Method for detecting anisole and four halogenated anisole in water by headspace solid phase microextraction-gas chromatography-mass spectrometry

Abstract

The invention provides a method for detecting anisole and four halogenated anisole in water by headspace solid phase microextraction-gas chromatography-mass spectrometry, which comprises the following steps: adding a water sample to be detected into a headspace sample injection bottle, then adding sodium chloride and deuterated 1, 2-dichlorobenzene, screwing a bottle cap and shaking uniformly to obtain a liquid to be detected; a sample injector provided with an extraction head is aged and then transferred to the position above a headspace sample injection bottle for headspace extraction, the extraction temperature ranges from 40 DEG C to 70 DEG C, the rotating speed ranges from 350 r / min to 750 r / min, and the extraction time ranges from 10 min to 40 min; the extraction head adopts CAR / DVB / PDMS as extraction fibers; and after the extraction is completed, performing thermal desorption on the sample injector at a sample injection port of a gas chromatograph-mass spectrometer, performing gas chromatography and mass spectrometry detection, and reading a response value. According to the invention, CAR / DVB / PDMS is adopted as the extraction fiber, so that the adsorption extraction effect on anisole and four halogenated anisole odor substances in the water body can be greatly improved, and the detection limit can be greatly reduced by combining the gas chromatography-tandem mass spectrometry technology. The method has the advantages of high extraction speed, low operation cost, no need of operations such as solvent extraction and digestion, and the like.

Description

Technical Field

[0001] This invention relates to the field of water sample testing technology, and in particular to a method for detecting anisole and four halogenated anisoles in water. Background Technology

[0002] Anisole is an organic compound commonly used in the production of synthetic resins, coatings, and pigments. Wastewater from these industrial processes primarily originates from the production of anisole in water. Anisole in water poses a potential threat to aquatic life and human health.

[0003] Halogenated anisole (HA) is a newly emerging odor-causing compound in drinking water, mainly generated by methylation of microorganisms in water supply pipelines or by the chlorination disinfection process of anisole. Halogenated anisole has a very low odor threshold, with 2,4,6-trichloroanisole (2,4,6-TCA) having the lowest odor threshold (0.05-10 ng / L). Currently, my country has not established national or industry standard analytical methods for halogenated anisole substances. GB 5749-2022 specifies a limit of 0.05 mg / L for anisole, and the standard detection method GB / T5750.8-2023(82) is a purge-trap gas chromatography-mass spectrometry method with a detection limit of 1.0 μg / L, which is insufficient for effectively monitoring trace amounts of anisole and its chlorinated products. Therefore, a highly sensitive and high-throughput detection method for anisole and halogenated anisole is urgently needed.

[0004] Various pretreatment enrichment techniques, such as purge-and-trap, liquid-liquid extraction, and solid-phase extraction, combined with GC-MS and GC-ECD, are used to lower the detection limit and improve analytical sensitivity. The study "Determination of Anisole in Water by Headspace Gas Chromatography-Tandem Mass Spectrometry" (Liu Li et al., *Physical and Chemical Testing - Chemical Analysis*, 2015, Vol. 51, No. 12: 1721-1723) reported the determination of anisole in water using HS-GC-MS with a detection limit of 5 ng / L; the study "Determination of Anisole and Methyl Tert-Butyl Ether in Water by Purge-and-Trap / Gas Chromatography-Mass Spectrometry" (Li Zhenguo, *Agriculture and Technology*, 2021, Vol. 41, No. 16: 14-16) reported the determination of anisole using purge-and-trap / gas chromatography-mass spectrometry with a detection limit of 300 ng / L. However, these methods involve complex pretreatment, have high detection limits, and their sensitivity is insufficient to meet the required levels. Summary of the Invention

[0005] This invention aims to provide a method for simultaneously determining anisole and four halogenated anisole odor compounds in water using fully automated headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry. Specifically, it can be used to determine anisole, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, and 2,4,6-tribromoanisole in water.

[0006] This invention is achieved using the following technical solution: A method for detecting anisole and four halogenated anisoles in water using headspace solid-phase microextraction-gas chromatography-mass spectrometry includes the following steps: S1. Sample preparation: Add the water sample to be tested to the headspace vial, then add sodium chloride and deuterated 1,2-dichlorobenzene (1,2-DCB D4), tighten the cap and shake well to obtain the test solution; S2. Headspace solid-phase microextraction: The injector equipped with the extraction head is aged at 250-300℃ for 1-40 min, and then transferred to the headspace vial for headspace extraction. The extraction temperature is 40-70℃, the rotation speed is 350-750 r / min, and the extraction time is 10-40 min. The extraction head uses CAR / DVB / PDMS as the extraction fiber. S3. After extraction, desorb the sampler at 200-260℃ for 0.5-5 min at the injection port of the gas chromatography-mass spectrometry instrument, with an injection depth of 35-55 mm. Then perform gas chromatography and mass spectrometry detection and read the response value.

[0007] In step S2, CAR (Carboxen) refers to carbon molecular sieve, DVB (Divinylbenzene) refers to divinylbenzene, and PDMS (Polydimethylsiloxane) refers to polydimethylsiloxane copolymer.

[0008] The inventors unexpectedly discovered that using CAR / DVB / PDMS as the extraction fiber significantly improves the adsorption and extraction efficiency for HAs compared to conventional PDMS, DVB / PDMS, and CAR / PDMS fibers. Combined with gas chromatography-tandem mass spectrometry (GC-MS / MS), the detection limit for HAs can be drastically reduced to 0.1-0.3 ng / L. This provides a highly sensitive detection method for identifying odor-causing substances in water, thus addressing water odor incidents. Based on the above findings, the applicant completed this invention.

[0009] Preferably, the extraction fiber is 50 / 30μm CAR / DVB / PDMS.

[0010] In step S1, based on 10 mL of the water sample to be tested, the amount of sodium chloride added is 1-5 g, and the amount of deuterated 1,2-dichlorobenzene added is 2-5 μg. Preferably, the amount of sodium chloride added is 3-5 g, and most preferably 4 g. Preferably, the amount of deuterated 1,2-dichlorobenzene added is 3-5 μg, and most preferably 4 μg.

[0011] In step S2, the extraction temperature is preferably 55-65℃, and most preferably 60℃; the extraction time is preferably 20-30 min, and most preferably 25 min; the rotation speed is preferably 550-750 r / min, and most preferably 650 r / min. In step S3, the desorption temperature is preferably 230-250℃, and most preferably 240℃; the desorption time is preferably 2-4 min, and most preferably 3 min; the injection depth is preferably 45-55 mm, and most preferably 50 mm.

[0012] Preferably, in step S3, the gas chromatography conditions are as follows: The chromatographic column is a DB-624 capillary column, (30-60) m × (0.25-0.32) mm × (1.4-1.8) μm; the carrier gas is helium; the flow rate is 1.0-2.0 ml / min; the injection method is splitless injection, the injection time is 1-2 min, and the injection port temperature is 240-250℃; the column temperature program is as follows: start at 40℃ and hold for 1-2 min, increase to 110℃ at 8-10℃ / min and hold for 1-2 min, then increase to 230-260℃ at 5-10℃ / min and hold for 3-10 min.

[0013] Preferably, in step S3, the mass spectrometry conditions are as follows: EI source electron energy 70eV, ion source temperature 230℃, interface temperature 260℃; solvent delay 2-15 min; detector voltage: 0.2KV relative to the tuning result.

[0014] Compared with existing technologies, this technical solution has the following advantages: This invention utilizes 50 / 30μm CAR / DVB / PDMS as the extraction fiber, which significantly improves the adsorption and extraction efficiency for anisole and four halogenated anisole odor substances in water. Combined with gas chromatography-mass spectrometry (GC-MS), the detection limit can be significantly reduced. This invention integrates sampling, extraction, and enrichment, is simple to operate, and offers advantages such as fast extraction speed, low operating cost, and elimination of solvent extraction and leaching. It provides a highly sensitive detection method for addressing water odor incidents and identifying odor-causing substances in water.

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a graph showing the adsorption effect of different extraction fibers on various target substances.

[0017] Figure 2 The peak area diagrams for the response of each target analyte at different extraction temperatures are shown.

[0018] Figure 3 The peak area diagrams of the target compounds at different extraction times are shown.

[0019] Figure 4 The peak area diagrams of the response of each target analyte at different desorption temperatures are shown.

[0020] Figure 5 The peak area diagrams of the response of each target analyte at different desorption times are shown.

[0021] Figure 6 The peak area diagrams of the response of each target object at different shaking velocities are shown.

[0022] Figure 7 The peak area diagrams show the response of each target analyte at different concentrations of sodium chloride.

[0023] Figure 8 The peak area diagrams of the response of each target at different injection depths are shown.

[0024] Figure 9 The chromatograms show the peak positions of five HAs at a mass concentration of 50 ng / L and deuterated 1,2-dichlorobenzene at a mass concentration of 20 ng / L. Detailed Implementation

[0025] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0026] Instrument: SHIMADZU GCMS-TQ8050 equipped with split / splitless injection ports, Shimadzu CTC (AOC-6000) autosampler.

[0027] Reagents: Anisole (1000 mg / L, Shanghai Absolute Standards, Inc.); 2,4,6-trichloroanisole (100 mg / L, O2si); 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, 2,4,6-tribromoanisole (1000 mg / L, Absolute Standards, Inc.); Deuterated 1,2-dichlorobenzene (2000 mg / L, Shanghai Absolute Standards, Inc.); Methanol: chromatographic grade; Sodium chloride: analytical grade; Laboratory water: freshly prepared; 20 mL headspace vials: glass, sealed threaded cap with PTFE septum; Helium, Argon (purity ≥99.999%).

[0028] Solid phase microextraction parameters: Extraction was performed at 60℃ and 650 rpm for 25 min. After extraction, the extraction fiber was desorbed at 240℃ for 3 min at the GC-MS inlet to a depth of 55 mm. 50 / 30 μm CAR / DVB / PDMS extraction fibers were used. New extraction fibers were aged at 270℃ for 30 min before analysis, and then aged at 270℃ for 1 min before each subsequent analysis.

[0029] Gas chromatography conditions: Column: Agilent VF-624MS (60m × 0.32 mm × 1.80μm); Carrier gas: Helium; Flow rate: constant flow, 2.0 ml / min; Injection mode: splitless; Injection time: 1 min; Injector temperature: 240℃; Temperature program: 40℃ (hold for 2 min), 8℃ / min to 110℃ (hold for 1 min), 10℃ / min to 260℃ (hold for 10 min).

[0030] Mass spectrometry conditions: Ion source temperature: 230℃; interface temperature: 260℃; solvent delay: 15 min; detector voltage: 0.2 kV relative to the tuning result. Quantitative and qualitative ions in MRM mode are shown in Table 1.

[0031] Table 1. Compound abbreviation, peak time, product ion, collision voltage Preparation of standard working solution: Prepare a 10 μg / L mixed standard working solution using methanol to prepare five commercially available HAs standard solutions. Prepare immediately before use. Preparation of internal standard working solution: Prepare a 100 μg / L internal standard working solution using methanol to prepare commercially available deuterated 1,2-dichlorobenzene.

[0032] Example 1 1. Sample preparation: Weigh 4g of sodium chloride into a headspace vial, add 10mL of water sample, add 2μL of 1,2-DCB D4, tighten the cap and shake well to obtain the test solution; 2. Headspace solid-phase microextraction: The sampler equipped with the extraction head was aged at 270℃ (new extraction fibers were aged for 30 min, and then aged for 1 min before each analysis), and then transferred to the headspace vial for headspace extraction. The extraction temperature was 60℃, the rotation speed was 650 r / min, and the extraction time was 25 min. The extraction head used CAR / DVB / PDMS as the extraction fiber. 3. After extraction, desorb the sampler at 240℃ for 3 minutes at the injection port of the gas chromatography-mass spectrometry instrument, with an injection depth of 50 mm. Then perform gas chromatography and mass spectrometry detection and read the response value.

[0033] Comparative Examples 1-3 The extraction fibers were replaced with 100μm PDMS, 85μm CAR / PDMS and 65μm DVB / PDMS fibers, respectively, and the rest was the same as in Example 1.

[0034] Figure 1 This study compares the adsorption effects of four extraction fibers on target analytes in water samples in Example 1 and Comparative Examples 1-3. The results show that PDMS adsorption capacity is relatively weak, while the 50 / 30μm CAR / DVB / PDMS fiber exhibits superior adsorption capacity for HAs compared to the other three fibers.

[0035] Examples 2-7 The extraction temperatures were 40℃, 45℃, 50℃, 55℃, 65℃, and 70℃, respectively, with other parameters the same as in Example 1. Figure 2 As shown, the responses of anisole and internal standard decreased at 60℃, while the responses of the other four HA compounds increased at 55℃-70℃. Therefore, 60℃ was selected as the optimal extraction temperature.

[0036] Examples 8-13 Extraction times were 10 min, 15 min, 20 min, 30 min, 35 min, and 40 min, respectively, with other parameters the same as in Example 1. Figure 3 As shown, at an extraction temperature of 60℃, the peak areas of the three HAs, namely anisole, 2,3,6-TCA and 2,4,6-TBA, no longer increased significantly after the extraction time exceeded 25 min, while the internal standard decreased. Considering the effects of experimental efficiency, 25 min was selected as the optimal extraction time.

[0037] Examples 14-19 The desorption temperatures were 200℃, 210℃, 220℃, 230℃, 250℃, and 260℃, respectively, with other parameters the same as in Example 1. Figure 4 As shown, the peak areas of the five HAs were highest at a desorption temperature of 240℃, and then decreased with increasing temperature. Therefore, 240℃ was selected as the optimal desorption temperature.

[0038] Examples 20-24 The desorption times were 0.5 min, 1 min, 2 min, 4 min, and 5 min, respectively, with other parameters the same as in Example 1. Figure 5 As shown, except for 2,3,4-TCA, whose peak area decreased at 3 min, the other 5 compounds all reached their peak values ​​at 3 min. Therefore, 3 min was selected as the optimal desorption time.

[0039] Examples 25-29 The rotational speeds were 250 rpm, 350 rpm, 450 rpm, 550 rpm, and 750 rpm, respectively, with other settings the same as in Example 1. Figure 6 As shown, the target response increases significantly with increasing rotational speed, and the peak area does not change much after 650 rpm, so 650 rpm is selected as the optimal condition.

[0040] Examples 30-34 The amounts of sodium chloride added were 0g, 1g, 2g, 3g, and 5g, respectively, and other details were the same as in Example 1. Figure 7 As shown, the response of the target substance increases with increasing sodium chloride content, and tends to stabilize at 4g. Therefore, the optimal salt content of 4g is selected as the best condition.

[0041] Examples 35-39 The injection depths were 30mm, 35mm, 40mm, 45mm, and 55mm, with other details the same as in Example 1. Figure 8 As shown, the target analyte response increases with increasing injection depth, but decreases slightly after 50 mm. Therefore, 50 mm is selected as the optimal injection depth.

[0042] Example 40 Determination of the detection limits for five HAs.

[0043] The calculations were performed according to Appendix A, <Methods for Determining Method Characteristic Indicators>, of HJ 168-2020, "Technical Guidelines for the Development of Standards for Environmental Monitoring and Analysis Methods". Seven parallel determinations were conducted using a mixed standard solution of five HAs at 1 ng / L added to the water body, with an internal standard concentration of 20 ng / L. Other steps were performed as described in Example 1. The method detection limits for the five HAs are shown in Table 2.

[0044] Table 2. Detection limits of five HAs by method Note: 1) The detection limit is generally rounded to one significant figure; 2) t - the t-distribution value (one-sided) when the degrees of freedom are n-1 and the confidence level is 99%.

[0045] Calculations show that the headspace solid-phase microextraction-gas chromatography-mass spectrometry method of this invention for detecting anisole and four halogenated anisoles in water has a detection limit of 0.1-0.3 ng / L, which is 10-50 times higher than the detection sensitivity of existing technologies. This method breaks through the detection limitations of existing technologies for the above-mentioned trace components, which is conducive to supporting the implementation of stricter environmental quality standards and assisting in early pollution warning and source tracing.

[0046] Example 41 Determination of the peak positions of each target analyte and internal standard.

[0047] A mixed standard solution of five HAs was added to the water at a concentration of 50 ng / L, with an internal standard concentration of 20 ng / L. Other steps were the same as in Example 1. Figure 9 The chromatograms showing the peak positions of five HAs and deuterated 1,2-dichlorobenzene are displayed.

[0048] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The scope of patent application of the present invention should not be limited by these embodiments. That is, any equivalent changes or modifications made in accordance with the spirit disclosed in the present invention still fall within the patent scope of the present invention.

Claims

1. A method for detecting anisole and four halogenated anisoles in water using headspace solid-phase microextraction-gas chromatography-mass spectrometry, characterized in that, Includes the following steps: S1. Sample preparation: Add the water sample to be tested to the headspace vial, then add sodium chloride and deuterated 1,2-dichlorobenzene, tighten the cap and shake well to obtain the test solution; S2. Headspace solid-phase microextraction: The injector equipped with the extraction head is aged at 250-300℃ for 1-40 min, and then transferred to the headspace vial for headspace extraction. The extraction temperature is 40-70℃, the rotation speed is 350-750 r / min, and the extraction time is 10-40 min. The extraction head uses CAR / DVB / PDMS as the extraction fiber. S3. After extraction, desorb the sampler at 200-260℃ for 0.5-5 min at the injection port of the gas chromatography-mass spectrometry instrument, with an injection depth of 35-55 mm. Then perform gas chromatography and mass spectrometry detection and read the response value.

2. The method as described in claim 1, characterized in that, The extraction fiber is 50 / 30μm CAR / DVB / PDMS.

3. The method as described in claim 1, characterized in that, In step S1, based on 10 mL of the water sample to be tested, the amount of sodium chloride added is 1-5 g, and the amount of deuterated 1,2-dichlorobenzene added is 2-5 μg.

4. The method as described in claim 3, characterized in that, The amount of sodium chloride added was 4g, and the amount of deuterated 1,2-dichlorobenzene added was 4μg.

5. The method as described in claim 1, characterized in that, In step S2, the extraction temperature is 55-65℃, the extraction time is 20-30 min, and the rotation speed is 550-750 r / min.

6. The method as described in claim 5, characterized in that, In step S2, the extraction temperature is 60℃, the extraction time is 25 min, and the rotation speed is 650 r / min.

7. The method as described in claim 1, characterized in that, In step S3, the desorption temperature is 230-250℃, the desorption time is 2-4 min, and the injection depth is 45-55 mm.

8. The method as described in claim 7, characterized in that, In step S3, the desorption temperature is 240℃, the desorption time is 3 min, and the injection depth is 50 mm.

9. The method as described in claim 1, characterized in that, In step S3, the gas chromatography conditions are as follows: the column is a DB-624 capillary column, (30-60) m × (0.25-0.32) mm × (1.4-1.8) μm; the carrier gas is helium; the flow rate is 1.0-2.0 ml / min; the injection method is splitless injection, the injection time is 1-2 min, and the injection port temperature is 240-250℃; the column temperature program is as follows: the initial temperature is 40℃ and held for 1-2 min, then increased to 110℃ at 8-10℃ / min and held for 1-2 min, and then increased to 230-260℃ at 5-10℃ / min and held for 3-10 min.

10. The method as described in claim 1, characterized in that, In step S3, the mass spectrometry conditions are as follows: EI source electron energy 70 eV, ion source temperature 230 ℃, interface temperature 260 ℃; solvent delay 2-15 min; detector voltage: 0.2 kV relative to the tuning result.

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