Method for detecting metal mercury in food

Abstract

The invention discloses a method for detecting metal mercury in food, and relates to the technical field of food detection. Comprising the following steps: extracting a mercury-containing solution from a to-be-detected food sample, preparing a ferrous sulfate / graphene oxide nano composite material, enriching mercury ions in the mercury-containing solution by using the nano composite material, and quantitatively analyzing the mercury ions on the nano composite material by adopting atomic fluorescence spectrometry. According to the method, the collected food sample is subjected to digestion pretreatment, the mercury-containing solution is prepared, metal mercury in the food can be fully and effectively extracted, the ferrous sulfate / graphene oxide nanocomposite is prepared, mercury ions on the nanocomposite are quantitatively analyzed through atomic fluorescence spectrometry, metal mercury detection is achieved, and the detection accuracy is high. The mercury ions in the mercury-containing solution can be fully adsorbed and enriched in the whole detection process, pollution source introduction and mercury loss are avoided, the accuracy of the detection result is ensured, the detection process is simple and clear and easy to operate, and the detection period is shortened to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of food detection, and in particular to a method for detecting metallic mercury in food. Background Art

[0002] Food testing refers to the inspection and analysis of the quality, safety and hygiene of food and its raw materials, additives, packaging materials, etc. through a series of physical, chemical, biological and other methods and technical means. Its purpose is to ensure that food complies with national or regional food safety standards and regulatory requirements and to safeguard the health and safety of consumers. It is of great significance to maintaining food safety, protecting consumer rights and interests, and promoting food trade and industry development.

[0003] Metallic mercury is also known as quicksilver and has many aliases, such as white mercury, beautiful girl, mercury, divine glue, original water, lead essence, flowing beads, original beads, red mercury, sand mercury, spiritual liquid, living treasure, Ziming, etc. It is a silvery-white heavy liquid with high density and surface tension, as well as good electrical and thermal conductivity. Due to the toxicity of metallic mercury and its compounds, its use in the pharmaceutical industry has been greatly reduced. Because mercury is a toxic heavy metal and has potential hazards to human health, the detection of metallic mercury in food is an important food safety detection task.

[0004] Most of the existing methods for detecting metallic mercury in food have complicated processes, are time-consuming and labor-intensive, have a long detection cycle, require high technical levels of operators, and improper operation can easily affect the accuracy of the detection results. In addition, the metallic mercury in food cannot be fully and effectively extracted, and pollution may be introduced during the detection process, resulting in mercury loss, which leads to inaccurate metallic mercury detection results. In addition, mercury ions cannot be fully enriched during the detection process, further reducing the detection accuracy, making it inconvenient to widely promote and apply, and unable to effectively help maintain food safety, protect consumer rights and interests, and promote food trade. Therefore, the present invention proposes a method for detecting metallic mercury in food to solve the problems existing in the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to propose a method for detecting metallic mercury in food, so as to solve the problems that the existing method for detecting metallic mercury in food is time-consuming and labor-intensive, has a long detection cycle, requires a high technical level of the operator, cannot fully and effectively extract the metallic mercury in the food, may introduce pollution and cause mercury loss during the detection process, thereby resulting in inaccurate metallic mercury detection results, and cannot fully enrich mercury ions during the detection process.

[0006] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a method for detecting metallic mercury in food, comprising the following steps:

[0007] Step 1: first collect the food sample to be tested, then digest and pre-treat the collected food sample, and then prepare the mercury-containing solution from the digestion product;

[0008] Step 2: Mix and stir the pre-prepared deionized water, the weighed graphene oxide powder and the ferrous sulfate nanoparticles, and then compound the mixed product by microwave-assisted method to obtain a nanocomposite material;

[0009] Step 3: Using the nanocomposite material as an adsorbent, mixing it with the mercury-containing solution, using the nanocomposite material to adsorb and enrich the mercury ions, and then separating the nanocomposite material enriched with mercury ions;

[0010] Step 4: Dry the separated nanocomposite material, and after drying, quantitatively analyze the mercury ions adsorbed on the nanocomposite material by atomic fluorescence spectroscopy to detect metallic mercury in food.

[0011] The further improvement lies in that in the step 1, the specific steps of digestion pretreatment of the food sample are: first, the collected food sample is cut into pieces and crushed by a crusher, then the crushed food sample is evenly mixed with nitric acid at a mass ratio of 1:1, and then the mixed product is placed in a microwave digestion instrument, and digested for 20 to 30 minutes at a microwave output power of 1400W to 1600W and a heating temperature of 150°C to 200°C to complete the digestion pretreatment.

[0012] A further improvement is that in the step 1, the specific steps of preparing the mercury-containing solution from the digestion product are: first pouring the digestion product into a centrifuge tube and placing it on a centrifuge for centrifugal treatment, filtering out the precipitate after the centrifugal treatment, and obtaining the supernatant is the mercury-containing solution.

[0013] A further improvement is that the digestion product is centrifuged on a centrifuge at a speed of 3000-5000 r / min for 5-10 min, and after the centrifugation, a semipermeable membrane is used to filter out the precipitate therein.

[0014] A further improvement is that in the step 2, the mixing mass ratio of the deionized water, graphene oxide powder and ferrous sulfate nanoparticles is 3:1:1-2, the deionized water, graphene oxide powder and ferrous sulfate nanoparticles are mixed and stirred in a magnetic stirrer, and the mixture is ultrasonically treated during the stirring process.

[0015] The further improvement lies in that: in the step 2, the specific steps of using the microwave-assisted method to compound the mixed product are: first placing the mixed product in a microwave reactor, then microwave-treating it at a microwave power of 700 to 800 W for 30 to 40 minutes, centrifugally filtering the mixed product after the microwave treatment to remove unreacted raw materials and by-products therein to obtain a nano-composite material, and then placing it in a vacuum drying oven for drying at a temperature of 100 to 200°C.

[0016] A further improvement is that in step three, the nanocomposite material and the mercury-containing solution are mixed and stirred by ultrasonic stirring, the ultrasonic frequency is 15 to 20 KHz, the ultrasonic stirring time is 20 to 30 minutes, and the nanocomposite material enriched with mercury ions is separated by magnetic separation.

[0017] The further improvement is that in the step 4, the specific steps of quantitatively analyzing the mercury ions adsorbed on the nanocomposite material are: firstly calibrating the AFS instrument with different known concentrations of mercury standard solutions, and recording the standard curves respectively, then placing the separated nanocomposite material in the sample cell of the AFS instrument for measurement and recording its fluorescence signal intensity, then comparing the recorded fluorescence signal intensity with the standard curve of the mercury standard solution, and finally finding the point on the standard curve that is closest to the recorded fluorescence signal intensity, and reading the concentration value corresponding to the point.

[0018] The beneficial effects of the present invention are as follows: the present invention can fully and effectively extract metallic mercury in food by digesting and pre-treating the collected food samples and preparing a mercury-containing solution; the present invention can realize metallic mercury detection by preparing a ferrous sulfate / graphene oxide nanocomposite material and quantitatively analyzing mercury ions on the nanocomposite material by atomic fluorescence spectroscopy; the whole detection process can fully adsorb and enrich the mercury ions in the mercury-containing solution, avoid introducing pollution sources and mercury loss, ensure the accuracy of the detection results; the detection process is simple and clear, easy to operate, and does not require high technical level of operators, and reduces the detection cycle to a certain extent. The present invention is worthy of wide promotion and application, and can bring effective help to maintaining food safety, protecting consumer rights and interests, and promoting food trade. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the process of the method for detecting metallic mercury in food of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Embodiment 1

[0023] See also Figure 1 This embodiment provides a method for detecting metallic mercury in food, comprising the following steps:

[0024] Step 1: Extract the mercury-containing solution from the food sample to be tested

[0025] First, a food sample to be tested is collected and placed in a sealed container for temporary storage to prevent the volatilization of mercury, and then the collected food sample is digested and pre-treated to digest organic matter in the food sample, release the mercury therein, and obtain a mercury-containing solution, which is stored in a sealed container for standby use. The specific steps are: first, the collected food sample is chopped and crushed by a grinder to increase the specific surface area of ​​the food sample for subsequent processing, and then the crushed food sample is mixed with nitric acid (concentration of 70%) at a mass ratio of 1:1, and then the mixed product is placed in a microwave digestion instrument, digested for 20 minutes at a microwave output power of 1400W and a heating temperature of 150°C to complete the digestion pretreatment, and then the digestion product is poured into a centrifuge tube and placed on a centrifuge, and centrifuged at a speed of 3000r / min for 5-10 minutes, and after the centrifugation, the precipitate therein is filtered out by a semipermeable membrane, and the obtained supernatant is the mercury-containing solution;

[0026] Step 2: Preparation of ferrous sulfate / graphene oxide nanocomposite material

[0027] First, graphene oxide powder, ferrous sulfate nanoparticles and deionized water are weighed respectively, wherein the mass ratio of graphene oxide powder, ferrous sulfate nanoparticles and deionized water is 1:1:3, then the deionized water and the weighed graphene oxide powder and ferrous sulfate nanoparticles are added into a magnetic stirrer for mixing and stirring evenly, and the mixture is ultrasonically treated during the stirring process to make the graphene oxide powder and the ferrous sulfate nanoparticles disperse more evenly, then the mixed product is placed in a microwave reactor, and then microwave-treated at a microwave power of 700 W for 30 minutes, and after the microwave treatment is completed, the mixed product is centrifuged and filtered to remove unreacted raw materials and by-products therein to obtain a nanocomposite material, and then placed in a vacuum drying oven for drying at a temperature of 100° C. to obtain a ferrous sulfate / graphene oxide nanocomposite material;

[0028] Step 3: Enriching mercury ions in mercury-containing solutions using nanocomposites

[0029] The nanocomposite prepared in step 2 is used as an adsorbent and mixed with the mercury-containing solution obtained in step 1 by ultrasonic stirring, which can promote full contact between the two and promote the adsorption of mercury ions. The high affinity of the nanocomposite to mercury ions is used to adsorb and enrich the mercury ions in the mercury-containing solution. The ultrasonic frequency is set to 15 KHz and the ultrasonic stirring time is 20 minutes. Since both graphene oxide and ferrous sulfate have good adsorption properties, the composite material can effectively adsorb mercury ions in the water sample. Then, the nanocomposite material enriched with mercury ions is separated from the solution by magnetic separation.

[0030] Step 4: Quantitative analysis of mercury ions on nanocomposites using atomic fluorescence spectroscopy

[0031] The nanocomposite separated in step three is dried, and after drying, the mercury ions adsorbed on the nanocomposite are quantitatively analyzed by atomic fluorescence spectrometry (AFS). The specific steps are as follows: first, the AFS instrument is calibrated with mercury standard solutions of different known concentrations, and the standard curves are recorded respectively, and then the separated nanocomposite is placed in the sample cell of the AFS instrument for measurement and its fluorescence signal intensity is recorded, and then the recorded fluorescence signal intensity is compared with the standard curve of the mercury standard solution, and finally, the point on the standard curve that is closest to the recorded fluorescence signal intensity is found, and the concentration value corresponding to the point is read to realize the detection of metallic mercury in food.

[0032] Embodiment 2

[0033] See also Figure 1 This embodiment provides a method for detecting metallic mercury in food, comprising the following steps:

[0034] Step 1: Extract the mercury-containing solution from the food sample to be tested

[0035] First, collect the food samples to be tested and put them into a sealed container for temporary storage to avoid the volatilization of mercury, then perform digestion pretreatment on the collected food samples to digest the organic matter in the food samples, release the mercury therein, prepare the mercury-containing solution, and store it in a sealed container for standby use. The specific steps are: first, cut the collected food samples into pieces and grind them with a grinder to increase the specific surface area of ​​the food samples for subsequent treatment, then mix the ground food samples with nitric acid (concentration of 70%) at a mass ratio of 1:1, then place the mixed product in a microwave digestion instrument, digest for 30 minutes at a microwave output power of 1600W and a heating temperature of 200°C to complete the digestion pretreatment, then pour the digestion product into a centrifuge tube and place it on a centrifuge, centrifuge it at a speed of 5000r / min for 10 minutes, filter out the precipitate therein with a semipermeable membrane after the centrifugation, and the obtained supernatant is the mercury-containing solution;

[0036] Step 2: Preparation of ferrous sulfate / graphene oxide nanocomposite material

[0037] First, graphene oxide powder, ferrous sulfate nanoparticles and deionized water are weighed respectively, wherein the mass ratio of graphene oxide powder, ferrous sulfate nanoparticles and deionized water is 1:2:3, then the deionized water and the weighed graphene oxide powder and ferrous sulfate nanoparticles are added into a magnetic stirrer for mixing and stirring evenly, and the mixture is ultrasonically treated during the stirring process to make the graphene oxide powder and the ferrous sulfate nanoparticles disperse more evenly, then the mixed product is placed in a microwave reactor, and then microwave-treated at a microwave power of 800 W for 40 minutes, and after the microwave treatment is completed, the mixed product is centrifuged and filtered to remove unreacted raw materials and by-products therein to obtain a nanocomposite material, and then placed in a vacuum drying oven for drying at a temperature of 200° C. to obtain a ferrous sulfate / graphene oxide nanocomposite material;

[0038] Step 3: Enriching mercury ions in mercury-containing solutions using nanocomposites

[0039] The nanocomposite prepared in step 2 is used as an adsorbent and mixed with the mercury-containing solution obtained in step 1 by ultrasonic stirring, which can promote full contact between the two and promote the adsorption of mercury ions. The high affinity of the nanocomposite to mercury ions is used to adsorb and enrich the mercury ions in the mercury-containing solution. The ultrasonic frequency is set to 20 KHz and the ultrasonic stirring time is 30 minutes. Since both graphene oxide and ferrous sulfate have good adsorption properties, the composite material can effectively adsorb mercury ions in the water sample. Then, the nanocomposite material enriched with mercury ions is separated from the solution by magnetic separation.

[0040] Step 4: Quantitative analysis of mercury ions on nanocomposites using atomic fluorescence spectroscopy

[0041] The nanocomposite separated in step three is dried, and after drying, the mercury ions adsorbed on the nanocomposite are quantitatively analyzed by atomic fluorescence spectrometry (AFS). The specific steps are as follows: first, the AFS instrument is calibrated with mercury standard solutions of different known concentrations, and the standard curves are recorded respectively, and then the separated nanocomposite is placed in the sample cell of the AFS instrument for measurement and its fluorescence signal intensity is recorded, and then the recorded fluorescence signal intensity is compared with the standard curve of the mercury standard solution, and finally, the point on the standard curve that is closest to the recorded fluorescence signal intensity is found, and the concentration value corresponding to the point is read to realize the detection of metallic mercury in food.

[0042] 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 metallic mercury in food, characterized in that: The following steps are involved: Step 1: first collect the food sample to be tested, then digest and pre-treat the collected food sample, and then prepare the mercury-containing solution from the digestion product; Step 2: Mix and stir the pre-prepared deionized water, the weighed graphene oxide powder and the ferrous sulfate nanoparticles, and then compound the mixed product by microwave-assisted method to obtain a nanocomposite material; Step 3: Using the nanocomposite material as an adsorbent, mixing it with the mercury-containing solution, using the nanocomposite material to adsorb and enrich the mercury ions, and then separating the nanocomposite material enriched with mercury ions; Step 4: Dry the separated nanocomposite material, and after drying, quantitatively analyze the mercury ions adsorbed on the nanocomposite material by atomic fluorescence spectroscopy to detect metallic mercury in food.

2. The method for detecting metallic mercury in food according to claim 1, characterized in that: In the step 1, the specific steps of digestion pretreatment of food samples are: first, the collected food samples are cut into pieces and crushed by a grinder, then the crushed food samples are evenly mixed with nitric acid at a mass ratio of 1:1, and then the mixed product is placed in a microwave digestion instrument, and digested for 20 to 30 minutes at a microwave output power of 1400W to 1600W and a heating temperature of 150°C to 200°C to complete the digestion pretreatment.

3. The method for detecting metallic mercury in food according to claim 1, characterized in that: In the step 1, the specific steps of preparing the mercury-containing solution from the digestion product are: first pouring the digestion product into a centrifuge tube and placing it on a centrifuge for centrifugal treatment, filtering out the precipitate after the centrifugal treatment, and obtaining the supernatant, which is the mercury-containing solution.

4. The method for detecting metallic mercury in food according to claim 3, characterized in that: The digestion product is centrifuged on a centrifuge at a speed of 3000-5000 r / min for 5-10 min. After the centrifugation, a semipermeable membrane is used to filter out the precipitate therein.

5. The method for detecting metallic mercury in food according to claim 1, characterized in that: In the step 2, the mixing mass ratio of the deionized water, graphene oxide powder and ferrous sulfate nanoparticles is 3:1:1-2. The deionized water, graphene oxide powder and ferrous sulfate nanoparticles are mixed and stirred in a magnetic stirrer, and the mixture is ultrasonically treated during the stirring process.

6. The method for detecting metallic mercury in food according to claim 1, characterized in that: In the step 2, the specific steps of using the microwave-assisted method to compound the mixed product are: first placing the mixed product in a microwave reactor, then microwave-treating it at a microwave power of 700 to 800 W for 30 to 40 minutes, centrifugally filtering the mixed product after the microwave treatment to remove unreacted raw materials and by-products therein to obtain a nano-composite material, and then placing it in a vacuum drying oven for drying at a temperature of 100 to 200°C.

7. The method for detecting metallic mercury in food according to claim 1, characterized in that: In the step three, the nanocomposite material and the mercury-containing solution are mixed and stirred by ultrasonic stirring, the ultrasonic frequency is 15 to 20 KHz, and the ultrasonic stirring time is 20 to 30 minutes. The nanocomposite material enriched with mercury ions is separated by magnetic separation.

8. The method for detecting metallic mercury in food according to claim 1, characterized in that: In the step 4, the specific steps of quantitatively analyzing the mercury ions adsorbed on the nanocomposite material are as follows: first, the AFS instrument is calibrated with mercury standard solutions of different known concentrations, and the standard curves are recorded respectively; then, the separated nanocomposite material is placed in the sample cell of the AFS instrument for measurement and its fluorescence signal intensity is recorded; then, the recorded fluorescence signal intensity is compared with the standard curve of the mercury standard solution; finally, the point on the standard curve that is closest to the recorded fluorescence signal intensity is found, and the concentration value corresponding to the point is read.

Images