Formaldehyde detection method and application

Abstract

The invention discloses a formaldehyde detection method. The formaldehyde detection method comprises the following steps: (1) preparing a solution of a substance to be detected; (2) adding an AgNO3 solution and an OPD solution into a buffer solution with the pH value of 3.5-6.5 to obtain a mixed solution; (3) adding a solution to be detected into the mixed solution, reacting for a period of time at a certain temperature, capturing an image through a colorimetric imaging device, converting the image into a digital RGB (Red, Green, Blue) value by adopting software, and calculating a G / B value of the digital RGB value; and (4) substituting the obtained G / B value into a formula G / B =-0.0744 C + 1.1587 for calculation, wherein the obtained C value is the content of formaldehyde in the substance to be detected. The invention also discloses application of the formaldehyde detection method in detection of the content of formaldehyde in vegetables or packaging materials. The method disclosed by the invention has the characteristics of convenience, rapidness and high sensitivity.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical chemistry, and specifically relates to a formaldehyde detection method and application. Background Art

[0002] Formaldehyde (HCHO) is a colorless, odorless, water-soluble gas. Its 35wt%-40wt% aqueous solution is also called formalin, which has antiseptic properties. Formaldehyde can react with DNA and protein, causing changes in their structure and function. It has strong direct toxicity and carcinogenic effects on the human body. Long-term exposure to low concentrations of formaldehyde may also cause damage to the human immune system, respiratory system, nervous system and liver.

[0003] Traditional formaldehyde detection methods include high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS), which can accurately detect formaldehyde and its content; however, these methods are bulky and expensive, and are difficult to meet the needs of on-site detection. Therefore, there is an urgent need for a simple, rapid, sensitive, reliable and low-cost formaldehyde detection method.

[0004] In recent years, detection technology based on o-phenylenediamine (OPD) has attracted widespread attention due to its advantages such as high sensitivity, design flexibility and ease of use. OPD is easily oxidized by various oxidants (such as Cu 2+ 、Ag + , H2O2) to form 2,3-diaminophenazine (DAP) with yellow fluorescence. Based on this reaction characteristic, researchers have developed a series of fluorescence / colorimetric sensors. Actuators, B. 2018; 260: 908-917 reported a simple upconversion fluorescence and colorimetric dual-modal sensor that detects H2O2, choline and acetylcholine chloride through an enzyme-controlled cyclic signal amplification strategy. Anal Chem. 2016; 88(2): 1355-1361 reported a Cu-based 2+ A fluorescence and colorimetric dual-modal sensing strategy was designed for the oxidation and colorimetric reactions of OPD, achieving highly sensitive inorganic pyrophosphatase activity determination.

[0005] On this basis, the formaldehyde detection method of the present invention is proposed. Summary of the invention

[0006] The present invention proposes a method for detecting formaldehyde by digital image colorimetry based on inhibiting OPD oxidation. In the method of the present invention, Ag +As an oxidant, OPD is oxidized to yellow DAP. The presence of formaldehyde can inhibit this oxidation, resulting in a decrease in the amount of DAP produced and a corresponding lighter solution color. Based on this inhibition, a rapid and highly sensitive on-site formaldehyde analysis method was established.

[0007] The technical solution of the present invention is as follows:

[0008] The first aspect of the present invention discloses a method for detecting formaldehyde, comprising the following steps:

[0009] (1) preparing a solution of the substance to be tested;

[0010] (2) adding a certain concentration of AgNO3 solution and a certain concentration of OPD solution into a buffer solution to obtain a mixed solution;

[0011] (3) adding the test solution of step (1) to the mixed solution of step (2), reacting at a certain temperature for a period of time, capturing an image thereof by a colorimetric imaging device, converting the image into a digital RGB value by software, and calculating its G / B value;

[0012] (4) Substituting the G / B value obtained in step (3) into the formula G / B=-0.0744C+1.1587 for calculation, the obtained C value is the formaldehyde content in the substance to be tested.

[0013] Preferably, the buffer solution in step (2) is a citric acid-sodium citrate solution.

[0014] Preferably, in step (3), the concentration of the OPD solution is maintained at 5-15 mmol / L, the concentration of the AgNO3 solution is maintained at 10-200 μmol / L, and the pH value of the solution is maintained at 3.0-5.5; the reaction temperature is room temperature, and the reaction time is 5-35 minutes.

[0015] Preferably, the concentration of the OPD solution is maintained at 10 mmol / L, the concentration of AgNO3 in the solution is maintained at 100 μmol / L, and the pH value of the solution is maintained at 4.5; the reaction temperature is 25° C., and the reaction time is 10 minutes.

[0016] Preferably, the colorimetric imaging device in step (3) is a smart phone or a smart camera.

[0017] Preferably, the software used in step (3) is Just Color Picker software.

[0018] The second aspect of the present invention discloses the application of the formaldehyde detection method for detecting formaldehyde content in vegetables or packaging materials.

[0019] Beneficial effects of the present invention:

[0020] The principle of the formaldehyde detection method of the present invention is as follows: based on Ag + (Soluble Ag salt, preferably AgNO3) is used as an oxidant to oxidize O-phenylenediamine (OPD) to 2,3-diaminophenazine (DAP) emitting yellow fluorescence. Along with the generation of silver nanoparticles (AgNPs), the high specific surface area and size effect make AgNPs exhibit significant oxidase-like activity, thereby further promoting the reaction of OPD with Ag. + The reaction between the two leads to an increase in the amount of DAP generated, which in turn enhances the fluorescence intensity. When formaldehyde is present, it induces the aggregation of AgNPs. This aggregation phenomenon reduces the catalytic efficiency of AgNPs, resulting in a decrease in the generation of DAP and a corresponding decrease in the fluorescence signal. Based on this inhibitory effect, the present invention establishes for the first time a convenient, rapid, and highly sensitive method for on-site instant detection of formaldehyde content in materials.

[0021] The detection limit (LOD) of the method of the present invention is 0.07 mg / L. The method of the present invention is used for detecting the formaldehyde content in vegetables or packaging materials, and has the characteristics of convenience, rapidity and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a colorimetric imaging device. DETAILED DESCRIPTION

[0023] The present invention is described clearly and completely below in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Other technical solutions obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0024] Example: Four vegetable samples and two packaging materials were selected from the market to determine the formaldehyde content. The four vegetables were Chinese cabbage, cabbage, broccoli and potato; the two packaging materials were vegetable transport cartons and fruit transport cartons. The steps are as follows:

[0025] (1) Cut the vegetables or cartons into pieces, weigh 2 g of the sample accurately to 0.1 mg, place it in a 50 mL stoppered conical flask, accurately add 20 mL of water, mix well, soak and extract at 40 °C for 24 h, centrifuge and decolorize, take the supernatant and filter it through a 0.45 μm organic filter membrane to obtain the test solution;

[0026] (2) adding a 200 μmol / L AgNO3 solution and a 20 mmol / L OPD solution to a citric acid-sodium citrate buffer solution to obtain a mixed solution, and adjusting the pH value to about 4.5;

[0027] (3) The test solution of step (1) was added to the mixed solution of step (2) respectively, so that the concentration of AgNO3 solution was 100 μmol / L, the concentration of OPD solution was 10 mmol / L, and the pH value of the solution was maintained at about 4.5; the reaction was carried out at 25°C for 10 minutes, and then Figure 1 The images were captured by a colorimetric imaging device on a smartphone, and the images were converted into digital RGB values ​​using Just Color Picker software (version 5.9), and their G / B values ​​were calculated;

[0028] (4) Substitute the G / B value obtained in step (3) into the formula G / B = -0.0744C + 1.1587 for calculation, and the obtained C value is the formaldehyde content in the substance to be tested.

[0029] The formaldehyde content in four kinds of vegetables and two kinds of cartons tested in this example is shown in the following table:

[0030] Sample No. HPLC(mg / Kg) Method of the present invention / (mg / Kg) Relative standard deviation / (%) Chinese cabbage 0.58 0.59 1.7 cabbage 0.61 0.58 -4.9 Broccoli 0.57 0.59 -3.5 potato 0.61 0.62 1.6 Vegetable Carton 7.30 7.60 4.1 Fruit Carton 7.00 7.20 2.9

[0031] Note: Relative standard deviation in the table = (C 本方法 -C HPLC ) / C HPLC The data of vegetable cartons and fruit cartons in the table are obtained after 10-fold dilution.

[0032] The first column in the table is the data measured by the HPLC method. From the data in the table, it can be seen that the error between the method of the present invention and the HPLC method is within an acceptable range (less than 5.0%); however, the method of the present invention does not require large instruments, can be measured on-site, has the characteristics of short detection time, high sensitivity, and simple operation; and shows better practicality.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting formaldehyde, characterized in that: The steps include: (1) preparing a solution of the substance to be tested; (2) adding a certain concentration of AgNO3 solution and a certain concentration of OPD solution into a buffer solution to obtain a mixed solution; (3) adding the test solution of step (1) to the mixed solution of step (2), reacting at a certain temperature for a period of time, capturing an image thereof by a colorimetric imaging device, converting the image into a digital RGB value by software, and calculating its G / B value; (4) Substituting the G / B value obtained in step (3) into the formula G / B=-0.0744C+1.1587 for calculation, the obtained C value is the formaldehyde content in the substance to be tested.

2. The method for detecting formaldehyde according to claim 1, characterized in that: The buffer solution in step (2) is a citric acid-sodium citrate solution.

3. The method for detecting formaldehyde according to claim 1, characterized in that: In step (3), the concentration of the OPD solution is maintained at 5-15 mmol / L, the concentration of the AgNO3 solution is maintained at 10-200 μmol / L, and the pH value of the solution is maintained at 3.0-5.5; the reaction temperature is room temperature, and the reaction time is 5-35 minutes.

4. The method for detecting formaldehyde according to claim 3, characterized in that: The concentration of OPD solution was maintained at 10 mmol / L, the concentration of AgNO3 in the solution was maintained at 100 μmol / L, and the pH value of the solution was maintained at 4.5; the reaction temperature was 25°C, and the reaction time was 10 minutes.

5. The method for detecting formaldehyde according to claim 1, characterized in that: The colorimetric imaging device in step (3) is a smart phone or a smart camera.

6. The method for detecting formaldehyde according to claim 1, characterized in that: The software used in step (3) is JustColor Picker software.

7. Use of the formaldehyde detection method according to any one of claims 1 to 6 for detecting formaldehyde content in vegetables or packaging materials.

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