Colorimetric detection method of carbofuran pesticide

Abstract

The invention discloses a colorimetric detection method of carbofuran pesticide, and the colorimetric detection method comprises the following steps: (1) extracting a fruit and vegetable sample to be detected by adopting an alkaline extracting solution to obtain an extracting solution containing carbofuran; (2) mixing the extracting solution with a strong oxidant solution and a 2, 6-dichloro-4-aminophenol solution, and performing chromogenic reaction to obtain a to-be-detected solution; (3) determining the absorbance of the liquid to be detected by adopting a spectrophotometer; and (4) comparing the absorbance with a threshold value, and judging whether the residual quantity of carbofuran in the fruit and vegetable sample is qualified or not. According to the rapid detection method for the carbofuran pesticide in the fruits and vegetables, the carbofuran specific color developing agent reacts with carbofuran to generate color change, whether the carbofuran pesticide in a sample is qualified or not is qualitatively judged through colorimetric analysis, the method is easy and convenient to operate and high in sensitivity, the cost of the color developing agent is low, and the method has commercialization prospects.

Description

Technical Field

[0001] The present application relates to a colorimetric detection method for the pesticide carbofuran, and belongs to the technical field of rapid pesticide detection. Background Art

[0002] Carbofuran is a broad-spectrum insecticide and nematicide, belonging to the class of carbamate pesticides. Because carbofuran can bind to cholinesterase and the reaction is irreversible, has a long residual effect in the soil, and is highly harmful to aquatic organisms, it is prohibited for use in some crops, but can be applied to crops such as rice, corn, peanuts, and cotton to control pests. With the migration and transformation of carbofuran pesticides in the environment and its bioaccumulation, it inevitably enters the human body. After the human body ingests carbofuran, it will cause a series of symptoms such as dizziness, headache, and nerve damage, posing a serious threat to people's health, so it is necessary to test carbofuran. my country's "National Food Safety Standard Maximum Residue Limits of Pesticides in Food" (GB2763-2021) stipulates that the maximum residue limits of carbofuran in vegetables (except potatoes) and fruits are 0.02 mg / kg, respectively. According to the relevant testing standards of the European Union, the maximum residue limits of chlorpyrifos in citrus fruits, pears, and vegetables (except potatoes) are 0.010, 0.001, and 0.002 mg / kg, respectively (EFSA, 2015).

[0003] The analysis and detection methods of carbofuran generally use large-scale instrumental methods such as gas chromatography (GC), high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (MS). These methods have good sensitivity and selectivity for low concentrations of carbofuran in samples, but the disadvantages are that the operation is cumbersome, time-consuming, and certain requirements are placed on experimental conditions and instrument operator skills. Existing commercial carbofuran detection methods include enzyme inhibition method and colloidal gold method. The enzyme inhibition method targets organophosphorus and carbamate pesticides and has no specificity for carbofuran. Although the colloidal gold method has good specificity and high sensitivity, it is expensive. Usually, the price of a single determination is higher than 20 yuan, and it cannot meet the daily monitoring needs of a large number of samples. Therefore, it is necessary to develop a simple, fast and low-cost carbofuran detection method. Summary of the invention

[0004] The present application adopts a colorimetric method, in which a color change is produced by the reaction of a carbofuran-specific color developer with carbofuran, and a colorimetric analysis is used to qualitatively determine whether the carbofuran pesticide in the sample is qualified. The method is simple to operate, has high sensitivity, and has a low cost of color developer, and has a commercial prospect.

[0005] The object of the present invention is to provide a method for rapidly detecting carbofuran based on the colorimetric principle. The method has good stability and high sensitivity and can meet the demand for rapid on-site detection of carbofuran pesticide in fruit and vegetable samples.

[0006] According to one aspect of the present application, a colorimetric detection method for carbofuran pesticide is provided, and the colorimetric detection method comprises the following steps:

[0007] (1) extracting the fruit and vegetable samples to be tested with an alkaline extract to obtain an extract containing carbofuran;

[0008] (2) mixing the extract with a strong oxidant solution and a 2,6-dichloro-4-aminophenol solution, and performing a color reaction to obtain a test solution;

[0009] (3) Using a spectrophotometer, measure the absorbance of the test solution;

[0010] (4) Compare the absorbance with the threshold value to determine whether the residual amount of carbofuran in the fruit and vegetable samples is qualified.

[0011] Optionally, an alkaline extract is used to extract the carbofuran pesticide in fruit and vegetable samples to obtain a test solution, and under certain temperature conditions, the test solution is subjected to a chemical color development reaction with a commercial stabilizing reagent 2,6-dichloro-4-aminophenol in the presence of a strong oxidant, thereby achieving highly sensitive detection of the carbofuran pesticide.

[0012] Optionally, the method for determining the threshold value includes:

[0013] (1) using alkaline extract to prepare a 0.04 mg / L carbofuran standard solution;

[0014] (2) Take 2 mL of the carbofuran standard solution, add 0.2-0.4 mL of a strong oxidant solution and 0.2-0.4 mL of a 2,6-dichloro-4-aminophenol solution thereto, mix well, and place in a 50-80° C. water bath for 5-10 min; use a spectrophotometer to measure the absorbance of the solution after the color reaction, and set the absorbance as the threshold value.

[0015] Optionally, in step (2), the concentration of the 2,6-dichloro-4-aminophenol solution is 1 to 3 mmol / L, and the solvent is ethanol.

[0016] Optionally, the concentration of the 2,6-dichloro-4-aminophenol solution is selected from any value of 1 mmol / L, 1.5 mmol / L, 2 mmol / L, 2.5 mmol / L, 3 mmol / L, or a range between any two of the above values.

[0017] Optionally, in step (1), the content of methanol in the alkaline extract is 10% to 20%, and the pH value thereof is 12 to 13.

[0018] Optionally, the alkaline substance in the alkaline extract is selected from sodium hydroxide and / or potassium hydroxide.

[0019] Optionally, the strong oxidant solution is selected from potassium periodate solution or hydrogen peroxide solution.

[0020] Optionally, the concentration of the strong oxidant solution is 3-5 mmol / L.

[0021] Optionally, the volume ratio of the extract, the strong oxidant solution, and the 2,6-dichloro-4-aminophenol solution is: 2 mL: 0.2-0.4 mL: 0.2-0.4 mL.

[0022] Optionally, the extract needs to be purified before being mixed with the strong oxidant solution and the 2,6-dichloro-4-aminophenol solution.

[0023] Optionally, the purification column is a solid phase extraction column filled with C18 and graphitized carbon black (GCB).

[0024] Optionally, the temperature of the color development reaction is 50-80°C.

[0025] Optionally, the temperature of the color development reaction is selected from any value of 50°C, 55°C, 60°C, 65°C, 70°C, 80°C or a range between any two of the above values.

[0026] Optionally, the color development reaction takes 5 to 10 minutes.

[0027] Optionally, the time of the color development reaction is selected from any value of 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or a range between any two of the above.

[0028] In this application, the specific detection steps of carbofuran in the sample are as follows:

[0029] (1) Pretreatment: Use scissors to cut the fruit and vegetable samples into pieces of about 1 cm, take 20 g of the sample and put it into a test tube, add 10 mL of alkaline extract to extract the carbofuran pesticide in the sample by shaking, which is equivalent to concentrating the carbofuran content in the sample by one time, and purify the extract through a purification column to obtain the test solution;

[0030] (2) Color reaction: In order to obtain a higher sensitivity for the detection of carbofuran, take 2 mL of the test solution, add 0.2-0.4 mL of a strong oxidant solution and 0.2-0.4 mL of a 2,6-dichloro-4-aminophenol solution, mix well, and place in a water bath at 50-80°C for 5-10 min.

[0031] (3) Detection: Use a spectrophotometer to record the absorbance of the solution after the color development reaction at a wavelength of 580 nm;

[0032] (4) Result determination: Compare the absorbance with the threshold value. If the value exceeds the threshold value, it is determined whether the residual amount of chlorpyrifos in the sample is qualified.

[0033] In this application, the threshold determination method is as follows:

[0034] GB2763 stipulates that the maximum residue limit of carbofuran in fruits and vegetables is 0.02 mg / Kg. Since the carbofuran in the sample is concentrated by one time in the pre-treatment step of carbofuran extraction, an alkaline extract can be used to prepare a carbofuran standard solution with a concentration of 0.04 mg / L. Take 2 mL of the above solution and add 0.2-0.4 mL of a strong oxidant solution and 0.2-0.4 mL of 2,6-dichloro-4-aminophenol solution thereto in sequence. After mixing, let it stand in a water bath at 50-80°C for 5-10 minutes. Use a spectrophotometer to measure the absorbance of the solution after the color development reaction, and set this absorbance as the threshold value. The result judgment of the fruit and vegetable samples needs to be compared with the absorbance obtained under the same reaction conditions.

[0035] The beneficial effects of this application include:

[0036] The present application provides a rapid detection method for carbofuran pesticides in fruits and vegetables. The method uses a carbofuran-specific color developer to react with carbofuran to produce a color change, and a colorimetric analysis is used to qualitatively determine whether the carbofuran pesticides in the sample are qualified. The method is simple to operate, has high sensitivity, and has a low cost of color developer, and has commercial prospects.

[0037] The colorimetric rapid detection method of carbofuran is simple to operate and uses a stable commercial indicator with good stability and high sensitivity. The detection limit can be as low as 0.02 mg / Kg. The test results can be obtained in less than 20 minutes during the entire detection process, making it suitable for on-site rapid detection of the pesticide. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the standard curve for the detection of carbofuran pesticide in this application. DETAILED DESCRIPTION

[0039] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0040] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0041] Example 1

[0042] Select certain reaction conditions to determine the standard curve for the detection of carbofuran pesticide:

[0043] Use potassium hydroxide solution with pH=12 and methanol content of 10% to prepare 0, 0.04, 0.08, 0.15, 0.30, and 0.60 mg / L carbofuran standard solutions, respectively. Take 2 mL of the above solutions and add 0.3 mL of potassium periodate aqueous solution with a concentration of 4 mmol / L and 0.3 mL of 2,6-dichloro-4-aminophenol ethanol solution with a concentration of 1 mmol / L, respectively. After mixing, let it stand in a 60°C water bath for 10 minutes. Use a spectrophotometer to measure the absorbance of the solution at 580 nm after the color reaction, and draw a standard curve for carbofuran detection with the carbofuran concentration as the horizontal axis and the absorbance of the solution after each concentration reaction as the vertical axis, as shown in FIG. Figure 1 As shown, through fitting, we get y = 0.4681x + 0.0424, R 2 =0.9999. Under this reaction condition, the judgment threshold is 0.061.

[0044] Example 2

[0045] The determination of carbofuran pesticide in apple samples was carried out using the color reaction conditions in Example 1:

[0046] (1) Pretreatment: Use scissors to cut the apple sample into pieces of about 1 cm, take 20 g of the sample and put it into a test tube, add 10 mL of sodium hydroxide solution with a pH of 13 and a methanol content of 10% to extract the carbofuran pesticide in the sample by shaking, and purify the extract through a purification column to obtain the test solution;

[0047] (2) Color reaction: Take 2 mL of the test solution and add 0.3 mL of a 4 mmol / L potassium periodate aqueous solution and 0.3 mL of a 1 mmol / L 2,6-dichloro-4-aminophenol ethanol solution, mix well and place in a 60°C water bath for 10 min.

[0048] (3) Detection: Using a spectrophotometer at a wavelength of 580 nm, the absorbance of the solution after the color reaction was recorded as 0.050;

[0049] (4) Result determination: The absorbance of 0.050 was compared with the threshold value of 0.061. It was lower than the threshold value, and it was determined that the residue of chlorpyrifos in the apple sample was lower than the national standard limit. The chlorpyrifos pesticide test of the sample was qualified.

[0050] At the same time, HPLC was used to determine the presence of carbofuran in apple samples pre-treated with QuECHERS, and the result was that no carbofuran was detected, which was consistent with the result of the above-mentioned colorimetric method.

[0051] Example 3

[0052] Select certain reaction conditions to determine the standard curve for the detection of carbofuran pesticide:

[0053] A potassium hydroxide solution with a pH of 13 and a methanol content of 10% was used to prepare standard solutions of 0, 0.04, 0.08, 0.15, 0.30, and 0.60 mg / L of carbofuran, respectively. 2 mL of the above solutions were taken and 0.3 mL of a 4.5 mmol / L potassium periodate aqueous solution and 0.4 mL of a 3 mmol / L 2,6-dichloro-4-aminophenol ethanol solution were added thereto in sequence. After mixing, the mixture was placed in a 50°C water bath for 8 min. The absorbance of the solution at 580 nm after the color reaction was determined by a spectrophotometer. The standard curve for carbofuran detection was drawn with the carbofuran concentration as the horizontal axis and the absorbance of the solution after each concentration reaction as the vertical axis. By fitting, y=0.3562x+0.0299, R 2 =0.9945. Under this reaction condition, the judgment threshold is 0.044.

[0054] Example 4

[0055] The determination of carbofuran pesticide in the cabbage sample spiked with 0.05 mg / kg carbofuran was carried out using the color reaction conditions in Example 3:

[0056] (1) Pretreatment: Use scissors to cut the cabbage sample into pieces of about 1 cm, take 20 g of the sample and put it into a test tube, add a potassium hydroxide solution with a pH of 13 and a methanol content of 10% to extract the carbofuran pesticide in the sample by shaking, and purify the extract through a purification column to obtain a test solution;

[0057] (2) Color reaction: Take 2 mL of the test solution and add 0.3 mL of a 4.5 mmol / L potassium periodate aqueous solution and 0.4 mL of a 3 mmol / L 2,6-dichloro-4-aminophenol ethanol solution, mix well and place in a 50°C water bath for 8 min.

[0058] (3) Detection: The absorbance of the solution after the color reaction was recorded at a wavelength of 580 nm using a spectrophotometer and was 0.052;

[0059] (4) Result determination: The absorbance of 0.052 was compared with the threshold value of 0.044. It was higher than the threshold value, and it was determined that the residual amount of chlorpyrifos in the cabbage sample was higher than the national standard limit. The sample failed the chlorpyrifos pesticide test.

[0060] At the same time, the high performance liquid chromatography method was used to determine the carbofuran in the spiked cabbage samples that had been pre-treated with QuECHERS. The test result was 0.043 mg / Kg, which exceeded the limit standard of 0.02 mg / Kg and was consistent with the result determined by the above-mentioned colorimetric method.

[0061] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A colorimetric detection method for carbofuran pesticide, characterized in that: The colorimetric detection method comprises the following steps: (1) extracting the fruit and vegetable samples to be tested with an alkaline extract to obtain an extract containing carbofuran; (2) mixing the extract with a strong oxidant solution and a 2,6-dichloro-4-aminophenol solution, and performing a color reaction to obtain a test solution; (3) Using a spectrophotometer, measure the absorbance of the test solution; (4) Compare the absorbance with the threshold value to determine whether the residual amount of carbofuran in the fruit and vegetable samples is qualified.

2. The colorimetric detection method according to claim 1, characterized in that The method for determining the threshold value includes: (1) using alkaline extract to prepare a 0.04 mg / L carbofuran standard solution; (2) Take 2 mL of the carbofuran standard solution, add 0.2-0.4 mL of a strong oxidant solution and 0.2-0.4 mL of a 2,6-dichloro-4-aminophenol solution thereto, mix well, and place in a 50-80° C. water bath for 5-10 min; use a spectrophotometer to measure the absorbance of the solution after the color reaction, and set the absorbance as the threshold value.

3. The colorimetric detection method according to claim 1, characterized in that In the step (2), the concentration of the 2,6-dichloro-4-aminophenol solution is 1 to 3 mmol / L, and the solvent is ethanol.

4. The colorimetric detection method according to claim 1, characterized in that In the step (1), the content of methanol in the alkaline extract is 10% to 20%, and the pH value thereof is 12 to 13; Preferably, the alkaline substance in the alkaline extract is selected from sodium hydroxide and / or potassium hydroxide.

5. The colorimetric detection method according to claim 1, characterized in that The strong oxidant solution is selected from potassium periodate solution or hydrogen peroxide solution; Preferably, the concentration of the strong oxidant solution is 3-5 mmol / L.

6. The colorimetric detection method according to claim 1, characterized in that: The volume ratio of the extract, the strong oxidant solution and the 2,6-dichloro-4-aminophenol solution is: 2 mL: 0.2-0.4 mL: 0.2-0.4 mL.

7. The colorimetric detection method according to claim 1, characterized in that The extract needs to be purified before being mixed with the strong oxidant solution and the 2,6-dichloro-4-aminophenol solution.

8. The colorimetric detection method according to claim 6, characterized in that: The purification column is a solid phase extraction column filled with C18 and graphitized carbon black.

9. The colorimetric detection method according to claim 1, characterized in that: The temperature of the color development reaction is 50-80°C.

10. The colorimetric detection method according to claim 1, characterized in that: The time of the color development reaction is 5 to 10 minutes.

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