Method for rapidly detecting cyromazine pesticide in cowpea

Abstract

The application discloses a method for rapidly detecting cyromazine pesticide in cowpea, and the method comprises the following steps: extracting cowpea to be detected to obtain an extract containing cyromazine; mixing the extract with a neutral red solution, heating to obtain a detection solution; detecting cyromazine in the detection solution, and performing quantitative analysis by using a standard curve. The method for rapidly detecting cyromazine pesticide residues in cowpea provided by the application is based on the principle of proton transfer, uses a spectrophotometer to determine the absorbance of the product generated by neutral red and cyromazine under heating, rapidly obtains the concentration of cyromazine, is high in accuracy, convenient to operate, and suitable for rapid detection of the pesticide residues in cowpea.

Description

Technical Field

[0001] This application relates to a method for rapid detection of cyromazine pesticide in cowpeas, belonging to the field of rapid pesticide detection technology. Background Technology

[0002] Cyromazine is a low-toxicity insecticide belonging to the insect growth regulator class. Its main mechanism of action is to cause morphological abnormalities in the larvae and pupae of dipterans, resulting in incomplete or inhibited adult emergence. It is mainly used to control American serpentine leafminers and leaf miners on leafy vegetables, beans, and fruit-bearing crops. This pesticide has contact and stomach poison effects, strong systemic conductivity, and a long residual effect. Cyromazine is highly soluble in water and can persist in soil or water, increasing the risk of environmental pollution. Furthermore, animal toxicology experiments have shown that cyromazine has a significant dose-response relationship, harming animal health, causing weight loss, hepatomegaly, and even leading to delayed skeletal development and decreased survival rates in fetuses.

[0003] Due to the known and undefined potential hazards of cyromazine, many countries, both domestically and internationally, have established maximum residue limits (MRLs) for cyromazine in agricultural products. my country's latest national food safety standard, GB 2763-2021, "Maximum Residue Limits for Pesticides in Food," stipulates the following MRLs: 4 mg / kg in lettuce and celery; 3 mg / kg in onions, bell peppers, and artichokes; and 0.5 mg / kg in cowpeas, green beans, peas, broad beans, and melons and fruits (excluding watermelon). In recent years, the State Administration for Market Regulation of my country has repeatedly reported excessive cyromazine residues in cowpeas in its food safety inspections. Therefore, developing a rapid method for detecting cyromazine in cowpeas and applying it to rapid on-site detection in cowpeas in the market is of great significance compared to the cumbersome process of sending samples to testing institutions for large-scale instrument testing of cyromazine residues. Summary of the Invention

[0004] The purpose of this invention is to provide a method for rapid detection of cyromazine pesticide in cowpeas based on the principle of proton transfer using a spectrophotometer. This method is simple to operate, has good stability and high sensitivity, and can meet the needs of rapid on-site detection of cyromazine pesticide in cowpeas.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] Rapid detection of cyromazine is based on the principle of proton transfer reaction. The NH bond of the phenolazine ring in neutral red breaks under heating conditions, producing H+. +Protons are transferred to the N atom of the triazine ring of cyromazine, thereby causing a change in the intensity of the neutral red spectrum. Different concentrations of cyromazine pesticide react with neutral red and cause different degrees of change in the intensity of the neutral red spectrum, thus obtaining the dose-response curve for detecting cyromazine.

[0007] According to one aspect of this application, a method for rapid detection of cyromazine pesticide in cowpeas is provided, the method comprising at least the following steps:

[0008] The cowpeas to be tested were extracted to obtain an extract containing cyromazine;

[0009] The extract was mixed with a neutral red solution and heated to obtain the test solution;

[0010] The cyromazine in the test solution was detected, and quantitative analysis was performed using a standard curve.

[0011] Optionally, the method for preparing the standard curve includes: preparing standard working solutions of cyromazine at different concentrations, adding neutral red solution to each solution and mixing, heating, and then using instrumental analysis to form a standard curve for quantitative analysis.

[0012] Optionally, the solvent in the neutral red solution is ethanol, and the concentration of the neutral red solution is 50 mg / L to 80 mg / L.

[0013] Optionally, the concentration of the neutral red solution is selected from any value among 50 mg / L, 60 mg / L, 70 mg / L, and 80 mg / L, or a range between any two of the above values.

[0014] Optionally, the extraction solvent is water; the mass ratio of the cowpeas to the water is 1:1.

[0015] Optionally, the ratio of the neutral red solution to the extract is 1:4.

[0016] Optionally, the heating temperature is 60℃~80℃, and the heating time is 10min~15min.

[0017] Optionally, the heating temperature is selected from any value among 60°C, 65°C, 70°C, and 80°C, or a range between any two of the above points.

[0018] Optionally, the heating time is selected from any value among 10 min, 12 min, and 15 min, or a range between any two of the above points.

[0019] Optionally, the instrument used for analysis is a spectrophotometer.

[0020] Optionally, the detection limit of the method is 0.5 mg / Kg.

[0021] As one of the optional detection methods, the specific steps are as follows:

[0022] (1) Standard curve plotting: Take 6 centrifuge tubes with a capacity of 5 mL each, add 2 mL of pure water and 0.5, 1.0, 2.0, 3.0 and 4.0 mg / L of cyromazine aqueous solution standard respectively, and add 0.5 mL of 50 mg / L neutral red ethanol solution. After mixing, heat in a 60℃ water bath for 10 min. Use a spectrophotometer to perform spectral scanning to determine the maximum absorption wavelength λ. Extract the absorbance A0 of the solution with pure water as the control and the absorbance A of each reaction solution at λ. Calculate the absorbance difference A-A0. The absorbance difference A-A0 is linearly related to the concentration of cyromazine.

[0023] (2) Sample pretreatment: Weigh a certain amount of cowpeas, cut them into segments about 0.5cm in length with scissors and put them into a beaker. Add purified water of the same weight as the cowpeas, extract by ultrasonication for 5 minutes, let stand, and take 2mL of supernatant as the test solution.

[0024] (3) Sample detection: Add 0.5 mL of 50 mg / L neutral red ethanol solution to 2 mL of the test solution, mix well, heat in a 60℃ water bath for 10 min, perform spectral scanning with a spectrophotometer, and extract the absorbance A of the reaction solution at λ. Calculate the concentration of cyromazine (mg / L) based on the absorbance A0 of the control solution and the standard curve obtained in step (1), and convert it to the concentration of cyromazine pesticide in the sample (mg / Kg).

[0025] The beneficial effects that this application can produce include:

[0026] The rapid detection method for cyromazine in cowpeas is simple to operate, with a detection limit of 0.5 mg / Kg, which meets the maximum residue limit standard for cyromazine in cowpeas in GB2763-2021. It is suitable for rapid on-site detection of cyromazine in cowpeas. Attached Figure Description

[0027] Figure 1 This is the standard curve for the detection of cyromazine in this application. Detailed Implementation

[0028] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0029] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0030] The spectrophotometer (Beijing Purkinje General, TU-1901) was set to a detection wavelength of 534 nm.

[0031] Recovery rate calculation formula: Recovery rate = (A / B) × 100%,

[0032] Where A is the detection concentration of cyromazine, in mg / L;

[0033] B represents the spiked concentration of cyromazine, in mg / L.

[0034] Example 1

[0035] Standard curve for the detection of cyromazine: Take six 5mL centrifuge tubes and add 2mL of pure water and 2mL of cyromazine aqueous solution standard with concentrations of 0.5, 1.0, 2.0, 3.0, and 4.0 mg / L, respectively. Then add 0.5mL of neutral red ethanol solution with a concentration of 50mg / L. After mixing, heat in a 60℃ water bath for 10min. Use a spectrophotometer to perform spectral scanning and determine the maximum absorption wavelength as 534nm. Extract the absorbance A0 of the solution with pure water as the control and the absorbance A of each reaction solution at 534nm, as shown in Table 1 below:

[0036] Table 1: Absorbance of cyromazine at different concentrations determined using neutral red light.

[0037] absorbance 0.553 0.532 0.495 0.468 0.452 0.427

[0038] The absorbance difference A-A0 was calculated based on Table 1. The absorbance difference A-A0 showed a linear relationship with the concentration of cyromazine, with the linear regression equation being y = -0.0253x - 0.0022, R0. 2 =0.9792 ( Figure 1 ).

[0039] Where x is the concentration, mg / L;

[0040] y represents the absorbance difference A-A0;

[0041] R is the linear correlation coefficient.

[0042] Example 2

[0043] Detection of cyromazine pesticide in cowpeas: Weigh 100g of cowpeas, cut them into 0.5cm long segments with scissors and place them in a beaker. Add 100mL of purified water and extract by sonication for 5min. Let stand and take 2mL of supernatant as the test solution. Add 0.5mL of 50mg / L neutral red ethanol solution to the 2mL test solution, mix well, and heat in a 60℃ water bath for 10min. Use a spectrophotometer to perform spectral scanning and extract the absorbance of the reaction solution at 534nm. The absorbance A = 0.550. Calculate the concentration of cyromazine as 0.03mg / L based on the absorbance A0 of the control solution obtained in Example 1 and the standard curve. Since the cowpeas were washed with purified water of equal weight during the pretreatment process, the residue in the cowpeas was 0.03 mg / kg, which is far below the detection limit of cyromazine in cowpeas. Therefore, the test result can be determined as not detected, and the cowpeas do not contain cyromazine pesticide residue.

[0044] Example 3

[0045] Detection of Cyromazine-Spiked Cowpeas: The cowpeas in Example 2 did not contain cyromazine pesticide residues. Using these cowpeas as a blank matrix, a spiking experiment was conducted. Three 50g portions of cowpeas were weighed and labeled #1, #2, and #3. The three portions were cut into 0.5cm lengths and placed in beakers. Cyromazine aqueous solution standard was added to each beaker, resulting in cyromazine pesticide concentrations of 0.6mg / kg, 1.0mg / kg, and 2.0mg / kg, respectively. Then, 50mL of purified water was added to each of the three spiked cowpeas, and the mixture was ultrasonically extracted for 5 minutes. After standing, 2mL of the supernatant was taken from each sample as the test solution. Three 2 mL aliquots of the test solution were each added with 0.5 mL of 50 mg / L neutral red ethanol solution. After mixing, the solutions were heated in a 60 °C water bath for 10 min. The spectrophotometer was used to scan the spectra, and the absorbance A of the reaction solution was extracted at 534 nm. The concentration of cyromazine was calculated based on the absorbance A0 of the control solution obtained in Example 1 and the standard curve, and then converted to the residue level in cowpeas. The spiked recovery rate was calculated, and the detection results and calculation results are listed in the table below. As can be seen from Table 2, the spiked recovery rate of cyromazine in cowpeas is between 95% and 112%, indicating that this method has high accuracy.

[0046] Table 2: Spiked recoveries of cyromazine in three cowpea samples

[0047] #1 0.534 0.65 0.6 108 #2 0.522 1.12 1.0 112 #3 0.503 1.89 2.0 95

[0048] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for rapid detection of cyromazine pesticide in cowpeas, characterized in that, The method includes at least the following steps: The cowpeas to be tested were extracted to obtain an extract containing cyromazine; The extract was mixed with a neutral red solution and heated to obtain the test solution; The cyromazine in the test solution was detected, and quantitative analysis was performed using a standard curve. The solvent used for extraction is water; The heating temperature is 60℃~80℃, and the heating time is 10 min~15 min; The preparation of the standard curve requires instrumental analysis, and the instrument used for instrumental analysis is a spectrophotometer.

2. The method according to claim 1, characterized in that, The method for preparing the standard curve includes: preparing standard working solutions of cyromazine at different concentrations, adding neutral red solution to each solution and mixing, heating, and then using instrumental analysis to form a standard curve for quantitative analysis.

3. The method according to claim 1, characterized in that, The solvent in the neutral red solution is ethanol, and the concentration of the neutral red solution is 50 mg / L to 80 mg / L.

4. The method according to claim 1, characterized in that, The ratio of cowpeas to water is 1:

1.

5. The method according to claim 1, characterized in that, The ratio of the neutral red solution to the extract is 1:

4.

6. The method according to claim 1, characterized in that, The detection limit of the method is 0.5 mg / Kg.

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