Chemical form analysis method of selenium in selenium-rich soil based on ICP-MS technology

Abstract

The invention discloses a chemical form analysis method of selenium in selenium-rich soil based on an ICP-MS (Inductively Coupled Plasma Mass Spectrometry) technology in the technical field of analytical chemistry. The chemical form analysis method comprises the following steps: S1, preparing an extracting agent, namely preparing 250mL of a 0.1 mol / L KH2PO4-K2HPO4 solution, 250mL of a 0.1 mol / L K2S2O8 solution and 400mL of a 3mol / L HCl solution; s3, preparing a standard solution; S4, diluting extracting solutions in various forms: respectively taking an ion exchange state extracting solution, an acid soluble state extracting solution and an organic matter combined state extracting solution, putting into a centrifugal tube, and then diluting with 2% HNO3 to obtain a water soluble state solution, an ion exchange state solution, an acid soluble state solution and an organic matter combined state diluted solution; s5, instrument debugging: after starting, vacuumizing, igniting, tuning and method editing, determining selenium in a standard solution and a sample solution; and S6, selenium concentration determination: sequentially determining the standard solution series in each form and the selenium diluent in each form. According to the scheme, the problems that in soil selenium form analysis, pretreatment such as acid adding and heating needs to be conducted on a form extracting solution, and the analysis result error is large are solved.

Description

Technical Field

[0001] The invention relates to the technical field of analytical chemistry, and in particular to a chemical form analysis method of selenium in selenium-rich soil based on ICP-MS technology. Background Art

[0002] Selenium is a trace element necessary for human and biological life activities. When studying the distribution, enrichment, migration and transformation of selenium in the environment, as well as its environmental geochemical behavior such as bioavailability, simply measuring its total amount cannot provide sufficient information. It is also necessary to study its chemical forms in the environment.

[0003] For the morphological analysis of selenium in soil, different forms are usually extracted step by step using different extractants, and then the extracts are treated and the content of selenium in different forms is determined by atomic fluorescence spectroscopy. Most of the current methods for analyzing the morphology of selenium in soil require the addition of acid and oxidant to the extract solutions of each form before using analytical instruments to determine selenium, in order to eliminate the matrix effect caused by high-concentration extractants and to oxidize and reduce selenium to the same valence state. The operation is very cumbersome and may bring new errors. Summary of the invention

[0004] The present invention aims to provide a chemical form analysis method for selenium in selenium-rich soil based on ICP-MS technology to solve the problems of soil selenium form analysis requiring pretreatment due to different matrices and inconsistent valence states, and large errors in analysis results.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for chemical form analysis of selenium in selenium-rich soil based on ICP-MS technology, comprising the following steps:

[0006] S1, preparation of extractant: prepare 250mL of 0.1mol / L KH2PO4-K2HPO4 solution, 250ml of 0.1mol / L K2S2O8 solution, and 400mL of 3mol / HCl solution;

[0007] S2, Extraction of soil selenium forms:

[0008] a. Water-soluble extract: weigh 1.0000g soil sample into a 15mL centrifuge tube, add 10mL distilled water, tighten the lid, place flat on an oscillator and shake for 1h, then centrifuge, take the supernatant and filter it with a 0.45um filter membrane into a 10mL centrifuge tube, add 0.2mL nitric acid, and place in a refrigerator for later use;

[0009] b. Ion exchange extract: add 10 mL of 0.1 mol / L KH2PO4-K2HPO4 solution to the centrifuge tube after taking the supernatant in step a, shake for 2 hours and centrifuge, take out the supernatant and filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use;

[0010] c. Acid-soluble extract: Add 10 mL of 3 mol / L HCl to the centrifuge tube after taking the supernatant in step b, heat in a constant temperature water bath at 90°C for 50 min, and take out the supernatant and filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use;

[0011] d. Organic matter bound extract: add 10 mL of 0.1 mol / L K2S2O8 to the centrifuge tube after taking the supernatant in step c, heat and shake in a 90°C constant temperature water bath for 2 h, then centrifuge for 20 min, take out the supernatant, filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use;

[0012] e. Residue state: Use 9 ml of mixed acid to wash the residue after taking the supernatant in step d into a 55 ml microwave digestion tank, place it in a microwave digestion instrument and digest it according to the set program. After the digestion is completed, place it on an acid remover and evaporate it at 140°C to about 1 ml, make it up to 50 ml with ultrapure water, dilute it 5 times with 2% nitric acid and store it for testing; the mixed acid includes 6 ml HNO3, 2 ml HCl and 1 ml HF;

[0013] S3, standard solution preparation:

[0014] a1. Preparation of water-soluble selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 1ml of concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0015] b1. Preparation of ion exchange selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 10ml 0.1mol / L KH2PO4-K2HPO4 and 1ml concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0016] c1. Preparation of acid-soluble selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 5ml of 3mol / L HCl, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0017] d1. Preparation of organically bound selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 5ml 0.1mol / L K2S2O8 and 1ml concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0018] e1. Preparation of residual selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 1ml of concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0019] (1) Water-soluble state without dilution;

[0020] (2) Dilute the ion exchange extract 5 times: Accurately pipette 2 ml of the ion exchange extract into a 10 ml plastic centrifuge tube, dilute to the mark with 2% HNO3, shake well, and wait for measurement.

[0021] (3) Dilute the acid-soluble and organic-bound extracts 10 times: pipette 1 ml of the acid-soluble extract and the organic-bound extract into corresponding 10 ml plastic centrifuge tubes, then dilute to the mark with 2% HNO3, shake well, and wait for testing;

[0022] S5, instrument debugging: using an inductively coupled plasma mass spectrometer (ICP-MS) after startup, vacuuming, ignition, tuning, method editing, and preheating until the instrument is stable, the standard solution series and selenium form extract are measured;

[0023] S6, Selenium concentration determination:

[0024] a2. Under the same operating conditions, the water-soluble selenium standard solution series and the sample water-soluble solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method;

[0025] b2. Under the same operating conditions, the ion exchange selenium standard solution series and the sample ion exchange dilution solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method;

[0026] c2. Under the same operating conditions, the acid-soluble selenium standard solution series and the sample acid-soluble dilution solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method;

[0027] d2. Under the same operating conditions, the organically bound selenium standard solution series and the sample organically bound selenium dilution solution were measured in sequence, and the selenium concentration of the sample solution was calculated using the standard curve method;

[0028] e2. Under the same operating conditions, the residual selenium standard solution series and the sample residual selenium solution were measured in sequence, and the selenium concentration of the sample solution was calculated using the standard curve method.

[0029] Beneficial effects of the present invention: The analytical method provided by the present invention utilizes ICP-MS technology and prepares an extracting liquid matrix that matches each form of extracting liquid, thereby eliminating the analytical error caused by the difference between each form of solution and the standard solution series, and at the same time reduces the cumbersome operation of pretreatment such as acid addition and heating of the extracting liquid in the form analysis, thereby reducing the potential analytical error, and the experimental results meet the requirements of form analysis. The method was used to analyze 10 selenium-rich soil samples, and the linear correlation coefficient of the standard curve was greater than 0.9998. The internal standard recovery rate of the sample solution determined by ICP-MS was between 85% and 110%, and the matrix effect of the selenium form extracting liquid was effectively controlled. The recovery rate of the soil selenium form analysis results (the ratio of the sum of each form of selenium to the total selenium in the soil) was between 87.2% and 109.7%, which fully met the quality requirements for soil selenium form analysis.

[0030] Furthermore, when shaking is performed in step a, the mixture is shaken at room temperature for 1 hour and then centrifuged at 4000 r / min for 20 minutes.

[0031] Furthermore, when shaking in step b, the mixture is shaken in the same manner at room temperature for 2 h and centrifuged at 4000 r / min for 20 min.

[0032] Furthermore, when shaking in step c, intermittent shaking is used, and then centrifugation is performed at a speed of 4000 r / min for 20 min.

[0033] Furthermore, in step d, the mixture is heated in a constant temperature water bath at 90° C. for 2 h with intermittent shaking, and then centrifuged at 4000 r / min for 20 min. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the water-soluble standard curve diagram in the embodiment;

[0035] Figure 2 It is the standard curve diagram of ion exchange state in the embodiment;

[0036] Figure 3 It is the acid-soluble standard curve diagram in the embodiment;

[0037] Figure 4 It is the standard curve diagram of organic binding state in the embodiment;

[0038] Figure 5 This is a standard curve diagram of the residue state in the examples. DETAILED DESCRIPTION

[0039] Implementation example Figure 1 ~Attached Figure 5 As shown:

[0040] A method for analyzing the chemical forms of selenium in selenium-rich soil based on ICP-MS technology comprises the following steps:

[0041] S1, preparation of extractant: prepare 250mL of 0.1mol / L KH2PO4-K2HPO4 solution, 250ml of 0.1mol / L K2S2O8 solution, and 400mL of 3mol / HCl solution;

[0042] S2, Extraction of soil selenium forms:

[0043] a. Water-soluble extract: weigh 1.0000g soil sample into a 15mL centrifuge tube, add 10mL distilled water, tighten the lid, place it flat on a Conn shaker at room temperature for 1h, then centrifuge at 4000r / min for 20min, take the supernatant and filter it with a 0.45um filter membrane into a 10mL centrifuge tube, add 0.2mL nitric acid, and place it in a refrigerator for later use;

[0044] b. Ion exchange extract: add 10 mL of 0.1 mol / L KH2PO4-K2HPO4 solution to the centrifuge tube after taking the supernatant in step a, oscillate for 2 h at room temperature, centrifuge at 4000 r / min for 20 min, take out the supernatant, filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use;

[0045] c. Acid-soluble extract: add 10 mL of 3 mol / L HCl to the centrifuge tube after taking the supernatant in step b, heat in a constant temperature water bath at 90°C for 50 min, and shake intermittently, then centrifuge at 4000 r / min for 20 min, take out the supernatant, filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use;

[0046] d. Organic matter bound extract: add 10 mL of 0.1 mol / L K2S2O8 to the centrifuge tube after taking the supernatant in step c, heat in a constant temperature water bath at 90°C for 2 h, and shake intermittently, then centrifuge at 4000 r / min for 20 min, take out the supernatant, filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use;

[0047] e. Residue state: Use 9 ml of mixed acid to wash the residue after taking the supernatant in step d into a 55 ml microwave digestion tank, place it in a microwave digestion instrument and digest it according to the set program. After the digestion is completed, place it on an acid remover and evaporate it at 140°C to about 1 ml, make it up to 50 ml with ultrapure water, dilute it 5 times with 2% nitric acid and store it for testing; the mixed acid includes 6 ml HNO3, 2 ml HCl and 1 ml HF;

[0048] S3, standard solution preparation:

[0049] a1. Preparation of water-soluble selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 1ml of concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0050] b1. Preparation of ion exchange selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 10ml 0.1mol / L KH2PO4-K2HPO4 and 1ml concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0051] c1. Preparation of acid-soluble selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 5ml of 3mol / L HCl, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0052] d1. Preparation of organically bound selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 5ml 0.1mol / L K2S2O8 and 1ml concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0053] e1. Preparation of residual selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 1ml of concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively;

[0054] S4, dilution of each form extract:

[0055] (1) Water-soluble state without dilution;

[0056] (2) Dilute the ion exchange extract 5 times: Accurately pipette 2 ml of the ion exchange extract into a 10 ml plastic centrifuge tube, dilute to the mark with 2% HNO3, shake well, and wait for measurement.

[0057] (3) Dilute the acid-soluble and organic-bound extracts 10 times: pipette 1 ml of the acid-soluble extract and the organic-bound extract into corresponding 10 ml plastic centrifuge tubes, then dilute to the mark with 2% HNO3, shake well, and wait for testing;

[0058] S5, instrument debugging: using an inductively coupled plasma mass spectrometer (ICP-MS) to perform sample determination after startup, vacuuming, ignition, tuning, and method editing;

[0059] S6, Selenium concentration determination:

[0060] a2. Under the same operating conditions, the water-soluble selenium standard solution series and the sample water-soluble solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method;

[0061] b2. Under the same operating conditions, the ion exchange selenium standard solution series and the sample ion exchange dilution solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method;

[0062] c2. Under the same operating conditions, the acid-soluble selenium standard solution series and the sample acid-soluble dilution solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method;

[0063] d2. Under the same operating conditions, the organically bound selenium standard solution series and the sample organically bound selenium dilution solution were measured in sequence, and the selenium concentration of the sample solution was calculated using the standard curve method;

[0064] e2. Under the same operating conditions, the residual selenium standard solution series and the sample residual selenium solution were measured in sequence, and the selenium concentration of the sample solution was calculated using the standard curve method.

[0065] Table 1 Selenium speciation analysis results and recovery rate statistics of selenium-rich soil

[0066]

[0067] It can be concluded from Table 1 that by preparing the extract matrix matching each form of extract, the analysis error caused by the difference between each form solution and the standard solution series is eliminated, and the cumbersome operation of pretreatment such as acid heating of the extract in the form analysis is reduced, which reduces the potential analysis error, and the experimental results meet the requirements of form analysis. This method was used to analyze 10 selenium-rich soil samples, and the linear correlation coefficient of the standard curve was greater than 0.9998. The recovery rate of the internal standard of the sample solution determined by ICP-MS was between 85% and 110%, and the matrix effect of the selenium form extract was effectively controlled. The recovery rate of the soil selenium form analysis results (the ratio of the sum of each form of selenium to the total selenium in the soil) was between 87.2% and 109.7%, which fully met the quality requirements of soil selenium form analysis.

Claims

1. A method for chemical speciation analysis of selenium in selenium-rich soil based on ICP-MS technology, characterized in that: The following steps are involved: S1, preparation of extractant: prepare 250mL of 0.1mol / L KH2PO4-K2HPO4 solution, 250ml of 0.1mol / L K2S2O8 solution, and 400mL of 3mol / HCl solution; S2, Extraction of soil selenium forms: a. Water-soluble extract: weigh 1.0000g soil sample into a 15mL centrifuge tube, add 10mL distilled water, tighten the lid, place flat on an oscillator and shake for 1h, then centrifuge, take the supernatant and filter it with a 0.45um filter membrane into a 10mL centrifuge tube, add 0.2mL nitric acid, and place in a refrigerator for later use; b. Ion exchange extract: add 10 mL of 0.1 mol / L KH2PO4-K2HPO4 solution to the centrifuge tube after taking the supernatant in step a, shake for 2 hours and centrifuge, take out the supernatant and filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use; c. Acid-soluble extract: Add 10 mL of 3 mol / L HCl to the centrifuge tube after taking the supernatant in step b, heat in a constant temperature water bath at 90°C for 50 min, and take out the supernatant, filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place in a refrigerator for later use; d. Organic matter bound extract: add 10 mL of 0.1 mol / L K2S2O8 to the centrifuge tube after taking the supernatant in step c, heat and shake in a 90°C constant temperature water bath for 2 hours, and then centrifuge for 20 minutes. Take out the supernatant and filter it with a 0.45 um filter membrane into a 10 mL centrifuge tube, add 0.2 mL of nitric acid, and place it in a refrigerator for later use; e. Residue state: Use 9 ml of mixed acid to wash the residue after taking the supernatant in step d into a 55 ml microwave digestion tank, place it in a microwave digestion instrument and digest it according to the set program. After the digestion is completed, place it on an acid remover and evaporate it at 140°C to about 1 ml, make it up to 50 ml with ultrapure water, dilute it 5 times with 2% nitric acid and store it for testing; the mixed acid includes 6 ml HNO3, 2 ml HCl and 1 ml HF; S3, standard solution preparation: a1. Preparation of water-soluble selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 1ml of concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively; b1. Preparation of ion exchange selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 10ml 0.1mol / L KH2PO4-K2HPO4 and 1ml concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively; c1. Preparation of acid-soluble selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 5ml of 3mol / L HCl, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively; d1. Preparation of organically bound selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 5ml 0.1mol / L K2S2O8 and 1ml concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively; e1. Preparation of residual selenium standard solution: add 0.0, 0.25, 0.5, 1.0, 5.0 ml of 500ug / L selenium standard working solution into five 50ml volumetric flasks, add 1ml of concentrated nitric acid, dilute to the scale with ultrapure water, shake well, the concentrations of this standard series of solutions are 0.0, 2.5, 5.0, 10.0, 50.0ug / L respectively; S4, dilution of each form extract: (1) Water-soluble state without dilution; (2) Dilute the ion exchange extract 5 times: Accurately pipette 2 ml of the ion exchange extract into a 10 ml plastic centrifuge tube, dilute to the mark with 2% HNO3, shake well, and wait for measurement. (3) Dilute the acid-soluble and organic-bound extracts 10 times: pipette 1 ml of the acid-soluble extract and the organic-bound extract into corresponding 10 ml plastic centrifuge tubes, then dilute to the mark with 2% HNO3, shake well, and wait for testing; S5, instrument debugging: using an inductively coupled plasma mass spectrometer (ICP-MS) after startup, vacuuming, ignition, tuning, method editing, and preheating until the instrument is stable, the standard solution series and selenium form extract are measured; S6, Selenium concentration determination: a2. Under the same operating conditions, the water-soluble selenium standard solution series and the sample water-soluble solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method; b2. Under the same operating conditions, the ion exchange selenium standard solution series and the sample ion exchange dilution solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method; c2. Under the same operating conditions, the acid-soluble selenium standard solution series and the sample acid-soluble dilution solution are measured in sequence, and the selenium concentration of the sample solution is calculated by the standard curve method; d2. Under the same operating conditions, the organically bound selenium standard solution series and the sample organically bound selenium dilution solution were measured in sequence, and the selenium concentration of the sample solution was calculated using the standard curve method; e2. Under the same operating conditions, the residual selenium standard solution series and the sample residual selenium solution were measured in sequence, and the selenium concentration of the sample solution was calculated using the standard curve method.

2. The method for chemical speciation analysis of selenium in selenium-rich soil based on ICP-MS technology according to claim 1, characterized in that: When shaking in step a, shake at room temperature for 1 hour, and then centrifuge at 4000 r / min for 20 minutes.

3. The method for chemical speciation analysis of selenium in selenium-rich soil based on ICP-MS technology according to claim 2, characterized in that: When shaking in step b, shake in the same manner at room temperature for 2 h, and centrifuge at 4000 r / min for 20 min.

4. The method for chemical speciation analysis of selenium in selenium-rich soil based on ICP-MS technology according to claim 3, characterized in that: When shaking in step c, intermittent shaking is used, and then centrifugation is performed at a speed of 4000 r / min for 20 min.

5. The method for chemical speciation analysis of selenium in selenium-rich soil based on ICP-MS technology according to claim 4, characterized in that: In step d, the mixture was heated in a constant temperature water bath at 90° C. for 2 h with intermittent shaking, and then centrifuged at 4000 r / min for 20 min.

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