Preparation Method of Standard Sample of Impurity Element Silver

Abstract

Preparation method of silver standard sample for impurity elements, characterized in that it includes: preparation of reagent materials → solution preparation → preparation of silver powder → smelting of silver standard sample → secondary smelting → analysis test and value determination detection.

Description

Technical Field

[0001] The present invention relates to the technical field of precious silver detection technology for silver standard preparation, and specifically to a preparation method for silver standard samples of impurity elements. Background Art

[0002] In analytical chemistry, reference materials (RM) are an important part of laboratory quality control. Since silver purification is carried out by electrolysis - smelting method, and the other chemical components of silver ores in different regions also have large differences, the types and contents of impurities vary greatly. Therefore, it is difficult to use the purified silver as a standard sample for analysis. Currently, the common methods for analyzing and testing the impurity content of silver samples include GB / T 11067 - 2006 series, YS / T 958 - 2014, and ISO 15096 - 2020. Although there are requirements for the methods, laboratory analysis and testing usually do not involve silver standard samples, which has a great impact on quality control and restricts the development of silver detection technology. Summary of the Invention

[0003] (I) Technical Problems to be Solved

[0004] In view of the deficiencies of the prior art, the present invention discloses a preparation method for silver standard samples of impurity elements to solve the problems raised in the above background art.

[0005] (II) Technical Solutions

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A preparation method for silver standard samples of impurity elements, including:

[0007] Preparation of reagent materials → Solution preparation → Preparation of silver powder → Smelting of silver standard samples → Secondary smelting → Analytical testing and value determination.

[0008] Preferably, the material preparation includes the following materials:

[0009] S1: Hydrochloric acid: Guaranteed reagent grade, with a mass fraction of 36% - 38%;

[0010] S2: Nitric acid: Guaranteed reagent grade, with a mass fraction of 65% - 68%;

[0011] S3: Electrolytic silver powder: The silver content is not less than 999.9‰. Before use, the content of possible elements should be detected;

[0012] S4: Tartaric acid solution (100 g / L): Dissolve tartaric acid (analytical pure) in ultrapure water for standby;

[0013] S5: Disodium Edetate Solution (EDTA, 20 g / L): Dissolve EDTA (analytical grade) in ultrapure water for later use;

[0014] S6: Hydrazine hydrate: Analytical grade;

[0015] S7: High-purity graphite crucible, with a diameter of 70 mm and a volume of 500 mL;

[0016] S8: Activated carbon powder. Before use, the presence of elements such as bismuth, copper, iron, lead, palladium, antimony, selenium, and tellurium should be excluded;

[0017] S9: Straw rope. Before use, the presence of elements such as bismuth, copper, iron, lead, palladium, antimony, selenium, and tellurium should be excluded.

[0018] Preferably, the solution preparation includes the following steps:

[0019] Solution A: Bismuth nitrate solution. Accurately weigh a certain mass of bismuth nitrate pentahydrate (analytical grade) into a 150 mL beaker, add 5 mL of nitric acid and 20 mL of pure water, and heat at low temperature until completely dissolved; among them, for bismuth element, the reagent conversion coefficient is 2.3211, and the recovery coefficient is 0.55 - 0.75;

[0020] Solution B: Copper nitrate solution. Accurately weigh a certain mass of copper nitrate trihydrate (analytical grade) into a 150 mL beaker, add 2 mL of nitric acid and 10 mL of pure water, and heat at low temperature until completely dissolved. Among them, for copper element, the reagent conversion coefficient is 3.8017, and the recovery coefficient is 0.35 - 0.45;

[0021] Solution C: Iron nitrate solution. Accurately weigh a certain mass of iron nitrate nonahydrate (analytical grade) into a 150 mL beaker, add 2 mL of nitric acid and 10 mL of pure water, and heat at low temperature until completely dissolved. Among them, for iron element, the reagent conversion coefficient is 7.2335, and the recovery coefficient is 0.30 - 0.50;

[0022] Solution D: Lead nitrate solution. Accurately weigh a certain mass of lead nitrate (analytical grade) into a 150 mL beaker, add 5 mL of nitric acid and 20 mL of pure water, and heat at low temperature until completely dissolved. Among them, for lead element, the reagent conversion coefficient is 1.5984, and the recovery coefficient is 0.40 - 0.60;

[0023] Solution E: Palladium solution. Weigh accurately a certain mass of palladium powder (palladium content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of hydrochloric acid and 5 mL of nitric acid, heat it at a low temperature until completely dissolved, add 2 mL of disodium ethylenediaminetetraacetate solution (20 g / L), evaporate it at 160 °C until the solution remains about 2 mL, then add 5 mL of nitric acid and 2 mL of disodium ethylenediaminetetraacetate solution (20 g / L), evaporate it at 160 °C until the solution remains about 2 mL, add 10 mL of ultrapure water, and heat it at a low temperature for 2 min. Among them, for palladium element, the recovery coefficient is 0.70 - 0.85;

[0024] Solution F: Antimony solution. Weigh accurately a certain mass of antimony powder (antimony content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 10 mL of nitric acid and 2 mL of tartaric acid (100 g / L), heat it until completely dissolved, add 10 mL of ultrapure water, and heat it at a low temperature for 2 min. Among them, for antimony element, the recovery coefficient is 0.25 - 0.40;

[0025] Solution G: Selenium solution. Weigh accurately a certain mass of selenium powder (selenium content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of nitric acid and 5 mL of ultrapure water, heat it at a low temperature until completely dissolved. Among them, for selenium element, the recovery coefficient is 0.85 - 1.00;

[0026] Solution H: Tellurium solution. Weigh accurately a certain mass of tellurium powder (tellurium content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of nitric acid and 5 mL of ultrapure water, heat it at a low temperature until completely dissolved. Among them, for tellurium element, the recovery coefficient is 0.80 - 0.95.

[0027] Preferably, the calculation formula for the weighed mass in the solution preparation is:

[0028] Mass to be weighed (g) = Mass of silver (g) × Expected content of element to be weighed (%) × Reagent conversion coefficient ÷ Recovery coefficient × 100%.

[0029] Preferably, the preparation of the silver powder includes dissolving electrolytic silver powder and reducing silver nitrate solution;

[0030] S1: Dissolving electrolytic silver powder

[0031] Weigh no more than 500 g of electrolytic silver powder into a 1000 mL beaker, add 100 mL of ultrapure water, then slowly add 50 mL of nitric acid, carefully heat it at a low temperature until the solution tends to be calm; then slowly add 50 mL of nitric acid and 50 mL of ultrapure water in turn, carefully heat it at a low temperature until the solution tends to be calm, repeat several times until the electrolytic silver powder is basically completely dissolved, cool it sufficiently. At this time, the volume of the silver nitrate solution should not exceed 600 mL, and the volume of nitric acid added should not exceed 300 mL;

[0032] S2: Reduce the silver nitrate solution

[0033] Transfer the pre-prepared solutions A - H to the silver nitrate solution with pure water, stir evenly, transfer the above mixed solution to a 3000 mL beaker, and slowly add hydrazine hydrate (analytical pure) dropwise with a burette while continuously stirring rapidly until the liquid changes from a black turbid solution to a colorless or light yellow transparent solution and granular silver powder can be seen. The liquid addition rate should be controlled during this process to prevent the solution from boiling violently due to heat release;

[0034] Add 50 mL of hydrazine hydrate to the above solution, let it stand and cool overnight, and stir rapidly for a few minutes every few hours to fully expel the bubbles in the solution and break up the granular silver powder. Then decant the supernatant. The initial supernatant should be retained. Transfer 10 mL into a 100 mL volumetric flask, slowly and carefully add 20 mL of hydrochloric acid, and make up the volume to the mark after cooling. Measure it on a machine and calculate the amount of unreduced impurity elements in the supernatant to adjust the element recovery coefficient. Add 2000 mL of hot water to the silver powder, stir rapidly for 3 - 5 minutes, let it stand for 1 hour and then decant the supernatant. Repeat this twice; Put the silver powder together with the beaker into an oven and dry it completely at 105℃ to remove the moisture, then take it out for standby.

[0035] Preferably, the standard sample for smelting silver includes three steps: pretreatment, sample preparation, and sample cleaning and treatment.

[0036] Preferably, the specific implementation steps include:

[0037] S1: Pretreatment

[0038] Cover the bottom of a high-purity graphite crucible with a layer of activated carbon powder 2 - 3 mm thick, carefully transfer the silver powder to the graphite crucible and spread it flat, then cover the silver powder with another layer of activated carbon powder 2 - 3 mm thick. Tie the pre-prepared straw rope into a knot, place it at the opening of the graphite crucible, roll it up to cover the mouth of the graphite crucible, and then cover the graphite crucible lid;

[0039] S2: Sample preparation

[0040] Place the prepared graphite crucible into a muffle furnace preheated to 1000℃ and maintained at this temperature for more than 30 minutes, and melt it for 10 minutes. Cut off the power, open the furnace door, gently shake the crucible in the muffle furnace with crucible tongs (10 turns counterclockwise and 10 turns clockwise respectively), close the furnace door, and continue to heat up to 1000℃. Repeat the above operation every 5 minutes within the subsequent 15 minutes, a total of 3 times. Take out the graphite crucible and place it on a horizontal iron plate, and cool the iron plate with running water to rapidly reduce the temperature;

[0041] S3: Sample cleaning and treatment

[0042] After sufficient cooling, take out the silver standard sample, brush the carbon ash on the silver ingot with soap, wash it, then put it into hot 5% hydrochloric acid and boil for several minutes, rinse it thoroughly with ultrapure water, clean it with absolute ethanol or acetone, dry it at a low temperature of 65°C, wrap it with filter paper, roll it into thin slices, and store it in a sealed / vacuum state.

[0043] Preferably, the specific implementation steps of the secondary smelting are as follows: First, after the silver standard sample is analyzed and tested, if lower-content impurity elements are required, or if there are doubts about the sample uniformity due to too high impurity content, or if a series of silver standard samples need to be prepared, then cut the thin slice of the silver standard sample into small pieces smaller than 5 mm × 5 mm, and add an appropriate amount of electrolytic silver powder and mix well. Just repeat the operations according to steps 3.1 to 3.3 once.

[0044] Preferably, the silver standard sample is recommended to verify its element content and uniformity by using the international standard method ISO 15096-2020 and the industry standard method YS / T 958-2014, and it is recommended to send the sample to two laboratories with relevant qualifications for result comparison and sample value determination.

[0045] The present invention discloses a preparation method of a silver standard sample for impurity elements, and its beneficial effects are as follows:

[0046] 1. The present invention uses a silver nitrate solution mixed with impurity elements to react with hydrazine hydrate to generate silver powder containing impurity elements, and then smelts a silver standard sample through a reducing closed system generated by carbon / carbon monoxide in a graphite crucible at high temperature. According to research, there is currently no series of silver standard samples containing eight impurity elements with controllable content within a certain range for laboratory analysis and testing. The present invention successfully proposes the principle and method for preparing a silver standard sample containing eight common impurity elements, and prepares a series of silver standard samples with good uniformity, customizable elements and values, and meeting the requirements of laboratory analysis and testing, filling the blank in the market demand for silver standard samples.

[0047] 2. The silver nitrate solution adopted in the present invention is easy to react with a solution containing chloride ions to generate silver chloride precipitation, which then adsorbs impurity elements such as palladium, causing insufficient and uneven reduction and difficult smelting. And common commercially available standard element solutions (such as platinum, palladium, gold, antimony, etc.) often use chloride ions as stabilizers, making it impossible to fully mix the above two. The present invention adopts a method of combining nitric acid with complexing stabilizers (such as tartaric acid, EDTA, etc.) to form a stable solution mainly in a nitric acid medium, providing a solution and idea for related silver solution preparation technologies. Specific embodiments

[0048] Example 1

[0049] The embodiment of the present invention discloses a preparation method of a silver standard sample for impurity elements, including:

[0050] Preparation of reagent materials → Solution preparation → Preparation of silver powder → Melting of silver standard sample → Secondary melting → Analysis testing and certification

[0051] The said material preparation includes the following materials:

[0052] S1: Hydrochloric acid: GR, mass fraction 36%;

[0053] S2: Nitric acid: GR, mass fraction 65%;

[0054] S3: Electrolytic silver powder: silver content not less than 999.9‰, the content of possible existing elements should be detected before use;

[0055] S4: Tartaric acid solution (100g / L): Dissolve tartaric acid (AR) in ultrapure water for standby;

[0056] S5: Disodium ethylenediaminetetraacetate solution (EDTA, 20g / L): Dissolve EDTA (AR) in ultrapure water for standby;

[0057] S6: Hydrazine hydrate: AR;

[0058] S7: High-purity graphite crucible, diameter 70mm, volume 500mL;

[0059] S8: Activated carbon powder, the presence of elements such as bismuth, copper, iron, lead, palladium, antimony, selenium, tellurium, etc. should be excluded before use;

[0060] S9: Straw rope, the presence of elements such as bismuth, copper, iron, lead, palladium, antimony, selenium, tellurium, etc. should be excluded before use.

[0061] The said solution preparation includes the following steps:

[0062] Solution A: Bismuth nitrate solution, accurately weigh a certain mass of bismuth nitrate pentahydrate (AR) into a 150mL beaker, add 5mL nitric acid and 20mL pure water, and heat at low temperature until completely dissolved; among them, for bismuth element, the reagent conversion coefficient is 2.3211 and the recovery coefficient is 0.55;

[0063] Solution B: Copper nitrate solution, accurately weigh a certain mass of copper nitrate trihydrate (AR) into a 150mL beaker, add 2mL nitric acid and 10mL pure water, and heat at low temperature until completely dissolved, among which, for copper element, the reagent conversion coefficient is 3.8017 and the recovery coefficient is 0.35;

[0064] Solution C: Ferric nitrate solution. Weigh accurately a certain mass of ferric nitrate nonahydrate (analytical pure) into a 150 mL beaker, add 2 mL of nitric acid and 10 mL of pure water, and heat it at a low temperature until completely dissolved. For iron element, the reagent conversion coefficient is 7.2335 and the recovery coefficient is 0.30;

[0065] Solution D: Lead nitrate solution. Weigh accurately a certain mass of lead nitrate (analytical pure) into a 150 mL beaker, add 5 mL of nitric acid and 20 mL of pure water, and heat it at a low temperature until completely dissolved. For lead element, the reagent conversion coefficient is 1.5984 and the recovery coefficient is 0.40;

[0066] Solution E: Palladium solution. Weigh accurately a certain mass of palladium powder (palladium content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of hydrochloric acid and 5 mL of nitric acid, heat it at a low temperature until completely dissolved, add 2 mL of disodium ethylenediaminetetraacetate solution (20 g / L), evaporate it at 160 °C until the solution remains about 2 mL, then add 5 mL of nitric acid and 2 mL of disodium ethylenediaminetetraacetate solution (20 g / L), evaporate it at 160 °C until the solution remains about 2 mL, add 10 mL of ultrapure water, and heat it at a low temperature for 2 min. For palladium element, the recovery coefficient is 0.70;

[0067] Solution F: Antimony solution. Weigh accurately a certain mass of antimony powder (antimony content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 10 mL of nitric acid and 2 mL of tartaric acid (100 g / L), heat it until completely dissolved, add 10 mL of ultrapure water, and heat it at a low temperature for 2 min. For antimony element, the recovery coefficient is 0.25 - 0.40;

[0068] Solution G: Selenium solution. Weigh accurately a certain mass of selenium powder (selenium content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of nitric acid and 5 mL of ultrapure water, and heat it at a low temperature until completely dissolved. For selenium element, the recovery coefficient is 0.85;

[0069] Solution H: Tellurium solution. Weigh accurately a certain mass of tellurium powder (tellurium content greater than 99.9%) into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of nitric acid and 5 mL of ultrapure water, and heat it at a low temperature until completely dissolved. For tellurium element, the recovery coefficient is 0.80.

[0070] The formula for calculating the mass to be weighed for solution preparation is:

[0071] Mass to be weighed (g) = Mass of silver (g) × Expected content of element to be weighed (%) × Reagent conversion coefficient ÷ Recovery coefficient × 100%.

[0072] Preferably, the preparation of the silver powder includes dissolving electrolytic silver powder and reducing silver nitrate solution;

[0073] S1: Dissolving electrolytic silver powder

[0074] Weigh no more than 500 g of electrolytic silver powder into a 1000 mL beaker, add 100 mL of ultrapure water, then slowly add 50 mL of nitric acid, and carefully heat it at a low temperature until the solution tends to be calm; then slowly add 50 mL of nitric acid and 50 mL of ultrapure water in turn, and carefully heat it at a low temperature until the solution tends to be calm. Repeat several times until the electrolytic silver powder is basically completely dissolved, and cool it sufficiently. At this time, the volume of the silver nitrate solution should not exceed 600 mL, and the volume of the added nitric acid should not exceed 300 mL;

[0075] S2: Reducing silver nitrate solution

[0076] Transfer the pre-prepared solutions A - H to the silver nitrate solution with pure water, stir evenly, transfer the above mixed solution to a 3000 mL beaker, and slowly add hydrazine hydrate (analytical pure) with a burette at a constant speed while continuously stirring rapidly until the liquid changes from a black turbid solution to a colorless or light yellow transparent solution and granular silver powder can be seen. The liquid addition speed should be controlled during this process to prevent the solution from generating violent boiling due to heat release;

[0077] Add 50 mL of hydrazine hydrate to the above solution, let it stand and cool overnight, and stir rapidly for a few minutes every few hours to fully expel the bubbles in the solution and break up the granular silver powder. Then decant the supernatant. The initial supernatant should be retained. Transfer 10 mL into a 100 mL volumetric flask, slowly and carefully add 20 mL of hydrochloric acid, make up the volume after cooling, measure it on a machine and calculate the amount of unreduced impurity elements in the supernatant to adjust the element recovery coefficient. Add 2000 mL of hot water to the silver powder, stir rapidly for 3 - 5 minutes, let it stand for 1 hour and then decant the supernatant. Repeat twice; put the silver powder together with the beaker into an oven and dry it completely at 105 °C to remove moisture, then take it out for standby.

[0078] The smelting silver standard sample includes three steps: pretreatment, sample preparation, and cleaning and treatment of the sample.

[0079] Preferably, the following are the specific implementation steps:

[0080] S1: Pretreatment

[0081] Cover the bottom of a high-purity graphite crucible with a layer of activated carbon powder 2 - 3 mm thick, carefully transfer the silver powder to the graphite crucible and spread it flat, then cover the silver powder with another layer of activated carbon powder 2 - 3 mm thick. Tie a knot in the pre-prepared straw rope, place it at the opening of the graphite crucible, roll it up to cover the mouth of the graphite crucible, and cover the graphite crucible lid;

[0082] S2: Sample preparation

[0083] Place the prepared graphite crucible into a muffle furnace preheated to 1000 °C and kept at this temperature for more than 30 min, and melt for 10 min. Cut off the power, open the furnace door, gently shake the crucible in the muffle furnace with crucible tongs (10 turns counterclockwise and 10 turns clockwise respectively), close the furnace door, and continue heating to 1000 °C. Repeat the above operation every 5 min within the subsequent 15 min for a total of 3 times. Take out the graphite crucible and place it on a horizontal iron plate, and cool the iron plate with running water to rapidly cool down;

[0084] S3: Cleaning and treatment of samples

[0085] After sufficient cooling, take out the silver standard sample, brush the carbon ash on the silver ingot with soap, wash it clean, place it in hot 5% hydrochloric acid and boil for several minutes, rinse it thoroughly with ultrapure water, clean it with absolute ethanol or acetone, dry it at a low temperature of 65 °C, wrap it with filter paper, roll it into thin slices, and then store it sealed / vacuum.

[0086] The specific implementation steps of the secondary smelting are as follows: First, after the silver standard sample is analyzed and tested, if lower content of impurity elements is required, or if there is doubt about the sample uniformity due to too high impurity content, or if a series of silver standard samples need to be prepared, then cut the silver standard sample thin slices into small pieces smaller than 5 mm × 5 mm, and add an appropriate amount of electrolytic silver powder and mix well. Just repeat the operations according to steps 3.1 - 3.3 once.

[0087] The above-mentioned analysis and testing and value determination and detection are to verify the element content and uniformity of the silver standard sample by using international standard methods and industry standard methods.

[0088] Example 2

[0089] According to the above solution of Example 1: Weigh 300.12 g of electrolytic silver powder (determined by YS / T 958-2014 and calculated by the difference method to have a silver content greater than 99.992%) and place it in a 1000 mL beaker. Add a total of 300 mL of ultrapure water and 200 mL of nitric acid (superior grade pure) in several portions to dissolve the electrolytic silver powder to form a silver nitrate solution. Weigh the corresponding reagents according to Table 1 to prepare Solutions A to H, wash them into the silver nitrate solution with ultrapure water, stir evenly, and transfer to a 3000 mL beaker. Slowly add about 500 mL of hydrazine hydrate using a 50 mL burette and assist with rapid stirring until the liquid changes from a black turbid solution to a colorless or light yellow transparent solution and granular silver powder can be seen. Add an additional 50 mL of hydrazine hydrate, stir once every 2 h, and let it stand overnight. Wash the silver powder twice with hot water and dry it. Place it in a graphite crucible pre-lined with activated carbon powder, and then lay another layer of activated carbon. Add a straw rope to cover the crucible mouth and cover it with a graphite crucible lid. Transfer the graphite crucible to a 1000 °C muffle furnace for melting. Gently shake the crucible several times during the process. After 25 min, take it out and place it on a horizontal iron plate to cool the iron plate with running water. Pour out the silver standard sample, clean it, roll it into a thin sheet and conduct tests. The test results are shown in Table 2 (determined by the YS / T 958-2014 method) and Table 3 (determined by the ISO 15096-2020 method).

[0090] The comparison of experimental parameters is as follows:

[0091]

[0092]

[0093]

[0094] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Preparation method of silver standard sample for impurity element, characterized in that, Including: Preparation of reagent materials → Solution preparation → Preparation of silver powder → Melting of silver standard sample → Secondary melting → Analytical testing and certification; The material preparation includes the following materials: S1: Hydrochloric acid: GR (Guaranteed Reagent), mass fraction is 36% - 38%; S2: Nitric acid: GR, mass fraction is 65% - 68%; S3: Electrolytic silver powder: silver content is not less than 999.9‰, and the content of possible elements should be detected before use; S4: Tartaric acid solution: Dissolve tartaric acid in ultrapure water for standby; S5: Disodium ethylenediaminetetraacetate solution: Dissolve EDTA in ultrapure water for standby; S6: Hydrazine hydrate: AR (Analytical Reagent); S7: High-purity graphite crucible, with a diameter of 70mm and a volume of 500mL; S8: Activated carbon powder, the presence of bismuth, copper, iron, lead, palladium, antimony, selenium, and tellurium elements should be excluded before use; S9: Straw rope, the presence of bismuth, copper, iron, lead, palladium, antimony, selenium, and tellurium elements should be excluded before use; The solution preparation includes the following steps: Solution A: Bismuth nitrate solution. Accurately weigh a certain mass of bismuth nitrate pentahydrate in a 150mL beaker, add 5mL of nitric acid and 20mL of pure water, and heat it at low temperature until completely dissolved; among them, for bismuth element, the reagent conversion coefficient is 2.3211, and the recovery coefficient is 0.55 - 0.75; Solution B: Copper nitrate solution. Accurately weigh a certain mass of copper nitrate trihydrate in a 150mL beaker, add 2mL of nitric acid and 10mL of pure water, and heat it at low temperature until completely dissolved. Among them, for copper element, the reagent conversion coefficient is 3.8017, and the recovery coefficient is 0.35 - 0.45; Solution C: Iron nitrate solution. Accurately weigh a certain mass of iron nitrate nonahydrate in a 150mL beaker, add 2mL of nitric acid and 10mL of pure water, and heat it at low temperature until completely dissolved. Among them, for iron element, the reagent conversion coefficient is 7.2335, and the recovery coefficient is 0.30 - 0.50; Solution D: Lead nitrate solution. Accurately weigh a certain mass of lead nitrate in a 150mL beaker, add 5mL of nitric acid and 20mL of pure water, and heat it at low temperature until completely dissolved. Among them, for lead element, the reagent conversion coefficient is 1.5984, and the recovery coefficient is 0.40 - 0.60; Solution E: Palladium solution. Accurately weigh a certain mass of palladium powder in a 150mL beaker, moisten it with a small amount of water, add 5mL of hydrochloric acid and 5mL of nitric acid, heat it at low temperature until completely dissolved, add 2mL of disodium ethylenediaminetetraacetate solution, evaporate at 160℃ until the solution remains about 2mL, then add 5mL of nitric acid and 2mL of disodium ethylenediaminetetraacetate solution, evaporate at 160℃ until the solution remains about 2mL, add 10mL of ultrapure water, and heat it at low temperature for 2min. Among them, for palladium element, the recovery coefficient is 0.70 - 0.85; Solution F: Antimony solution. Weigh accurately a certain mass of antimony powder into a 150 mL beaker, moisten it with a small amount of water, add 10 mL of nitric acid and 2 mL of tartaric acid, heat until completely dissolved, add 10 mL of ultrapure water, and heat at low temperature for 2 min. Among them, for antimony element, the recovery coefficient is 0.25 - 0.40; Solution G: Selenium solution. Weigh accurately a certain mass of selenium powder into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of nitric acid and 5 mL of ultrapure water, heat at low temperature until completely dissolved. Among them, for selenium element, the recovery coefficient is 0.85 - 1.00; Solution H: Tellurium solution. Weigh accurately a certain mass of tellurium powder into a 150 mL beaker, moisten it with a small amount of water, add 5 mL of nitric acid and 5 mL of ultrapure water, heat at low temperature until completely dissolved. Among them, for tellurium element, the recovery coefficient is 0.80 - 0.95; The preparation of the silver powder includes dissolving electrolytic silver powder and reducing silver nitrate solution; S1: Dissolve electrolytic silver powder Weigh no more than 500 g of electrolytic silver powder into a 1000 mL beaker, add 100 mL of ultrapure water, then slowly add 50 mL of nitric acid, and carefully heat at low temperature until the solution tends to be calm; then slowly add 50 mL of nitric acid and 50 mL of ultrapure water in turn, and carefully heat at low temperature until the solution tends to be calm. Repeat several times until the electrolytic silver powder is basically completely dissolved, and cool it sufficiently. At this time, the volume of the silver nitrate solution should not exceed 600 mL, and the volume of the added nitric acid should not exceed 300 mL; S2: Reduce silver nitrate solution Transfer the pre-prepared Solutions A - H to the silver nitrate solution with pure water, stir evenly, transfer the above mixed solution to a 3000 mL beaker, and use a burette to slowly add hydrazine hydrate uniformly and continuously stir rapidly until the liquid changes from a black turbid solution to a colorless or light yellow transparent solution and granular silver powder can be seen. The liquid addition speed should be controlled during this process to prevent the solution from generating violent boiling due to heat release; Add 50 mL of hydrazine hydrate to the above solution, let it stand and cool overnight, and stir rapidly for a few minutes every few hours to drive out the bubbles in the solution and break up the granular silver powder. Then decant the supernatant. The initial supernatant should be retained. Pipette 10 mL into a 100 mL volumetric flask, slowly and carefully add 20 mL of hydrochloric acid, and make up the volume after cooling. Measure on the machine and calculate the amount of unreduced impurity elements in the supernatant to adjust the element recovery coefficient. Add 2000 mL of hot water to the silver powder, stir rapidly for 3 - 5 minutes, let it stand for 1 hour and then decant the supernatant. Repeat twice; Put the silver powder together with the beaker into the oven and dry it completely at 105 °C to remove the moisture, then take it out for standby.

2. The preparation method of the silver standard sample of impurity element according to claim 1, characterized in that: The calculation formula for the mass to be weighed in the preparation of the solution is: Mass to be weighed = Mass of silver × Expected content of the element to be weighed × Reagent conversion coefficient ÷ Recovery coefficient × 100%.

3. The preparation method of the silver standard sample of impurity elements according to claim 1, characterized in that: The melting of the silver standard sample includes three steps: pretreatment, sample preparation, and cleaning and treatment of the sample.

4. The preparation method of the impurity element silver standard sample according to claim 3, characterized in that: The melting of the silver standard sample includes the following specific implementation steps: S1: Pretreatment Cover the bottom of a high-purity graphite crucible with a layer of activated carbon powder 2-3 mm thick. Carefully transfer the silver powder into the graphite crucible and spread it evenly. Then, lay another layer of activated carbon powder 2-3 mm thick on the silver powder. Tie the pre-prepared straw rope into a knot and place it at the opening of the graphite crucible. Roll it up to cover the mouth of the graphite crucible, and then cover the graphite crucible lid. S2: Sample preparation Place the prepared graphite crucible into a muffle furnace that has been pre-heated to 1000 °C and held at this temperature for over 30 minutes. Melt for 10 minutes, cut off the power, open the furnace door, gently shake the crucible inside the muffle furnace with crucible tongs, close the furnace door, continue heating to 1000 °C, and repeat the above operation every 5 minutes within the subsequent 15 minutes, for a total of 3 times. Take out the graphite crucible and place it on a horizontal iron plate, and cool the iron plate with running water to rapidly cool down. S3: Cleaning and treatment of the sample After sufficient cooling, take out the silver standard sample, scrub the carbon ash on the silver ingot with soap, wash it clean, place it in hot 5% hydrochloric acid and boil for several minutes, rinse it thoroughly with ultrapure water, clean it with absolute ethanol or acetone, dry it at a low temperature of 65 °C, wrap it with filter paper, roll it into a thin sheet, and then store it sealed / vacuum.

5. The preparation method of the impurity element silver standard sample according to claim 1, characterized in that: The specific implementation steps of the secondary smelting are as follows: First, after the silver standard sample has been analyzed and tested, if lower impurity element content is required, or if there are doubts about the sample uniformity due to excessive impurity content, or if a series of silver standard samples need to be prepared, then cut the silver standard sample thin sheet into small pieces smaller than 5 mm × 5 mm, and add an appropriate amount of electrolytic silver powder and mix well. The preparation steps of the silver powder can be repeated once.

6. The preparation method of the standard sample of impurity element silver according to claim 1, characterized in that: The analysis and testing and certification testing are to verify the element content and uniformity of the silver standard sample using international standard methods and industry standard methods.

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