Method for determining forms of methyl mercury, ethyl mercury and inorganic mercury in food

Abstract

The invention discloses a method for determining forms of methyl mercury, ethyl mercury and inorganic mercury in food, and relates to the technical field of food heavy metal determination, and the method comprises the following steps: releasing a target object by mixing an extracting solution, removing matrix interference by SAX column purification, and determining the forms of methyl mercury, ethyl mercury and inorganic mercury in food by combining a high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) combined technology. And trace determination of methyl mercury, ethyl mercury and inorganic mercury in a complex matrix is realized. The method disclosed by the invention has the advantages of strong anti-interference performance, high recovery rate and good accuracy, and provides a basis for determining the mercury content of different forms of various foods so as to formulate a more complete and accurate food safety standard. The method is suitable for food quality control and safety evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal determination in food, and more particularly to the technical field of a method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food. Background Art

[0002] Mercury pollution is a significant global environmental issue. Different forms of mercury exhibit varying physiological activities and toxicities, with methylmercury being the most toxic. Currently, GB 2762, "National Food Safety Standard - Limits of Contaminants in Food," and a growing number of green product standards, stipulate limits not only for total mercury but also for methylmercury. With the advancement of science and technology and the deepening of public awareness of health, measuring only total mercury and methylmercury in food is clearly insufficient to meet people's needs for a healthy lifestyle. Measuring only total mercury cannot assess health risks; understanding the levels of methylmercury, ethylmercury, and inorganic mercury is also necessary to develop precise detection methods.

[0003] Traditional methods (such as atomic fluorescence spectrometry) cannot simultaneously detect multiple mercury forms, and complex food matrices (such as proteins, fats, and polysaccharides) can easily interfere with test results. Existing combined techniques (such as high-performance liquid chromatography-atomic fluorescence spectrometry) can distinguish mercury forms, but their sensitivity is insufficient, pretreatment steps struggle to effectively remove matrix interference, and recovery rates are low, making them difficult to meet trace detection requirements. Therefore, it is crucial to develop sensitive and efficient methods for detecting different mercury forms in food. Existing patents disclose the following technologies: Patent publication number CN110146452A, titled "A Method for Rapidly Detecting Mercury Ions in Food," discloses the following: It comprises three steps: (1) digestion of the food sample to be tested; (2) extraction of mercury ions from the food nitrate solution using an ionic liquid; and (3) mixing the ionic liquid with a deoxyribozyme reaction system with catalase catalytic activity, detecting the UV-visible absorbance of the aqueous phase at 418 nm, and determining the mercury ion concentration based on a working curve. This method combines the efficient and highly selective ion enrichment capabilities of the ionic liquid with the catalytic activity of the deoxyribozyme, achieving efficient and rapid enrichment of mercury ions from the highly acidic and oxidizing food digest solution. The enriched ionic liquid is then directly used for convenient, sensitive, and specific deoxyribozyme-catalyzed colorimetric detection of mercury ions. This method is rapid and simple, and can also be applied to the detection of mercury ions in complex media such as soil and haze particles, or extended to the detection of other heavy metal ions.

[0004] The patent with publication number CN117419997A and patent name: "A method for rapid extraction of heavy metal mercury in food testing" discloses the following content: take the food sample to be tested and heat and digest it under the assistance of microwaves, then disperse the adsorption material containing magnetic iron into the solution for sufficient adsorption, and finally wash and desorb the adsorption material before it can be used for subsequent testing. The present invention also provides a method for preparing the adsorption material containing magnetic iron, which comprises dispersing hexadecyltrimethyl quaternary ammonium salt in deionized water and adjusting the pH value to 7-10, adding magnetic ferrosoferric oxide and mixed silane after stirring and fully reacting under certain conditions, and then washing and drying to obtain the product. The method for rapid extraction of heavy metal mercury in food testing provided by the present invention is simple to operate, and the materials used are easy to obtain. Experiments have confirmed that the method for rapid extraction of heavy metal mercury in food testing provided by the present invention has better accuracy, and is particularly effective for different food samples.

[0005] Patent publication number CN103335990B, entitled "A Method for Determining Methylmercury and Ethylmercury in Animal Flesh," discloses the following: pretreatment of animal flesh samples; microwave-assisted extraction; analysis using liquid chromatography-atomic fluorescence spectrometry; and finally, data collection and processing using a data processor to determine the methylmercury and ethylmercury content in fish flesh. The present invention applies microwave-assisted extraction and HPLC-AFS to the detection of methylmercury and ethylmercury in animal flesh. The extraction process is optimized. By rationally controlling the selection and concentration of the mobile phase in chromatographic analysis, and the concentration of hydrochloric acid, the choice of reducing agent, and the lamp current in atomic fluorescence analysis, the process flow is simplified, enabling rapid and convenient determination of the methylmercury and ethylmercury content in animal flesh. The detection method of the present invention is not only simple and rapid, but also stable, and exhibits high sensitivity, good accuracy, and strong anti-interference capabilities.

[0006] The innovation of most of the patented technologies listed above lies in providing different extraction methods for heavy metal mercury in food testing. However, the extraction methods provided above cannot meet the requirements for the accurate determination of the content of methylmercury, ethylmercury and inorganic mercury forms. Summary of the Invention

[0007] The purpose of the present invention is to solve the above technical problems and provide a method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food.

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions: The present invention provides a method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food, comprising the following steps: Step 1: Preparation of mixed solution: ① Measure approximately 800 mL of ultrapure water and pour it into a 1 L volumetric flask. In a fume hood, use a pipette to accurately transfer 8.3 mL of concentrated hydrochloric acid and slowly add it to the water while stirring. Continue stirring for 5 minutes to ensure uniform mixing. ② Accurately weigh 5.000 g of L-cysteine using an electronic balance. Slowly add the powder to the HCl solution and stir magnetically until completely dissolved (approximately 30-60 minutes at room temperature). ③ Use a pipette to slowly measure 0.93 mL of Triton X-100, or accurately weigh 1.000 g; add it dropwise to the solution to avoid excessive foaming; continue stirring until the solution is clear (approximately 10-20 minutes); ④ Add ultrapure water to a volume of 1 L, seal the volumetric flask, invert and shake at least 10 times to mix thoroughly. This will give a mixed extract containing 0.1 mol / L HCl, 1% L-cysteine, and 0.5% Triton X-100. This solution should be used immediately after preparation or stored in a dark place (≤4°C) and used within 24 hours to prevent L-cysteine oxidation. Step 2: Sample preparation: Take the edible part of the food sample, freeze-dry it, then grind it, pass it through a 60-mesh sieve, put it into a clean polyethylene sample bottle, and seal it for later use; Step 3. Extraction: Weigh 0.3000-0.5000 g of the processed sample powder and place it in a 25 ml plastic centrifuge tube. Add 8 mL of mixed extract (0.1 mol / L HCl-1% L-cysteine-0.5% Triton X-100). Vortex at room temperature for 5 min, then perform ultrasonic extraction at 45 °C for 30 min, shaking three times during the process; centrifuge at 12,000 rpm / min for 15 min.

[0009] Step 4: Purification: Accurately transfer 5 ml of the supernatant after extraction, filter it through a 0.22 μm nylon filter membrane, and purify it through a SAX strong anion exchange solid phase extraction column to remove interference such as polysaccharides and pigments.

[0010] Step 5. Prepare a mixed standard solution of the three mercury species: Purchase standard materials for methylmercury solution, ethylmercury solution, and inorganic mercury, and prepare a standard dilution solution with a concentration of 1 μg / ml, respectively. Accurately pipette 0 ml, 0.5 ml, 1.0 ml, 2.0 ml, 5.0 ml, and 10.0 ml of each of the three mercury species standard dilutions into six 100 ml volumetric flasks. Bring the solution to the mark with mobile phase and mix thoroughly. This yields a mixed standard solution of mercury species with concentrations of 0.0, 5.0, 10.0, 20.0, 50.0, and 100.0 μg / L for methylmercury, ethylmercury, and inorganic mercury, respectively.

[0011] Step 6. Analysis and Detection: Analytical testing utilizes HPLC-ICP-MS. After extraction and purification, methylmercury, ethylmercury, and inorganic mercury in the sample are separated by liquid chromatography. Differences in HPLC retention times reveal the different forms of the elements. Inductively coupled plasma mass spectrometry (ICP-MS) serves as the HPLC detector, tracking the changes in the various forms of the element, simplifying the chromatogram and enabling both qualitative and quantitative analysis of the elemental forms. The chromatographic separation process utilizes a C18 column (5 μm particle size, 12 nm pore size, 4.6 × 150 mm dimensions). The mobile phase consists of 5% methanol, 0.05 mol / L ammonium acetate, and 0.2% L-cysteine. Flow rate: 1.0 mL / min, room temperature, injection volume: 10 μL. Run time: 600 s. ICP-MS detection was performed using helium collision reaction mode with a monitoring mass of 202Hg. The retention times of the three different mercury forms were: methylmercury: 180s, inorganic mercury: 110s, and ethylmercury: 390s. The integration times were: methylmercury: 20s, inorganic mercury: 20s, and ethylmercury: 40s. Step 7. Optimization of liquid chromatography conditions: By adjusting the contents of methanol, ammonium acetate, and L-cysteine in the mobile phase, and adjusting the flow rate, column temperature, and run time of the mobile phase, the separation efficiency of methylmercury, ethylmercury, and inorganic mercury was improved (see Table 1).

[0012] Optimization of mass spectrometry conditions: Instrument conditions were optimized using 10 μg / L Li, Co, U, and In mass spectrometry tuning solutions; the mass number detected was 202 mercury; and the retention time, integration time, and run time of the 50 μg / L mixed standard solution of mercury species prepared in step 5 were optimized to effectively separate the chromatographic peaks of methylmercury, ethylmercury, and inorganic mercury, thereby improving the accuracy and sensitivity of detection (see Table 2).

[0013] Table 1 Liquid chromatography separation process conditions after optimization of step 7

[0014] Table 2 Mass spectrometry separation process conditions after optimization in step 7

[0015] The beneficial effects of the present invention are as follows: Mercury detection in food is mostly limited to inorganic and methylmercury detection, making it difficult to simultaneously determine methylmercury, ethylmercury, and inorganic mercury species in food. Researchers used a mixed extraction solution of L-cysteine and Triton X-100, along with a SAX column for selective adsorption of anionic interfering compounds, to effectively address matrix interference and minimize its impact on the target. Furthermore, HPLC-ICP-MS coupling enabled the simultaneous determination of methylmercury, ethylmercury, and inorganic mercury species in food. Specifically, a mixed extraction solution of 0.1 mol / L HCl, 1% L-cysteine, and 0.5% Triton X-100 enhanced the release efficiency of fat-soluble mercury while inhibiting matrix adsorption. The hydrochloric acid in this mixed extraction solution provides an acidic environment for the release of mercury species. L-cysteine chelates mercury, preventing adsorption loss. Triton X-100 disrupts the lipid structure of fat-containing samples, enhancing extraction efficiency. This application demonstrates this point, breaking with established technical biases.

[0016] 2. The present invention utilizes HPLC-ICP-MS coupling technology to simultaneously determine the forms of methylmercury, ethylmercury, and inorganic mercury in food. This method can also be applied to other fields (such as soil, environment, and health products) for simultaneous determination of methylmercury, ethylmercury, and inorganic mercury forms, expanding its application areas. The closed system is immune to contamination interference, improving the accuracy of the results. This method offers simple and efficient sample processing, a wide linear range, and high accuracy. Liquid chromatography is used for separation, and the different forms of the elements are reflected by differences in HPLC retention times. Inductively coupled plasma mass spectrometry serves as the HPLC detector, tracking the changes in the various forms of the element being measured, resulting in a simple chromatogram. This method is suitable for detecting the content of methylmercury, ethylmercury, and inorganic mercury in various foods, facilitating large-scale testing.

[0017] 3. This invention represents a significant technological advancement in the simultaneous determination of methylmercury, ethylmercury, and inorganic mercury species in food, resolving existing challenges in the simultaneous determination of methylmercury, ethylmercury, and inorganic mercury species. This invention provides strong support for food safety and possesses broad application prospects and significant market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 : Flow chart of the measurement system.

[0020] Figure 2 : Chromatograms of standard samples of methylmercury, ethylmercury and inorganic mercury.

[0021] Figure 3 : Schematic diagram of the standard curves of methylmercury, ethylmercury and inorganic mercury.

[0022] Figure 4 : Comparison of chromatograms of spiked and unspiked samples. DETAILED DESCRIPTION

[0023] To make the technical problems, technical solutions, and technical effects of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0025] Example 1 This embodiment provides a method for determining the forms of methylmercury, ethylmercury, and inorganic mercury in food, comprising the following specific steps: S1. Reagent preparation: S11, mixed extract: S111. Measure approximately 800 mL of ultrapure water and pour it into a 1 L volumetric flask. In a fume hood, use a pipette to accurately transfer 8.3 mL of concentrated hydrochloric acid and slowly add it to the water while stirring. Continue stirring for 5 minutes to ensure uniform mixing.

[0026] S112. Accurately weigh 5.000 g of L-cysteine using an electronic balance. Slowly add the powder to the HCl solution and stir magnetically until completely dissolved (approximately 30-60 minutes at room temperature).

[0027] S113. Use a pipette to slowly measure 0.93 mL of Triton X-100, or accurately weigh 1.000 g. Add dropwise to the solution, avoiding excessive foaming. Stir continuously until the solution is clear (approximately 10–20 minutes).

[0028] S114. Add ultrapure water to a volume of 1 L. Seal the volumetric flask, invert and shake at least 10 times, and mix thoroughly to obtain a mixed extract solution containing 0.1 mol / L HCl, 1% L-cysteine, and 0.5% Triton X-100. This solution should be used immediately or stored in a dark place and refrigerated (≤4°C) and used within 24 hours to prevent L-cysteine oxidation. In this extract, hydrochloric acid provides an acidic environment to release mercury species. L-cysteine chelates mercury, preventing adsorption loss. Triton X-100 disrupts the lipid structure of fat-containing samples, enhancing extraction efficiency. S12, mobile phase: 5% Methanol + 0.05 mol / L Ammonium Acetate + 0.2% L-Cysteine: Add approximately 800 ml of deionized water to a beaker, weigh 3.85 g of ammonium acetate, and stir until completely dissolved. Weigh 2.0 g of L-Cysteine and slowly add it to the above solution. Use a graduated cylinder to measure 50 ml of methanol and slowly add it to the solution, stirring to mix thoroughly. Transfer the solution to a 1 L volumetric flask and dilute to the mark with deionized water. Filter through a 0.45 μm organic filter membrane, and degas in an ultrasonic water bath for 30 minutes. Prepare immediately before use.

[0029] S2. Preparation of standard solution: Methylmercury solution standard substance: standard value 76.3μg / g Ethyl mercury solution standard substance: standard value 73.8μg / g Inorganic mercury single element standard substance: standard value 1000μg / ml Methylmercury Standard Dilution (1 μg / ml): The standard value of the methylmercury solution standard substance is 76.3 μg / g, which converts to a mercury content of 70.992 μg / g. Remove all the methylmercury solution standard substance and weigh it to 1.2549 g. Quickly add methanol solution to a mass of 8.9088 g, resulting in a 10 μg / ml methylmercury standard stock solution. Accurately pipette 1 ml of the 10 μg / ml methylmercury standard solution into a 10 ml volumetric flask with mobile phase, shake well, and set aside. This yields the 1 μg / ml methylmercury standard dilution solution, which should be prepared immediately before use.

[0030] Ethylmercury Standard Dilution (1 μg / ml): The standard value of the ethylmercury solution standard substance is 73.8 μg / g, which converts to a mercury content of 64.479 μg / g. Remove all the ethylmercury solution standard substance and weigh it to 1.2275 g. Quickly add methanol solution to a mass of 7.9148 g, resulting in a 10 μg / ml ethylmercury standard stock solution. Accurately pipette 1 ml of the 10 μg / ml methylmercury standard solution into a 10 ml volumetric flask with mobile phase, shake well, and set aside to obtain the 1 μg / ml ethylmercury standard stock solution. Prepare this dilution immediately before use.

[0031] Inorganic mercury standard dilution (1 μg / ml): Accurately pipette 1 ml of the single-element mercury standard substance into a 100 ml volumetric flask and dilute to volume with pure water to obtain an inorganic mercury standard stock solution with a concentration of 10 μg / ml. Accurately pipette 1 ml of the inorganic mercury standard stock solution into a 10 ml volumetric flask, dilute to volume with mobile phase, and shake well for later use. The resulting concentration is the inorganic mercury standard dilution solution that is prepared for future use. Prepare this dilution solution immediately before use.

[0032] Mercury form standard mixed solution: Take 6 100ml volumetric flasks, accurately pipette 0ml, 0.5ml, 1.0ml, 2.0ml, 5.0ml, and 10.0ml of three forms of mercury standard dilutions, respectively, dilute to the scale with mobile phase, and mix well to obtain mercury form standard mixed solutions with methylmercury, ethylmercury, and inorganic mercury concentrations of 0.0, 5.0, 10.0, 20.0, 50.0, and 100.0μg / L.

[0033] S3. Sample preparation: Commercially available algae samples were selected as sample 1, fish samples as sample 2, fungus samples as sample 3, fish products as sample 4, meat products as sample 5, and condiments as sample 6. The edible parts were taken, freeze-dried and then crushed, passed through a 60-mesh sieve, and placed in clean polyethylene sample bottles, which were sealed and stored for later use.

[0034] S4, extraction process: Weigh the following number of processed samples: Sample 1 was divided into four parts: 1# 0.5001g, 2# 0.5005g, 3# 0.5008g, and 4# 0.5002g.

[0035] Sample 2, four parts: 5# 0.4001g, 6# 0.4008g, 7# 0.4005g, 8# 0.4010g, Sample 3, two portions: 9# 0.4502g, 10# 0.4517g.

[0036] Sample 4, two portions: 11# 0.4511g, 12# 0.4521g.

[0037] Sample 5, two portions: 13# 0.4505g, 14# 0.4511g.

[0038] Two portions of sample 6: 15# 0.4512g, 16# 0.4508g.

[0039] Place the sample in a 25ml plastic centrifuge tube and add 8ml of a mixed extraction solution (0.1mol / L HCl-1% L-cysteine-0.5% Triton X-100). For tubes 3, 4, 7, and 8, add a mixed standard solution of three different mercury species, with spike levels of 2μg / L for tubes 3 and 7, and 5μg / L for tubes 4 and 8. Cap all tubes, vortex at room temperature for 5 minutes, and then ultrasonically extract at 45°C for 30 minutes, shaking three times during the extraction. After ultrasonic extraction, centrifuge at 12,000 rpm / min for 15 minutes.

[0040] S5. Purification treatment: Accurately transfer 5 ml of the supernatant from the extraction and filter through a 0.22 μm nylon membrane. Purify the filtered solution using a SAX strong anion exchange solid-phase extraction column to remove interferences such as polysaccharides and pigments. Collect the purified solution in a plastic colorimetric tube and prepare it for analysis. Simultaneously perform a blank test.

[0041] S6. Analysis and determination: Under the optimized instrument conditions, the mixed standard working solutions of the three forms of mercury were sampled separately, and the standard working curve was drawn with the concentration as the horizontal axis and the peak area as the vertical axis. The standard working curve was used to quantitatively determine the test solutions of each sample. The response values of methylmercury, ethylmercury and inorganic mercury in the sample solutions should all be within the linear range of the instrument.

[0042] S7. Experimental results: S71. Through optimization, verification and repeated testing of liquid phase and mass spectrometry conditions, the standard curve information and correlation coefficients of methylmercury, ethylmercury and inorganic mercury are shown in Table 3: Table 3 Standard curves and correlation coefficients of compounds

[0043] S72. Sample measurement results: Six different types of food available on the market were selected as samples 1 to 6, and the content of three forms of mercury, methylmercury, ethylmercury and inorganic mercury, was determined. The results are shown in Table 4.

[0044] Table 4 Sample test table

[0045] S73. Samples 1 and 2 were used for spiked test. The recovery results are shown in Table 5: Table 5 Spike test results

[0046] This study investigated a method for the simultaneous determination of methylmercury, ethylmercury, and inorganic mercury in food. A mixed extraction solution of 0.1 mol / L HCl, 1% L-cysteine, and 0.5% Triton X-100 was used, and an SAX column was used for selective adsorption of anionic interfering substances (such as organic acids and pigments). Analytical detection employed HPLC-ICP-MS. This closed system is immune to contamination interference, improving the accuracy of results. This method offers simple and efficient sample preparation, a wide linear range, and high accuracy. High-performance liquid chromatography (HPLC) separation is performed, and elemental forms are characterized by differences in HPLC retention time. Inductively coupled plasma-mass spectrometry (ICP-MS) serves as the HPLC detector, tracking the changes in the various forms of the element under investigation, resulting in a simplified chromatogram. This method is suitable for the determination of methylmercury, ethylmercury, and inorganic mercury in various foods, facilitating large-scale testing.

Claims

1. A method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food, characterized in that: The steps include: S1. Sample preparation: Take the edible part of the food, freeze-dry it, crush it, sieve it, put it into a clean polyethylene sample bottle, seal it and store it for later use; S2. Preparation of a mixed extract: preparing a mixed extract comprising L-cysteine and Triton X-100; S3. Extraction of target substances in the sample: Weigh the sample prepared in step S1, add the mixed extract, and release methylmercury, ethylmercury, and inorganic mercury in the sample through vortex oscillation, ultrasonic extraction, and centrifugal filtration; S4, purification: the supernatant of the solution after the extraction treatment in step S3 is removed, filtered through a nylon filter membrane, and then purified by a SAX strong anion exchange solid phase extraction column; S5. Prepare a standard mixed solution of mercury forms; S6. Analysis and detection: HPLC-ICP-MS combined technology is used for determination, with high performance liquid chromatography for separation and inductively coupled plasma mass spectrometry as the detector of high performance liquid chromatography for qualitative and quantitative analysis of elemental forms.

2. The method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food according to claim 1, characterized in that: In step S1, sample pretreatment, high performance liquid chromatography separation, and inductively coupled plasma mass spectrometry determination steps are required.

3. The method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food according to claim 1, characterized in that: In step S2, the mixed extract is a solution containing 0.1 mol / L HCl, 1% L-cysteine and 0.5% Triton X-100.

4. The method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food according to claim 1, characterized in that: In step S3, the extraction process is as follows: 0.3-0.5 g of the processed sample powder is weighed and placed in a 25 ml plastic centrifuge tube, 8 ml of the mixed extract is added, vortexed at room temperature for 5 min, and then ultrasonically extracted at 45°C for 30 min, shaking 3 times during the process; and centrifuged at 12,000 rpm / min for 15 min.

5. The method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food according to claim 1, characterized in that: In step S6, the on-machine measurement adopts HPLC-ICP-MS coupling technology, and liquid chromatography is used for separation. The different forms of elements are reflected according to the difference in retention time of high-performance liquid chromatography. Inductively coupled plasma mass spectrometry is used as the detector of high-performance liquid chromatography to track the changes in various forms of the elements to be measured, making the chromatogram simpler and performing qualitative and quantitative analysis of the element forms at the same time.

6. The method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food according to claim 1, characterized in that: In step S6, inductively coupled plasma mass spectrometry is performed in He collision reaction cell mode, and the monitoring mass number is 202 mercury; the retention times of the three different forms of mercury are methylmercury: 180 s, inorganic mercury: 110 s, and ethylmercury: 390 s; the integration time is methylmercury: 20 s, inorganic mercury: 20 s, and ethylmercury: 40 s.

7. The method for determining the forms of methylmercury, ethylmercury and inorganic mercury in food according to claim 1, characterized in that: The chromatographic column in the chromatographic separation process is C 18 Column; mobile phase: 5% methanol + 0.05 mol / L ammonium acetate + 0.2% L-cysteine; flow rate: 1.0 mL / min, room temperature, injection volume: 10 μL, run time: 600 s.

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