Method for simultaneously determining multiple heavy metals by combining X-ray fluorescence spectrometer with gas phase enrichment material

Abstract

The invention discloses a method for simultaneously measuring multiple heavy metals by combining an X-ray fluorescence spectrometer with a gas phase enrichment material, which comprises the following steps: carrying out thermal evaporation on a sample to be measured, and carrying out catalytic pyrolysis on gaseous substances generated by thermal evaporation, enriching heavy metals in a gaseous analyte subjected to catalytic pyrolysis by using a composite porous material loaded with nanoparticles; and placing the composite porous material capturing the various heavy metals under an X-ray fluorescence spectrophotometer for detection. The preparation method of the nano-particle loaded composite porous material comprises the following steps: immersing a porous material into a synthetic precursor mixed solution of nano-silver, nano-nickel and nano-silicon dioxide, stirring under specific conditions, drying and forming. Through a surface enrichment effect and a matrix simplification effect, complex sample detection is converted into analysis of a uniform composite material, the detection sensitivity of XRF to various trace heavy metals (mercury, cadmium, arsenic, lead and the like) is greatly improved, and the method has the advantages of being high in interference resistance, rapid, portable on site and the like.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, specifically to a method for simultaneously determining multiple heavy metals using an X-ray fluorescence spectrometer coupled with a gas-phase enrichment material. Background Technology

[0002] Heavy metals such as mercury (Hg), cadmium (Cd), arsenic (As), and lead (Pb) pose a serious threat to the ecological environment and human health. Currently, although the benchmark methods for laboratory detection of heavy metals (such as ICP-MS, AAS, and AFS) are highly sensitive, they rely on complex sample pretreatment (such as acid digestion), large-scale equipment, and professional operators, making it difficult to meet the needs of rapid on-site detection.

[0003] X-ray fluorescence spectroscopy (XRF) technology has the advantages of being fast, non-destructive, and capable of simultaneous analysis of multiple elements. Portable XRF is particularly suitable for on-site screening. However, XRF faces two major challenges when directly detecting trace heavy metals in complex matrices: (1) the detection limit is usually at the high mg / kg level, which is difficult to meet the detection requirements of low content standards (such as the screening value of Hg in soil is often below 0.5 mg / kg, and the limit value of Cd in grains in the national food safety standard is 0.2 mg / kg); (2) the complex matrix composition can cause serious absorption-enhancement effects and spectral interference, which significantly affect the accuracy of quantification.

[0004] Existing enrichment techniques, such as using chelated fibers, resin materials, graphene, or graphylene for heavy metal ion enrichment in water samples, can improve sensitivity, but they are usually still applicable to liquid samples and do not solve the fundamental problem of direct analysis of solid samples. Converting target elements in solid samples into a gaseous phase via thermal evaporation and then capturing them, followed by XRF analysis, is a highly promising technical approach. However, the successful implementation of this approach depends on the optimization of three core aspects: high-capacity, high-selectivity, multi-target element gas-phase enrichment materials; efficient, accurate, and controllable evaporation and transport of specific elemental forms; effective elimination of matrix interference substances; and low-interference, high-sensitivity detection of the enriched material.

[0005] In the prior art, invention patent CN112649457A discloses a rapid X-ray fluorescence analysis method for trace heavy metal mercury in solid samples. This method uses thermal desorption to evaporate mercury from the solid sample, then captures it using a carbon fiber filter membrane, and finally detects it using XRF. While this carbon fiber filter membrane can capture a certain amount of mercury, repeated tests by those skilled in the art have revealed that it cannot achieve 100% mercury capture. It merely employs a physical adsorption method similar to that used in air filters to calculate atmospheric particulate matter content. This significantly affects the stability and accuracy of XRF detection of mercury. Furthermore, the patent does not evaluate the precision and accuracy of the method. Repeated verification has shown that the desired effect cannot be achieved; the highest capture efficiency is less than 20%, making practical application impossible. Therefore, this patent only discovers that the fiber membrane can capture mercury (a physical adsorption capacity inherent in any porous material) and initially demonstrates XRF signal, but it does not solve the problems of efficient (100%) capture and enrichment, XRF detection accuracy, and interference resistance. Secondly, this patented technology is only applicable to mercury capture and cannot utilize XRF multi-element analysis capabilities. Mercury, cadmium, arsenic, lead, and other heavy metals are hazardous elements of greatest concern in food safety, environmental quality, and agricultural production. Ultimately, the problem lies in the lack of a highly efficient, multi-element specific material for thermal evaporation gas-phase enrichment, and the absence of a method to precisely control the speciation of target heavy metal elements during evaporation and transport, thus facilitating 100% capture and matrix simplification.

[0006] Therefore, there is an urgent need for an integrated technical solution that can systematically solve the above problems and achieve broad-spectrum on-site detection of various heavy metals. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for the simultaneous determination of multiple heavy metals using X-ray fluorescence spectrometry coupled with a gas-phase enrichment material. By utilizing a composite porous material loaded with nanoparticles, and through the coupling of gas-phase enrichment with X-ray fluorescence spectroscopy, rapid and highly sensitive detection of multiple trace heavy metals in solid, liquid, and gaseous samples can be achieved.

[0008] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for simultaneously determining multiple heavy metals using X-ray fluorescence spectrometry coupled with a gas-phase enrichment material, comprising the following steps: The sample to be tested is thermally evaporated, and the gaseous substances generated by thermal evaporation are catalytically pyrolyzed. The gaseous analytes after catalytic pyrolysis are enriched for heavy metals using a composite porous material loaded with nanoparticles. The enriched material containing heavy metals is then placed under an X-ray fluorescence spectrometer for detection.

[0009] Specifically, the following steps are included: Thermal evaporation injection: The solid or liquid sample to be tested is placed in a thermal evaporation device and heated and atomized under a specific atmosphere (such as air or argon-hydrogen mixture) through electrothermal evaporation, laser thermal evaporation, microwave thermal evaporation or plasma evaporation, so that the target heavy metal elements (Hg, Cd, As, Pb, etc.) in the sample escape in the form of atomic vapor or volatile compounds, or the gas sample is directly introduced into the gas phase enrichment unit.

[0010] Catalysis and Transport: The gaseous substances produced by evaporation are passed through a catalytic pyrolysis or transport unit. This unit is filled with a catalyst (such as MgO, kaolin, MnO2, Mn3O4, CoO, Al2O3, or combinations thereof), and its function is to: Speciation: Ensure that heavy metals in different chemical forms (such as organic mercury, inorganic arsenic, etc.) are uniformly converted into atomic or specific compound forms that are easy to capture.

[0011] Matrix interference elimination: decomposes, adsorbs or transforms interfering substances (such as fine particulate matter, organic interfering molecules, etc.) generated by co-evaporation of the sample matrix, thus "purifying" the gas path.

[0012] Gas-phase enrichment: After catalysis / transportation, the gaseous analyte is introduced into the gas-phase enrichment unit by a carrier gas, where it comes into contact with a composite porous material loaded with nanoparticles. The target heavy metal is efficiently and stably captured by the nanoparticles through alloy formation or specific adsorption, and enriched on the material surface. This process can achieve a capture efficiency close to 100%.

[0013] XRF detection: The composite porous material containing the target heavy metal is directly placed under an X-ray fluorescence spectrometer for detection. Since the target element is trapped on the surface of a homogeneous, known matrix, the analytical matrix is ​​greatly simplified, eliminating the matrix effect of the original sample. The intensity of the characteristic X-rays of the heavy metal obtained from XRF analysis is proportional to the original content in the sample, thus achieving accurate quantification.

[0014] This invention creates a key material—a composite porous material loaded with nanoparticles. This material is the core for achieving efficient and broad-spectrum gas-phase enrichment.

[0015] Porous materials: Three-dimensional interconnected porous materials with high specific surface area, excellent thermal stability, and chemical stability are selected, such as melamine / polyurethane / polyvinyl alcohol sponges, activated carbon sponges, aerogels, and metal foams. These structures provide an ideal platform for loading nanoparticles and for the rapid diffusion and capture of gaseous analytes.

[0016] Nanoparticles: Nanoparticles loaded onto porous materials that can form stable alloys with target heavy metal atoms or compounds or undergo specific surface chemisorption. These nanoparticles are selected from, but are not limited to: Nano-silver (AgNPs): It has excellent amalgamation effect on mercury (Hg), which can achieve efficient Hg capture, while not interfering with the Hg spectrum of XRF.

[0017] Nickel nanoparticles (NiNPs): They have an amalgamation-like effect on cadmium (Cd), enabling efficient Cd capture without interfering with Cd spectra in XRF.

[0018] Nano-silica (SiO2NPs): exhibits strong surface adsorption or reactivity for metalloid elements such as arsenic (As), lead (Pb), and selenium (Se).

[0019] Nano-selenium (SeNPs) and mercapto-containing (-SH) nanomaterials have extremely strong complexing ability for soft acid metal ions such as cadmium (Cd), lead (Pb), and mercury (Hg).

[0020] By combining nanoparticles with different functions, this material can be made to have a broad-spectrum ability to capture a variety of heavy metals (Hg, Cd, As, Pb, etc.).

[0021] Preferably, the method for preparing the composite porous material loaded with nanoparticles includes the following steps: a. Surface modification: Sodium hydroxide, polyethyleneimine (PEI), dopamine hydrochloride, etc. are used to treat the surface of porous materials to change the hydrophobicity of the material surface and introduce abundant functional groups such as amino and phenolic hydroxyl groups to enhance its surface activity and adsorption capacity for nanoparticle precursors.

[0022] Preparation of AgNPs precursor solution: Weigh silver nitrate (AgNO3) and polyvinylpyrrolidone (PVP), dissolve them together in deionized water, and stir to fully dissolve the solutes to obtain AgNPs precursor solution.

[0023] Preparation of NiNPs precursor solution: Weigh nickel nitrate hexahydrate (Ni(NO3)2·6H2O), dissolve it in anhydrous ethanol; after sonicating the solution, add sodium citrate and stir for a period of time to allow the components to react and mix fully, thus obtaining the NiNPs precursor solution.

[0024] Preparation of SiO2NPs precursor sol: Anhydrous ethanol, tetraethyl orthosilicate (TEOS) and deionized water were mixed in proportion, and the pH of the mixture was adjusted to 3.5~4.0. The system was stirred at 60℃ for 2 hours. After the reaction was completed, SiO2NPs precursor sol was obtained.

[0025] b. Nanoparticle loading: The porous material is immersed in a synthetic precursor mixture of nano-silver, nano-nickel and nano-silica, stirred, dried and shaped under specific conditions; or the above-mentioned functional nanoparticles are uniformly and firmly loaded on the surface of the modified porous substrate by vapor deposition or electroplating.

[0026] Specifically: The AgNPs precursor solution, NiNPs precursor solution and SiO2NPs precursor sol prepared above are mixed evenly; 2g of polyethylene glycol-6000 (PEG-6000) is added to the mixed solution and the pH value of the system is adjusted to 7.0~7.5; then the composite porous material is immersed in the mixed solution and stirred continuously to ensure that the nanoparticles are fully loaded on the surface of the porous material.

[0027] Post-processing: The loaded composite porous material is taken out and washed with anhydrous ethanol to remove unbonded impurities and excess components from the surface; after washing, it is dried to finally obtain AgNPs, NiNPs and SiO2NPs composite porous materials.

[0028] The present invention also provides a system for implementing the above method, the system comprising the following steps: A thermal evaporation device, equipped with a carrier gas introduction unit; A catalytic pyrolysis or transport unit; A gas-phase enrichment unit containing the aforementioned loaded nanoparticle composite porous material; An X-ray fluorescence spectrometer.

[0029] Preferably, the thermal evaporation device, the catalytic pyrolysis unit, and the gas phase enrichment unit can be integrated into a compact, portable device that can be used in conjunction with a portable XRF to achieve true on-site rapid simultaneous detection of multiple trace heavy metals.

[0030] The beneficial effects of this invention are as follows: (1) Extremely high detection sensitivity and ultra-low detection limit: By “gas phase enrichment”, trace heavy metals dispersed in macroscopic samples are concentrated into a small two-dimensional / three-dimensional region, generating a strong “surface enrichment effect”. Combined with the high sensitivity of XRF to surface elements, the detection limit of various heavy metals can be reduced by 1-3 orders of magnitude, or even to the μg / kg level, meeting the requirements of heavy metal limit standards in most solid samples.

[0031] (2) Fundamentally eliminate matrix interference: Through the process of "thermal evaporation-gas phase transport-trapping", the target element is separated from the complex original sample matrix and fixed on a simple and uniform enrichment material. This "matrix simplification effect" completely solves the problem of inaccurate quantification caused by absorption-enhancement effect and spectral interference in traditional XRF direct analysis, and greatly improves the accuracy and reliability of the analysis results.

[0032] (3) Achieve true on-site rapid detection: The entire process is simple and fast (completed within minutes), without the need for complex wet digestion or microwave digestion processes. The system can be integrated into a portable device, perfectly matching portable XRF, and is particularly suitable for applications such as environmental emergency monitoring, on-site food safety screening, and rapid analysis in mines.

[0033] (4) Broad-spectrum multi-element detection capability: By designing and loading nanoparticles with different functions, this enrichment material can be flexibly configured to achieve simultaneous and efficient capture of multiple high-risk heavy metals such as mercury, cadmium, arsenic, and lead, giving full play to the advantages of XRF for simultaneous multi-element analysis. It is a multi-purpose instrument with extremely high efficiency.

[0034] (5) High capture efficiency and good stability: Based on the strong alloying or chemical adsorption between nanomaterials and heavy metals, its capture efficiency for gaseous heavy metals is much higher than that of physical adsorption materials (such as carbon fiber membranes), which can achieve nearly 100% quantitative capture, ensuring the high precision and accuracy of the method.

[0035] (6) One material with multiple uses and expanded applications: The composite porous material loaded with nanoparticles can not only be used for enrichment in analysis and detection, but its high efficiency in capturing heavy metals also makes it a high-performance purification material that can be directly used for the treatment and remediation of water or gas polluted by heavy metals, and has broad application prospects. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the gas-phase enrichment material synthesis and its solid sample introduction system; wherein, 1. Material modification; 2. Nanoparticle loading; 3. Thermal evaporation device; 4. Catalytic pyrolysis unit; 5. Gas phase enrichment unit; 6. X-ray fluorescence spectrometer; Figure 2 These are scanning electron microscope (SEM) images of the porous material before and after loading with silver nanoparticles; where (i) is the SEM image of the porous material before loading with silver nanoparticles; and (ii) is the SEM image of the porous material after loading with silver nanoparticles. Figure 3 AgNPs porous materials capture Hg 0 XPS spectra afterward (Ag 3d and Hg 4f); Figure 4It is the capture efficiency of different composite porous materials for Hg, Cd, As, and Pb; Figure 5 It is a standard curve for quantitative analysis of Hg, Cd, As, and Pb enriched on composite porous materials using XRF; Figure 6 It is the effect of AgNPs sponges on different concentrations of Hg² + Adsorption removal rate of aqueous solution; Figure 7 This is a comparison of the effects of loading nano-silver onto different substrate sponges. Detailed Implementation

[0037] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0038] Example 1: Preparation of AgNPs-coated porous materials Add 3 mL of PEI solution to 97 mL of deionized water, immerse blank melamine-coated porous polymer material (sponge) for 1 h, and dry at 45 °C. Then immerse the sponge in 1.5% dopamine hydrochloride solution (ethanol:water = 8:2) for 1 h and heat-cur at 80 °C. Subsequently, immerse the sponge in 50 mM AgNO3 solution for 1 h. Under ice bath stirring, first add 0.5 M KBH4 containing 1% PVP and react for 5 min, then transfer to 0.02 M KBH4 and react for 30 min. Finally, wash with deionized water and ethanol, and dry at 45 °C to obtain AgNPs sponge. SEM showed that its surface was successfully loaded with uniformly distributed silver nanospheres (…). Figure 2 ).

[0039] Example 2: System Integration and Hg Detection in Soil according to Figure 1 A solid-phase gas-phase enrichment (ETV-GPE)-XRF system was constructed. 0.5 g of soil sample was weighed into a sample boat and placed in thermal evaporation device 3 (700℃) for evaporation. The evaporated gaseous material was purged with an airflow of 350 mL / min and passed through catalytic pyrolysis unit 4 (550℃, filled with MnO2 / CoO), where Hg was converted and maintained in its atomic state. 0 Hg 0Subsequently, the AgNPs sponge in the gas phase enrichment unit 5 was captured to form Ag-Hg amalgam. The sponge was removed, and the Hg Lα line intensity was measured using X-ray fluorescence spectrometry 6. The results showed that the detection limit of this method for Hg in soil was as low as 31 μg / kg, with a linear range of 0-80 ng and RSD ≤ 12%. The mercury concentrations measured by this method all met the certification values ​​of CRM standards, and the spiked recoveries fluctuated between 86.7% and 104%, fully demonstrating the excellent accuracy and applicability of this method. In addition, compared with the XRF detection limit of approximately 0.2 mg / kg reported in the literature (Jiang Aosong, Huang Yujuan, Li Zhu, et al. Applicability analysis of X-ray fluorescence spectrometry for the detection of heavy metals in soil [J / OL]. Journal of Ecology and Rural Environment, 1-18 [2025-11-24]), the mercury detection capability was improved by about 20 times.

[0040] Example 3: Preparation of SeNPs and NiNPs / SiO2NPs composite porous materials Nano-selenium (SeNPs) composite porous material: Prepare a 2 mmol / L sodium selenite solution, add a small amount of chitosan and stir until completely dissolved. Adjust the pH of the system to 5.0-6.0, then immerse the porous material (sponge) in this mixed solution. Prepare a 2 mmol / L ascorbic acid solution and slowly add it dropwise to the above sodium selenite-chitosan mixture. During the addition process, the color of the composite porous material gradually changes from the initial state to orange-red, and finally to red or dark red. Continue stirring the reaction for 2 hours to ensure the Se... 4+ After complete reduction, the material is cleaned and vacuum dried to obtain a red SeNPs composite porous material.

[0041] Preparation of NiNPs composite porous materials: After alkaline washing and acid washing, the porous material (sponge) is first irradiated with ultraviolet light, then a 20 g / L silane coupling agent (APTES) solution is prepared and pre-hydrolyzed for 72 hours. The porous material is then immersed in the solution and heated thoroughly for 20 minutes. After removing the material, it is immersed in a mixed solution of nickel sulfate, sodium hypophosphite, and sodium pyrophosphate for 10 minutes, then rinsed thoroughly. Next, it is immersed in a freshly prepared NaBH4 solution for reduction for 20 minutes. After washing and drying, the NiNPs composite porous material is obtained.

[0042] Preparation of SiO2NPs composite porous material: Add 2 g of polyethylene glycol (PEG-400) to 50 mL of anhydrous ethanol and disperse thoroughly. Then add 8 mL of tetraethoxysilane (TEOS) and stir until completely dispersed. Immerse the porous material (sponge) in this solution and continue stirring. Prepare a water-hydrochloric acid mixture and adjust its pH to 2.5-3.0. Slowly add the pre-dispersed solution dropwise through a constant pressure dropping funnel, continuing stirring until the porous material gradually turns milky white. Finally, wash with anhydrous ethanol and dry to obtain the SiO2NPs composite porous material.

[0043] Example 4: Preparation of composite porous materials of AgNPs, NiNPs and SiO2NPs AgNO3 and PVP were dissolved in deionized water and stirred to prepare an AgNPs precursor solution. Ni(NO3)2·6H2O was dissolved in anhydrous ethanol, sonicated, and then sodium citrate was added and stirred for a period of time to obtain a NiNPs precursor solution. Anhydrous ethanol, TEOS, and deionized water were mixed, the pH was adjusted to 3.5-4.0, and the mixture was stirred at 60℃ for 2 h to prepare a SiO2NPs precursor sol. After mixing the three precursor solutions, 2 g of PEG-6000 was added to adjust the pH to 7.0-7.5. The composite porous material was then immersed in this solution and stirred continuously. Finally, the mixture was washed with anhydrous ethanol and dried to form a composite porous material loaded with AgNPs, NiNPs, and SiO2NPs.

[0044] Example 5: Multi-element application example For cadmium: using a similar process to that for Hg, with the ETV temperature optimized to 1000℃, NiNPs composite porous material sponges can effectively capture atomic Cd by forming a Ni-Cd solid solution. 0 Simultaneously, SiO2NPs are used to capture As and Pb.

[0045] For arsenic and lead: During ETV evaporation and catalytic pyrolysis, As and Pb are converted into gaseous oxides by controlling the atmosphere (e.g., adding a small amount of oxygen), and captured using porous materials loaded with nano-silica. The specific adsorption between As and Pb in silica is utilized for enrichment, followed by XRF detection.

[0046] For mercury, cadmium, arsenic, and lead: During ETV evaporation and catalytic pyrolysis, by controlling the temperature (e.g., complete evaporation of mercury at 700℃ and evaporation of cadmium at 1000℃) and atmosphere (air, argon, hydrogen), the composite porous material can simultaneously and effectively capture atomic Hg. 0 Cd 0 And oxidized arsenic and lead, which were further detected by XRF.

[0047] like Figure 4-5 As shown, the above composite porous material can achieve a capture rate of over 95% for Hg, Cd, As, and Pb, according to the test results. Furthermore, XRF was used to establish linear relationships, and the correlation coefficients r for Hg, Cd, As, and Pb all exceeded 0.99.

[0048] Example 6: Enrichment and Removal of Hg from Water Samples The AgNPs sponge prepared in Example 1 was placed in a vacuum filtration device, and 500 mL of Hg²⁺-containing fluid was filtered. + The water sample was analyzed. The filtrate showed that the sponge removed over 95% of the Hg, demonstrating the material's potential for treating heavy metal wastewater.

[0049] Example 7: Applicability of different nanoparticles to porous materials Following the same method as in Example 1, nano-silver was synthesized on sponges such as polyurethane sponge and polyvinyl alcohol sponge, and the adsorption and recovery rate of Hg was above 95%. Figure 6 This demonstrates its wide applicability.

[0050] The core of this invention lies in the creation of porous enrichment materials such as polymers and carbon-based materials loaded with nanoparticles. These materials can efficiently and stably capture gaseous heavy metal atoms or compounds introduced through thermal evaporation and can be directly used for XRF analysis. Through surface enrichment and matrix simplification effects, this invention transforms the detection of complex samples into the analysis of homogeneous composite materials, greatly improving the detection sensitivity of XRF for various trace heavy metals (such as mercury, cadmium, arsenic, and lead). It also possesses advantages such as strong anti-interference capabilities, rapid processing, and on-site portability. Furthermore, this material can also be used for the remediation of heavy metal pollution in water and gaseous media.

[0051] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for simultaneously measuring a plurality of heavy metals by using an X-ray fluorescence spectrometer in combination with a gas phase enrichment material, characterized by, The method comprises the following steps: The sample to be tested is subjected to thermal evaporation, and the gaseous substances generated by thermal evaporation are subjected to catalytic pyrolysis, and the gaseous analytes subjected to catalytic pyrolysis are enriched in heavy metals by using the composite porous material loaded with nanoparticles; The composite porous material captured with multiple heavy metals is placed under an X-ray fluorescence spectrometer for detection.

2. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 1, characterized by, The specific steps of the thermal evaporation are as follows: The solid or liquid sample to be tested is placed in an evaporation device, and is subjected to heating and atomization by means of electric heating evaporation, laser thermal evaporation, microwave thermal evaporation or plasma evaporation in a specific atmosphere, so that multiple target heavy metal elements in the sample are in the form of atomic vapor or volatile compounds, or the gaseous sample is directly introduced into a gas-phase enrichment unit.

3. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 1, characterized by, The specific steps of the catalytic pyrolysis are as follows: The gaseous substances generated by thermal evaporation are passed through a catalytic pyrolysis unit, so as to ensure that different chemical forms of heavy metals are uniformly converted into atomic or specific compound forms which are easy to be captured; the unit is filled with one or more of catalysts MgO, kaolin, MnO2, Mn3O4, CoO and Al2O3.

4. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 1, characterized by, The nanoparticles are materials capable of forming alloys with heavy metals or undergoing specific surface adsorption, including one or more of nano-silver, nano-nickel, nano-silicon dioxide or nano-selenium, and thiol-containing nanomaterials.

5. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 4, characterized by, The porous material is melamine / polyurethane / polyvinyl alcohol sponge, activated carbon sponge, aerogel or foamed metal.

6. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 4, characterized by, The preparation method of the composite porous material loaded with nanoparticles is as follows: The porous material is immersed in a mixed solution of nano-silver, nano-nickel and nano-silicon dioxide synthetic precursors, and is subjected to stirring, drying and molding under specific conditions.

7. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 6, characterized by, The specific preparation method is as follows: Nano-silver, nano-nickel and nano-silicon dioxide precursors are prepared respectively, and are uniformly mixed; polyethylene-6000 is added to the mixed solution, and the pH value of the system is adjusted to 7.0-7.5; Subsequently, the porous material is immersed in the mixed solution, and the nanoparticles are fully loaded on the surface of the porous material by continuous stirring; the loaded porous material is taken out, washed, dried, and the composite porous material loaded with nanoparticles is obtained.

8. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 7, characterized by, The preparation method of the nano-silver, nano-nickel and nano-silicon dioxide precursors is as follows: Preparation of nano-silver precursor solution: silver nitrate and polyvinylpyrrolidone are weighed, and are dissolved in deionized water by stirring to make a nano-silver precursor solution; Preparation of nano-nickel precursor solution: nickel nitrate hexahydrate is weighed and dissolved in anhydrous ethanol; after ultrasonic treatment of the solution, sodium citrate is added and stirred for a period of time to make the components fully react and mix, and a nano-nickel precursor solution is obtained; Preparation of nano-silicon dioxide precursor sol: anhydrous ethanol, tetraethyl orthosilicate and deionized water are mixed in a certain proportion, and the pH value of the mixed system is adjusted to 3.5-4.0; nano-silicon dioxide precursor sol is prepared by stirring reaction.

9. The method for simultaneously determining a plurality of heavy metals using an X-ray fluorescence spectrometer in combination with a gas-phase enrichment material according to claim 1, characterized by, The heavy metals include mercury, cadmium, arsenic and lead.

10. System for implementing the method according to any one of claims 1 to 9, characterized in that, The method comprises sequentially connected: A thermal evaporation device for the thermal evaporation introduction of a sample, and provided with a necessary carrier gas introduction unit; A catalytic pyrolysis unit for converting gaseous analytes and maintaining effective transmission thereof; A gas-phase enrichment unit provided with the composite porous material loaded with nanoparticles as claimed in claim 4 or 5; and An X-ray fluorescence spectrometer. X-ray fluorescence spectrometer for detecting the enriched material.

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