An extractant and its use for the extraction of metals from complex matrices

Abstract

The present application relates to a kind of extractant and its application in the extraction of metal in complex matrix, it is related to the field of chemical separation, by weight parts, the extractant includes the following components: glycine hydrochloride aqueous solution 5~10 parts, extraction aid 0.01~0.1 parts and organic acid aqueous solution 2~5 parts;Wherein, the extraction aid is cyclodextrin and ammonium citrate salt as raw material and obtained by low temperature plasma treatment.The extractant provided by the present application is compounded by using specific proportion of glycine hydrochloride aqueous solution, specific extraction aid and organic acid aqueous solution, which can extract multiple metals in complex matrix simultaneously, has the characteristics of strong universality, high extraction rate, mild and harmless extraction system components, simple and efficient extraction operation, etc., provides a new means for complex matrix sample detection pretreatment, and has wide practical application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical separation technology, and in particular to an extractant and its application in extracting metals in a complex matrix. BACKGROUND

[0002] Elemental analysis technology mainly includes pretreatment technology and detection technology. According to literature, the detection technology of elemental analysis is mainly divided into mass spectrometry, spectroscopy, chromatography, electrochemical technology, immunological technology, etc. For example, the commonly used mass spectrometry in the laboratory, such as inductively coupled plasma mass spectrometry, spectroscopy includes atomic absorption spectrometry, atomic fluorescence spectrometry, X-ray fluorescence spectrometry, chemiluminescence analysis, Raman spectroscopy, etc. With the development of technology, the development of detection technology is limited by the contradiction of sample pretreatment technology, especially the elemental analysis in the complex matrix. This problem has become the main bottleneck for many technologies to achieve rapid and automatic.

[0003] The most widely used and highest accepted pretreatment technology at present mainly includes wet digestion, microwave digestion method, high-pressure digestion method, etc. The core defects of these methods mainly include: (1) high risk, high concentration and large amount of dangerous chemical reagents are used; (2) low efficiency, long processing period; (3) high cost, large energy consumption in processing and cleaning process, not saving water and electricity resources; (4) not environmentally friendly, releasing a large amount of harmful gas and acid mist to cause pollution. For example, the microwave digestion method pretreatment disclosed in “HJ832-2017-Digestion of Microwave Digestion Method for Total Amount of Metal Elements in Soil and Sediment” uses nitric acid, hydrochloric acid and hydrofluoric acid as digestion liquid, which has high concentration and large amount; at the same time, the whole instrument uses three-stage temperature program for microwave digestion, and the whole pretreatment takes about 1 hour, which has long processing period and low efficiency.

[0004] Therefore, it is urgent to develop a simple, fast and low-risk mild extraction method to meet the detection needs of complex matrix samples. SUMMARY

[0005] To solve the above problems, the present application provides an extractant and its application in extracting metals in a complex matrix.

[0006] In a first aspect, the present application provides an extractant, which comprises the following components in parts by weight:

[0007] 5-10 parts of aqueous glycine hydrochloride solution, 0.01-0.1 parts of extraction aid and 2-5 parts of aqueous organic acid solution;

[0008] The extraction aid is obtained by using cyclodextrin and ammonium citrate as raw materials and being treated by low-temperature plasma.

[0009] Further, the extractant comprises the following components by weight fraction:

[0010] The aqueous glycine hydrochloride solution is 7.5 parts, the extraction aid is 0.05 parts, and the aqueous organic acid solution is 3 parts.

[0011] Further, the aqueous glycine hydrochloride solution has a concentration of 1% to 5% by weight fraction, and the aqueous organic acid solution has a concentration of 1% to 5% by weight fraction.

[0012] Further, the weight ratio of the cyclodextrin to the ammonium citrate salt is (3-5):1.

[0013] Further, the preparation method of the extraction aid comprises the following processes:

[0014] The cyclodextrin and the ammonium citrate salt are mixed to obtain a mixture;

[0015] The mixture is placed in a cavity of a low-temperature plasma treatment device, vacuumized, oxygen is introduced when the vacuum degree of the cavity reaches below 10 Pa, and the low-temperature plasma treatment is performed under the conditions of an oxygen flow of 25-35 cm 3 / min and a power of 75-80 W for 30-40 s to obtain the extraction aid.

[0016] Further, the complex matrix comprises at least one of wheat, rice, corn, brown rice, vegetables, tea, and infant cereal-based food; the metal comprises at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium, and lead; the organic acid comprises at least one of formic acid, acetic acid, citric acid, and oxalic acid; the cyclodextrin comprises at least one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin; and the ammonium citrate salt comprises at least one of triammonium citrate and dihydrogen ammonium citrate.

[0017] In a second aspect, the embodiments of the present application provide an application of the extractant of any one of the first aspect in extracting a metal in a complex matrix, wherein the complex matrix comprises at least one of wheat, rice, corn, brown rice, vegetables, tea, and infant cereal-based food; and the metal comprises at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium, and lead.

[0018] In a third aspect, the present application provides a method for extracting a metal from a complex matrix, which comprises the following steps:

[0019] The complex matrix sample is crushed to obtain a to-be-tested sample;

[0020] The to-be-tested sample is added into the extractant of any one of the first aspect for mixing, and then solid-liquid separation is performed to obtain an extractant containing the metal.

[0021] Further, the particle size of the sample to be tested is less than 0.50 mm; the weight-volume ratio of the sample to be tested and the extractant is (1-5):(50-1000) in g / ml.

[0022] Further, the working parameters of the mixing include that the temperature is 10-40℃ and the time is 1-30s.

[0023] Further, the complex matrix includes at least one of wheat, rice, corn, brown rice, vegetables, tea and infant cereal-based food; and the metal includes at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium and lead.

[0024] The above technical solution provided by the embodiment of the present application has at least the following advantages compared with the prior art:

[0025] The embodiment of the present application provides an extractant and application thereof in extraction of metals in a complex matrix. The extractant is obtained by compounding a glycine hydrochloride aqueous solution, a specific extraction aid and an organic acid aqueous solution in specific proportions. The extractant can extract multiple metals in a complex matrix at the same time, has the characteristics of strong universality, high extraction rate, mild and harmless extraction system components, simple and efficient extraction operation and the like, provides a new means for complex matrix sample detection pretreatment, and has wide practical application value. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0028] Figure 1 The flowchart of the method for extracting metals from a complex matrix provided by the embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or prepared by existing methods.

[0031] In a first aspect, the embodiments of the present application provide an extractant, which comprises the following components in parts by weight:

[0032] 5-10 parts of aqueous glycine hydrochloride solution, 0.01-0.1 parts of extraction aid, and 2-5 parts of aqueous organic acid solution;

[0033] The extraction aid is obtained by using cyclodextrin and ammonium citrate as raw materials and low-temperature plasma treatment.

[0034] The extractant provided by the embodiments of the present application is obtained by compounding aqueous glycine hydrochloride solution, specific extraction aid and aqueous organic acid solution in specific proportions. The extractant can extract multiple metals in a complex matrix at the same time, has the characteristics of strong universality, high extraction rate, mild and harmless extraction system components, simple and efficient extraction operation, etc., provides a new means for complex matrix sample detection pretreatment, and has wide practical application value.

[0035] In some specific embodiments, the extractant comprises the following components in parts by weight:

[0036] 7.5 parts of aqueous glycine hydrochloride solution, 0.05 parts of extraction aid, and 3 parts of aqueous organic acid solution.

[0037] In some specific embodiments, the concentration of the aqueous glycine hydrochloride solution is 1%-5% by weight percentage; and the concentration of the aqueous organic acid solution is 1%-5% by weight percentage.

[0038] In some specific embodiments, the weight ratio of the cyclodextrin to the ammonium citrate is (3-5):1.

[0039] In some specific embodiments, the preparation method of the extraction aid comprises the following processes:

[0040] The cyclodextrin and the ammonium citrate are mixed to obtain a mixture;

[0041] The mixture is placed in a cavity of a low-temperature plasma treatment device, vacuumized, and when the vacuum degree of the cavity reaches below 10 Pa, oxygen is introduced, and the low-temperature plasma treatment is performed under the conditions of an oxygen flow rate of 25-35 cm 3 / min and a power of 75-80 W for 30-40 s to obtain the extraction aid.

[0042] In some embodiments, the complex matrix includes at least one of wheat, rice, corn, brown rice, vegetables, tea and infant cereal-based food; the metal includes at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium and lead, preferably rubidium, strontium, cesium and lead; the organic acid includes at least one of formic acid, acetic acid, citric acid and oxalic acid, preferably acetic acid; the cyclodextrin includes at least one of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, preferably γ-cyclodextrin; and the ammonium citrate salt includes at least one of triammonium citrate and dihydrogen ammonium citrate, preferably triammonium citrate.

[0043] It should be noted that, if no special description is made, the raw materials involved in the extractant provided by the embodiments of the present application can be selected from commercially available products or self-made according to the prior art or using existing equipment; meanwhile, the preparation of the extractant can be obtained by stirring and mixing the components after being weighed in proportion, which will not be described here.

[0044] In a second aspect, based on the same general inventive concept, the embodiments of the present application provide an application of the extractant of any one of the first aspect in extracting metals in a complex matrix, wherein the complex matrix includes at least one of wheat, rice, corn, brown rice, vegetables, tea and infant cereal-based food; and the metal includes at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium and lead.

[0045] The extractant provided by the present application can extract multiple metals in a complex matrix at the same time, has the characteristics of strong universality, high extraction rate, mild and harmless components of the extraction system, simple and efficient operation, etc., provides a new means for the pretreatment of complex matrix sample detection, and has wide practical application value.

[0046] In a third aspect, based on the same general inventive concept, the present application provides a method for extracting metals from a complex matrix, as shown in Figure 1 The method includes the following steps:

[0047] The complex matrix sample is crushed to obtain a to-be-tested sample;

[0048] The to-be-tested sample is added into the extractant of any one of the first aspect for mixing, and then solid-liquid separation is performed to obtain an extractant containing metals.

[0049] The method for extracting metals from a complex matrix provided by the present application at least has the following characteristics:

[0050] (1) The extraction reagent is a low-concentration weak acid solution, which has simple components, mild conditions and simple operation;

[0051] (2) The extraction process takes less than 1 minute, and the entire operation process takes less than 10 minutes, and the extraction efficiency is high;

[0052] (3) The metal extraction rate can reach more than 90%, and the metal extraction rate is high and has strong universality.

[0053] In some specific embodiments, the particle size of the sample to be tested is less than 0.50 mm; and the weight-volume ratio of the sample to be tested and the extractant is (1-5):(50-1000) in g / ml.

[0054] In some specific embodiments, the working parameters of the mixing include a temperature of 10-40℃ and a time of 1-30s.

[0055] In some specific embodiments, the complex matrix includes at least one of wheat, rice, corn, brown rice, vegetables, tea, and infant cereal-based food; and the metal includes at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium, and lead.

[0056] In some specific embodiments, the mixing can be performed by hand shaking, swinging, or overturning.

[0057] In some specific embodiments, the solid-liquid separation process includes standing for 0-5 min or freezing / centrifuging at room temperature at 1000-8000 rpm for 0-5 min, and then passing through a filter membrane with a pore size of less than 0.75 µm.

[0058] In some specific embodiments, the extract containing the metal can be detected by using existing detection methods to detect the amount of the metal, such as atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled emission spectrometry, X-ray fluorescence spectrometry, etc. atomic spectrometry method; chemiluminescence analysis, ultraviolet-visible spectrophotometry, infrared spectrometry, Raman spectrometry, etc. molecular spectroscopy; inductively coupled plasma mass spectrometer, isotope analysis mass spectrometer, etc. mass spectrometry; immune analysis method; electrochemical analysis method, etc. detection method.

[0059] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and are not used to limit the scope of the application. The experimental methods in the following examples are not specified, and the methods are generally determined according to the national standards. If there is no corresponding national standard, the methods are determined according to the general international standards, conventional conditions, or the conditions recommended by the manufacturers.

[0060] Example 1

[0061] This example provides an extractant, which includes the following components in weight parts:

[0062] glycine hydrochloride aqueous solution 7.5 parts, extraction aid 0.05 parts, and organic acid aqueous solution 3 parts;

[0063] The extraction aid is obtained by taking cyclodextrin and ammonium citrate salt as raw materials and being subjected to low-temperature plasma treatment, and the specific preparation method comprises the following process: 4:1 by weight of gamma-cyclodextrin and triammonium citrate are mixed to obtain a mixture; the mixture is placed in the cavity of a low-temperature plasma treatment device, vacuumized, oxygen is introduced when the vacuum degree of the cavity reaches below 10 Pa, and low-temperature plasma treatment is carried out under the condition that the oxygen flow is 30 cm 3 / min and the power of the power source is 77 W for 35 s to obtain the extraction aid;

[0064] The concentration of the glycine hydrochloride aqueous solution is 3% by weight percentage.

[0065] The concentration of the organic acid aqueous solution is 3% by weight percentage, and the organic acid is acetic acid.

[0066] The preparation method of the above-mentioned extraction aid comprises the following process: the components are weighed according to the weight ratio and then mixed and stirred to prepare the extraction aid.

[0067] Example 2

[0068] The example provides an extraction aid, which comprises the following components by weight fraction:

[0069] Glycine hydrochloride aqueous solution 5 parts, extraction aid 0.01 part and organic acid aqueous solution 2 parts;

[0070] The extraction aid is obtained by taking cyclodextrin and ammonium citrate salt as raw materials and being subjected to low-temperature plasma treatment, and the specific preparation method comprises the following process: 3:1 by weight of alpha-cyclodextrin and dihydrogen ammonium citrate are mixed to obtain a mixture; the mixture is placed in the cavity of a low-temperature plasma treatment device, vacuumized, oxygen is introduced when the vacuum degree of the cavity reaches below 10 Pa, and low-temperature plasma treatment is carried out under the condition that the oxygen flow is 25 cm 3 / min and the power of the power source is 80 W for 30 s to obtain the extraction aid;

[0071] The concentration of the glycine hydrochloride aqueous solution is 1% by weight percentage.

[0072] The concentration of the organic acid aqueous solution is 1% by weight percentage, and the organic acid is acetic acid.

[0073] The preparation method of the above-mentioned extraction aid comprises the following process: the components are weighed according to the weight ratio and then mixed and stirred to prepare the extraction aid.

[0074] Example 3

[0075] The example provides an extraction aid, which comprises the following components by weight fraction:

[0076] 10 parts of a glycine hydrochloride aqueous solution, 0.1 part of an extraction aid, and 5 parts of an organic acid aqueous solution;

[0077] The extraction aid is obtained by using cyclodextrin and ammonium citrate as raw materials and performing low-temperature plasma treatment, and the specific preparation method comprises the following process: β-cyclodextrin and diammonium hydrogen citrate with a weight ratio of 5:1 are mixed to obtain a mixture; the mixture is placed in a cavity of a low-temperature plasma treatment device, vacuumized, and when the vacuum degree of the cavity reaches 10 Pa or below, oxygen is introduced, and low-temperature plasma treatment is performed under the condition that the oxygen flow is 35 cm 3 / min and the power of the power source is 75 W for 40 s to obtain the extraction aid;

[0078] The concentration of the glycine hydrochloride aqueous solution is 5% by weight;

[0079] The concentration of the organic acid aqueous solution is 5% by weight, and the organic acid is acetic acid.

[0080] The preparation method of the above extraction agent comprises the following process: the components are weighed and mixed and stirred according to the weight ratio to prepare the extraction agent.

[0081] Example 4

[0082] This example provides an extraction agent and a preparation method thereof, which are different from those of Example 1 only in that the weight ratio of the γ-cyclodextrin to the ammonium citrate is adjusted to 1:1; the remaining steps and parameters are the same.

[0083] Comparative Example 1

[0084] This example provides an extraction agent and a preparation method thereof, which are different from those of Example 1 only in that the extraction aid is obtained by using cyclodextrin as a raw material and performing low-temperature plasma treatment, and the specific preparation method comprises the following process: γ-cyclodextrin is mixed to obtain a mixture; the mixture is placed in a cavity of a low-temperature plasma treatment device, vacuumized, and when the vacuum degree of the cavity reaches 10 Pa or below, oxygen is introduced, and low-temperature plasma treatment is performed under the condition that the oxygen flow is 30 cm 3 / min and the power of the power source is 77 W for 35 s to obtain the extraction aid; the remaining steps and parameters are the same.

[0085] Comparative Example 2

[0086] This example provides an extractant and its preparation method, differing from Example 1 only in that the extraction aid is obtained by treating ammonium citrate salt with low-temperature plasma. The specific preparation method includes the following steps: mixing triammonium citrate to obtain a mixture; placing the mixture in the cavity of a low-temperature plasma treatment device, evacuating the vacuum, and when the vacuum level reaches below 10 Pa, introducing oxygen at a flow rate of 30 cm⁻¹. 3 The extraction aid was obtained by performing low-temperature plasma treatment for 35 s at a power rate of 77 W / min and a power supply of 77 W; the remaining steps and parameters were the same.

[0087] Comparative Example 3

[0088] This example provides an extractant and its preparation method, which differs from Example 1 only in that the extraction aid is obtained by compounding cyclodextrin and ammonium citrate as raw materials. The specific preparation method includes the following process: mixing γ-cyclodextrin and triammonium citrate in a weight ratio of 4:1 to obtain the extraction aid; the remaining steps and parameters are the same.

[0089] Test case

[0090] This example examines the extraction effect of the extractants obtained in Examples 1-4 and Comparative Examples 1-3 on metals in complex matrices such as wheat, rice, and corn.

[0091] Test method (referred to as the pretreatment method for extraction): Taking wheat, rice, and corn as examples, each was used as a complex matrix sample. 0.22 g of complex matrix sample powder with a particle size <0.50 mm was accurately weighed into a centrifuge tube. Then, 50 ml of the extract obtained in Examples 1-4 and Comparative Examples 1-3 was added to each centrifuge tube containing the complex matrix sample powder. The mixture was swirled for 30 s, allowed to stand for 3 min, and 5 mL of the supernatant was collected using a syringe filter and filtered through a 0.45 µm filter membrane to obtain an extract containing metal. The metal-containing extract was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The main parameters involved in the ICP-MS detection method are shown in Table 1, obtaining the metal content information in the complex matrix.

[0092] Table 1

[0093]

[0094] Data processing method: the extraction rate (E) obtained by the above extraction pretreatment method is calculated from the detection content result C1 of the extraction pretreatment method and the detection content result C2 of the existing microwave digestion method pretreatment (referring to “HJ832-2017-Digestion of soil and sediment metal elements by microwave digestion method”) and the detection method shown in table 1, the extraction rate E (%) = C1 ÷ C2 × 100%. The test data results are shown in tables 2, 3 and 4.

[0095] Table 2 Metal extraction rate E (%) of examples 1-4 and comparative examples 1-3 with wheat as a complex matrix sample

[0096] metal Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mg 100.9 92.7 94.3 90.5 60.3 49.6 70.8 K 100.3 98.1 97.6 91.4 64.7 52.0 69.2 Ca 99.8 93.5 94.7 92.1 68.0 57.2 72.6 Mn 102.2 99.8 98.9 94.0 71.9 48.7 80.3 Cu 105.7 98.3 97.4 93.6 62.5 51.9 68.5 Zn 103.4 98.2 98.7 91.3 67.1 58.4 84.9 Rb 102.5 90.6 91.1 78.2 34.6 19.8 42.7 Sr 101.9 91.7 92.5 62.8 3.8 6.1 30.4 Cd 100.6 95.4 95.8 90.9 76.2 60.3 75.1 Cs 102.3 92.9 93.6 64.4 2.1 18.7 41.3 Ba 104.7 96.1 97.5 91.7 75.4 54.5 77.0 Pb 104.5 91.8 90.6 59.4 24.1 7.4 38.9

[0097] Table 3 Metal extraction rate E (%) of example 1 with rice as a complex matrix sample

[0098] metal Example 1 Mg 99.8 K 100.7 Ca 100.3 Mn 101.2 Cu 100.9 Zn 101.4 Rb 104.5 Sr 102.6 Cd 103.9 Cs 100.2 Ba 105.5 Pb 103.1

[0099] Table 4 Metal extraction rate E (%) of example 1 with corn as a complex matrix sample

[0100] metal Example 1 Mg 103.0 K 101.7 Ca 98.9 Mn 105.6 Cu 104.5 Zn 106.3 Rb 101.9 Sr 102.8 Cd 102.1 Cs 104.4 Ba 99.6 Pb 100.2

[0101] From tables 2, 3 and 4, compared with the comparative examples, the extractant provided by the examples of the application has a higher metal extraction rate in the complex matrix sample, especially for Rb, Sr, Cs and Pb. In addition, through the characteristics of the extractant provided by comparative example 1 and comparative example 2, the extraction effect of Sr, Cs and other metals is not obvious, and the extractants provided by comparative example 1, comparative example 2 and example 1 can be used jointly, and are applied in complex matrix containing Sr, Cs and other metals respectively to selectively separate and extract Sr, Cs and other metals, providing a new means for the separation of Sr, Cs and other metals.

[0102] In summary, the examples of the application provide an extractant and its application in extracting metals in a complex matrix. The extractant is obtained by compounding a specific proportion of glycine hydrochloride aqueous solution, a specific extraction aid and an organic acid aqueous solution. The extractant can extract multiple metals in a complex matrix at the same time, has the characteristics of strong universality, high extraction rate, mild and harmless extraction system components, simple and efficient extraction operation, etc., provides a new means for complex matrix sample detection pretreatment, and has wide practical application value.

[0103] Various embodiments of the present application can take on a variety of scopes; it should be understood that a scope in the form of a range is described merely for the sake of convenience and brevity, and should not be construed as a rigid limitation of the scope of the present application; therefore, it should be considered that the range described has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that a range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integral) within the indicated range.

[0104] The foregoing is considered as illustrative only of the principles of the application. Numerous modifications and adaptations will be apparent to those skilled in the art in view of the above descriptions of the embodiments. Thus, the scope of the application should be determined by the broadest interpretation of the principles disclosed herein and their equivalents, and will not be restricted to the described embodiments.

Claims

1. An extractant, characterized in that, The extractant comprises the following components in parts by weight: 5-10 parts glycine hydrochloride aqueous solution, 0.01-0.1 parts extraction aid, and 2-5 parts organic acid aqueous solution; The extraction aid is obtained by treating cyclodextrin and ammonium citrate as raw materials with low-temperature plasma. The preparation method of the extraction aid includes the following steps: mixing the cyclodextrin and the ammonium citrate to obtain a mixture; placing the mixture in the cavity of the low-temperature plasma treatment device, evacuating the vacuum, and when the vacuum degree of the cavity reaches below 10 Pa, introducing oxygen at an oxygen flow rate of 25~35 cm⁻¹. 3 The extraction aid is obtained by performing low-temperature plasma treatment for 30-40 s at a power rate of 75-80 W / min and a power supply of 75-80 W; wherein the weight ratio of the cyclodextrin to the ammonium citrate is (3-5):1, the cyclodextrin includes at least one of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin; and the ammonium citrate includes at least one of triammonium citrate and diammonium hydrogen citrate. The concentration of the glycine hydrochloride aqueous solution is 1% to 5% by weight. The concentration of the aqueous organic acid solution is 1% to 5% by weight, and the organic acid includes at least one of formic acid, acetic acid, citric acid and oxalic acid.

2. The extractant according to claim 1, characterized in that, The extractant comprises the following components in parts by weight: 7.5 parts glycine hydrochloride aqueous solution, 0.05 parts extraction aid and 3 parts organic acid aqueous solution.

3. The application of the extractant according to any one of claims 1 to 2 in the extraction of metals in a complex matrix, characterized in that, The complex matrix includes at least one of wheat, rice, corn, brown rice, vegetables, tea, and infant cereal foods; the metal includes at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium, and lead.

4. A method for extracting metals from a complex matrix, characterized in that, The method includes the following steps: The complex matrix sample is crushed to obtain the sample to be tested; The sample to be tested is added to the extractant according to any one of claims 1 to 2 and mixed, and then solid-liquid separation is performed to obtain an extract containing metal.

5. The method for extracting metals from a complex matrix according to claim 4, characterized in that, The particle size of the sample to be tested is <0.50 mm; the weight-volume ratio of the sample to be tested and the extractant is (1~5):(50~1000) in g / ml.

6. The method for extracting metals from a complex matrix according to claim 4, characterized in that, The operating parameters for the mixture include: temperature of 10~40℃ and time of 1~30s.

7. The method for extracting metals from a complex matrix according to claim 4, characterized in that, The complex matrix includes at least one of wheat, rice, corn, brown rice, vegetables, tea, and infant cereal foods; the metal includes at least one of magnesium, potassium, manganese, copper, zinc, rubidium, strontium, cadmium, cesium, barium, and lead.

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