CN102608279A - Method for analyzing and detecting nano titanium dioxide in food - Google Patents

Abstract

The invention discloses a method for analyzing and detecting nanometer titanium dioxide in food. For typical food samples containing titanium dioxide additives, different pretreatment processes are used to dissolve the titanium dioxide, the titanium dioxide is enriched by centrifugation, and the separated titanium dioxide is washed with an organic solvent. Then, the existence and particle size distribution of nano-titanium dioxide are determined through transmission electron microscope observation and software statistics. At the same time, the separated nano-titanium dioxide was fully characterized, and the basic information of the nanoparticles was comprehensively characterized by scanning electron microscope, X-ray diffractometer, X-ray energy spectrum, etc., and the total content of titanium dioxide was determined by inductively coupled plasma emission spectrometer, combined with The particle size distribution gives the mass concentration data of the nanoparticles. The invention has simple separation operation, can efficiently separate nano-titanium dioxide particles in food, is applicable to the detection of nano-titanium dioxide in various foods, and provides basic data for labeling and safety evaluation of nano-products.

Description

Method for analyzing and detecting nano-titanium dioxide in food

technical field

The invention relates to a method for detecting and analyzing nanometer-sized food additives. The method is convenient, quick and efficient, and belongs to the fields of nano analytical chemistry and nano inorganic materials.

Background technique

With the rapid development of nanomaterials in the 21st century, the application of nanomaterials has been involved in food, medicine, coatings, plastics, catalysts, electronic products and other fields. The nano-products that are constantly put on the shelves have greatly increased the opportunities for consumers to come into contact with nano-materials. However, due to research findings that some nanomaterials have negative effects, their safety issues have been widely concerned, and people have doubts about the safety of nanometer products. For the sake of public health and the healthy and sustainable development of nanotechnology, it is imminent to analyze, detect and evaluate the safety of nanomaterials in related products.

In recent years, nanotechnology has developed rapidly in the food industry, and nanomaterials are used to improve the texture and color of food and improve the absorption efficiency of nutrients in food. At the same time, some food additives, such as titanium dioxide, commonly known as titanium dioxide, have also reached the nanometer scale due to the improvement of the manufacturing process. The human body is increasingly likely to ingest nanomaterials through food. Therefore, scientific researchers and relevant government departments have begun to pay attention to how to conduct quantitative and qualitative analysis of nanomaterials in food, and then assess the exposure level of the population, and conduct risk assessment and safety evaluation. Finally, on this basis, management regulations are formulated to regulate the production of nanometer products. Consumption. 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 analyzing and detecting nano-titanium dioxide in food. The analysis and detection process is simple to operate, and can efficiently separate nano-titanium dioxide particles in food. The method has good applicability and can be used for various food samples. The method also provides the qualitative and quantitative characterization of nano-titanium dioxide in complete food samples, providing basic data for 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 analyzing and detecting nano-titanium dioxide in food, comprising the steps of:

1) Isolation of nano titanium dioxide particles from food samples;

2) Digest the titanium dioxide particles separated in step 1), constant volume, use inductively coupled plasma emission spectrometer to measure the content of titanium element, and convert the total amount of titanium dioxide;

3) Then, use a transmission electron microscope to observe the particle shape and particle size of the nano-titanium dioxide particles separated in step 1), and use the software to count the particle size distribution of the titanium dioxide particles to obtain the particle size distribution data of the titanium dioxide particles;

4) Simultaneously with step 3), perform a qualitative and quantitative comprehensive characterization of the nano-TiO2 obtained from step 1), namely:

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

ii) Using an X-ray diffractometer to characterize the nano-titanium dioxide particles separated in step 1), obtain its X-ray diffraction pattern, and analyze the crystal form of titanium dioxide;

ⅲ) Using high-resolution transmission electron microscope to confirm the interplanar distance and elemental composition of the nano-titanium dioxide separated in step 1), that is, crystal form and chemical composition;

iv) Combining the total content of titanium dioxide obtained in step 2) and the particle size distribution data of titanium dioxide particles obtained in step 3), the mass concentration data and particle number concentration data of nano titanium dioxide particles are obtained.

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

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

b) Then, pour the white 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 titanium dioxide 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 technical scheme of the present invention:

The food sample in step 1) is a sugar-coated chewing gum sample;

Step c) specifically, the precipitate in step b) is washed once with deionized water, then washed twice with acetone, washed once with absolute ethanol, and then freeze-dried to separate titanium dioxide from sugar-coated chewing gum .

As the second technical scheme of the present invention:

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

Step c) specifically, the precipitate in step b) is washed once with deionized water, then once with acetone, twice with acetic acid, once with absolute ethanol, and then freeze-dried to obtain from Titanium dioxide is isolated from confectionery.

As the third technical scheme of the present invention:

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

In step c), the precipitate in step b) is washed once with deionized water, then twice with acetone, once with absolute ethanol, and then freeze-dried to separate titanium dioxide from the instant granule.

As a further preferred technical solution of the above-mentioned technical solution of the present invention , in the above step a), the pretreatment process uses deionized water to completely dissolve the food sample, so that the titanium dioxide is dissolved.

，在步骤2）中，以浓硝酸和40%氢氟酸的消解体系，190°C的消解温度，在微波消解仪上消解步骤1）分离出得二氧化钛，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 and 40% hydrofluoric acid, and the digestion temperature of 190°C to digest the titanium dioxide separated in step 1) on a microwave digestion instrument, and then use 2% dilute nitric acid to determine Allow.

，步骤3）中的图像处理软件为图像处理和分析库软件软件，可统计从步骤1）中获得的纳米二氧化钛颗粒粒径分布，并得到粒径分布柱状图。 As a further preferred technical solution of the above-mentioned technical solution of the present invention

, the image processing software in step 3) is an image processing and analysis library software software, which can count the particle size distribution of nano-titanium dioxide particles obtained in step 1), and obtain a particle size distribution histogram.

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

The method for analyzing and detecting nano-titanium dioxide in food of the present invention has simple separation operation means, can efficiently separate the nano-titanium 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 a transmission electron micrograph of nano-titanium dioxide separated from 6 kinds of chewing gums in Example 1 of the present invention and a histogram of particle size distribution obtained through statistics.

Fig. 2 is a scanning electron micrograph of nano-titanium dioxide separated from a kind of chewing gum in Example 1 of the present invention.

Fig. 3 is an X-ray diffraction pattern of nano-titanium dioxide separated from a kind of chewing gum in Example 1 of the present invention.

Fig. 4 is the high-resolution transmission electron micrograph and X-ray energy spectrogram of the nano-titanium dioxide separated from a kind of chewing gum in Example 1 of the present invention.

Fig. 5 is a transmission electron micrograph of nano-titanium dioxide separated from three kinds of candies in Example 2 of the present invention and a histogram of particle size distribution obtained through statistics.

Fig. 6 is a transmission electron micrograph of nano-titanium dioxide separated from an instant granule in Example 3 of the present invention and a histogram of particle size distribution obtained through statistics.

Detailed ways

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

Embodiment one:

Referring to Figures 1 to 4, a method for analyzing and detecting nano-titanium dioxide in food is characterized in that it comprises the following steps:

1) Isolation of nano titanium dioxide particles from food samples;

2) Digest the titanium dioxide particles separated in step 1), constant volume, use inductively coupled plasma emission spectrometer to measure the content of titanium element, and convert the total amount of titanium dioxide;

3) Then, use a transmission electron microscope to observe the particle shape and particle size of the nano-titanium dioxide particles separated in step 1), and use the software to count the particle size distribution of the titanium dioxide particles to obtain the particle size distribution data of the titanium dioxide particles;

4) Simultaneously with step 3), perform a qualitative and quantitative comprehensive characterization of the nano-TiO2 obtained from step 1), namely:

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

ii) Using an X-ray diffractometer to characterize the nano-titanium dioxide particles separated in step 1), obtain its X-ray diffraction pattern, and analyze the crystal form of titanium dioxide;

ⅲ) Using high-resolution transmission electron microscope to confirm the interplanar distance and elemental composition of the nano-titanium dioxide separated in step 1), that is, crystal form and chemical composition;

iv) Combining the total content of titanium dioxide obtained in step 2) and the particle size distribution data of titanium dioxide particles obtained in step 3), the mass concentration data and particle number concentration data of nano titanium dioxide particles are obtained.

In this example, a simple and easy method is used to separate titanium dioxide particles from food samples, the centrifugation method is used to enrich titanium dioxide, the separated titanium dioxide is cleaned with an organic solvent, and the nanoparticles are confirmed by electron microscopy. At the same time, a comprehensive qualitative and quantitative characterization analysis of nano-titanium dioxide in the sample was carried out, and various techniques were used to provide the morphology, particle number concentration, mass concentration, particle size distribution, crystal form, etc. of nano-titanium dioxide. Parameters, which give basic information for product labeling and safety evaluation. The method for analyzing and detecting nano-titanium dioxide in food in this embodiment has simple operation means, can efficiently separate nano-titanium dioxide particles in food, has good applicability, and can be used for various food samples.

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

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

b) Then, pour the white 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 titanium dioxide particles are separated.

In this example, different pretreatment processes were used to dissolve titanium dioxide on the sampled food samples, and the dissolved white solution was poured into a centrifuge tube, and the precipitate was collected after centrifugation. After the precipitate was washed with a cleaning solution, the separation was observed with a transmission electron microscope. Nano-titanium dioxide is obtained, and the particle size distribution of the particles is determined statistically by software. The separation operation method of this embodiment is simple, and the nano-titanium dioxide 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 were used to dissolve titanium dioxide for the sampled food samples, and the dissolved white solution was poured into a centrifuge tube, and the precipitate was collected after centrifugation, and the precipitate was deionized water, acetone, absolute ethanol, After washing with acetic acid, observe the separated nano-titanium dioxide with a transmission electron microscope, and determine the particle size distribution of the particles through software statistics.

In this embodiment, specifically:

The food sample in step 1) is a sugar-coated chewing gum sample;

Step c) specifically, the precipitate in step b) is washed once with deionized water, then washed twice with acetone, washed once with absolute ethanol, and then freeze-dried to separate titanium dioxide from sugar-coated chewing gum .

In this example, sugar-coated chewing gum samples are taken as an example to provide a comprehensive analysis and characterization scheme for nano-titanium dioxide particles. The sample sugar-coated chewing gum icing was completely dissolved with 12.5 ml of solvent, the dissolved white solution was poured into a centrifuge tube, and centrifuged at 21000 g for 15 minutes. After centrifugation, the precipitate was collected, washed once with deionized water, twice with acetone, and once with absolute ethanol, and freeze-dried to obtain titanium dioxide separated from the chewing gum. Disperse the separated titanium dioxide with a dispersant, drop it on the carbon-coated support film, observe it with a transmission electron microscope, and use the software to count the particle size to obtain a particle size distribution histogram. Use the same treatment method for other types of chewing gum, as shown in Figure 1 shown. At the same time, the isolated titanium dioxide was redispersed with a dispersant, dropped on a silicon wafer, and characterized by a scanning electron microscope, as shown in Figure 2; the isolated nano titanium dioxide particles were characterized by an X-ray diffractometer, and its X The ray diffraction pattern is shown in Figure 3; the interplanar spacing and elemental composition of the separated nano-titanium dioxide were confirmed by high-resolution transmission electron microscopy, as shown in Figure 4. At the same time, combining the total content of titanium dioxide obtained in step 2) and the particle size distribution data of titanium dioxide particles obtained in step 3), the mass concentration data and particle number concentration data of nano titanium dioxide particles are obtained.

In this example, the sugar-coated chewing gum is sampled and analyzed, and the titanium dioxide in it is fully characterized, and the basic information of nanoparticles is comprehensively characterized by scanning electron microscope, X-ray diffractometer, nanoparticle tracking technology, X-ray energy spectrum, etc. . At the same time, the total content of titanium dioxide is measured by an inductively coupled plasma emission spectrometer, and the mass concentration data of nanoparticles are given according to the particle size distribution.

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. 5, specifically:

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

Step c) specifically, the precipitate in step b) is washed once with deionized water, then once with acetone, twice with acetic acid, once with absolute ethanol, and then freeze-dried to obtain from Titanium dioxide is isolated from confectionery.

Dissolve the sample candy completely with 20 ml of solvent, pour the dissolved solution into a centrifuge tube, and centrifuge at 21000 g for 15 minutes. Collect the precipitate after centrifugation, wash the precipitate once with deionized water, once with acetone, twice with acetic acid, once with absolute ethanol, and freeze-dry to obtain titanium dioxide isolated from candy. Disperse the titanium dioxide with a dispersant and drop it on carbon Plated on the support film, observed by transmission electron microscope, and used the software to count the particle size to obtain the particle size distribution histogram, and adopt the same treatment method for other brands of candy.

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. 6, specifically:

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

In step c), the precipitate in step b) is washed once with deionized water, then twice with acetone, once with absolute ethanol, and then freeze-dried to separate titanium dioxide from the instant granule.

Completely dissolve a small amount of instant granule powder with 20ml of solvent, pour the solution into a centrifuge tube after the powder is completely dissolved, and centrifuge at 21000g for 15 minutes. Collect the precipitate after centrifugation, wash the precipitate once with deionized water, twice with acetone, and once with absolute ethanol, freeze-dry to obtain titanium dioxide separated from the instant granule, disperse the titanium dioxide with a dispersant, and drop it on the carbon-plated support film Above, use transmission electron microscope to observe, and use software to count the particle size to get the histogram of particle size distribution.

Embodiment four:

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

In this embodiment, in step 1), the pretreatment process uses deionized water to completely dissolve the food sample, so that titanium dioxide is dissolved. Afterwards, in step 2), use the digestion system of concentrated nitric acid and 40% hydrofluoric acid, and the digestion temperature of 190°C, and separate the titanium dioxide obtained in step 1) on a microwave digestion instrument, and use 2% dilute nitric acid after the digestion is complete Volume. In this example, the separated titanium dioxide particles were digested, constant volume, and the content of titanium element was measured by an inductively coupled plasma emission spectrometer, and the total amount of titanium dioxide was converted, combined with the total content of titanium dioxide obtained in step 2) and step 3 ) to obtain the particle size distribution data of titanium dioxide particles, and obtain the mass concentration data and particle number concentration data of nano-titanium dioxide particles. As shown in Table 1, it is the mass concentration and particle number concentration data of nano-titanium dioxide (diameter less than 200nm) in all titanium dioxide separated from 6 varieties of chewing gum in this example, which can be given for chewing gum product labeling and safety evaluation. accurate relevant information.

Table 1. Nano-TiO2 in chewing gum samples

Mass Concentration vs. Particle Number Concentration in All TiO2

statistical results Variety 1 Variety 2 Variety 3 Variety 4 Variety 5 Variety 6 Nano titanium dioxide mass concentration 65.10% 71.20% 86.10% 85.80% 82.50% 72.70% Nano-TiO2 Particle Number Concentration 93.20% 95.10% 97.60% 97.80% 97.20% 93.50%

Embodiment five:

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

In this embodiment, the software in step 2) is preferably image processing and analysis library software software, which can count the particle size distribution of nano-titanium dioxide particles obtained in step 1), and obtain a particle size distribution histogram. The image processing and analysis library software software can use ImageJ software, and the same type of ImageJ software can perform area and pixel statistics of pictures, calculate distance and angle, create histograms and profiles, and perform Fourier transform.

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 purpose of the invention of the present invention. The changes, modifications, substitutions, combinations, and simplifications 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 analyzing and detecting nano-titanium dioxide in food, they all belong to protection scope of the present invention.

Claims (9)

1. A method for analyzing and detecting nano-titanium dioxide in food, characterized in that, comprising the steps: 1) Isolation of nano titanium dioxide particles from food samples; 2) Digest the titanium dioxide particles separated in step 1), constant volume, use inductively coupled plasma emission spectrometer to measure the content of titanium element, and convert the total amount of titanium dioxide; 3) Then, use a transmission electron microscope to observe the particle shape and particle size of the nano-titanium dioxide particles separated in step 1), and use the software to count the particle size distribution of the titanium dioxide particles to obtain the particle size distribution data of the titanium dioxide particles; 4) Simultaneously with step 3), perform a qualitative and quantitative comprehensive characterization of the nano-TiO2 obtained from step 1), namely: i) Characterize the morphology, size and surface of the titanium dioxide particles separated in step 1) using a scanning electron microscope; ii) Using an X-ray diffractometer to characterize the nano-titanium dioxide particles separated in step 1), obtain its X-ray diffraction pattern, and analyze the crystal form of titanium dioxide; ⅲ) Using high-resolution transmission electron microscope to confirm the interplanar distance and elemental composition of the nano-titanium dioxide separated in step 1), that is, crystal form and chemical composition; iv) Combining the total content of titanium dioxide obtained in step 2) and the particle size distribution data of titanium dioxide particles obtained in step 3), the mass concentration data and particle number concentration data of nano titanium dioxide particles are obtained. 2. The method for analyzing and detecting nano-titanium dioxide in food according to claim 1, characterized in that: the process of separating nano-titanium dioxide particles from food samples in the step 1) includes the following steps: a) Dissolving the titanium dioxide from the food sample in step 1) through a pretreatment process to obtain a white solution; b) Then, pour the white solution dissolved in step a) into a centrifuge tube, and collect the precipitate after centrifugation; c) Then, the precipitate in the step b) is washed and dried with a cleaning solution, and the titanium dioxide particles are separated. 3. The method for analyzing and detecting nano-titanium dioxide in food according to claim 2, characterized in that: the cleaning solution in the step c) is different combinations of deionized water, acetone, absolute ethanol and acetic acid. 4. the method for analyzing and detecting nano titanium dioxide in food according to claim 3, is characterized in that: The food sample in the step 1) is a sugar-coated chewing gum sample; The step c) specifically includes washing the precipitate in the step b) once with deionized water, then twice with acetone, once with absolute ethanol, and then freeze-dried to obtain the sugar-coated chewing gum Titanium dioxide was isolated. 5. the method for analyzing and detecting nano titanium dioxide in food according to claim 3, is characterized in that: The food sample in the step 1) is a candy sample; The step c) specifically includes washing the precipitate in the step b) once with deionized water, then once with acetone, twice with acetic acid, once with absolute ethanol, and then freeze-dried , Titanium dioxide can be separated from candy. 6. the method for analyzing and detecting nano titanium dioxide in food according to claim 3, is characterized in that: The food sample in step 1) is an instant granule sample; The step c) is specifically, the precipitate in the step b) is washed once with deionized water, then washed twice with acetone, washed once with absolute ethanol, and then freeze-dried, which can be obtained from the instant granule Titanium dioxide was isolated. 7. The method for analyzing and detecting nano-titanium dioxide in food according to any one of claims 2 to 6, characterized in that: in the step a), the pretreatment process uses deionized water to completely dissolve the food sample , so that titanium dioxide is dissolved. 8. The method for analyzing and detecting nano-titanium dioxide in food according to any one of claims 1 to 6, characterized in that: in the step iv), the digestion system of concentrated nitric acid and 40% hydrofluoric acid is used for 190 °C digestion temperature, digest the titanium dioxide separated in step 1) on a microwave digestion apparatus, and dilute to volume with 2% dilute nitric acid after the digestion is complete. 9. The method for analyzing and detecting nano-titanium dioxide in food according to any one of claims 1 to 6, characterized in that: the software in step 3) is image processing and analysis library software, which can count 1) The particle size distribution of the nano-titanium dioxide particles obtained in 1), and a histogram of the particle size distribution was obtained.

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