Method for eliminating interference in determination of mass number of high-purity metal by ICP-MS

Abstract

The invention relates to a method for eliminating interference in ICP-MS (Inductively Coupled Plasma Mass Spectrometry) determination of high-purity metal mass number, which comprises the following steps: (1) sample digestion: carrying out acid digestion treatment on a high-purity metal sample to obtain a digestion solution; (2) mass number interference elimination: removing a matrix in the high-purity metal sample from the digestion solution by a chemical complexing, oxidation reduction, precipitation or ion exchange method; when the mass number of the trace element to be detected is easily interfered by polyatoms, eliminating the interference by the digestion solution through a chemical pretreatment means to obtain a separated liquid; and (3) sample determination: correcting errors caused by mass number interference in the separated liquid by adopting an internal standard method or a cold plasma technology, and then introducing ICP-MS (Inductively Coupled Plasma Mass Spectrometry) for trace element detection. The method is easy to operate and low in cost, interference, especially mass number interference, of the matrix elements in the high-purity metal sample to the trace elements to be measured can be effectively removed, and the accuracy of ICP-MS measurement is greatly improved.

Description

Technical Field

[0001] The invention relates to the fields of analytical chemistry and material analysis, and in particular to a method for eliminating interference in the determination of mass numbers of high-purity metals by ICP-MS. Background Art

[0002] Inductively coupled plasma mass spectrometry (ICP-MS) is a highly sensitive trace element analysis technique that is widely used in the fields of environment, geology, biology, and materials science. However, during the ICP-MS analysis process, the mass number signal is often interfered by the presence of a large number of coexisting elements in the sample matrix or isotope interference between the elements to be measured, which in turn affects the accuracy of the analysis results. Therefore, how to effectively eliminate these mass number interferences is a key issue in improving the accuracy of ICP-MS analysis. Although traditional physical shielding and collision / reaction cell technologies can partially eliminate interference, their effects are limited, especially in complex matrix samples, where interference elimination is still a difficulty. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for eliminating interference in the mass number of high-purity metals determined by ICP-MS, which can improve the accuracy of analysis results and has strong applicability.

[0004] In order to solve the above problems, the present invention discloses a method for eliminating interference in the determination of mass number of high-purity metals by ICP-MS, comprising the following steps: ⑴Sample digestion: The high-purity metal sample is subjected to acid digestion treatment to obtain a digestion solution; ⑵ Elimination of mass number interference: The digestion solution is used to remove the matrix in the high-purity metal sample by chemical complexation, oxidation-reduction, precipitation or ion exchange; when the trace element to be measured is susceptible to polyatomic interference mass number, the digestion solution is used to eliminate these interferences by chemical pretreatment means to obtain a separated liquid; ⑶Sample determination: The separated liquid can be introduced into ICP-MS for trace element detection after correcting the error caused by mass number interference using internal standard method or cold plasma technology.

[0005] The acid used for digestion in step (1) includes nitric acid, hydrochloric acid, hydrofluoric acid or a mixture thereof, and the acid concentration and the order of addition are optimized and matched according to the properties of the metal to be measured.

[0006] The complexing agent used in the step (2) chemical complexing method includes EDTA, DTPA or aminopolyacetic acid compounds.

[0007] The chemical pretreatment means in step (2) refers to oxidation-reduction, ion exchange resin or solvent extraction technology.

[0008] In step (3), the cold plasma technology includes adjusting the instrument radio frequency power or sampling depth.

[0009] Compared with the prior art, the present invention has the following advantages: 1. The present invention selectively removes or converts interfering elements by chemical pretreatment or changing radio frequency power, thereby effectively removing the interference of matrix elements in high-purity metal samples on the trace elements to be measured, especially mass number interference, greatly improving the accuracy of ICP-MS determination.

[0010] 2. Compared with other interference elimination methods (such as collision cell, reaction cell, etc.), the present invention can specifically eliminate specific interference caused by complex matrices, has stronger adaptability, and is suitable for a variety of high-purity metal samples.

[0011] 3. The present invention is simple to operate, has low cost, does not require expensive equipment improvements, can be implemented under existing laboratory conditions, and has high application value. DETAILED DESCRIPTION

[0012] A method for eliminating interference in the determination of mass number of high-purity metals by ICP-MS, comprising the following steps: ⑴Sample digestion: High-purity metal samples (such as copper, aluminum, titanium, etc.) are subjected to acid digestion treatment to obtain a digestion solution.

[0013] According to the characteristics of the metal, select a suitable acid or acid mixture. The acid used for digestion includes nitric acid, hydrochloric acid, hydrofluoric acid or a mixture thereof, and the acid concentration and order of addition are optimized and matched according to the properties of the metal to be tested to ensure complete dissolution of the sample.

[0014] The digestion process should be carried out in a clean environment to avoid the introduction of external impurities. For insoluble metals (such as titanium, etc.), high-pressure microwave digestion or melting method can be used to ensure complete dissolution of the sample.

[0015] ⑵ Elimination of mass number interference: In order to solve the interference of matrix elements in high-purity metal samples, the matrix in the digestion solution is removed by chemical complexation, oxidation-reduction, precipitation or ion exchange. When the trace elements to be measured are susceptible to multi-atomic interference (such as oxide ions, chloride ions, etc.) in mass number, the digestion solution is chemically pretreated to eliminate these interferences to improve the detection sensitivity of impurity elements, thus obtaining a separated liquid.

[0016] Among them: chemical pretreatment means refer to oxidation-reduction, ion exchange resin or solvent extraction technology.

[0017] Specific methods include: ① Complexing agent treatment: For base metals (such as copper, zinc, etc.) that easily form stable complexes with complexing agents, add appropriate complexing agents to complex the base elements and remove them from the solution.

[0018] The complexing agent used is a specific selective chelating agent, including EDTA, DTPA or aminopolyacetic acid compounds, to improve the separation efficiency.

[0019] ② Precipitation method to remove matrix elements: By adding appropriate precipitants (such as sodium hydroxide, barium sulfate, ammonia water, etc.), the matrix elements are made to form insoluble precipitates, and the matrix metal is removed by filtration or centrifugal separation.

[0020] ③ For elements that are prone to isotope interference (such as yttrium, strontium, neodymium, etc.), the interfering elements can be removed by ion exchange or extraction.

[0021] ④ Redox reaction: Add an appropriate amount of oxidant (such as hydrogen peroxide) or reductant (such as ascorbic acid) to control the redox state in the solution and convert the chemical form of the interfering substance into a form that does not interfere with ICP-MS determination.

[0022] ⑶Sample determination: The separated liquid can be introduced into ICP-MS for trace element detection after correcting the error caused by mass number interference using internal standard method or cold plasma technology.

[0023] Among them: cold plasma technology includes the adjustment of instrument RF power or sampling depth. By modifying the plasma operating parameters, reducing the ICP power (600-800W), increasing the carrier gas flow rate, lengthening the sampling depth, and reducing the polyatomic ion interference generated by argon gas, the background signal is significantly lower than the analytical signal, thereby making the sensitivity of trace iron, calcium, and potassium in the sample to be tested higher.

[0024] For interference caused by matrix elements or other impurity elements, internal standard elements are selected based on the similarity of the ionization characteristics of the interfering elements and the analyzed elements. The internal standard elements are used to correct instrument drift and signal fluctuations, further improving the measurement accuracy.

[0025] The present invention ensures highly sensitive detection results by optimizing the working parameters of ICP-MS (such as sampling depth, radio frequency power, etc.) and signal correction technology.

[0026] Example 1: Detection of trace amounts of arsenic (As) in high purity copper samples High-purity copper samples often contain trace amounts of arsenic. Due to the presence of the copper matrix, CCu and ArCl polyatomic ions may be generated during the ICP-MS detection process, interfering with the 75As signal. This embodiment removes the interference of the copper matrix through chemical pretreatment to achieve accurate detection of arsenic.

[0027] Steps: 1. Sample preparation: Take 1 gram of high-purity copper sample, weigh it accurately, and put it into a polytetrafluoroethylene digestion tank.

[0028] 2. Sample digestion: Add 10 mL of pure nitric acid (HNO3, extra pure) to the digestion tank to completely dissolve the copper sample.

[0029] Place the digestion tank in a high-pressure microwave digestion system, heat the tank from an initial temperature of 100 °C to 180 °C, and maintain the temperature for 30 minutes. During the entire digestion process, the lid of the digestion tank is tightly closed to prevent gas from escaping. Ensure that the copper sample is completely dissolved into a uniform solution. After the digestion is completed, take out the digestion tank and cool it naturally to room temperature.

[0030] 3. Matrix separation: Add an appropriate amount of EDTA solution (0.1 M) to the digestion solution to form a stable copper complex with EDTA. The amount of EDTA added is twice the molar amount of copper content in the digestion solution.

[0031] After stirring evenly, the solution is transferred to an ion exchange column (carboxylic acid type cation exchange resin) for separation. This step is used to remove the copper matrix through the combined action of the complexing agent and the resin.

[0032] 4. Elution and collection: Elute with an appropriate amount of deionized water and collect the separated solution in a clean polytetrafluoroethylene bottle. At this point, the arsenic element remains in the solution, while most of the copper matrix has been removed. Dilute the collected solution with deionized water to a 50 mL constant volume flask. Filter using a 0.22 μm filter membrane to remove possible tiny particles and obtain a clear test solution.

[0033] 5. ICP-MS determination: (1) Calibration standard curve Using a standard arsenic solution of known concentration, prepare a series of standard solutions of different concentrations (e.g., 0.1 ng / mL, 0.5 ng / mL, 1.0 ng / mL, 5.0 ng / mL), measure the signal intensity of the standard solution in ICP-MS, and plot a standard curve of arsenic concentration and signal intensity.

[0034] (2) Sample measurement The treated sample solution was injected into the ICP-MS instrument, the signal of mass number 75 (arsenic) was monitored, the signal intensity of the sample was recorded, and the concentration of arsenic was calculated using the standard curve.

[0035] (3) Internal standard calibration To compensate for matrix effects and instrument drift, an appropriate internal standard element Y was selected and an internal standard solution of known concentration was added to the sample and standard solution. During data processing, the arsenic signal was corrected according to the signal intensity of the internal standard element to ensure the accuracy and stability of the measurement results.

[0036] 6. Results Analysis and Verification According to the standard curve and the signal intensity after internal standard correction, the actual content of arsenic in the sample (in ng / mL) is calculated. According to the digestion and dilution process of the sample, the concentration of arsenic in the high-purity copper sample (in mg / kg or other appropriate units) is converted.

[0037] Perform recovery test: add a known amount of arsenic standard solution to the high purity copper sample, repeat the above steps, and calculate the recovery rate of arsenic (the spike recovery rate should be between 93% and 105%). See Table 1 for specific results: Table 1 Example 2: Detection of trace amounts of vanadium (V) in high purity aluminum samples When detecting trace amounts of vanadium in a high-purity aluminum sample, polyatomic ions (such as 35Cl, 16O) in the aluminum matrix may interfere with the signal of 51 V. In this embodiment, the interference of aluminum oxide ions is reduced by chemical oxidation to achieve accurate determination of vanadium.

[0038] Steps: 1. Sample preparation: Take 0.5 g of high-purity aluminum sample, weigh it accurately, and put it into a quartz digestion tube.

[0039] 2. Sample digestion: Add 5 mL of hydrofluoric acid (HF), 5 mL of hydrochloric acid (HCL) and 5 mL of nitric acid (HNO3) to the sample and heat at low temperature in a fume hood to digest until the sample is completely dissolved. The reagents used are of high purity.

[0040] 3. Matrix separation: After digestion, cool the solution to room temperature and transfer it into a 125mL separatory funnel. Add 10mL of 1% sodium fluoride solution and mix well. Adjust the solution pH to 3.5. Then add 20mL of 1% 8-hydroxyquinoline and isobutanol solution for extraction and separation.

[0041] 4. Oxidation treatment: Add 1 mL of 30% hydrogen peroxide (H2O2) solution and 3 mL of nitric acid (HNO3) solution to the organic phase solution, fully mix the vanadium in the oxidized sample, and convert it to a high oxidation state to reduce polyatomic interference.

[0042] 5. Dilution and filtration: Dilute the oxidized solution to 50 mL, make up to volume with deionized water, and filter through a 0.22 μm filter membrane to obtain a clear solution.

[0043] 6. ICP-MS determination: (1) Calibration standard curve Using a vanadium standard solution with known concentration, prepare a series of standard solutions with different concentrations (e.g., 0.1 ng / mL, 0.5 ng / mL, 1.0 ng / mL, 5.0 ng / mL), measure the signal intensity of the standard solution in ICP-MS, and draw a standard curve of vanadium concentration and signal intensity.

[0044] (2) Sample measurement The treated sample solution was injected into the ICP-MS instrument, the signal of mass number 51 (vanadium) was monitored, the signal intensity of the sample was recorded, and the concentration of vanadium was calculated using the standard curve.

[0045] 7. Result analysis: According to the standard curve and the signal intensity after internal standard correction, the actual content of vanadium in the sample (in ng / mL) is calculated. According to the digestion and dilution process of the sample, the concentration of vanadium in the high-purity aluminum sample (in mg / kg or other appropriate units) is converted.

[0046] Perform recovery test: add a known amount of vanadium standard solution to the high purity aluminum sample, repeat the above steps, and calculate the recovery rate of vanadium to show the reliability of the method. The specific results are shown in Table 2: Table 2 Example 3: Detection of trace amounts of selenium (Se) in high purity tellurium ingot samples High-purity tellurium ingot samples often contain trace amounts of selenium. Due to the presence of the matrix, polyatomic ions may be generated during ICP-MS detection, interfering with the signal of 80Se. In this embodiment, chemical pretreatment is performed to remove the interference of the tellurium matrix and achieve accurate detection of selenium.

[0047] Steps: 1. Sample preparation: Take 0.5000 g of high-purity tellurium ingot sample, weigh it accurately, and put it into a polytetrafluoroethylene digestion tank.

[0048] 2. Sample digestion: Add 6 mL of pure nitric acid (HNO3, high-grade purity) and 2 mL of hydrofluoric acid (HF) to the digestion tank, seal the digestion tank, and place it at 180 °C for 0.5 hour to ensure that the sample is completely dissolved.

[0049] Place the digestion tank in a high-pressure microwave digestion system, heat from an initial temperature of 100 °C to 180 °C, and maintain the temperature for 30 minutes. During the entire digestion process, the lid of the digestion tank is tightly closed to prevent gas from escaping. Ensure that the sample to be tested is completely dissolved into a uniform solution. After the digestion is completed, take out the digestion tank and cool it naturally to room temperature.

[0050] 3. Matrix separation: Adjust the acidity of the digestion solution to 3 mol / L and add an appropriate amount of hydroxylamine hydrochloride (NH2·OH·HCl) to selectively reduce selenium to elemental selenium precipitate, which can then be filtered out.

[0051] 4. Dilution: Use dilute nitric acid to dissolve and dilute, and then measure after constant volume.

[0052] 5. ICP-MS determination: (1) Calibration standard curve Use a selenium standard solution with known concentration to prepare a series of standard solutions with different concentrations (e.g., 0.1 ng / mL, 1.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL), measure the signal intensity of the standard solution in ICP-MS, and draw a standard curve of selenium concentration and signal intensity.

[0053] (2) Sample measurement The treated sample solution was injected into the ICP-MS instrument, the signal of mass number 80 (selenium) was monitored, the signal intensity of the sample was recorded, and the concentration of selenium was calculated using the standard curve.

[0054] (3) Internal standard calibration To compensate for matrix effects and instrument drift, an appropriate internal standard element Y was selected and an internal standard solution of known concentration was added to the sample and standard solution. During data processing, the selenium signal was corrected according to the signal intensity of the internal standard element to ensure the accuracy and stability of the measurement results.

[0055] 6. Results Analysis and Verification According to the standard curve and the signal intensity after internal standard correction, the actual content of selenium in the sample (in ng / mL) is calculated. According to the digestion and dilution process of the sample, the concentration of selenium in the high-purity tellurium ingot sample (in mg / kg or other appropriate units) is converted.

[0056] Perform recovery test: add a known amount of selenium standard solution to the tellurium ingot sample, repeat the above steps, and calculate the recovery of selenium (the spike recovery should be between 92% and 103%). See Table 3 for specific results: Table 3 Example 4: Detection of trace iron (Fe) in high purity ammonium rhenate powder samples High-purity ammonium rhenate samples often contain trace amounts of iron. Due to the presence of the matrix, polyatomic ions ArO are generated during ICP-MS detection, interfering with the signal of 56Fe. This embodiment changes the RF power to remove the interference of the rhenium matrix and achieve accurate detection of iron.

[0057] Steps: 1. Sample preparation: Take 0.5000 g of high-purity ammonium rhenate sample and accurately weigh it into a 100 mL beaker.

[0058] 2. Sample digestion: Add 10 mL of high-grade pure nitric acid (1+3) to a beaker, heat to completely dissolve the ammonium rhenate sample, cool to room temperature, add 10 mL of water and 0.5 mL (1%) tartaric acid solution while shaking, heat to a slight boil, remove and cool to ensure that the sample is completely dissolved.

[0059] 3. Matrix separation: Transfer the test solution into a 125mL separatory funnel, dilute the volume to 60mL with pure water, add 20mL of tributyl phosphate (TBP) organic solvent, keep the extraction volume and the water phase at 3:1, and shake in a constant temperature flip shaking extractor for 2 minutes. Let it stand to separate the layers, put the water phase into another separatory funnel, and perform cross-current extraction three times according to the above process. Collect the residual phase in a beaker, heat and concentrate it at low temperature, cool it, transfer it to a 50mL volumetric flask, dilute it to the scale with deionized water, mix it well and then measure it.

[0060] 4. Cold flame plasma condition setting: The RF power of the plasma condition was reduced to 800w, and the possibility of forming polyatomic ions based on argon was reduced by using low-temperature plasma. At the same time, the sampling depth was adjusted to 18mm. Using a larger sampling depth was beneficial to optimizing the sensitivity of the elements to be measured.

[0061] 5. ICP-MS determination: (1) Calibration standard curve Using a standard iron solution with known concentration, prepare a series of standard solutions with different concentrations (e.g., 0.5 ng / mL, 1.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL), measure the signal intensity of the standard solutions in ICP-MS, and plot a standard curve of iron concentration versus signal intensity.

[0062] (2) Sample measurement The treated sample solution was injected into the ICP-MS instrument, the signal of mass number 56 (iron) was monitored, the signal intensity of the sample was recorded, and the iron concentration was calculated using the standard curve.

[0063] (3) Internal standard calibration To compensate for matrix effects and instrument drift, an appropriate internal standard element Y was selected and an internal standard solution of known concentration was added to the sample and standard solution. During data processing, the iron signal was corrected according to the signal intensity of the internal standard element to ensure the accuracy and stability of the measurement results.

[0064] 6. Results Analysis and Verification According to the standard curve and the signal intensity after internal standard correction, the actual iron content in the sample (in ng / mL) is calculated. According to the digestion and dilution process of the sample, the iron concentration in the ammonium rhenate sample (in mg / kg or other appropriate units) is converted.

[0065] Perform recovery test: add a known amount of iron standard solution to the ammonium rhenate sample, repeat the above steps, and calculate the recovery of iron (the spike recovery should be between 92% and 98%). See Table 4 for specific results: Table 4

Claims

1. A method for eliminating interference in the determination of mass number of high-purity metals by ICP-MS, comprising the following steps: ⑴Sample digestion: The high-purity metal sample is subjected to acid digestion treatment to obtain a digestion solution; ⑵ Elimination of mass number interference: The digestion solution is used to remove the matrix in the high-purity metal sample by chemical complexation, oxidation-reduction, precipitation or ion exchange; When the trace element to be measured is susceptible to polyatomic interference mass numbers, the digestion solution is chemically pretreated to eliminate these interferences, thereby obtaining a separated liquid; ⑶Sample determination: The separated liquid can be introduced into ICP-MS for trace element detection after correcting the error caused by mass number interference using internal standard method or cold plasma technology.

2. The method for eliminating interference in determining the mass number of high-purity metals by ICP-MS as claimed in claim 1, characterized in that: The acid used for digestion in step (1) includes nitric acid, hydrochloric acid, hydrofluoric acid or a mixture thereof, and the acid concentration and the order of addition are optimized and matched according to the properties of the metal to be measured.

3. The method for eliminating interference in determining the mass number of high-purity metals by ICP-MS as claimed in claim 1, characterized in that: The complexing agent used in the step (2) chemical complexing method includes EDTA, DTPA or aminopolyacetic acid compounds.

4. The method for eliminating interference in determining the mass number of high-purity metals by ICP-MS as claimed in claim 1, characterized in that: The chemical pretreatment means in step (2) refers to oxidation-reduction, ion exchange resin or solvent extraction technology.

5. The method for eliminating interference in determining the mass number of high-purity metals by ICP-MS as claimed in claim 1, characterized in that: In step (3), the cold plasma technology includes adjusting the instrument radio frequency power or sampling depth.

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