Method for determining phenolic substances in 2, 4-D recovery liquid

Abstract

The invention belongs to the field of chemical detection and analysis, and particularly relates to a method for determining 2-(2, 6-dichlorophenoxy) acetic acid, 2, 6-dichlorophenol, 2, 4-dichlorophenoxyacetic acid, 2, 4-dichlorophenol, 2, 4, 6-trichlorophenoxyacetic acid and 2, 4, 6-trichlorophenol substances in phenol recovery liquid through liquid chromatography. The method comprises the following steps: rapidly injecting a phenol recovery liquid sample into a liquid chromatogram, rapidly eluting through a mobile phase, changing the interaction between the sample and a C18 stationary phase, gradually separating molecules of different components in a column, and detecting the content of 2-(2, 6-dichlorophenoxy) acetic acid, 2, 6-dichlorophenol, 2, 4-dichlorophenoxyacetic acid, 2, 4-dichlorophenol, 2, 4, 6-trichlorophenoxyacetic acid and 2, 4, 6-trichlorophenoxyacetic acid. The content of 2, 6-trichlorophenol is reduced. According to the method, the mass fraction of the 2-(2, 6-dichlorophenoxy) acetic acid, the mass fraction of the 2, 6-dichlorophenol, the mass fraction of the 2, 4-dichlorophenoxyacetic acid, the mass fraction of the 2, 4-dichlorophenol, the mass fraction of the 2, 4-trichlorophenoxyacetic acid and the mass fraction of the 2, 4-trichlorophenol can be safely, rapidly and accurately measured through the liquid chromatography, and timely and accurate data guidance is provided for adjustment of 2, 4-D production process parameters and product quality control.

Description

Technical Field

[0001] The invention relates to the field of chemical detection and analysis, and in particular to a method for determining 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a phenol recovery liquid. Background Art

[0002] 2,4-Dichlorophenoxyacetic acid, also known as 2,4-D, is not only a plant growth regulator, but also a highly selective hormone-type phenoxy acid herbicide widely used in agricultural and forestry production. It promotes or inhibits the excessive growth of weeds' conductive tissues, causing the weeds' stems and leaves to twist, the stem base to thicken, and the stems to swell and crack, ultimately causing the death of the plants. The synthetic route of 2,4-D usually uses phenol chlorination to produce 2,4-dichlorophenol, which is condensed with chloroacetic acid in the presence of sodium hydroxide to form 2,4-D sodium salt, and then acidified to form 2,4-D technical production.

[0003] In the production process of the pesticide product 2,4-D, a large amount of recovery liquid is produced, which contains toxic and harmful organic pollutants such as 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol. The determination of the content of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the phenol recovery liquid is of great significance to the synthesis of 2,4-D, and also helps to guide the adjustment of 2,4-D production process parameters.

[0004] The reported detection methods for phenolic compounds mainly include photometry, gas chromatography, and gas chromatography-mass spectrometry. However, the analysis speed is slow, a large amount of organic extraction solvents or derivatization reagents are required, and only some phenolic targets can be detected. In order to meet the needs of simultaneous liquid chromatography detection of these six phenolic compounds and facilitate rapid determination in production, this experiment used liquid chromatography to simultaneously perform qualitative and quantitative analysis of these six phenolic compounds in phenol recovery liquid. Summary of the invention

[0005] The present invention provides a method for determining 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a phenol recovery liquid. The method mainly comprises the following steps: (1) Weigh standard samples of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol, add mobile phase to make up the volume, and then perform liquid chromatography detection. The peak area unit is microvolt to obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (2) The recovered phenol samples were fixed to volume with mobile phase and subjected to liquid chromatography detection to establish chromatograms of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol, and obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (3) The chromatographic peak retention time ranges of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol obtained in step (2) were compared with those in step (1) and the contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the sample were calculated using the following formula.

[0006] ω1=(A2m1ω) / A1m2 Where: ω1--mass fraction of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid, and 2,4,6-trichlorophenol in the sample, expressed in %; ω--Mass fraction of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid, and 2,4,6-trichlorophenol in the standard sample, expressed in %; A2--The average value of the peak areas of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid, and 2,4,6-trichlorophenol in the sample solution; A1--The average value of the peak areas of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid, and 2,4,6-trichlorophenol in the standard solution; m1--The mass value of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid, and 2,4,6-trichlorophenol standard samples, in grams (g); m2--The numerical value of the mass of the sample, in grams (g).

[0007] In step (1) described above, the process implemented is as follows: weigh 0.2 g of standard samples of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a 50 mL volumetric flask, dilute to 50 mL with mobile phase, prepare to form a stock solution, then pipette 5 mL of the stock solution into a 50 mL volumetric flask, dilute to scale with mobile phase, shake well, and perform liquid chromatography detection. The peak area unit is microvolt to obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; In the step (2), the weight of the phenol recovery liquid sample weighed is 0.15-1 g, and the sample concentration is 0.3-2 mg / mL.

[0008] The above-mentioned process is implemented by using the liquid chromatography parameters of step (1) to perform liquid phase analysis and detection, establish chromatograms of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol, and obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol.

[0009] The liquid phase inspection conditions in step (1) or step (2) are the same, and the liquid chromatography conditions are: The chromatographic column was Hypersil GOLD 150 × 4.6 mm 5 μm; Injection system: column temperature: 25~30℃; flow rate: 0.8~1.5mL / min; more preferably, the column temperature of the injection system is 30℃ and the injection flow rate is 1.25mL / min.

[0010] The mobile phase is phosphoric acid water and methanol solution; its concentration gradient program is: 0 -15min40% solvent A, 60% solvent B; The solvent is a phosphoric acid aqueous solution with a pH of 2-4, and the solvent B is a methanol solution. Preferably, the solvent A is a phosphoric acid aqueous solution with a pH of 2-3.

[0011] For those skilled in the art, in the operation of steps (1) and (2), preferably, the prepared sample is placed in a bottle to fill it up without leaving any gaps, and then liquid phase detection is performed.

[0012] In the liquid chromatography operation of step (1) and step (2), the detection system is a variable wavelength ultraviolet detector, and the detection wavelength is 2855 nm.

[0013] This method can be used to easily analyze the content ratios of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the production phenol recovery liquid samples. The test results are accurate, time-saving and efficient, and can provide timely and accurate data guidance for the adjustment of 2,4-D production process parameters and product quality control.

[0014] Beneficial effects of the present invention: 1. The mobile phase used in the present invention is a mixed solution of phosphoric acid water and methanol water; the peak emerges quickly, and the peak shape is sharp without tailing, and the detection limit is low.

[0015] 2. Dilute the sample with the mobile phase by a certain multiple, inject the solution into the liquid chromatograph, and separate by isocratic elution on the C18 chromatographic column. Then, the contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol can be quickly and accurately separated and measured in a short time. This detection method can complete the test within 15 minutes, greatly shortening the detection time and improving work efficiency.

[0016] 3. This method is simple and easy to use, and its detection accuracy and precision are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : Chromatograms of phenol recovery liquid samples 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in Example 1.

[0018] Figure 2: Chromatograms of phenol recovery liquid samples 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in Comparative Example 1.

[0019] Figure 3 : Chromatograms of phenol recovery liquid samples 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in Comparative Example 2.

[0020] Figure 4 : Chromatograms of phenol recovery liquid samples 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in Comparative Example 3.

[0021] Figure 5 : Chromatograms of phenol recovery liquid samples 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in Comparative Example 4. DETAILED DESCRIPTION

[0022] The present invention is further described below with reference to embodiments, but the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0023] Example 1 Instrument manufacturer: Thermo Fisher U3000 chromatograph; A method for determining 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a phenol recovery liquid comprises the following steps: (2) Weigh 0.2 g of standard samples of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a 50 mL volumetric flask, dilute to 50 mL with mobile phase, prepare a stock solution, then pipette 5 mL of the stock solution into a 50 mL volumetric flask, dilute to scale with mobile phase, shake well, and perform liquid chromatography detection. The peak area unit is microvolt to obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (3) Weigh 0.5 g of the phenol recovery liquid sample and dilute it to 50 mL with the mobile phase, shake well, then draw 5 mL of the above solution into a 50 mL volumetric flask, dilute it to the mark with the mobile phase, shake well, and the sample concentration is 1 mg / mL. Use the liquid chromatography parameters of step (1) to perform liquid chromatography analysis and detection, establish the chromatograms of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol, and obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (3) The contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the sample are calculated based on the retention time range of the chromatographic peak obtained in step (2) and the curve fitted in step (1).

[0024] The parameters of liquid chromatography in the step are: The chromatographic column was Hypersil GOLD 150 × 4.6 mm 5 μm; Injection system: column temperature: 30°C; flow rate: 1.25mL / min; The mobile phase is phosphoric acid water and methanol solution; its concentration isocratic program is: 0 -15min40% solvent A, 60% solvent B, solvent A is a phosphoric acid aqueous solution with a pH of 3, and solvent B is a methanol solution.

[0025] Detection system: variable wavelength UV detector.

[0026] Detection wavelength: 285 nm.

[0027] The analysis results of the contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the phenol recovery liquid are as follows: Figure 1 Liquid chromatography can quickly and accurately measure the contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in phenol recovery liquid, and the detection result is accurate, time-saving and efficient. The method of the present invention can provide timely and accurate guidance for workshop production processes.

[0028] Example 2 Instrument manufacturer: Thermo Fisher U3000 chromatograph; A method for determining 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a phenol recovery liquid comprises the following steps: (4) Weigh 0.2 g of standard samples of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in a 50 mL volumetric flask, dilute to 50 mL with mobile phase, prepare a stock solution, then pipette 5 mL of the stock solution into a 50 mL volumetric flask, dilute to scale with mobile phase, shake well, and perform liquid chromatography detection. The peak area unit is microvolt to obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (5) Weigh 1 g of the phenol recovery liquid sample and dilute it to 50 mL with the mobile phase, shake well, then draw 5 mL of the above solution into a 50 mL volumetric flask, dilute it to the mark with the mobile phase, shake well, and the sample concentration is 2 mg / mL. Use the liquid chromatography parameters of step (1) to perform liquid chromatography analysis and detection, establish the chromatograms of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol, and obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (3) The contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the sample are calculated based on the retention time range of the chromatographic peak obtained in step (2) and the curve fitted in step (1).

[0029] The parameters of liquid chromatography in the step are: The chromatographic column was Hypersil GOLD 150 × 4.6 mm 5 μm; Injection system: column temperature: 30°C; flow rate: 1.25mL / min; The mobile phase is phosphoric acid water and methanol solution; its concentration isocratic program is: 0 -15min40% solvent A, 60% solvent B, solvent A is a phosphoric acid aqueous solution at pH 4, solvent B is a methanol solution.

[0030] Detection system: variable wavelength UV detector.

[0031] Detection wavelength: 285 nm.

[0032] The analysis results of the contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the phenol recovery liquid are as follows: Figure 1 Liquid chromatography can quickly and accurately measure the contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in phenol recovery liquid, and the detection result is accurate, time-saving and efficient. The method of the present invention can provide timely and accurate guidance for workshop production processes.

[0033] Comparative Example 1 The method and conditions were the same as those in Example 1. 0.05 g of the phenol recovery liquid sample was weighed and the concentration was 0.1 mg / mL. 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol basically overlapped and could not be well separated.

[0034] Comparative Example 2 The method and conditions are the same as those in Example 1. 2 g of the phenol recovery liquid sample is weighed, and the concentration is 4 mg / mL. The peaks of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol cannot be separated well, and there are problems such as broad peaks, peak tailing, and insufficient separation. This shows that the chromatographic separation effect of the phenol recovery liquid sample is better when the concentration is appropriate.

[0035] Comparative Example 3 The method and conditions were the same as those in Example 1. The pH of phosphoric acid in the mobile phase was 1. Even if the running time was extended, the standards of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol did not produce any peaks.

[0036] Comparative Example 4 The method and conditions are the same as those in Example 1, and the pH of phosphoric acid water in the mobile phase is 6. Even if the running time is extended, 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol standards do not produce peaks at all. This indicates that phosphoric acid water in the mobile phase adjusts the appropriate pH value conditions to quickly and accurately determine 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the phenol recovery liquid sample.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can make appropriate modifications to the technical cases described in the above embodiments. However, the modified parts cannot deviate from the scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for determining phenolic substances in 2,4-D recovery liquid, characterized in that: The following steps are involved: (1) Weigh standard samples of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol respectively, add mobile phase to constant volume, and calculate the retention time range of the chromatographic peak by calculating the peak area in microvolts; (2) Add the 2,4-D recovery liquid sample to the mobile phase to make up the volume, mix well, and then perform liquid chromatography detection to establish the chromatograms of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol, and obtain the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol; (3) The contents of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol in the phenol recovery sample are calculated by comparing the chromatographic peak retention time range of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol obtained in step (2) with the peak area of ​​the corresponding standard retention time in step (1).

2. The method for determining phenolic substances in 2,4-D recovery liquid according to claim 1, characterized in that: In step (1), 0.2 g of standard samples of 2-(2,6-dichlorophenoxy)acetic acid, 2,6-dichlorophenol, 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, 2,4,6-trichlorophenoxyacetic acid and 2,4,6-trichlorophenol were weighed into a 50 mL volumetric flask, and the volume was adjusted to 50 mL with mobile phase to prepare a stock solution. Then 5 mL of the stock solution was pipetted into a 50 mL volumetric flask, the volume was adjusted to the scale with mobile phase, and the solution was shaken well. The parameters of the liquid chromatography were adjusted to obtain a 0.4 mg / mL standard stock solution.

3. The method for determining phenolic substances in the 2,4-D recovery liquid according to claim 1, characterized in that: The liquid phase inspection conditions in step (1) or step (2) are the same, and the liquid chromatography conditions are: The chromatographic column was Hypersil GOLD 150 × 4.6 mm 5 μm; Injection system: column temperature: 25~45℃; flow rate: 0.8~1.5mL / min; The mobile phase was a solution of phosphoric acid and methanol.

4. The method for determining phenolic substances in 2,4-D recovery liquid according to claim 1, characterized in that: Solvent A is a phosphoric acid aqueous solution with a pH of 2-4, and solvent B is a methanol solution.

5. The method for determining phenolic substances in 2,4-D recovery liquid according to claim 4, characterized in that: The concentration isocratic program of the mobile phase is: 40% solvent A, 60% solvent B from 0 to 15 min.

6. The method for determining phenolic substances in 2,4-D recovery liquid according to claim 1, characterized in that: In step (2), the mass of the phenol recovery liquid weighed is 0.15-1 g, and the sample concentration is 0.3-2 mg / mL.

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