Color developing test paper for aflatoxin detection and preparation method thereof

Abstract

The invention discloses color developing test paper for aflatoxin detection and a preparation method thereof. The method comprises the following steps: adding montmorillonite into Fe (OH) 3 colloid, mixing, dropwise adding the mixture onto a nitrocellulose membrane, and airing; the mixed solution of Fe (OH) 3 colloid and montmorillonite has an adsorption effect on aflatoxin, color blocks are formed under the particle aggregation effect, and visual detection of aflatoxin is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of aflatoxin detection, and relates to a color developing test paper for aflatoxin detection and a preparation method thereof. Background Art

[0002] Aflatoxin is a natural toxin produced by Aspergillus fungi. It is widely distributed in nature, especially in tropical and subtropical regions, and thus poses a serious threat to food safety and human health. Aflatoxin is a class of toxins with multiple subtypes, including Aflatoxin B1, B2, G1, G2, M1 and M2, among which B1 is the most common and most toxic subtype. Aflatoxin is a potential strong carcinogen. Long-term exposure to aflatoxin can lead to various health problems, the most serious of which is liver cancer. In addition, aflatoxin is also associated with diseases such as liver damage, immune system suppression, reproductive problems and growth retardation. Therefore, countries have established regulatory standards and limits for aflatoxin to ensure that aflatoxin in food does not exceed safe levels. These standards and limits vary depending on the type of food and national regulations. Producers and farmers also take a series of measures to reduce the risk of aflatoxin, such as taking mold prevention measures in farmland and keeping food dry and hygienic when storing it.

[0003] Aflatoxin is mainly formed under high temperature and high humidity conditions, and usually appears in crops that are susceptible to mold contamination, such as corn, peanuts, cottonseed, rice, wheat, nuts, etc. These molds will multiply on these crops and produce aflatoxin. Therefore, the monitoring and control of aflatoxin in the field of food safety is very important. At present, the method for rapid detection of aflatoxin on the market is the gold label test paper method. This method uses the specific binding phenomenon of antigen-antibody. If aflatoxin is present in the sample, they will combine together to form an antibody-antigen complex. The test strip usually includes a detection line and a control line. The detection line is coated with antibodies, and the control line is coated with control antibodies that are not related to aflatoxin. According to the color change on the test strip, the user can determine whether aflatoxin is present in the sample. Generally, the degree of color change of the detection line is proportional to the concentration of aflatoxin. However, this method is usually not very sensitive, and the biological material is greatly disturbed by the environment, which may cause errors in the measurement. Summary of the invention

[0004] The invention provides a color test paper for aflatoxin detection and a preparation method thereof. The test paper is provided with a mixed solution of ferric hydroxide colloid and montmorillonite. When a sample to be tested contains aflatoxin, the ferric hydroxide colloid has a strong adsorption effect on the aflatoxin, thereby forming agglomeration, causing the montmorillonite to aggregate and precipitate, and producing an obvious color change reaction.

[0005] The technical solution adopted by the present invention is as follows: a color test paper for aflatoxin detection, on which a mixture of Fe(OH)3 colloid and montmorillonite is coated.

[0006] Preferably, the mass ratio of Fe(OH)3 colloid to montmorillonite is 1:0.0012.

[0007] Preferably, the test paper is a nitrocellulose membrane.

[0008] Preferably, the purity of montmorillonite is 90%.

[0009] The method for preparing the above-mentioned color test paper for aflatoxin detection comprises the following steps: Step 1, adding a certain amount of montmorillonite powder to the Fe(OH)3 colloidal solution and mixing it evenly by ultrasonic vibration; Step 2, drip the mixed solution in step 1 onto the test paper and fully dry it at 40℃~60℃.

[0010] Preferably, in step 1, the density of Fe(OH)3 colloid is 3.4-3.9 g / cm 3 .

[0011] Preferably, in step 1, ultrasonic oscillation is performed to achieve uniform mixing, and the ultrasonic oscillation time is more than 20 minutes, more preferably, the ultrasonic oscillation time is 30 minutes.

[0012] The invention also provides a color development kit for detecting aflatoxin.

[0013] Compared with the prior art, the present invention has the following advantages: (1) The present invention first discovered that when a mixed solution of ferric hydroxide colloid and montmorillonite is dripped onto nitrocellulose and dried, it will produce an adsorption and aggregation effect on aflatoxin, thereby developing color, which can be observed directly by a camera or by an optical microscope. Compared with conventional gold-labeled test paper, the preparation process is simpler, and there is no need to set up a detection T line and a quality control C line on the nitrocellulose membrane, making the detection more convenient, greatly reducing the difficulty of aflatoxin detection, and realizing simple detection of aflatoxin.

[0014] (2) The method of the present invention can be further extended to the detection test strips of other high molecular organic substances, and then to the detection application of other toxins, so as to realize the visual detection of aflatoxin and other toxins, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 (a) and (b) are the color development effects of the test paper made of Fe(OH)3 colloid and montmorillonite mixed solution on aflatoxin. The red circle indicates the agglomeration effect of the colored blocks after color development.

[0016] Figure 2 (a) and (b) are the color development effects of aflatoxin on the test paper made of a mixed solution of Fe(OH)3 colloid and montmorillonite under an optical microscope, and the red circle is the agglomerated color block.

[0017] Figure 3 (a) and (b) are the color development effects of the test paper made from a mixed solution of Fe(OH)3 colloid and montmorillonite on clean water.

[0018] Figure 4 (a) and (b) are the color development effects of test paper made from a mixed solution of Fe(OH)3 colloid and montmorillonite with increased montmorillonite content on aflatoxin.

[0019] Figure 5 (a) and (b) are the color development effects of aflatoxin on the test paper made from a mixed solution of Fe(OH)3 colloid and montmorillonite with increased iron hydroxide colloid content.

[0020] Figure 6 (a) and (b) are the color development effects of aflatoxin on the test paper made using only Fe(OH)3 colloid. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0022] In the following examples, the iron hydroxide colloid used can be purchased commercially or prepared by referring to conventional methods. The specific preparation method is as follows: Step 1: Prepare reactants and reagents: prepare ferric chloride solution (FeCl3) and sodium hydroxide solution (NaOH) as reactants, and prepare an appropriate amount of deionized water for dilution.

[0023] Step 2: Mix the reactants: Slowly mix appropriate amounts of ferric chloride solution and sodium hydroxide solution in a container. Pay attention to maintaining a proper molar ratio of the reactants. Generally speaking, the molar ratio of ferric chloride to sodium hydroxide should be 1:2.

[0024] Step 3: Stirring and heating: Use a magnetic stirrer to stir the mixture evenly and heat it to an appropriate temperature. The heating temperature can be adjusted according to the specific experimental conditions, generally between 60-80 degrees Celsius.

[0025] Step 4 Reaction process: During the stirring and heating process, observe the changes in the reaction solution. At the beginning, the reaction solution may appear yellow or brown, and as the reaction proceeds, the color will gradually change to brown-black, which is the formation of iron hydroxide colloid.

[0026] Step 5 Cooling and dilution: After the reaction is completed, the reaction solution is cooled to room temperature and diluted with deionized water to the required concentration. The purpose of dilution is to adjust the concentration of the colloid to make it suitable for specific application requirements. Example 1

[0027] Step 1: Take 1.5 ml of commercial ferric hydroxide colloid (Hebei Hongzhuangyuan Education Technology Co., Ltd., density 3.7 g / ml). ), add 0.0067 g of montmorillonite powder (Guzhang County Shanlin Shiyu Mineral Products Co., Ltd., purity 90%) in an argon-protected glove box, and mix thoroughly by ultrasonic shaking for 0.5 h.

[0028] Step 2, dripping (spreading) the mixed solution in step 1 onto the nitrocellulose membrane, drying it at 55°C until it is fully dry, and obtaining aflatoxin detection colorimetric test paper.

[0029] Characterization experiments and results: (1) Drop the purchased 5 mg / ml aflatoxin B1 antigen onto the above aflatoxin detection color test paper. After standing for 10 minutes, you can see that the sample with the aflatoxin solution added has particles that aggregate and develop color, such as Figure 1 As shown in (a) and (b) in the figure, the red circle indicates the agglomeration effect of the colored blocks after color development, that is, obvious agglomeration occurs after the aflatoxin solution is added, but not before the aflatoxin is added. The effect diagram under the color development optical microscope is also given, as shown in FIG. Figure 2 As shown in (a) and (b), Figure 2 The red circular mark in (b) indicates that there is obvious agglomeration under optical microscope observation.

[0030] Comparative Example 1 This comparative example is substantially the same as Example 1, except that the aflatoxin solution is replaced with clean water. Figure 3 (a) in the figure shows that compared with the case where water is added, Figure 3 There was no significant change in (b).

[0031] Comparative Example 2 This comparative example is roughly the same as Example 1, the only difference being that the amounts of ferric hydroxide colloid and montmorillonite are 1.5 ml (density 3.7 g / ) and 0.015g, that is, the aflatoxin detection color test paper was prepared after increasing the montmorillonite content. It can be found that the change before and after adding aflatoxin to the test paper is not obvious, and the ideal detection effect cannot be achieved. Figure 4 As shown in (a) and (b).

[0032] Comparative Example 3 This comparative example is roughly the same as Example 1, the only difference being that the amounts of ferric hydroxide colloid and montmorillonite are 2.5 ml and 0.0067 g, respectively, i.e., the aflatoxin detection color test paper is prepared after increasing the content of ferric hydroxide colloid. It can be found that the change before and after adding aflatoxin to the test paper is not obvious, and the ideal detection effect cannot be achieved. Figure 5 As shown in (a) and (b).

[0033] Comparative Example 4 This comparative example is roughly the same as Example 1, except that montmorillonite is not added to the ferric hydroxide colloid, that is, only the ferric hydroxide colloid is used to prepare the aflatoxin detection color test paper. It can be found that the change before and after the addition of aflatoxin on the test paper is not obvious, and the ideal detection effect cannot be achieved. Figure 6 As shown in (a) and (b).

Claims

1. A color test paper for aflatoxin detection, characterized in that: The test paper is coated with a mixture of Fe(OH)3 colloid and montmorillonite.

2. The color developing test paper as claimed in claim 1, characterized in that, The mass ratio of Fe(OH)3 colloid to montmorillonite is 1:0.0012.

3. The color developing test paper as claimed in claim 1, characterized in that, It is characterized in that The test paper is made of nitrocellulose membrane.

4. The color developing test paper as claimed in claim 1, characterized in that, It is characterized in that The purity of montmorillonite is greater than 90%.

5. A method for preparing a color test paper for aflatoxin detection according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1, adding a certain amount of montmorillonite powder to the Fe(OH)3 colloidal solution and mixing it evenly by ultrasonic vibration; Step 2: drip the mixed solution in step 1 onto the test paper and fully dry it at 40°C to 60°C.

6. The method according to claim 5, characterized in that The density of Fe(OH)3 colloid is 3.4~3.9g / cm 3 .

7. The method according to claim 5, characterized in that Ultrasonic oscillation is performed to uniformly mix the mixture, and the ultrasonic oscillation time is more than 20 minutes, and more preferably, the ultrasonic oscillation time is 30 minutes.

8. A kit for detecting aflatoxin comprising the color developing test paper according to any one of claims 1 to 4.

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