Extraction head for detecting phenolic compounds and detection method thereof

Abstract

The invention discloses an extraction head for detecting phenolic compounds and a detection method thereof, and the extraction head is a composite material of 3, 6-diaminocarbazole and 1-hexadecyl-3-methylimidazolium tetrafluoroborate. Therefore, the obtained coating is more compact in structure and smaller in particle size, and the formed coating is more stable in performance, can effectively detect phenolic compounds and has higher sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry and environmental analysis, and particularly relates to an extraction head for detecting phenolic compounds and a detection method thereof. BACKGROUND

[0002] Phenolic compounds have a special aromatic odor, are easy to oxidize, and are soluble in organic solvents such as ethanol and trichloromethane, and are important raw materials for manufacturing high polymer materials and synthetic fibers; when volatile phenolic compounds are absorbed by the human body, they can cause poisoning and even death. Therefore, the detection of phenolic compounds in water has certain significance, especially the six phenolic compounds of phenol, m-cresol, 4-nitrophenol, pentachlorophenol, 2, 4-dichlorophenol and 2, 4, 6-trichlorophenol have been listed in the blacklist of priority controlled pollutants in water in China, and it is of certain practical significance to construct a high-sensitivity analysis of their content in the environment. The sample pretreatment in the current detection method of phenolic compounds in water samples is complex, time-consuming and high-cost. SUMMARY

[0003] In order to solve the above problems, the present application provides an extraction head for detecting phenolic compounds and a detection method thereof.

[0004] According to one aspect of the present application, an extraction head for detecting phenolic compounds is provided, which is a composite material of polymerized 3, 6-diaminocarbazole and 1-hexadecyl-3-methyl imidazole tetrafluoroborate.

[0005] The beneficial effect is that the extraction head has good polymerization effect of 3, 6-diaminocarbazole and 1-hexadecyl-3-methyl imidazole tetrafluoroborate, the obtained coating structure is more dense, the particle size is smaller, the formed coating performance is more stable, and the phenolic compounds can be effectively detected with high sensitivity.

[0006] In some embodiments, the method for preparing the extraction head comprises: configuring a mixed solution of monomers as 3, 6-diaminocarbazole and IL as 1-hexadecyl-3-methyl imidazole tetrafluoroborate; inserting an electrode system into the mixed solution to prepare a composite extraction head by cyclic voltammetry.

[0007] The beneficial effect is that such an extraction head can effectively detect phenolic compounds with high sensitivity.

[0008] In some embodiments, the electrode system is: Ag / AgCl as a reference electrode; platinum wire as an auxiliary electrode; and stainless steel wire as a working electrode.

[0009] The beneficial effect is that such an extraction head can effectively detect phenolic compounds with high sensitivity.

[0010] In some embodiments, the preparation method further comprises the following steps: Preparation of the sample injection device of the composite extraction head; Aging of the composite extraction head of the sample injection device, and natural air drying after aging is completed for standby, wherein the aging comprises the following steps: The temperature is raised from 0℃ to 90℃ and kept for 30min; The temperature is raised from 90℃ to 180℃ and kept for 30min; The temperature is raised from 180℃ to 230℃ and kept for 60min.

[0011] The beneficial effect is that such an extraction head can effectively detect phenolic compounds with high sensitivity.

[0012] According to another aspect of the present application, a detection method of phenolic compounds is provided, comprising the following steps: Headspace extraction of phenolic compounds by the composite extraction head of claims 1-4; Construction of gas chromatography-mass spectrometry, and detection of phenolic compounds by the extraction head.

[0013] In some embodiments, the headspace extraction of phenolic compounds by the composite extraction head comprises the following steps: Configuration of phenolic standard solution; Configuration of phenolic working solution; HS-SPME operation is performed, and after completion, GC-MS operation is performed.

[0014] The beneficial effect is that the extraction head has good polymerization effect of polymeric 3, 6-diaminocarbazole and 1-hexadecyl-3-methyl imidazole tetrafluoroborate, the obtained coating structure is more dense, the particle size is smaller, and the performance of the formed coating is more stable. Such an extraction head can effectively detect phenolic compounds with high sensitivity.

[0015] In some embodiments, the HS-SPME operation comprises the following steps: Saturated sodium chloride solution and phenolic standard solution are added to the extraction bottle to form a first mixed solution; Water bath heating and stirring of the first mixed solution; Inserting the sample injection device into the headspace extraction bottle, and exposing the extraction head of the sample injection device to the upper space of the extraction bottle for headspace extraction.

[0016] Its beneficial effects are: the extraction head is polymerized with 3,6-diaminocarbazole and 1-hexadecyl-3-methylimidazolium tetrafluoroborate, which has a better polymerization effect, resulting in a denser coating structure, smaller particle size, and more stable coating performance. Such an extraction head can effectively detect phenolic compounds and has high sensitivity.

[0017] In some implementations, GC-MS operation includes the following steps: After completing the HS-SPME operation steps, Retract the extraction head into the protective sleeve, quickly insert it into the GC-MS injection port, analyze it, and then perform GC-MS separation and detection.

[0018] Its beneficial effects are: the extraction head is polymerized with 3,6-diaminocarbazole and 1-hexadecyl-3-methylimidazolium tetrafluoroborate, which has a better polymerization effect, resulting in a denser coating structure, smaller particle size, and more stable coating performance. Such an extraction head can effectively detect phenolic compounds and has high sensitivity.

[0019] In some implementations... Extraction time is 10-35 min; and / or the stirring speed range is 200 r / min-700 r / min; And / or the extraction temperature is 20 ℃-70 ℃; and / or the salt volume is 8 mL-12 mL; And / or the parsing time is 5 minutes.

[0020] In some embodiments, the extraction time is 30 minutes; And / or the stirring speed range is 500 r / min; And / or the extraction temperature is 50 °C; And / or the volume of the salt is 10 mL; And / or the resolution time is 5 minutes.

[0021] Its beneficial effect is that it can effectively detect phenolic compounds under these parameters and has high sensitivity. Attached Figure Description

[0022] Figure 1 This is a cyclic voltammogram of the electropolymerization of 6-diaminocarbazole according to an embodiment of this invention application; Figure 2 This is a cyclic voltammogram of the electropolymerization of 3,6-diaminocarbazole and 1-hexadecyl-3-methylimidazolium tetrafluoroborate according to an embodiment of this invention. Figure 3 This is a SEM image of polymerized 3,6-diaminocarbazole; Figure 4 This is a SEM image of polymerized 3,6-diaminocarbazole; Figure 5 This is a SEM image of the product doped with 1-hexadecyl-3-methylimidazolium tetrafluoroborate; Figure 6 This is a SEM image of the product doped with 1-hexadecyl-3-methylimidazolium tetrafluoroborate; Figure 7 This is a view of the effect of extraction time on the response peak area; Figure 8 This is a view showing the effect of stirring rate on the response peak area; Figure 9 This is a view of the effect of temperature on the response peak area; Figure 10 This is a view showing the effect of salt volume on the response peak area; Figure 11 This is a view of the effect of resolution time on the response peak area; Figure 12 It is a curve of a mixed phenolic compound standard solution. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] I. Instrument and Reagent Instructions Table 1 - Main Instruments

[0025] Table 2 - Main Reagents II. Specific Implementation Methods Example 1: Preparation of different types of SPME coatings 1. Stainless steel wire treatment Measure several 2.0 cm stainless steel wires with a steel ruler and grind them smooth. Sonicate them for 5 min in a solution prepared with nitric acid:water = 1:1 (HNO3:H2O). Rinse them 2-3 times with deionized water and anhydrous ethanol respectively, and air dry them under natural conditions for later use.

[0027] 2. Electrochemical polymerization of SPME coating The SPME coating method employed electrochemical deposition, with preparation performed on an electrochemical workstation (CHI600E). The experiment used a single-cell three-electrode mode, with Ag / AgCl as the reference electrode, platinum wire as the auxiliary electrode, and stainless steel wire as the working electrode. Cyclic voltammetry was used for preparation, with a scan potential ranging from 1.2 V to 2.0 V and a scan rate of 0.1 V / s. The electrolyte was an acetonitrile solution containing 0.01 mol / L 3,6-diaminocarbazole, 20 μg / mL 1-hexadecyl-3-methylimidazolium tetrafluoroborate, and 0.1 mol / L tetrabutylammonium perchlorate. CV scanning was used to polymerize the 3,6-diaminocarbazole-IL SPME coating. For the preparation of the 3,6-diaminocarbazole coating, the electrolyte was an acetonitrile solution containing 0.01 mol / L 3,6-diaminocarbazole (20 μg / mL) and 0.1 mol / L tetrabutylammonium perchlorate.

[0028] 3. Coating aging and sample injector fabrication After the coating is prepared, it is taken out and placed on a foam board to air dry naturally, and then aged in a TF1200-80 vacuum tube furnace.

[0029] Table 3 - Aging Procedure

[0030] After aging, epoxy resin and acyl oxy resin (1:1) were mixed, and the extraction head was attached to a laboratory-made solid phase microextraction handle and allowed to air dry.

[0031] Example 2: Solution Preparation 1. Preparation of standard solutions Table 4 - Preparation of Standard Solutions

[0032] The solvent used to prepare the solution is methanol, and the solution is stored in a refrigerator.

[0033] 2. Preparation of working fluid Table 5 - Preparation of Working Fluid

[0034] The working solution is prepared by diluting with a saturated NaCl solution.

[0035] Example 3: Headspace Extraction HS-SPME-GC-MS Operation Procedure For HS-SPME operation, transfer 10.00 mL of saturated sodium chloride solution into a 15.00 mL extraction flask, place a magnetic stir bar inside, add 0.05 mL of the standard solution from Table 4, seal the flask with raw rubber tape, plug it with a rubber stopper, and then seal it with an aluminum cap. Heat and stir in a water bath.

[0036] 2. GC-MS Operations After the HS-SPME step is completed, retract the extraction head into the protective sleeve, pull out the SPME device and insert it into the GC-MS injection port (to prevent loss due to the volatilization of extracted compounds, it should be inserted into the injection port as soon as possible), pull it out after 5 minutes of analysis, and then perform analysis and detection.

[0037] The GC condition parameters are as follows: Table 6 - GC Conditions

[0038] The MS condition parameters are as follows: Table 7 - MS Condition Parameters

[0039] Table 8- C8H9ClO, C6H4ClFO, C8H 10 Characteristic selected ions of O

[0040] III. Effect Comparison 1. Voltammetric behavior of extraction coatings prepared by electropolymerization A solid-phase microextraction head was prepared using cyclic voltammetry, and cyclic voltammetry was recorded using acetonitrile as the medium. During the electrochemical polymerization process, the stainless steel wire surface turned black, confirming the formation of the composite coating.

[0041] from Figure 1 As can be seen, when 3,6-diaminocarbazole is used as the monomer, a distinct upward peak was observed at an oxidation potential of 1.0 V in the first CV curve. Two more distinct oxidation peaks appeared at potentials of approximately 1.3 V and 1.6 V. Subsequently, with increasing scan number, the peak current weakened, and the oxidation potential decreased. This is related to the monomer electrochemical reaction during the electropolymerization process. The reason is that the upward peak at 1.0 V is mainly due to the polymerization of the amino structure, while the subsequent two distinct oxidation peaks are oxidation peaks produced by the electrochemical reaction of the carbazole ring structure polymerization.

[0042] from Figure 2 It can be seen that the oxidation peak appears at around 1.7 V in the first cycle. As the number of polymerization cycles increases, the oxidation peak shifts to the right and the peak current increases, indicating that the polymerized 3,6-diaminocarbazole and 1-hexadecyl-3-methylimidazolium tetrafluoroborate are well combined and more stable than other coatings.

[0043] 2. Microscopic characterization of different extraction coatings like Figures 3-4As shown, the microstructure of the prepared extraction coating was characterized using scanning electron microscopy (SEM). The SEM image of 3,6-diaminocarbazole obtained by polymerization with 3,6-diaminocarbazole as the monomer under a potential of 0.4-1.8 V is shown below. Figure 3 and Figure 4 As can be seen from the figure, the resulting polymer coating consists of continuous particles with a particle size of approximately 200 nm, exhibiting a porous structure; in its low-magnification structure ( Figure 4 It can be observed that a dense film is formed and grows tightly on the surface of the steel wire, indicating that the polymer coating has good stability.

[0044] like Figures 5-6 As shown, particulate polymers can be observed on the surface of the dense polymer coating. The dense structure is related to the polymerization of carbazole with amino groups, while the particulate structure is related to the polymerization of carbazole rings. This structure is more pronounced in its low-magnification images. Figures 3-4 Compared to the SEM image of the polymerized 3,6-diaminocarbazole, the coating structure is more compact and the particle size is smaller.

[0045] This indicates that the addition of IL, namely 1-hexadecyl-3-methylimidazolium tetrafluoroborate, to the electrolyte has a significant impact on the structure of the polymer membrane, which is consistent with the results of its electrochemical CV curve.

[0046] IV. Condition Optimization Using the coating prepared in Example 1, namely 3,6-diaminocarbazole doped with 1-hexadecyl-3-methylimidazolium tetrafluoroborate, as the extraction head, the extraction time, extraction temperature, stirring rate, extraction salt volume, and desorption time were optimized.

[0047] 1. Extraction time like Figure 7 As shown, the effect of the constructed analytical method on the peak area of ​​the target analyte is observed when the extraction time varies from 10 to 35 min. As the figure shows, the peak area response increases with increasing extraction time, reaching its maximum at 30 min; subsequently, further increases in extraction time lead to a decrease in peak area. Therefore, the optimal extraction time should be 30 min. This is because the extraction amount of the target analyte in the extraction coating increases with extraction time, but as the extraction time increases, the target analyte is released again from the coating into the headspace, restoring the equilibrium.

[0048] 2. Stirring speed In headspace extraction, the stirring rate is closely related to mass transfer. Figure 8It can be seen that when the stirring speed range is 200 r / min - 700 r / min, the response peak area increases with increasing stirring speed, and reaches its maximum value at 500 r / min, followed by a decrease. This indicates that within a suitable stirring speed range, increasing the stirring speed can improve the extraction rate, because a faster stirring speed facilitates the volatilization of the three phenolic compounds, thereby improving the extraction efficiency. (C8H9ClO, C6H4ClFO, and C8H...) 10 The optimal stirring rate for all three phenolic compounds is 500 r / min.

[0049] 3. Extraction temperature In headspace extraction, appropriately increasing the extraction temperature can shorten the time to reach equilibrium, but it also affects the coefficient of thermal expansion of the extracted coating. The effect of varying the extraction temperature between 20 ℃ and 70 ℃ on the response peak area was investigated.

[0050] Depend on Figure 9 It is known that the response peak area reaches its maximum value at an extraction temperature of 50 ℃, and then decreases as the temperature continues to rise. Therefore, the optimal temperature for headspace extraction should be 50 ℃. The reason for the decrease in peak area is that excessively high temperatures increase the coefficient of thermal expansion of the coating, leading to a decrease in the coating's peak area, which in turn reduces the coating's extraction capacity, thus resulting in a decrease in the response peak area.

[0051] 4. Salt volume The effect of varying salt volume from 8 mL to 12 mL on peak area was investigated. Figure 10 It is known that the optimal salt volume for headspace extraction of the three target components should be 10 mL, at which point the response peak areas all reach their maximum values. This is related to the concentration changes of the target analytes in the headspace, and also affects their concentration balance with the SPME coating.

[0052] 5. Resolution time After headspace extraction is complete, the extraction apparatus should be inserted into the GC-MS inlet as soon as possible to complete the analysis. If the analysis time is too short, incomplete analysis may occur, leading to a reduced analyte concentration and introducing errors; conversely, if the analysis time is too long, it is detrimental to the experimental detection and analysis. Therefore, this experiment optimized the analysis time, and the results are as follows: Figure 11 As shown, the optimal resolution time is 5 minutes, at which point the response peak area reaches its maximum and the effect is best.

[0053] Example 4 Detection and Analysis Under the optimized conditions described above, a coating prepared by doping 3,6-diaminocarbazole with 1-hexadecyl-3-methylimidazolium tetrafluoroborate was used as the extraction head. GC-MS was then used to detect mixed phenolic compounds of different concentrations. The experimental results...Figure 12 As shown in the figure. The results indicate that the peak area response increases with increasing standard solution concentration, exhibiting a good linear relationship. (4-Chloro-3,5-dimethylphenol, 2,6-dimethoxyphenol, 3-chloro-4-fluorophenol R) 2 The values ​​were 0.9994, 0.9991, and 0.9957, respectively, showing good response within the range of 0.1 mg / mL to 0.5 mg / mL. To demonstrate experimental reproducibility, the target component was determined in triplicate, with an RSD of 15.32%.

[0054] Example 6: Actual Sample Testing Using the coating prepared from 3,6-diaminocarbazole doped with 1-hexadecyl-3-methylimidazolium tetrafluoroborate in Example 1 as the extraction head, GC-MS was used to analyze the bottled drinking water from Mile Mountain Spring. The water sample was filtered, shaken, and a certain amount was transferred, with excess NaCl added to prepare a saturated salt solution. 10 mL was transferred to a headspace vial, sealed with raw rubber tape, plugged with a rubber stopper, and then sealed with an aluminum cap. Headspace extraction was performed under optimized conditions, and the extraction device was then inserted into the GC-MS inlet for analysis. The experimental results showed that 4-chloro-3,5-dimethylphenol, 2,6-dimethoxyphenol, and 3-chloro-4-fluorophenol were not detected. To further evaluate the determination method, the same extraction head was used to spike and recover the drinking water; the recovery rates are shown in Table 9. Table 9 - Spike Recovery Rate of Actual Samples

[0055] Therefore, the detection method of this application can detect 4-chloro-3,5-dimethylphenol, 2,6-dimethoxyphenol and 3-chloro-4-fluorophenol in bottled drinking water from Mile Mountain Spring. The spiked recovery rate is between 90% and 115%, indicating that the method has certain practicality and reliability.

[0056] The above descriptions are merely some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An extraction head for detecting phenolic compounds, characterized in that, The extraction head is a composite material of 3,6-diaminocarbazole and 1-hexadecyl-3-methylimidazolium tetrafluoroborate.

2. The extraction head according to claim 1, characterized in that, The method for preparing the extraction head includes: Prepare a mixed solution with 3,6-diaminocarbazole as the monomer and 1-hexadecyl-3-methylimidazolium tetrafluoroborate as the solvent; The electrode system was inserted into the mixed solution, and a composite extraction head was prepared by cyclic voltammetry.

3. The extraction head according to claim 2, characterized in that, The electrode system consists of: Ag / AgCl as the reference electrode; platinum wire as the auxiliary electrode; and stainless steel wire as the working electrode.

4. The extraction head for detecting phenolic compounds according to claim 2, characterized in that, The preparation method further includes the following steps: A sample introduction device for preparing a composite extraction head; The composite extraction head of the sample introduction device is aged, and after aging, it is air-dried for later use. The aging process includes the following steps: After raising the temperature from 0℃ to 90℃, maintain the temperature for 30 minutes. After raising the temperature from 90℃ to 180℃, maintain the temperature for 30 minutes. The temperature was raised from 180℃ to 230℃ and then kept at that temperature for 60 minutes.

5. A method for detecting phenolic compounds, characterized in that, Includes the following steps: The composite extraction head described in claims 1-4 is used for headspace extraction of phenolic compounds; A gas chromatography-mass spectrometry (GC-MS) model was constructed, and the extraction head was used to detect phenolic compounds.

6. The detection method according to claim 5, characterized in that, The headspace extraction of phenolic compounds using the composite extraction head includes the following steps: Prepare phenolic standard solutions; Prepare phenolic working solutions; Perform the HS-SPME operation; upon completion, Perform GC-MS operation.

7. The detection method according to claim 6, characterized in that, The HS-SPME operation includes the following steps: A saturated sodium chloride solution and a phenolic standard solution are added to the extraction flask to form the first mixture. The first mixture was heated and stirred in a water bath; Insert the injection device into the headspace extraction vial and expose the extraction head of the injection device above the extraction vial for headspace extraction.

8. The detection method according to claim 7, characterized in that, The GC-MS operation includes the following steps: After the HS-SPME operation steps are completed, Retract the extraction head into the protective sleeve, quickly insert it into the GC-MS injection port, analyze it, and then perform GC-MS separation and detection.

9. The detection method according to claim 8, characterized in that, Extraction time is 10-35 min; and / or the stirring speed range is 200 r / min-700 r / min; And / or the extraction temperature is 20 ℃-70 ℃; and / or the salt volume is 8 mL-12 mL; And / or the parsing time is 5 minutes.

10. The detection method according to claim 9, characterized in that, The extraction time is 30 minutes; And / or the stirring speed range is 500 r / min; And / or the extraction temperature is 50 °C; And / or the volume of the salt is 10 mL; And / or the resolution time is 5 minutes.

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