Detection method of N,N-dimethylaniline and extraction head

Abstract

The present application discloses a method for detecting N,N-dimethylaniline, comprising the following steps: preparing a PPY+N-MWCNT+MoS2 composite extraction head; performing headspace extraction of N,N-dimethylaniline with the composite extraction head; constructing a gas chromatography-mass spectrometry (GC-MS), and using the extraction head to detect N,N-dimethylaniline. The beneficial effects are as follows: The PPY+N-MWCNT+MoS2 composite extraction head has better extraction efficiency and mechanical stability for N,N-dimethylaniline. Applying the method of the present application to the detection of N,N-dimethylaniline in actual samples has good sensitivity and practicability.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, and in particular to a detection method and an extraction head for N,N-dimethylaniline. Background Art

[0002] N,N-dimethylaniline (DMA), also known as dimethyl phenyl amine, belongs to the aniline compounds. It is a colorless to light yellow oily liquid with a pungent odor and is highly toxic. It can decompose and release toxic aniline gas under high heat conditions. It is often used as a dye intermediate for the production of vanillin, azo dyes and triphenylmethane dyes; it can also be used as a solvent, stabilizer, analytical reagent and important chemical raw material. In this case, DMA may be discharged into the environment, causing potential pollution to the environment; it is also genotoxic. Genotoxic impurities have a direct effect on human DNA, causing DNA damage, thus carrying carcinogenic, teratogenic or mutagenic properties. Even a very small amount of genotoxic impurities can cause extremely serious harm to the human body. Therefore, its analysis has attracted people's attention. At present, some scholars have used gas chromatography to determine DMA in amoxicillin sodium and liquid chromatography-mass spectrometry to determine DMA in quetiapine fumarate. However, these methods require a large amount of organic solvents as extractants during sample pretreatment, which does not meet the requirements of green environmental protection. Therefore, a green, low-sample-volume, convenient, fast, and solvent-free sample pretreatment technology is one of the important research contents for detecting DAM. Summary of the invention

[0003] In view of the above existing problems, the present invention provides a detection method and an extraction head for N,N-dimethylaniline.

[0004] According to one aspect of the present invention, a method for detecting N,N-dimethylaniline is provided, comprising the following steps: preparing a PPY+N-MWCNT+MoS2 composite extraction head; extracting N,N-dimethylaniline in the headspace of the composite extraction head; constructing a gas chromatography-mass spectrometer (GC-MS), and using the extraction head to detect N,N-dimethylaniline. The beneficial effect is that the PPY+N-MWCNT+MoS2 composite extraction head has better extraction efficiency and mechanical stability for N,N-dimethylaniline. The method of the present application is used for the detection of N,N-dimethylaniline in actual samples, with good sensitivity and practicality.

[0005] In some embodiments, the preparation of the composite extraction head includes the following steps: preparing a mixed solution containing PY, MoS2, and N-MWCNT; placing an electrode system into the mixed solution, and performing CV scanning to prepare the composite extraction head. The beneficial effect is that the composite extraction head prepared in this way has good conductivity and mechanical stability, and has good sensitivity for N,N-dimethylaniline detection.

[0006] In some embodiments, the PY is 7.5 μL / mL; and / or the MoS2 is 0.4 mg / mL; and / or the COOH-MWCNTs is 0.02 mg / mL. The beneficial effects are as follows: The prepared extraction head has good electrical conductivity and mechanical stability, and has good sensitivity for the detection of N,N-dimethylaniline.

[0007] In some embodiments, the following steps are further included: fixing the extraction head in a self-made injector, and after air-drying, an injector device of PPY+N-MWCNT+MoS2 is prepared. The beneficial effects are as follows: to purify the impurities on the extraction head and improve the detection accuracy and sensitivity.

[0008] In some embodiments, the aging conditions are as follows: inserting the injector device into the vaporization chamber of the gas chromatograph for aging, setting the injector port temperature to 90 °C, and aging for 30 min; then continuously raising the injector port temperature to 230-250 °C, and continuously aging for 1.5 h and then setting aside for standby. The beneficial effects are as follows: It can purify the impurities on the extraction head and improve the detection accuracy and sensitivity.

[0009] In some embodiments, the headspace extraction of N,N-dimethylaniline by the composite extraction head includes the following steps: adding saturated sodium chloride solution into the extraction container to form a first mixed solution; stirring the first mixed solution and performing constant-temperature water bath; then adding N,N-dimethylaniline solution and stirring; inserting the injector device into the extraction bottle and exposing the extraction head to the solution headspace, and performing headspace extraction under stirring; retracting the extraction head into the protective sleeve, quickly inserting it into the vaporization chamber of the gas chromatograph, and pushing out the extraction head for desorption, and then performing GC-MS separation and detection. The beneficial effects are as follows: It is more convenient to perform subsequent detection operations.

[0010] In some embodiments, the temperature of the constant-temperature water bath is: 60 °C; the stirring is magnetic stirring, the stirring speed is 200-400 r / min, and the stirring time is 30-50 min. The beneficial effects are as follows: The coating of the extraction head is evenly distributed at this temperature, and the stability is better, so it has better electrical conductivity and sensitivity for the detection of target substances.

[0011] In some embodiments, the extraction time is 30-50 min; and / or the extraction temperature is 20-70 °C; and / or the desorption time is 3-5 min. The beneficial effects are as follows: The coating of the extraction head is evenly distributed at this temperature and time, and the stability is better, so it has better electrical conductivity and sensitivity for the detection of target substances.

[0012] In some embodiments, the cyclic voltammetry range of the CV scan is 0 - 1.5V; the scan rate is 0.05mV / S, and the number of scans is 100 cycles. The beneficial effects are as follows: The coating of the extraction head prepared thereby is evenly distributed and has good stability, thus having better electrical conductivity and sensitivity for detecting target substances.

[0013] According to another aspect of the present application, an extraction head for detecting N,N-dimethylaniline, characterized in that the extraction head comprises a composite material of PY, MoS2, and N-MWCNT. The beneficial effects are as follows: The coating of the extraction head is evenly distributed and has good stability, thus having better electrical conductivity and sensitivity for detecting target substances. The beneficial effects are as follows: The coating of the extraction head is evenly distributed and has good stability, thus having better electrical conductivity and sensitivity for detecting target substances. Description of the Drawings

[0014] Figure 1 Schematic diagram of preparing the coating for the present application;

[0015] Figure 2 Voltammetric behavior of the preparation of the Poly-PY extraction head for the present application;

[0016] Figure 3 Voltammetric behavior diagram of the Poly-PPY+N-MWCNT extraction head;

[0017] Figure 4 Voltammetric behavior diagram of the Poly-PPY+MoS2 extraction head;

[0018] Figure 5 Voltammetric behavior diagram of the preparation of the Poly-PY+N-MWCNT+MoS2 extraction head;

[0019] Figure 6 Peak area responses of different extraction heads to N,N-dimethylaniline;

[0020] Figure 7 Effect of stirring rate on the peak area;

[0021] Figure 8 Effect of extraction temperature on the peak area;

[0022] Figure 9 Effect of extraction time on the peak area;

[0023] Figure 10 Effect of NaCl concentration on the peak area;

[0024] Figure 11 Effect of NaCl volume on the peak area

[0025] Figure 12 To analyze the influence of the analysis time on the peak area;

[0026] Figure 13 It is the standard working curve of N,N-dimethylaniline (DMA);

[0027] Figure 14 It is the chromatogram of the spiked sample of the actual sample at 0.5 µg / mL;

[0028] Figure 15 It is the chromatogram of the spiked sample of the actual sample at 1 µg / mL;

[0029] Figure 16 It is the chromatogram of the spiked sample of the actual sample at 2 µg / mL;

[0030] Figure 17 It is the spiked standard curve. Specific implementation mode

[0031] The present invention will be further described in detail below with reference to the attached drawings, experimental operation conditions, examples, etc.

[0032] I. Description of instruments and reagents

[0033] 1. Main instruments and models

[0034] Gas chromatography-mass spectrometry (Shimadzu GCMS-QP2010), scanning electron microscope (SEM, FEI Company, USA), electrochemical workstation (PGSTAT302N, Switzerland), ultrasonic cleaner (KQ5200E), constant temperature magnetic stirrer (model S10-3), injector (self-made in the experiment).

[0035] 2. Reagents

[0036] Methanol (extra grade chromatographic pure, Changtai Xingye Co., Ltd.), molybdenum disulfide, nitrogen-doped carbon nanotubes (Nanjing Xianfeng Nanomaterials Technology Co., Ltd.), acetonitrile (AR, Tianjin Kemiou Chemical Reagent Co., Ltd.), sodium chloride (AR, Tianjin Fuyu Fine Chemical Co., Ltd.), N,N-dimethylaniline (AR, International Group Chemical Reagent Co., Ltd.). All other reagents not mentioned in this experiment are of analytical grade.

[0037] 3. Acidified nitrogen-doped carbon nanotubes

[0038] Weigh 0.2 g of N-MWCNTs and measure 100 mL of concentrated HNO3 into a round-bottom flask, heat it to 100 °C in a fume hood with a thermostatic heating magnetic stirrer, and reflux for 2 h. After the reflux is completed, let it cool naturally to room temperature, and then wash it by centrifugation with ethanol solution multiple times. Air dry for later use.

[0039] II. GC operation conditions

[0040] Using an Rtx-5Ms chromatographic column as the separation column, the column oven temperature was 50 °C; the inlet temperature was 250 °C, and the injection mode was splitless; the pressure was 73.0 kPa; the total flow rate was 44.0 mL / min; the column flow rate was 1.27 mL / min; the linear velocity was 40.8 cm / sec; the purge flow rate was 3.0 mL / min; the column oven temperature program was set as follows: hold at 50 °C for 3 min, then increase the temperature to 110 °C at a rate of 10 °C / min, and then increase the temperature to 120 °C at a rate of 2 °C / min and hold for 1 min. The ion source temperature was 230 °C; the interface temperature was 200 °C; the solvent delay was 3 min.

[0041] III. Examples

[0042] Example 1: Preparation of a composite SPME fiber

[0043] (1) Treatment of stainless steel wires

[0044] Take several stainless steel wires with a length of 1.7 cm and a radius of 0.3 mm. Polish them with 1000-mesh sandpaper and straighten them with a steel ruler. Then, ultrasonically clean them in a mixed solution of nitric acid and water (5:1, V / V) for 3 - 5 min, and finally rinse them with ethanol several times and dry them for later use.

[0045] (2) Preparation of the solid-phase microextraction coating

[0046] Assemble a three-electrode electrochemical working system with a platinum wire as the counter electrode, a saturated calomel electrode as the reference electrode, and a stainless steel wire as the working electrode. Immerse it in 5 mL of an electrolyte solution containing 7.5 μL / mL PY, 0.4 mg / mL MoS2, and 0.02 mg / mL N-MWCNT. Scan it 100 cycles at a speed of 0.05 mV / s in the cyclic voltammetry range of 0 - 1.5 V to prepare the SPME coating. Then, rinse and remove the surface impurities with ethanol and deionized water, and dry it for later use ( Figure 1 ). After that, bond the extraction fiber to the self-made injector handle of this experiment with a mixed resin of epoxy resin and polyamide resin in a ratio of 1:1, dry it, and wait for the resin to cure to obtain a manual headspace solid-phase microextraction injector of PPY + N-MWCNT + MoS2.

[0047] In addition, for the manual headspace solid-phase microextraction injectors of PPY, PPY + N-MWCNT, PPY + MoS2, and PPY + IL + N-MWCNT + MoS2, except for the different electrolyte compositions, the other parameters are the same as the above preparation method, and the aging conditions are also the same.

[0048] Example 2: Headspace extraction

[0049] Add 6 mL of saturated sodium chloride solution and 5 μL / mL of DMA prepared in a 10 mL extraction bottle, and add a magnetic stir bar. Then seal it airtight with raw tape, plug in a rubber stopper, and seal it with an aluminum cap. Next, place this extraction bottle in a constant temperature water bath at 60 °C, and under magnetic stirring at 400 r / min, insert the injector of the self-made extraction head aged in this experiment into the headspace extraction bottle, and push the extraction head out of the protective sleeve and expose it above the extraction bottle for headspace extraction for 50 min.

[0050] Example 3: GC-MS Analysis

[0051] After the headspace extraction is completed, retract the extraction head into the protective sleeve, and insert it into the injection port of the gas chromatograph vaporization chamber set up and ready according to the GC operating conditions within the shortest time. Then push out the extraction head in the handle protective sleeve, and after fully desorbing for 4.5 min, pull out the injector containing the extraction head. After 5 min, the GC-MS automatically performs separation and detection. The qualitative and quantitative ions of N,N-dimethylaniline are shown in Table 1.

[0052] Table 1 Characteristic selected ion table of N,N-dimethylaniline

[0053]

[0054] Comparison of extraction heads in Example 4

[0055] 1. Cyclic voltammetric behavior of the extraction head

[0056] In this application, CV is used to prepare the solid-phase microextraction head. A stainless-steel wire is used as the working electrode, a platinum wire as the counter electrode, and a saturated calomel electrode as the reference electrode to assemble a three-electrode electrochemical working system. Immerse the three electrodes in the electrolytes of PY, PY+N-MWCNT, PY+MoS2, and PY+N-MWCNT+MoS2, and perform electrodeposition polymerization under the parameter conditions of scanning at a speed of 0.05 mV / S for 100 cycles. The corresponding figure of its voltammetric behavior is Figures 2 - 5 . Figure 2 Compared with other figures, its voltammetric curve is relatively messy. This is because the polymerization solution is carried out in a neutral environment and lacks electrolytes, resulting in slower electron transfer during pyrrole polymerization. Its maximum peak current is 0.00065 A. From Figure 2 it can be seen that with the increase in the number of polymerization cycles and the growth of the polymerization time, the peak current gradually increases, indicating that PPY has good conductivity. Figure 3The oxidation potential of PY is about 0.9 V. At this potential, an obvious oxidation peak appears. Meanwhile, as the voltage increases to 1.2 V, a peroxide peak appears. Its maximum peak current is 0.0014 A. Due to the increase in the number of polymerization cycles and the growth of the polymerization time, the peak current gradually increases, indicating that the polymer coating has good conductivity after being doped with N-MWCNT. Figure 4 The oxidation potential of PY is about 0.6 V. At this potential, an obvious oxidation peak appears. Meanwhile, as the voltage increases to 1.2 V, a peroxide peak appears. Its maximum peak current is 0.0025 A. Due to the increase in the number of polymerization cycles and the growth of the polymerization time, the peak current gradually increases, indicating that the polymer coating has good conductivity after being doped with MoS2. Figure 5 Its maximum peak current is 0.001875 A, and as the number of polymerization cycles and the polymerization time increase, the peak current gradually increases, indicating that the polymer coating has good conductivity after being doped with MoS2 and N-MWCNT.

[0057] 2. Response of the extraction head to DMA

[0058] In this embodiment, it is mainly to verify the response of different extraction heads to the peak area of the same target analyte DMA. As can be seen from the columnar ( Figure 6 ) graph processed from the experimental data, the peak area of the target analyte of the PPY+C+MoS2 extraction head is relatively large; the peak areas of the PPY, PPY+C, and PPY+MoS2 extraction heads in response to the target analyte are moderate. In the electrolyte, after adding MoS2 on the basis of pyrrole monomer and adding N-MWCNT, the peak area of the target analyte detected by the obtained extraction head is much larger than the previous two, and the effect is significant. The reason is that MoS2 and N-MWCNT effectively increase the specific surface area of the extraction head, thereby improving the adsorption capacity.

[0059] 3. Comparison of the stability of the extraction head

[0060] The better extraction heads PPY, PPY+N-MWCNT, PPY+MoS2, and PPY+N-MWCNT+MoS2 are all subjected to 5 repeated experiments to compare the stability of their coatings and the stability of the peak areas of the target analytes detected. Among the four extraction heads, the best one in terms of stability is PPY+N-MWCNT+MoS2PPY+N-MWCNT. Among them, the PPY+N-MWCNT+MoS2 extraction head with the best peak area of the target analyte detected has a stable coating during the experiment and good stability. Therefore, the PPY+N-MWCNT+MoS2 extraction head is finally selected to determine DMA.

[0061] Example 5 Condition Optimization

[0062] 1. Stirring rate

[0063] The stirring rate affects the diffusion of the target analyte from the liquid phase to the gas phase in the headspace vial, but too high a rotation speed is likely to bring about excessive errors. The results show that ( Figure 7 ), the peak area of the target analyte gradually increases. However, due to the imperfect experimental equipment, it is difficult to control the stirring rate precisely. The higher the rate, the more difficult it is to control, which will lead to larger systematic errors and accidental errors in the experiment. Therefore, the stirring rate selected in this experiment is 400 r / min.

[0064] 2. Extraction temperature

[0065] The experiment recorded the change in peak area when the extraction temperature varied from 20 °C to 70 °C ( Figure 8 ). As the temperature increased, the peak area of the target analyte extracted in the experiment became larger and larger. As shown in the figure, as the temperature rose, the extraction efficiency of the coating increased. The extraction efficiency was the highest at 60 °C. However, when the temperature continued to rise, the extraction effect decreased instead. This should be related to the properties of the extraction head prepared in the experiment, the volatility of the target analyte, and the set temperature. An increase in temperature will increase the volatility of the analyte to be measured, so that the analyte to be measured cannot be well adsorbed on the extraction head, but instead circulates and volatilizes in the headspace vial. Of course, too high a temperature also increases the vapor pressure of the gas phase and promotes the adsorption process of the coating. At the same time, the adsorption of the extraction head is an exothermic process. Too high a temperature will cause the distribution coefficient to decrease and the adsorption ability of the coating to decrease, resulting in a decrease in the sensitivity of the extraction head when detecting the target analyte. This leads to an unsatisfactory detection effect and it is impossible to measure the desired optimal peak area to analyze the optimization conditions of the extraction head prepared in the experiment

[20] . Therefore, the experiment was carried out at 60 °C.

[0066] 3. Extraction time

[0067] In order to explore the extraction heads prepared under different factors, the experiment further investigated the effect of extraction time on the extraction efficiency ( Figure 9 ). It can be seen from the DMA curve relationship that as the extraction time increases, the peak area increases; when the extraction time is further increased, the response decreases, probably because the adsorption of the extraction head reaches equilibrium. Therefore, the extraction time selected in this experiment is 50 min.

[0068] 4. Salt concentration

[0069] The experiment investigated the effect of salt concentration on the extraction efficiency ( Figure 10 ). It can be seen from the DMA curve relationship that as the salt concentration increases, the peak area increases; when the salt solution reaches saturation, the peak area is the largest and the adsorption of the extraction head reaches equilibrium. Therefore, the salt concentration selected in this experiment is 0.3 g / mL.

[0070] 5. Salt solution volume

[0071] The extraction bottle used in the experiment was 10 mL. After adding a certain volume of salt solution and DMA, the remaining space would be the space for extracting volatile substances. The results showed that ( Figure 11 ), as the volume of the salt solution increased, the peak area increased; when the volume of the salt solution was further increased, the response decreased, probably because the adsorption of the extraction head reached equilibrium. Therefore, the volume of the salt solution selected in this experiment was 6 mL.

[0072] 6. Desorption time

[0073] The experiment investigated the effect of desorption time on the adsorption effect. The obtained results ( Figure 12 ) showed that as the desorption time increased, the peak area increased; when the desorption time was further increased, the response decreased, indicating that the adsorbed substances were fully desorbed. Therefore, the desorption time selected in this experiment was 4.5 min.

[0074] Analysis performance of Example 6

[0075] 1. Method and evaluation

[0076] Under the optimized conditions, different concentrations of DMA were analyzed under the optimized experimental conditions. From Figure 13 it can be seen that in the linear range of 0.135 - 5 μg / mL, the linear relationship between the peak area and the concentration of DMA was: y = 5772099C - 1890175. It can be seen from the figure that the response peak area increased with the increase of the concentration, and showed a good linear correlation. It can be obtained from Table 2 that this method had good sensitivity and a detection limit of 0.0135 μg / mL (10 times signal-to-noise ratio, 10σ). It indicated that this analytical method had a wide linear range and sensitivity. At the same time, the same concentration of DMA was analyzed in parallel 5 times with 1 extraction head, and the relative standard deviation (RSD) was 4.4% respectively. Samples with the same concentration were analyzed with 3 extraction heads prepared in parallel, and their RSD values were 9.3% respectively, indicating good reproducibility of the extraction heads.

[0077] Table 2 Analytical parameters of N,N-dimethylaniline by PPY+N-MWCNT+MoS2 extraction head

[0078]

[0079] 2. Water sample treatment and inspection

[0080] The established analytical method was used to detect the target analyte in industrial wastewater. The determination was carried out according to the test method, and DMA was not detected. Figures 14 - 16The GC chromatograms of the PPY+N-MWCNT+MoS2 coating after extraction of the actual samples and standard solutions with different concentrations are presented. The concentration of the analyte can be calculated based on the chromatographic peak area and the spiked linear regression equation. Further, a spiked recovery test was carried out by adding standard solutions with a concentration of 0.5-2 μg / mL, and the recovery rate was between 97.50 %-101.92 % (Table 3).

[0081] Table 3 Determination of sample recovery rate

[0082]

[0083] In this application, cyclic voltammetry (CV) was used to electro-polymerize pyrrole (PY) as the polymerization monomer on the surface of a stainless-steel wire. At the same time, nitrogen-doped multi-walled carbon nanotubes (N-MWCNT) and molybdenum disulfide (MoS2) were used as dopants to prepare the extraction head. Then, the extraction head was fixed on a self-made injector, and DMA in the sample was extracted by the headspace extraction method. Subsequently, it was combined with gas chromatography-mass spectrometry (GC-MS) for the detection and analysis of DMA. According to the experimental data, under optimized conditions, the linear range of this method for DMA was 0.135-5 µg / mL, and the detection limit was 0.0135 µg / mL (S / N=10). The spiked recovery rate in industrial wastewater was between 97.50%-101.92%, indicating that this method can be used for the detection of DMA in the environment ( Figure 17 ).

[0084] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A detection method for N,N-dimethylaniline, characterized in that, It includes the following steps: Prepare a PPY+N-MWCNT+MoS2 composite extraction head, Use the composite extraction head to perform headspace extraction on N,N-dimethylaniline; Construct a gas chromatography-mass spectrometry (GC-MS), and use the extraction head to detect N,N-dimethylaniline; Preparing the composite extraction head includes the following steps: Configure a mixed solution containing PY, MoS2, and N-MWCNT; Immerse the electrode system into the mixed solution and perform CV scanning to prepare the composite extraction head; The PY is 7.5 μL / mL; and / or the MoS2 is 0.4 mg / mL; and / or the N-MWCNT is 0.02 mg / mL; It also includes the following steps: Fix the extraction head in a self-made injector, dry it, and obtain an injection device of PPY+N-MWCNT+MoS2; Among them, the GC operating conditions are as follows: Use a chromatographic column Rtx-5Ms as the separation column, the column oven temperature is 50 °C; the inlet temperature is 250 °C, and the splitless injection mode is used; the pressure is 73.0 kPa; the total flow rate is 44.0 mL / min; the column flow rate is 1.27 mL / min; the linear velocity is 40.8 cm / sec; the purge flow rate is 3.0 mL / min; the column oven program temperature setting: maintain at 50 °C for 3 min, increase the temperature to 110 °C at a rate of 10 °C / min, and then increase the temperature to 120 °C at a rate of 2 °C / min and maintain for 1 min; the ion source temperature is 230 °C; the interface temperature is 200 °C; the solvent delay is 3 min.

2. The detection method of N,N-dimethylaniline according to claim 1, wherein The aging conditions are: Insert the injection device into the vaporization chamber of the gas chromatography for aging, set the inlet temperature to 90 °C, and age for 30 min; then continuously increase the inlet temperature to 230-250 °C and continuously age for 1.5 h and then set aside for use.

3. The detection method of N,N-dimethylaniline according to claim 1, wherein The headspace extraction of N,N-dimethylaniline by the composite extraction head includes the following steps: Add saturated sodium chloride solution to the extraction container to form a first mixed solution; Stir the first mixed solution and perform constant temperature water bath; Add N,N-dimethylaniline solution and stir; Insert the injection device into the extraction bottle and expose the extraction head to the solution headspace, and perform headspace extraction under stirring; Retract the extraction head into the protective sleeve, quickly insert it into the gas chromatography vaporization chamber, push out the extraction head for desorption, and then perform GC-MS separation and detection.

4. The detection method of N,N-dimethylaniline according to claim 3, wherein The temperature of the constant temperature water bath is: 60 °C; The stirring is magnetic stirring, the stirring speed is 200-400 r / min, and the stirring time is 30-50 min.

5. According to the method for detecting N,N-dimethylaniline described in claim 3, characterized in that The extraction time is 30-50 min; and / or the extraction temperature is 20-70 °C; and / or the desorption time is 3-5 min.

6. The detection method of N,N-dimethylaniline according to claim 1, wherein, The cyclic voltammetry range of the CV scanning is 0-1.5 V; the scanning rate is 0.05 mV / S, and the number of scans is 100 cycles.

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