Non-targeted screening analysis method for chlorinated and brominated organic pollutants in sludge

Abstract

The application discloses a non-target screening analysis method for chlorinated and brominated organic pollutants in sludge. The method comprises the following steps: different extractants are respectively taken for sludge samples, different polar target compounds in the samples can be extracted, different solid-phase extraction columns are respectively used for purifying and concentrating the samples, and instrument analysis is carried out based on liquid chromatography tandem high-resolution mass spectrometry (LC-HRMS) and gas chromatography tandem high-resolution mass spectrometry (GC-HRMS), so that information of chlorinated and brominated organic compounds in the samples can be obtained as completely as possible. The obtained instrument data is subjected to data format conversion by using MS Convert software, mass spectrum data extraction by using an XCMS Online website, and language processing by using RStudio, so that the chlorinated and brominated organic compounds in the sludge samples can be screened quickly and accurately. The application solves the technical problem that the analysis method for halogenated organic pollutants in the prior art does not have the non-target screening capability for multiple halogenated organic pollutants.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental pollutant analysis, in particular to a non-target screening analysis method for chlorinated and brominated organic pollutants in sludge. BACKGROUND

[0002] This section is intended to provide background information to facilitate a better understanding of various embodiments. Information described herein, including that in this Background section, should not be considered as admitted prior art merely by virtue of its inclusion in this section.

[0003] Halogenated organic pollutants (HOPs) are a large class of organic compounds containing halogen atoms, which are widely distributed in the natural environment. Most HOPs have the characteristics of persistent organic pollutants (POPs), and more than 60% of the 610 kinds of POPs analyzed are halogenated organic pollutants. Various halogenated organic compounds such as halogenated aliphatic hydrocarbons, polychlorinated biphenyls, chlorinated phenols, and organochlorine pesticides are listed as “priority controlled pollutants” by some countries. With the increasing number of halogenated organic compounds detected in the environment, their environmental chemical behavior, control methods, and ecotoxicological effects have attracted much attention, and the establishment of accurate and efficient halogenated organic compound analysis methods is the basis for the above research. Therefore, the screening and identification of unknown halogenated organic compounds in various complex environmental media are particularly important in environmental analysis. At present, the quantitative analysis methods of halogenated organic compounds based on liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) have high sensitivity, but they are only for a certain kind or a certain class of halogenated organic compounds and do not have non-target screening capability. Therefore, it is urgent to establish a rapid and simple systematic screening method for multiple halogenated organic compounds.

[0004] In view of the above problems, no effective solution has been proposed so far. SUMMARY

[0005] The embodiments of the present application provide a non-target screening analysis method for chlorinated and brominated organic pollutants in sludge, to solve the technical problem that the halogenated organic pollutant analysis method in the related art does not have the capability of simultaneously performing non-target screening on multiple halogenated organic pollutants.

[0006] According to an aspect of the embodiments of the present application, a non-targeted screening analysis method of chlorinated and brominated organic pollutants in sludge is provided, comprising: freezing and drying the collected sludge sample by a freeze dryer, grinding it through a 200-mesh sieve, and taking 2 g of the sample, 1 g of which is used as sample 1 and 1 g of which is used as sample 2, and placing them in different 15-mL centrifuge tubes; adding methanol as an extractant to the sample 1 centrifuge tube and adding a mixed solution of n-hexane and dichloromethane (v:v = 1:1) as an extractant to the sample 2 centrifuge tube; performing ultrasonic extraction, and centrifuging the extract obtained after the extraction of sample 1 and sample 2, respectively, and collecting the supernatant in the centrifuge tube; collecting the supernatant of sample 1 and the supernatant of sample 2 obtained after 3 times of ultrasonic extraction and centrifugation, and using a nitrogen blowing instrument to blow the supernatant of sample 1 and the supernatant of sample 2 to near dryness, and redissolving sample 1 with 5 mL of 5% methanol-water solution and redissolving sample 2 with 1 mL of a mixed solution of n-hexane and dichloromethane (v:v = 1:1); loading the redissolved sample 1 solution onto an activated solid-phase extraction column, washing it with a 2% acetic acid-5% methanol-water solution (v:v:v = 2:5:93), and then eluting it with methanol, and collecting the eluent of sample 1; loading the redissolved sample 2 solution onto an activated solid-phase purification column, eluting it with a mixed solution of n-hexane and dichloromethane (v:v = 1:1), and collecting the eluent of sample 2; using a nitrogen blowing instrument to blow the eluents of sample 1 and sample 2 to near dryness, redissolving sample 1 with methanol and transferring it to a 2-mL sample vial, and then adding methanol to 1 mL; redissolving sample 2 with n-hexane and transferring it to a 2-mL sample vial, and then adding n-hexane to 1 mL; using liquid chromatography-high resolution mass spectrometry (LC-HRMS) to detect sample 1, obtaining instrument analysis data of sample 1, using gas chromatography-high resolution mass spectrometry (GC-HRMS) to detect sample 2, and obtaining instrument analysis data of sample 2; using MSConvert software to convert the instrument analysis data of sample 1 and sample 2 to mzXML data format, and uploading them to the XCMS Online website for mass spectrometry data extraction and processing; running the results obtained after the extraction and processing of the XCMS Online website through an RStudio language program for screening, and obtaining the mass-to-charge ratio of the candidate chlorinated and brominated organic compound parent ion. The XCMS Online website can extract the mass-to-charge ratio (m / z), the corrected retention time (RT), and the response intensity (intensity) of a single chromatographic peak in the Total Ion Chromatogram (TIC) of a specific format data (the data format of the present application is mzXML).

[0007] Optionally, sample 1 is used for detecting polar substances, and sample 2 is used for detecting moderately polar or non-polar substances.

[0008] Optionally, when the sample 1 and the sample 2 are subjected to ultrasonic extraction: the extraction solvent volume of the sample 1 and the sample 2 is 5 mL; the extraction time of the ultrasonic extraction is 15 min.

[0009] Optionally, the centrifugal speed of the centrifuge is 8500 r / min, the centrifugal time is 10 min, and the temperature is 4 DEG C.

[0010] Optionally, when the sample 1 is purified and concentrated by using the solid phase extraction column, the solid phase extraction column is a Cleanert PEP solid phase extraction column; the solutions used for activation are 5 mL of methanol and 5 mL of water respectively; the solution used for elution is 5 mL of a 2% acetic acid-5% methanol-water solution (v:v:v = 2:5:93); and the solution used for elution is 5 mL of methanol.

[0011] Optionally, when the sample 2 is purified by using the solid phase extraction column, the solid phase extraction column is a Supelclean ENVI-Carb TM solid phase extraction column; the solutions used for activation are 5 mL of dichloromethane and 5 mL of n-hexane respectively; and the solution used for elution is a mixed solution of 5 mL of n-hexane and dichloromethane (v:v = 1:1).

[0012] In the embodiments of the present application, different polar target compounds in the sludge sample can be extracted by using different extraction solvents, different solid phase extraction columns are used for purifying and concentrating the sample, and liquid chromatography tandem high resolution mass spectrometry (LC-HRMS) and gas chromatography tandem high resolution mass spectrometry (GC-HRMS) are used for instrument analysis, so that information of chlorinated and brominated organic compounds in the sample can be obtained as completely as possible. The instrument data obtained are converted into data formats by using MS Convert software, mass spectrometry information is extracted by using the XCMS Online website, and RStudio language processing is performed, so that chlorinated and brominated organic compounds in the sludge sample can be screened quickly and accurately. The present application solves the technical problem in the prior art that the analysis method of halogenated organic pollutants does not have the ability of non-target screening of multiple halogenated organic pollutants at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings, which are included to provide a further understanding of the present application, form a part of the present application and illustrate the illustrative embodiments of the present application and the description thereof, and do not constitute improper limitations on the present application. In the drawings:

[0014] Figure 1 is a flowchart of a non-target screening analysis method of chlorinated and brominated organic pollutants in sludge according to an embodiment of the present application;

[0015] Figure 2is a schematic diagram of an optional analysis method for detecting polar substances in sludge according to an embodiment of the present application;

[0016] Figure 3 is a schematic diagram of an optional analysis method for detecting medium-polar or non-polar substances in sludge according to an embodiment of the present application;

[0017] Figure 4 is a schematic diagram of chlorinated organic compounds screened in the data analysis process according to an embodiment of the present application;

[0018] Figure 5 is a schematic diagram of brominated organic compounds screened in the data analysis process according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to enable persons skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative labor should fall within the scope of protection of the present application.

[0020] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0021] According to an aspect of an embodiment of the present application, an example of a non-targeted screening analysis method for chlorinated and brominated organic pollutants in sludge is provided. Figure 1 is a flowchart of a non-targeted screening analysis method for chlorinated and brominated organic pollutants in sludge according to an embodiment of the present application, as shown in Figure 1 The method can include the following steps:

[0022] Step S101, the collected sludge sample is subjected to freeze-drying treatment by a freeze dryer, ground through a 200-mesh sieve, and 2 g of the sample is taken, of which 1 g is used as sample 1 and 1 g is used as sample 2, and placed in different 15-mL centrifuge tubes (15 mL here represents volume or capacity).

[0023] The sample 1 is used for detecting polar substances, and the sample 2 is used for detecting medium-polar or non-polar substances.

[0024] Step S102, methanol is added to the centrifuge tube of sample 1, and a mixed solution of n-hexane and dichloromethane (v:v = 1:1) is added to the centrifuge tube of sample 2 as an extractant (v represents volume, v:v represents the volume ratio of n-hexane and dichloromethane, and similar expressions are similar, which will not be repeated hereinafter).

[0025] Step S103, the extraction method is ultrasonic extraction, and the supernatant part in the centrifuge tube is collected after the extractive liquid obtained by extracting sample 1 and sample 2 respectively is subjected to centrifugation by a centrifuge.

[0026] When the sample 1 and the sample 2 are subjected to ultrasonic extraction: the volume of the extractant in the centrifuge tube of the sample 1 and the sample 2 is 5 mL, and the extraction time of ultrasonic extraction is 15 min.

[0027] Step S104, the supernatant of sample 1 and the supernatant of sample 2 obtained by repeatedly undergoing 3 times of ultrasonic extraction and centrifugation are collected, the supernatant of sample 1 and the supernatant of sample 2 are blown to near dryness by a nitrogen blowing instrument, and the sample 1 is redissolved with 5 mL of 5% methanol-water solution, and the sample 2 is redissolved with 1 mL of a mixed solution of n-hexane and dichloromethane (v:v = 1:1). Near dry here means that the liquid content is less than a certain value (such as 1%, 2%, which can be determined according to industry regulations or specific needs).

[0028] When the supernatant part in the centrifuge tube is extracted after the extractive liquid obtained by extracting the sample is subjected to centrifugation by a centrifuge: the centrifugal speed of the centrifuge is 8500 r / min, the centrifugation time is 10 min, and the temperature is 4℃.

[0029] Step S105, after the redissolved sample 1 solution is loaded into the activated solid-phase extraction column, it is eluted with 2% acetic acid-5% methanol-water solution (v:v:v = 2:5:93), and then eluted with methanol, and the eluate of sample 1 is collected. After the redissolved sample 2 solution is loaded into the activated solid-phase extraction column, it is eluted with a mixed solution of n-hexane and dichloromethane (v:v = 1:1), and the eluate of sample 2 is collected.

[0030] When purifying and concentrating sample 1 using a solid phase extraction column: the solid phase extraction column is a Cleanert PEP solid phase extraction column; the solutions used for activation are 5 mL of methanol and 5 mL of water, respectively; the solution used for elution is 5 mL of methanol.

[0031] When purifying and concentrating sample 2 using a solid phase extraction column: the solid phase extraction column is a Supelclean ENVI-Carb TM The solid phase extraction column is a Supelclean ENVI-Carb solid phase extraction column; the solutions used for activation are 5 mL of dichloromethane and 5 mL of n-hexane, respectively; the solution used for elution is 5 mL of a mixed solution of n-hexane and dichloromethane (v:v = 1:1).

[0032] Step S106, the eluate of sample 1 and the eluate of sample 2 are blown to near dryness using a nitrogen blowing instrument. After sample 1 is redissolved using methanol, it is transferred to a 2 mL sample injection vial and diluted to 1 mL with methanol. After sample 2 is redissolved using n-hexane, it is transferred to a 2 mL sample injection vial and diluted to 1 mL with n-hexane.

[0033] Step S107, the solution of sample 1 obtained after pretreatment is detected using LC-HRMS (i.e., liquid chromatography tandem high-resolution mass spectrometry), and the instrument analysis data of sample 1 are obtained. The solution of sample 2 obtained after pretreatment is detected using GC-HRMS (i.e., gas chromatography tandem high-resolution mass spectrometry), and the instrument analysis data of sample 2 are obtained.

[0034] Step S108, after the instrument analysis data of sample 1 and the instrument analysis data of sample 2 are converted to mzXML data format using MSConvert software, they are uploaded to the XCMS Online website for mass spectrum data extraction processing. The XCMS Online website can extract the mass-to-charge ratio (m / z) of a single chromatographic peak in the total ion chromatogram (Total Ion Chromatogram) of data in a specific format, the corrected retention time (RT), and calculate the response intensity (intensity) of the chromatographic peak.

[0035] Step S109, after the results obtained after extraction and processing by the XCMS Online website are screened by the RStudio language program, the mass-to-charge ratios of the candidate chlorinated and brominated organic compound parent ions are obtained.

[0036] In the embodiments of the present application, different extractants are used to extract different polar target compounds in the sludge sample, and different solid-phase extraction columns are used to purify and concentrate the sample. Based on liquid chromatography-high resolution mass spectrometry (LC-HRMS) and gas chromatography-high resolution mass spectrometry (GC-HRMS), the information of chlorinated and brominated organic compounds in the sample can be obtained as completely as possible. The instrument data obtained is converted into data format by using MS Convert software, the mass spectrometry information is extracted by using XCMS Online website, and the language is processed by using RStudio, so that the chlorinated and brominated organic compounds in the sludge sample can be screened quickly and accurately. The present application solves the technical problem in the related art that the analysis method of halogenated organic pollutants does not have the non-target screening capability for multiple halogenated organic pollutants.

[0037] As an optional embodiment, the present application provides a pretreatment method for analyzing chlorinated and brominated organic compounds in a sludge sample. According to the characteristics of the polarity difference of chlorinated and brominated organic compounds in the sample, different extractants are used to extract different polar target compounds in the sludge sample, and different solid-phase extraction columns are used to purify and concentrate the sample. Based on liquid chromatography-high resolution mass spectrometry (LC-HRMS) and gas chromatography-high resolution mass spectrometry (GC-HRMS), the information of chlorinated and brominated organic compounds in the sample can be obtained as completely as possible. The instrument data obtained is converted into data format by using MS Convert software, the mass spectrometry information is extracted by using XCMS Online website, and the language is processed by using RStudio, so that the chlorinated and brominated organic compounds in the sludge sample can be screened quickly and accurately. The present application solves the technical problem in the related art that the analysis method of halogenated organic pollutants does not have the non-target screening capability for multiple halogenated organic pollutants.

[0038] (1) As shown in Figure 2 For sample 1 (detecting polar chlorinated and brominated organic compounds in sludge): 1 g of cold-dried, ground and sieved sludge sample was accurately weighed, 5 mL of methanol was added to a 15 mL centrifuge tube, and ultrasonic extraction was performed. The obtained extract was centrifuged at 8500 r / min and 4°C for 10 min, and the supernatant was extracted. The extraction was repeated 3 times, and the supernatants were combined. The sample supernatant was blown to near dryness by using a nitrogen blowing instrument, and then redissolved in 5 mL of 5% methanol-water solution. Cleanert PEP solid-phase extraction column was used to purify and concentrate the sludge sample. The solid-phase extraction column was activated with 5 mL of methanol and water, respectively. After loading, 5 mL of 2% acetic acid-5% methanol-water (v:v:v=2:5:93) solution was used for elution, and finally 5 mL of methanol was used for elution. The eluate was collected, blown to near dryness by using a nitrogen blowing instrument, redissolved with methanol, transferred to a 2 mL sample vial, and diluted to 1 mL with methanol. Liquid chromatography-high resolution mass spectrometry was used for instrument analysis.

[0039] (2) As shown in Figure 3As shown, for sample 2 (detecting medium-polar or non-polar chlorinated and brominated organics in sludge): accurately weigh 1 g of cold-dried, ground and sieved sludge sample, add 5 mL of a mixed solution of n-hexane and dichloromethane (v:v = 1:1) in a 15 mL centrifuge tube, ultrasonic extraction, and after centrifugation at 8500 r / min at 4°C for 10 min, the supernatant is extracted, repeated extraction 3 times, and the supernatant is combined; the sample supernatant is blown to near dryness with a nitrogen blowing instrument, and then redissolved in 1 mL of a mixed solution of n-hexane and dichloromethane (v:v = 1:1); the Supelclean ENVI-Carb TM The solid phase extraction column is used for purification and concentration of the sample. The solid phase extraction column is activated with 5 mL of n-hexane and dichloromethane, respectively, and after loading, elution is performed with 5 mL of a mixed solution of n-hexane and dichloromethane (v:v = 1:1). The eluate is collected, blown to near dryness with nitrogen, redissolved with n-hexane, transferred to a 2 mL sample vial, and diluted to 1 mL with n-hexane, and analyzed by gas chromatography-tandem high-resolution mass spectrometry.

[0040] The present application provides a non-targeted screening analysis method for chlorinated and brominated organics in sludge samples, which mainly uses MS Convert software to convert the obtained instrument data into data format, extracts mass spectrometry information from XCMS Online website, and processes language with RStudio, and finally calculates m / z with Xcalibur software to match the elemental composition of chlorinated and brominated organics to obtain the molecular formula. The specific operation steps are as follows:

[0041] (1) Convert the obtained raw instrument data into mzXML format by MS Convert software.

[0042] (2) Upload the data converted into mzXML format to the XCMS Online website for data preprocessing.

[0043] (3) Download the results in the process of (2), and change the file format to ".csv" format.

[0044] (4) Rename the "into" list header in the data file table obtained in (3) to "int", delete other columns in the file table, and add a sequence column before the first column of the modified data table.

[0045] (5) Run the RStudio language program for the data table obtained in (4) to obtain the candidate m / z of chlorinated and brominated organics.

[0046] (6) Calculate m / z with Xcalibur software to match the elemental composition of chlorinated and brominated compounds to obtain the molecular formula of chlorinated and brominated organics.

[0047] The related process is realized by computer software, and the specific implementation mode is as follows (the character "#" represents the interpretation of a paragraph or a line of code):

[0048]

[0049]

[0050] As shown in Figure 4 and Figure 5 , the present application provides a legend of chlorinated and brominated organic compounds screened in the data analysis process.

[0051] Compared with the prior art, the method has the advantages and positive effects that: by taking different extractants for the sludge samples, different polar target compounds in the samples can be extracted, different solid-phase extraction columns are used for purifying and concentrating the samples, and based on liquid chromatography tandem high-resolution mass spectrometry and gas chromatography tandem high-resolution mass spectrometry, the information of chlorinated and brominated organic compounds in the samples can be obtained as completely as possible. By using MS Convert software to convert the obtained instrument data, XCMS Online website mass spectrum information extraction and RStudio language processing, the chlorinated and brominated organic compounds in the sludge samples can be screened quickly and accurately.

[0052] It should be noted that, for the foregoing method embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the action sequence described, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification all belong to preferred embodiments, and the actions and modules involved are not necessarily necessary for the present application.

Claims

1. A method of non-targeted screening analysis of chlorinated and brominated organic pollutants in sludge, characterized in that, Comprising: The collected sludge sample was treated by freeze-drying machine, ground through 200 mesh sieve, and 2 g sample was taken, 1 g as sample 1 and 1 g as sample 2, and placed in different 15 mL centrifuge tubes; Methanol was added to the centrifuge tube of sample 1, and a mixed solution of n-hexane and dichloromethane with a volume ratio of v:v = 1:1 was added to the centrifuge tube of sample 2 as an extractant; The extraction method was ultrasonic extraction, and the supernatant in the centrifuge tube was collected after the extracted liquid obtained by extracting sample 1 and sample 2 respectively was centrifuged by a centrifuge; The supernatant of sample 1 and the supernatant of sample 2 obtained by repeatedly experiencing 3 times of ultrasonic extraction and centrifugation were collected, and the supernatant of sample 1 and the supernatant of sample 2 were blown to near dryness by nitrogen blowing instrument, and 5 mL of 5% methanol-water solution was used to re-dissolve sample 1, and 1 mL of mixed solution of n-hexane and dichloromethane with a volume ratio of v:v = 1:1 was used to re-dissolve sample 2; After re-dissolving, the solution of sample 1 was loaded onto the activated solid phase extraction column, and a 2% acetic acid-5% methanol-water solution with a volume ratio of v:v:v = 2:5:93 was used for elution, followed by methanol elution, and the eluent of sample 1 was collected; the solution of sample 2 obtained after re-dissolving was loaded onto the activated solid phase extraction column, and a mixed solution of n-hexane and dichloromethane with a volume ratio of v:v = 1:1 was used for elution, and the eluent of sample 2 was collected; The eluent of sample 1 and the eluent of sample 2 were blown to near dryness by nitrogen blowing instrument, sample 1 was re-dissolved with methanol and transferred to a 2 mL sample vial, and the volume was made to 1 mL with methanol; sample 2 was re-dissolved with n-hexane and transferred to a 2 mL sample vial, and the volume was made to 1 mL with n-hexane; The solution of sample 1 obtained after pretreatment was detected by liquid chromatography-tandem high-resolution mass spectrometry, and the instrument analysis data of sample 1 was obtained; the solution of sample 2 obtained after pretreatment was detected by gas chromatography-tandem high-resolution mass spectrometry, and the instrument analysis data of sample 2 was obtained; After the instrument analysis data of sample 1 and the instrument analysis data of sample 2 were converted to mzXML data format by MSConvert software, they were uploaded to XCMS Online website for mass spectrum data extraction and processing, XCMS Online website could extract the mass-to-charge ratio, corrected retention time and calculate the response intensity of single chromatographic peak in the total ion chromatogram of specific format data from the website; After the results obtained after extraction and processing by XCMS Online website were screened by RStudio language program, the mass-to-charge ratio of the candidate chlorinated and brominated organic compound parent ions was obtained.

2. The method of claim 1, wherein: Sample 1 is used to detect polar substances, and sample 2 is used to detect moderately polar or non-polar substances.

3. The method of claim 1, wherein, During ultrasonic extraction of sample 1 and sample 2: The volume of extractant in the centrifuge tube of sample 1 and sample 2 was 5 mL.

4. The method of claim 1, wherein, During ultrasonic extraction of sample 1 and sample 2: The extraction time of ultrasonic extraction was 15 min.

5. The method of claim 1, wherein, After the sample is extracted, the supernatant in the centrifuge tube is extracted after the centrifuge is centrifuged: The centrifuge speed is 8500 r / min, the centrifugation time is 10 min, and the temperature is 4°C.

6. The method of claim 1, wherein, When the sample 1 is purified and concentrated by using the solid phase extraction column: The solid phase extraction column is Cleanert PEP solid phase extraction column; The solutions used for activation are 5 mL of methanol and 5 mL of water, respectively; The solution used for elution is 5 mL of methanol. When the sample 2 is purified and concentrated by using the solid phase extraction column:

7. The method of claim 1, wherein, The solutions used for activation are 5 mL of dichloromethane and 5 mL of n-hexane, respectively; The solid phase extraction column was Supelclean ENVI-Carb TM Solid phase extraction column; The solution used for elution is a mixed solution of 5 mL of n-hexane and dichloromethane, with a volume ratio of v:v = 1:

1. ​

Images