

[0036]

[0037] Table 2 Conventional MRM detection conditions for PFECA

[0038]

[0039] Example 4, for the detection of fruit and vegetable samples, rapeseed is taken as an example to illustrate the detection effect.

[0040] Weigh 7.5g of rapeseed and crush it in a 50mL polypropylene centrifuge tube, add 15mL of acetonitrile and vortex for 5min. Then add 6.0g of anhydrous magnesium sulfate and 1.5g of sodium chloride, shake quickly to mix, oscillate for 15min, and centrifuge at 10000r / min for 5min. Take the above 6mL supernatant in a 15mL high-speed centrifuge tube, add 1.8g of anhydrous magnesium sulfate, vortex for 5min, centrifuge at 10000r / min for 5min, take 4mL of supernatant through a 0.22μm filter membrane, and transfer to a glass bottle. Evaporate to dryness under a nitrogen flow at 40℃, reconstitute with 100μL of methanol, and perform UPLC-MS / MS analysis.

[0041] The results showed that the content of GenX in the rapeseed obtained by the method established by the present invention was 0.02 ng / g, and PFO2HpA was not detected. Figure 4 UPLC-MS / MS images of GenX and PFO2HpA in rapeseed.

[0042] Example 5, for the detection of meat samples, this example takes pork as an example to illustrate the detection effect.

[0043] Weigh 7.5g of pork and crush it in a 50mL polypropylene centrifuge tube, add 15mL of acetonitrile and vortex for 5min. Then add 6.0g of anhydrous magnesium sulfate and 1.5g of sodium chloride, shake quickly to mix, oscillate for 15min, and centrifuge at 10000r / min for 5min. Take the above 6mL supernatant in a 15mL high-speed centrifuge tube, add 0.5mL of trifluoroacetic acid and 1.8g of anhydrous magnesium sulfate, vortex for 5min, centrifuge at 10000r / min for 5min, take 4mL of supernatant through a 0.22μm filter membrane, and transfer to a glass bottle. Evaporate to dryness under a nitrogen flow at 40℃, reconstitute with 100μL of methanol, and perform UPLC-MS / MS analysis.

[0044] The results showed that the content of GenX in the pork obtained by the method established by the present invention was 0.3 ng / g, and the content of PFO2HpA was 0.2 ng / g.

[0045] Example 6, for the detection of aquatic product samples, this example takes hairtail as an example to illustrate the detection effect.

[0046] Skin and bones were removed from the hairtail to obtain the edible part. 7.5 g was weighed and crushed into a 50 mL polypropylene centrifuge tube, and 15 mL acetonitrile was added and vortexed for 5 min. Then 6.0 g anhydrous magnesium sulfate and 1.5 g sodium chloride were added, and the mixture was quickly shaken and mixed, oscillated for 15 min, and centrifuged at 10,000 r / min for 5 min. The above 6 mL supernatant was placed in a 15 mL high-speed centrifuge tube, 0.5 mL trifluoroacetic acid and 1.8 g anhydrous magnesium sulfate were added, vortexed for 5 min, and centrifuged at 10,000 r / min for 5 min. Then 4 mL of the supernatant was filtered through a 0.22 μm filter membrane and transferred to a glass bottle. Evaporate to dryness under a nitrogen gas flow at 40 ° C, reconstitute with 100 μL methanol, and perform UPLC-MS / MS analysis.

[0047] The results showed that the content of GenX in the hairtail obtained by the method established by the present invention was 1.5 ng / g, and the content of PFO2HpA was 0.7 ng / g.

[0048] Example 6, for the detection of environmental water samples, this example takes industrial wastewater as an example to illustrate the detection effect.

[0049] 7.5 mL of water sample was transferred to a 50 mL centrifuge tube, 15 mL of acetonitrile was added, vortexed for 5 min, and allowed to stand for 5 min. The above 6 mL of organic layer was transferred to a centrifuge tube, 25 mg of PSA and 25 mg of GCB were added for purification, and 4 mL of supernatant was filtered through a 0.22 μm filter membrane and transferred to a glass bottle. The sample was evaporated to dryness under a nitrogen gas flow at 40 ° C, and reconstituted with 100 μL of methanol for UPLC-MS / MS analysis.

[0050] The results show that the content of GenX in the industrial wastewater obtained by the method established by the present invention is 8.3 ng / g, and the content of PFO2HpA is 2.6 ng / g. Figure 5 UPLC-MS / MS graph of GenX and PFO2HpA in industrial wastewater.

[0051] Example 7, for the detection of milk samples, this example takes milk as an example to illustrate the detection effect.

[0052] 7.5 g of milk was placed in a 50 mL polypropylene centrifuge tube, and 15 mL of acetonitrile and 0.5 mL of trifluoroacetic acid were added, vortexed for 5 min, and allowed to stand for 5 min. The above 6 mL of organic layer was placed in a centrifuge tube, and 25 mg of PSA and 25 mg of GCB were added for purification. After centrifugation at 10,000 r / min for 5 min, 4 mL of supernatant was filtered through a 0.22 μm filter membrane and transferred to a glass bottle. Evaporate to dryness under a nitrogen flow at 40 ° C, reconstitute with 100 μL of methanol, and perform UPLC-MS / MS analysis.

[0053] The results showed that the method established by the present invention did not detect GenX and PFO2HpA in milk.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A mass spectrometry method for ultrasensitive detection of perfluoroalkyl ether carboxylic acids, characterized in that: The method comprises the following steps: (1) preparing the product into a sample to be tested; (2) subjecting the sample to be tested to ultra-high performance liquid chromatography-tandem mass spectrometry detection; in the ESI negative ion mode, performing a full scan on the perfluoroalkyl ether carboxylic acid to obtain [MH-CO2] or [CF3(CF2) n O] fragment; secondly, select the appropriate [CF3(CF2) n O] fragment as the parent ion, and scan the daughter ions to obtain daughter ion information; (3) obtain the content of perfluoroalkyl ether carboxylic acid in the product; The perfluoroalkyl ether carboxylic acid is PFO2HpA; The PFO2HpA was fully scanned by secondary mass spectrometry to obtain [M-CF2COOH] produced by the cleavage of the ether oxygen bond. - m / z 201 parent ion; right m / z 201 Perform daughter ion scanning to obtain characteristic daughter ions formed by ether oxygen bond cleavage m / z 85; the ion pair of PFO2HpA was established as 201 / 85; Chromatographic detection conditions: chromatographic column: Waters Acquity BEH C18 column, 1.7 μm, 2.1×50 mm; mobile phase: 2.5 mmol / L ammonium acetate aqueous solution / methanol = 95 / 5 (A), methanol / 2.5 mmol / L ammonium acetate aqueous solution = 95 / 5 (B); flow rate: 0.3 mL / min; gradient elution program: 0~0.2 min, 95%~5% A; 0.2~3 min, 5% A; 3~5 min, 5%~95% A; injection volume: 1 μL; Mass spectrometry detection conditions: monitoring mode: multiple reaction monitoring (MRM); ion source: ESI; scanning mode: negative ion scanning; source temperature: 150 °C; cone voltage: 10 V; capillary voltage: 2.5 kV; desolvation temperature: 450 °C; desolvation flow rate: 1000 L / hr; cone gas flow rate: 150 L / hr; nebulizer pressure: 7.0 bar.

2. The mass spectrometry method according to claim 1, characterized in that The step (1) specifically comprises: grinding or crushing the sample to be tested, adding an organic solvent, extracting and purifying the sample to be tested using the QuEChERS method, and performing ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) detection.

3. The mass spectrometry method according to claim 2, characterized in that The organic solvent is acetonitrile, ethyl acetate, and dichloromethane.

4. The mass spectrometry method according to claim 2, characterized in that When the sample to be tested is a biological sample, it is necessary to add acid to precipitate the protein of the biological sample or to obtain the sample to be tested after high-speed centrifugation.

5. Use of the mass spectrometry method according to any one of claims 1 to 4 to detect perfluoroalkyl ether carboxylic acids in products.

6. The use according to claim 5, characterized in that: The products include environmental water samples, food, food contact materials or aquatic products.

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