Colorimetric detection method of zinc thiazole

Abstract

The invention discloses a colorimetric detection method of zinc thiazole, and the colorimetric detection method comprises the following steps: (1) extracting a fruit and vegetable sample with an extracting solution to obtain a to-be-detected solution containing zinc thiazole; (2) dropwise adding the to-be-detected liquid onto the zinc thiazole colorimetric detection test paper, after the to-be-detected liquid is absorbed by the absorbent cotton piece below the zinc thiazole colorimetric detection test paper, observing the color of the zinc thiazole colorimetric detection test paper to be compared with a zinc thiazole standard colorimetric card, and judging whether the residual quantity of zinc thiazole in the fruit and vegetable sample is qualified or not; the extracting solution is a phosphoric acid buffer solution with the pH value of 7-8; the zinc thiazole colorimetric test paper is obtained by treating an immobilized reagent and an indicator. Whether the zinc thiazole pesticide content in a sample is qualified or not is qualitatively judged through color change generated before and after reaction of the test paper and zinc thiazole, and the method is easy and convenient to operate, accurate in result, high in sensitivity and low in color developing agent cost and has commercialized application prospects.

Description

Technical Field

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

[0002] Zinc thiazole is a thiadiazole organic zinc pesticide independently developed and created by China. It is a new generation of highly effective, low-toxic and safe agricultural fungicide for the prevention and control of bacterial diseases of crops. Zinc thiazole has both protective and systemic bactericidal therapeutic effects, and is currently widely used in vegetables, rice and some fruit trees. Studies have shown that zinc thiazole has adverse effects on the growth, development and reproductive capacity of parent Daphnia gracilis, and there is a certain aquatic ecological risk; in addition, zinc thiazole is also defined as a new thyroid disruptor, which can cause hyperplasia of thyroid tissue in rats, showing an obvious time-effect relationship. Therefore, it is necessary to detect zinc thiazole in fruits and vegetables. my country's national food safety standard maximum residue limits of pesticides in food GB2723-2021 stipulates that the maximum residue limit of cucumbers, tangerines, oranges and oranges is 0.5mg / Kg, and the maximum residue limit of peaches is 1mg / Kg.

[0003] Since the melting point of zinc thiazole is greater than 300°C, it is insoluble in water and most organic solvents, and is only slightly soluble in N,N-dimethylformamide (DMF), it is difficult to directly analyze it using gas chromatography or liquid chromatography. Some studies have used a method of converting zinc thiazole into thiadiazole, and the amount of thiadiazole is determined by high-performance liquid chromatography-diode array detector to perform quantitative analysis of zinc thiazole, but this method is cumbersome to operate and is affected by conversion efficiency. For this reason, the present application adopts a chemical color development method, and an indicator that can react with zinc thiazole to prepare a thiazole zinc colorimetric test paper by fixing it on a paper base. The color change produced before and after the test paper reacts with zinc thiazole is used to qualitatively determine whether the thiazole zinc pesticide content in the sample is qualified. The method is simple to operate, the results are accurate, the sensitivity is high, the cost of the developer is low, and it has a prospect of commercial application. Summary of the invention

[0004] The object of the present invention is to provide a method for rapid detection of zinc thiazole based on the colorimetric principle. The method has good stability and high sensitivity and can meet the needs of on-site rapid detection of zinc thiazole pesticides in fruit and vegetable samples.

[0005] According to one aspect of the present application, a colorimetric detection method for zinc thiazole is provided, and the colorimetric detection method comprises the following steps:

[0006] (1) extracting the fruit and vegetable samples with an extracting solution to obtain a test solution containing zinc thiazole;

[0007] (2) dropping the test solution onto the zinc thiazole colorimetric test paper, and after the absorbent cotton sheet below the zinc thiazole colorimetric test paper absorbs the test solution, observing the color of the zinc thiazole colorimetric test paper and comparing it with the zinc thiazole standard colorimetric card to determine whether the zinc thiazole residue in the fruit and vegetable sample is qualified;

[0008] The extract is a phosphate buffer solution with a pH value of 7 to 8;

[0009] The thiazole zinc colorimetric test paper is obtained by treating a fixed reagent and an indicator.

[0010] Optionally, the preparation method of the thiazole zinc colorimetric test paper comprises:

[0011] (1) stirring a mixture containing n-octyltriethoxysilane, hydrochloric acid, PEG-400, ethanol, a surfactant, and water to obtain a solid support reagent;

[0012] (2) applying a solution containing a solid-carrying reagent and an indicator dropwise to a hydrophilic area on the filter paper and drying the solution to obtain the zinc thiazole colorimetric test paper.

[0013] Optionally, the mass ratio of n-octyltriethoxysilane, hydrochloric acid, PEG-400, ethanol, surfactant and water is:

[0014] 1:(0.5~0.8):(2~3):(4~6):(0.1~0.12):(2~3).

[0015] Optionally, the surfactant is selected from silwet L-77 and / or silwet L-7001.

[0016] Optionally, the indicator is 1-(2-pyridyl azo)-2-naphthol.

[0017] Optionally, the concentration of 1-(2-pyridylyazo)-2-naphthol in the solution is 4 to 8 mg / L.

[0018] Optionally, the concentration of 1-(2-pyridylyazo)-2-naphthol in the solution is selected from any value of 4 mg / L, 5 mg / L, 6 mg / L, 7 mg / L, 8 mg / L, or a range between any two of the above values.

[0019] Optionally, the stirring temperature is 60°C to 80°C.

[0020] Optionally, the stirring time is 5 to 8 hours.

[0021] Optionally, the stirring time is selected from any value among 5h, 6h, 7h, 8h or a range between any two of the above.

[0022] Optionally, the stirring speed is 600-800 rpm.

[0023] Optionally, the stirring rotation speed is selected from any value of 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm or a range between any two of the above values.

[0024] Optionally, the preparation method of the zinc thiazole standard colorimetric card comprises:

[0025] Thiazole zinc standard solutions of different concentrations were prepared with the extract, and the standard solutions were added dropwise onto the thiazole zinc colorimetric test paper. After the absorbent cotton sheet under the thiazole zinc colorimetric test paper absorbed the test solution, the color of the thiazole zinc colorimetric test paper was recorded using an instrument to obtain the thiazole zinc colorimetric test paper under the corresponding conditions.

[0026] As a specific implementation, the present application is implemented through the following technical solutions:

[0027] A test paper for colorimetric detection of zinc thiazole is prepared, specifically, a solid material is used to dissolve an indicator that can undergo a chemical color reaction with zinc thiazole, 1 to 3 microliters of the above solution is dripped onto a hydrophilic area of ​​a filter paper with a hydrophilic-hydrophobic structure, and after the solution is dried, a zinc thiazole colorimetric detection test paper is prepared and stored away from light.

[0028] The specific detection steps of zinc thiazole 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 10 g of the sample and put it into a test tube, add 10 mL of extraction solution to shake and extract the zinc thiazole pesticide in the sample to obtain the test solution;

[0030] (2) Detection: Place an absorbent cotton pad under the thiazole zinc colorimetric test paper, take 0.5 mL of the test solution and drop it onto the test paper. After the solution is absorbed by the absorbent cotton pad below, compare it with the standard colorimetric card;

[0031] (3) Result determination: Determine whether the residual amount of zinc thiazole in the sample is qualified based on the result of comparing the color of the test paper after reaction with the standard colorimetric card.

[0032] The standard colorimetric card preparation method is as follows:

[0033] Use the extract to prepare thiazole zinc solutions with concentrations of 0, 0.5 and 1.0 mg / L, respectively. Take 0.5 mL of the above solution and drop it onto the thiazole zinc colorimetric test paper. After the solution is absorbed, use a flatbed scanner to record the color of the test paper after the reaction, which is the standard colorimetric card.

[0034] The beneficial effects of this application include:

[0035] The preparation method of the thiazole zinc colorimetric rapid detection test paper provided in the present application is simple. Since a stable commercial indicator is used, the test paper has good stability and high sensitivity. The detection limit can be as low as 0.1 mg / Kg. The test result can be obtained in less than 5 minutes during the entire detection process. The test paper is suitable for on-site rapid detection of the pesticide.

[0036] The present application adopts a chemical color development method, and an indicator capable of undergoing a color development reaction with zinc thiazole is immobilized on a paper base to prepare a zinc thiazole colorimetric test paper. The color change before and after the test paper reacts with zinc thiazole is used to qualitatively determine whether the zinc thiazole pesticide content in the sample is qualified. The method is simple to operate, has accurate results, high sensitivity, and low cost of the color developer, and has a prospect of commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the standard color chart of zinc thiazole pesticide for this application. DETAILED DESCRIPTION

[0038] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0039] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0040] Example 1

[0041] Preparation of Thiazole Zinc Colorimetric Test Paper:

[0042] The preparation method of the solid support material is as follows: n-octyl triethoxysilane, hydrochloric acid, PEG-400, ethanol, silwet L-77, and water are mixed in a mass ratio of 1:0.5:3:5:0.1:2, and stirred at a speed of 800 rpm for 6 hours at 80°C to prepare a solid support reagent; the solid support material is used to dissolve an indicator 1-(2-pyridyl azo)-2-naphthol that can react with zinc thiazole to produce a chemical color development reaction, so that the indicator concentration is 5 mg / L; 2 microliters of the above solution is dripped onto a hydrophilic area on a filter paper with a hydrophilic and hydrophobic structure, and after the solution is dried, a zinc thiazole colorimetric detection test paper is prepared and stored in the dark.

[0043] Example 2.

[0044] Preparation of Thiazole Zinc Colorimetric Test Paper:

[0045] The preparation method of the solid support material is as follows: n-octyl triethoxysilane, hydrochloric acid, PEG-400, ethanol, silwet L-7001 and water are mixed in a mass ratio of 1:0.8:2:6:0.12:3, and stirred at a speed of 600 rpm for 8 hours at 80°C to prepare a solid support reagent; the solid support material is used to dissolve an indicator 1-(2-pyridyl azo)-2-naphthol that can react with zinc thiazole to produce a chemical color development reaction, so that the indicator concentration is 8 mg / L; 1 microliter of the above solution is absorbed and dripped onto a hydrophilic area on a filter paper with a hydrophilic and hydrophobic structure, and after the solution is dried, a zinc thiazole colorimetric detection test paper is prepared and stored in the dark.

[0046] Example 3.

[0047] Preparation of Thiazole Zinc Standard Color Card:

[0048] Thiazole zinc solutions with concentrations of 0, 0.5 and 1.0 mg / L were prepared using a phosphate buffer solution with a pH of 7. 0.5 mL of the solution was added dropwise to the thiazole zinc colorimetric test paper prepared in Example 1. After the solution was absorbed, the color of the test paper after the reaction was recorded using a flatbed scanner. Figure 1 As shown, in the presence of zinc thiazole, the color of the test paper changes from yellow to red, and as the concentration of zinc thiazole increases, the color of the test paper becomes darker.

[0049] Example 4.

[0050] The determination of zinc thiazole pesticide in cucumber samples spiked with 0.8 mg / Kg zinc thiazole was carried out using the zinc thiazole colorimetric test paper in Example 1:

[0051] The specific detection steps of zinc thiazole in the sample are as follows:

[0052] (1) Pretreatment: Use scissors to cut the cucumber sample into pieces of about 1 cm, take 10 g of the sample and put it into a test tube, add 10 mL of pH 7 phosphate buffer solution to shake and extract the zinc thiazole pesticide in the sample to obtain the test solution;

[0053] (2) Detection: Place an absorbent cotton pad under the thiazole zinc colorimetric test paper, take 0.5 mL of the test solution and drop it onto the test paper. After the solution is absorbed by the absorbent cotton pad below, compare it with the standard colorimetric card;

[0054] (3) Result determination: According to the color of the test paper after reaction Figure 1 By comparing with the standard colorimetric card, it was found that the color of the test paper after the reaction was between 0.5 and 1 mg / L. According to the maximum residual limit of zinc thiazole in cucumbers of 0.5 mg / Kg, the residual amount of zinc thiazole in the sample was judged to be unqualified.

[0055] 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 zinc thiazole, characterized in that: The colorimetric detection method comprises the following steps: (1) extracting the fruit and vegetable samples with an extraction solution to obtain a test solution containing zinc thiazole; (2) dropping the test solution onto the zinc thiazole colorimetric test paper, and after the absorbent cotton sheet below the zinc thiazole colorimetric test paper absorbs the test solution, observing the color of the zinc thiazole colorimetric test paper and comparing it with the zinc thiazole standard colorimetric card to determine whether the zinc thiazole residue in the fruit and vegetable sample is qualified; The extract is a phosphate buffer solution with a pH value of 7 to 8; The thiazole zinc colorimetric test paper is obtained by treating a fixed reagent and an indicator.

2. The colorimetric detection method according to claim 1, characterized in that The preparation method of the zinc thiazole colorimetric test paper comprises: (1) stirring a mixture containing n-octyltriethoxysilane, hydrochloric acid, PEG-400, ethanol, a surfactant, and water to obtain a solid support reagent; (2) applying a solution containing a solid-carrying reagent and an indicator dropwise to a hydrophilic area on the filter paper and drying the solution to obtain the zinc thiazole colorimetric test paper.

3. The colorimetric detection method according to claim 2, characterized in that The mass ratio of n-octyl triethoxysilane, hydrochloric acid, PEG-400, ethanol, surfactant and water is: 1：(0.5～0.8)：(2～3)：(4～6)：(0.1～0.12)：(2～3)。 4. The colorimetric detection method according to claim 3, characterized in that The surfactant is selected from Silwet L-77 and / or Silwet L-7001.

5. The colorimetric detection method according to claim 1, characterized in that The indicator is 1-(2-pyridyl azo)-2-naphthol.

6. The colorimetric detection method according to claim 5, characterized in that: The concentration of 1-(2-pyridyl azo)-2-naphthol in the solution is 4-8 mg / L.

7. The colorimetric detection method according to claim 2, characterized in that The stirring temperature is 60°C to 80°C.

8. The colorimetric detection method according to claim 2, characterized in that: The stirring time is 5 to 8 hours.

9. The colorimetric detection method according to claim 2, characterized in that: The stirring speed is 600-800 rpm.

10. The colorimetric detection method according to claim 1, characterized in that: The preparation method of the zinc thiazole standard colorimetric card comprises: Thiazole zinc standard solutions of different concentrations were prepared with the extract, and the standard solutions were added dropwise onto the thiazole zinc colorimetric test paper. After the absorbent cotton sheet under the thiazole zinc colorimetric test paper absorbed the test solution, the color of the thiazole zinc colorimetric test paper was recorded using an instrument to obtain the thiazole zinc colorimetric test paper under the corresponding conditions.

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