CN102914535A - Method for separating and detecting nano silica in food - Google Patents

Abstract

The invention discloses a method for separating and detecting nano silicon dioxide in food. For typical food samples containing silicon dioxide additives, different pretreatment processes are used to dissolve silicon dioxide, and centrifugation is used to enrich the silicon dioxide. The separated silicon dioxide is washed with an organic solvent, and then the presence of nanometer silicon dioxide is observed and confirmed by a transmission electron microscope. At the same time, the separated nano-silica was fully characterized, and the basic information of the nanoparticles was comprehensively characterized by scanning electron microscopy and X-ray energy spectrum, and the total content of silica was determined by inductively coupled plasma emission spectrometer. The invention has simple separation operation, can efficiently separate nano-silica particles in food, is applicable to the detection of nano-silica in various foods, and provides basic data for labeling and safety evaluation of nano-products.

Description

Method for separating and detecting nano silicon dioxide in food

technical field

The invention relates to a method for separating and detecting nano-silica in food, which is a method for detecting and analyzing nano-sized food additives. It belongs to the field of nano analytical chemistry and nano inorganic materials.

Background technique

With the rapid development of nanotechnology in the 21st century, the application of nanomaterials has been involved in food, medicine, paint, plastics, catalysts, electronic products and other fields. More and more nano-products have greatly increased the opportunities for consumers to come into contact with nano-materials. Studies have found that nanomaterials have certain negative effects, so people have doubts about the safety of nanoscale products. For the sake of public health and the healthy and sustainable development of nanotechnology, it is now necessary to analyze and detect nanomaterials in related products and conduct safety assessments.

In recent years, the application of nanotechnology in the food industry has developed rapidly, and nanomaterials are used to add food packaging bags to improve the freshness of food. At the same time, the particle size of some traditional food additives, such as silicon dioxide as an anticaking agent, has also reached the nanometer scale due to the improvement of the manufacturing process. There is an increasing possibility that the human body can ingest nanomaterials through food. Therefore, researchers and relevant government departments have begun to pay attention to how to conduct qualitative and quantitative analysis of nanomaterials in food, label nanoparticles in food, evaluate the exposure level of the population, and conduct risk assessment and safety evaluation. On this basis, relevant management departments can know to formulate laws and regulations to regulate the production, labeling and consumption of nano-products. However, due to the complex food matrix and the low content of nanomaterials in food, how to separate and analyze artificially added nanomaterials from food is a major difficulty in this field.

Contents of the invention

In order to solve the problems in the prior art, the object of the present invention is to provide a method for separating and detecting nano silicon dioxide in food. The separation process is simple to operate and can efficiently separate nano-silica particles in food. The method has good applicability and can be used for various food samples. In addition, the qualitative and quantitative characterization of nano-silica in complete food samples is also given, which provides basic data for the labeling and safety evaluation of nano-products in the future.

In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A method for separating and detecting nano silicon dioxide in food, comprising the steps of:

1) Isolation of nano-silica particles from food samples;

2) Digest the silica particles separated in step 1), constant volume, measure the content of silicon element by inductively coupled plasma emission spectrometer, and convert the total amount of silica,

3) Then, observe the particle morphology and particle size of the nano-silica particles separated in step 1) using a transmission electron microscope;

4) Simultaneously with step 3), conduct a qualitative and quantitative comprehensive characterization of the nano-silica obtained from step 1), namely:

i) Characterize the shape, size and surface of the silica particles separated in step 1) using a scanning electron microscope;

ii) Using high-resolution transmission electron microscopy to confirm the elemental composition of the nano-silicon dioxide isolated in step 1);

As a specific technical solution of the present invention, the process of separating nano-silica particles from food samples in the above step 1) includes the following steps:

a) Dissolving the silicon dioxide from the food sample in step 1) through a pretreatment process to obtain a transparent solution;

b) Then, pour the transparent solution dissolved in step a) into a centrifuge tube, and collect the precipitate after centrifugation;

c) Then, the precipitate in step b) is washed with a cleaning solution, dried, and the silica particles are separated.

The cleaning solution in step c) of the technical solution of the present invention is preferably different combinations of deionized water, acetone, absolute ethanol and acetic acid.

As the first preferred technical solution of the present invention:

The food sample in step 1) is a direct liquid beverage sample;

Step c) specifically, the precipitate in step b) is washed once with deionized water, then once with acetone, and then twice with acetic acid, and then freeze-dried to separate the carbon dioxide from the direct liquid beverage. silicon.

As the second preferred technical solution of the present invention:

The food sample in step 1) is an instant granule sample;

Step c) specifically, the precipitate in step b) is washed once with deionized water, then once with acetone, then once with acetic acid, and once with absolute ethanol, and then freeze-dried to obtain instant Silica was isolated from the infusion sample.

As the third preferred technical solution of the present invention:

The food sample in step 1) is a puffed food sample;

Step c) specifically, wash the precipitate in step b) once with deionized water, then once with acetone, then once with absolute ethanol, then twice with acetic acid, and then freeze-dried to obtain the puffed Silica is isolated from food.

，在上述步骤a）中，前处理过程对于三种不同类型样品分别有不同处理方法： As a further preferred technical solution of the above-mentioned technical solution of the present invention

, in the above step a), the pretreatment process has different processing methods for three different types of samples:

1. For direct liquid beverage samples, they can be cleaned directly with cleaning reagents.

2. For the instant granule sample, first dissolve it completely with deionized water at about 100 degrees Celsius.

3. For puffed food samples, use concentrated nitric acid to digest them completely at about 120 degrees Celsius.

，在步骤2）中，以浓硝酸和40%氢氟酸和硼酸的消解体系，190°C的消解温度，在微波消解仪上消解步骤1）分离出得二氧化硅，消解完全后用2%稀硝酸定容。 As a further preferred technical solution of the above-mentioned technical solution of the present invention

, in step 2), use the digestion system of concentrated nitric acid, 40% hydrofluoric acid and boric acid, and the digestion temperature of 190°C to digest the silica obtained in step 1) on a microwave digestion instrument, and use 2 after the digestion is complete % dilute nitric acid to volume.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

The method for separating nano silicon dioxide in food has simple operation means, can efficiently separate nano silicon dioxide particles in food, has good applicability, and can be used for various food samples. At the same time, taking a food sample as an example, it provides a comprehensive analysis and characterization solution for nanoparticles. This method completely characterizes the nanomaterials in food samples qualitatively and quantitatively, and provides basic data for the labeling and safety evaluation of nano-products in the future.

Description of drawings

Fig. 1 is the transmission electron micrograph of the nano-silicon dioxide separated from 3 kinds of direct liquid beverages in Example 1 of the present invention.

Fig. 2 is a scanning electron microscope photograph of nano silicon dioxide separated from a direct liquid beverage in Example 1 of the present invention.

Figure 3 is a high-resolution transmission electron microscope image and X-ray energy spectrum image of nano-silicon dioxide separated from a direct liquid beverage in Example 1 of the present invention.

Fig. 4 is a transmission electron micrograph of nano silicon dioxide separated from 6 kinds of instant granules in Example 2 of the present invention.

Fig. 5 is a transmission electron micrograph of nano-silicon dioxide separated from 3 kinds of puffed foods in Example 3 of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, preferred embodiment of the present invention is described in detail as follows:

Embodiment one:

Referring to Figures 1 to 3, a method for separating and detecting nano silicon dioxide in food, comprising the following steps:

1) Isolation of nano-silica particles from food samples;

2) Digest the silica particles separated in step 1), constant volume, measure the content of silicon element by inductively coupled plasma emission spectrometer, and convert the total amount of silica,

3) Then, observe the particle morphology and particle size of the nano-silica particles separated in step 1) using a transmission electron microscope;

4) Simultaneously with step 3), conduct a qualitative and quantitative comprehensive characterization of the nano-silica obtained from step 1), namely:

i) Characterize the shape, size and surface of the silica particles separated in step 1) using a scanning electron microscope;

ii) Using high-resolution transmission electron microscopy to confirm the elemental composition of the nano-silica isolated in step 1),

In this example, a simple and easy method is used to separate silica particles from food samples, and the centrifugation method is used to achieve the purpose of enriching silica, and the separated silica is cleaned with an organic solvent, and electron Microscopic technology confirmed the existence of nanoparticles; at the same time, a comprehensive qualitative and quantitative characterization analysis was carried out on the nano-silica in the sample, and a variety of techniques were used to provide parameters such as the morphology, chemical composition and content of nano-silica. Product labeling and safety evaluation provide basic information. The method for separating nano-silicon dioxide in food in this embodiment has simple operation means and can efficiently separate nano-silicon dioxide particles in food. The method has good applicability and can be used for various food samples.

In this embodiment, the process of isolating nano-silica particles from food samples in step 1) includes the following steps:

a) Dissolving the silicon dioxide from the food sample in step 1) through a pretreatment process to obtain a transparent solution;

b) Then, pour the transparent solution dissolved in step a) into a centrifuge tube, and collect the precipitate after centrifugation;

c) Then, the precipitate in step b) is washed with a cleaning solution, dried, and the silica particles are separated.

In this example, different pretreatment processes were used to dissolve the silicon dioxide for the sampled food samples, and the dissolved transparent solution was poured into a centrifuge tube, and the precipitate was collected after centrifugation. Observe the separated nano-silica, and determine the chemical composition of the nano-silica by high-resolution transmission electron microscope. The separation operation method of this embodiment is simple, and the nano-silica particles in the food can be separated efficiently. The method has good applicability and can be used for various food samples.

In this embodiment, the cleaning solution in step c) is different combinations of deionized water, acetone, absolute ethanol and acetic acid. In this example, different pretreatment processes are used to dissolve the silicon dioxide for the sampled food samples, and the dissolved transparent solution is poured into a centrifuge tube, and the precipitate is collected after centrifugation. The precipitate is deionized water, acetone, anhydrous After washing with ethanol and acetic acid, the isolated nano-silica was observed with a transmission electron microscope, and the chemical composition of the nano-silica was determined through a high-resolution transmission electron microscope.

In this embodiment, specifically:

The food sample in step 1) is a direct liquid beverage sample;

Step c) specifically, the precipitate in step b) is washed once with deionized water, then once with acetone, and then twice with acetic acid, and then freeze-dried to separate the carbon dioxide from the direct liquid beverage. silicon.

This example provides a solution for the comprehensive analysis and characterization of nano-silica particles, taking direct liquid beverage samples as an example. Pour 10ml of liquid sample into a centrifuge tube and centrifuge at 21000 g for 15 minutes. After centrifugation, the precipitate was collected, washed once with deionized water, once with acetone, and twice with acetic acid, and freeze-dried to obtain the silica separated from the direct liquid beverage. Disperse the separated silicon dioxide with a dispersant, drop it on the carbon-coated support film, observe it with a transmission electron microscope, and use the same treatment method for other types of liquid beverages, as shown in Figure 1. At the same time, the separated silicon dioxide was redispersed with a dispersant, dropped on a silicon wafer, and characterized by a scanning electron microscope, as shown in Figure 2; The elemental composition of silicon is shown in Figure 3.

In this example, the direct liquid beverage was sampled and analyzed, the silicon dioxide in it was fully characterized, and the basic information of the nanoparticles was comprehensively characterized by scanning electron microscope, nanoparticle tracking technology, X-ray energy spectrum, etc. At the same time, the total content of silicon dioxide was determined by inductively coupled plasma optical emission spectrometer.

Embodiment two:

The technical solution of this embodiment is basically the same as that of Embodiment 1, the difference is that:

In this embodiment, referring to Fig. 4, specifically:

The food sample in step 1) is an instant granule sample; the pretreatment process is to dissolve the instant granule sample with deionized water at about 100 degrees Celsius.

Step c) specifically, the precipitate in step b) is washed once with deionized water, then once with acetone, then once with acetic acid, and once with absolute ethanol, and then freeze-dried to obtain instant Silica is separated from the granule.

Dissolve a small amount of instant granule powder completely with 20 ml of deionized water at 100 degrees Celsius, pour the dissolved solution into a centrifuge tube, and centrifuge at 21,000 g for 15 minutes. Collect the precipitate after centrifugation, wash the precipitate once with deionized water, once with acetone, once with acetic acid, once with absolute ethanol, and freeze-dry to obtain the silica separated from the instant granule, and disperse the silica with a dispersant , dripped on the carbon-coated support film, observed with a transmission electron microscope, and adopted the same treatment method for other brands of instant granules.

Embodiment three:

The technical solutions of this embodiment are basically the same as those of the foregoing embodiments, except that:

In this embodiment, referring to Fig. 5, specifically:

The food sample in step 1) is a puffed food sample; the pretreatment process is to completely digest the sample with concentrated nitric acid at about 120 degrees Celsius.

Step c) specifically, wash the precipitate in step b) once with deionized water, then wash once with acetone, then wash once with absolute ethanol, and then wash twice with acetic acid, and then freeze-dry to obtain the puffed Silica is isolated from food.

A certain amount of puffed food is completely digested with 20ml concentrated nitric acid at 120 degrees Celsius. After the solids are completely digested, the solution is poured into a centrifuge tube and centrifuged at 21000g for 15 minutes. Collect the precipitate after centrifugation, wash the precipitate once with deionized water, once with acetone, once with absolute ethanol, and then twice with acetic acid, and then freeze-dry to obtain silica isolated from puffed food. The dispersant is dispersed, dropped on the carbon-coated support film, and observed with a transmission electron microscope.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and various changes can also be made according to the present invention. All changes, modifications, Substitution, combination, and simplification should all be equivalent replacement methods, as long as they meet the purpose of the invention, as long as they do not deviate from the technical principle and inventive concept of the method for separating nano-silica in food, they all belong to the protection of the present invention scope.

Claims (8)

1. one kind is separated the method that detects nano silicon in the food, it is characterized in that, comprises the steps:

1) from food samples, isolates nanometer silicon dioxide particle;

2) the isolated nanometer silicon dioxide particle of step 1) is cleared up, constant volume utilizes the inductively coupled plasma emission spectrometer to measure silicon content, and converses the silicon dioxide total amount,

3) the isolated nanometer silicon dioxide particle of step 1) is utilized transmission electron microscope observation granule-morphology and particle diameter;

4) with the step 3) while, the nano silicon that obtains is carried out comprehensive sign of quantitative and qualitative analysis from step 1), be:

ⅰ) utilize scanning electron microscope that its pattern, size and surface are characterized the isolated nanometer silicon dioxide particle of step 1);

ⅱ) utilize high resolving power transmitted electron Electronic Speculum to confirm that the element of the isolated nano silicon of step 1) forms.

2. separation according to claim 1 detects the method for nano silicon in the food, and it is characterized in that: the process of isolating nanometer silicon dioxide particle in the described step 1) from food samples comprises the steps:

A) adopt pretreatment process with the silicon dioxide stripping food samples in the described step 1), obtain clear solution;

B) then, pour in the centrifuge tube centrifugal rear collecting precipitation thing into dissolving the clear solution that in the described step a);

C) then, the sediment in the described step b) with cleaning fluid cleaning, drying, is isolated nanometer silicon dioxide particle.

3. separation according to claim 2 detects the method for nano silicon in the food, and it is characterized in that: the cleaning fluid in the described step c) is the various combination of deionized water, acetone, absolute ethyl alcohol and acetic acid.

4. separation according to claim 3 detects the method for nano silicon in the food, it is characterized in that:

Food samples in the described step 1) is direct liquid beverage sample;

Described step c) is specially, and with the sediment in the described step b) with washed with de-ionized water once, then cleans once with acetone, cleans twice with acetic acid again, then carries out freeze-drying, can isolate silicon dioxide from direct liquid beverage.

5. separation according to claim 3 detects the method for nano silicon in the food, it is characterized in that:

Food samples in the described step 1) is the instant sample;

Described step c) is specially, and with the sediment in the described step b) with washed with de-ionized water once, then cleans once with acetone, clean once with acetic acid again, also clean once with absolute ethyl alcohol, then carry out freeze-drying, can from instant, isolate silicon dioxide.

6. separation according to claim 3 detects the method for nano silicon in the food, it is characterized in that:

Food samples in the described step 1) is the dilated food sample;

Described step c) is specially, and with the sediment washed with de-ionized water in the described step b) once, then cleans once with acetone, clean once with absolute ethyl alcohol again, clean twice with acetic acid again, then carry out freeze-drying, can from dilated food, isolate silicon dioxide.

7. the described separation of any one detects the method for nano silicon in the food according to claim 2～6, it is characterized in that: in described step a), described pretreatment process adopts deionized water or red fuming nitric acid (RFNA) that food samples is dissolved fully, and silicon dioxide is dissolved.

8. the described separation of any one detects the method for nano silicon in the food according to claim 1～6, it is characterized in that: in described step 2) in, Acid system with red fuming nitric acid (RFNA) and 40% hydrofluorite and boric acid, the digestion condition of 190 ° of C, clear up described step 1) at microwave dissolver and isolate to get silicon dioxide, clear up fully rear with 2% rare nitric acid constant volume.

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