The detection of impurity content in iron powder samples (atomic absorption flame method), due to the high main content of iron, has significant interference with the determination of most impurities. Therefore, the curve drawing using matrix matching method is relatively simple and appropriate. The content ratios of Ca, Co, Cr, Cu, K, Mg, Mn, Na, Ni, and Zn in the iron powder sample were determined, as well as the influence of iron on the measured elements.

Sample processing of iron powder:

1. Background (99.99% high-purity iron powder):

称取m₁=3.200g high-purity iron powder (99.985%) placed in 250mLIn a conical flask, moisten with a small amount of water and slowly add 60mLHydrochloric acid (shake the bottle while adding to prevent splashing due to violent reactions), after the reaction is stable, place it on an electric furnace and heat it at low temperature until the reaction stops (no longer bubbling), remove it and cool it down, then add 15%mLNitric acid, heat again until there is no obvious yellow smoke, remove and cool slightly, then add 12mLPerchloric acid, cover with a surface dish, then heat at high temperature on an electric furnace until white smoke is emitted (near dry state, yellow black color (oxidation)), remove and cool slightly, add 30mLHydrochloric acid, then heated on an electric furnace until dissolved, removed and cooled, and diluted to V with pure water₁=100mL.

2. Sample:

称取m₂=0.500g of iron powder to be tested is placed in a 250mL conical flask, moistened with a small amount of water, and slowly added to 10mLHydrochloric acid (shake the bottle while adding to prevent splashing due to violent reactions), after the reaction is stable, place it on an electric furnace and heat it at low temperature until the reaction stops (no longer bubbling), remove it and cool it down, then add 2.5mLNitric acid, heat again until there is no obvious yellow smoke, remove and cool slightly, then add 2mLPerchloric acid, cover with a surface dish, then heat at high temperature on an electric furnace until white smoke is emitted (near dry state, yellow black color (oxidation)), remove and cool slightly, add 5mLHydrochloric acid, then heated on an electric furnace until dissolved, removed and cooled, and diluted to V with pure water₂=100mL.

3. Sample dissolution analysis:

(1) Reduced iron powder: The sample appears bright gray with low viscosity. When hydrochloric acid is added, the reaction is intense and the dissolution is fast. This is metallic iron;

(2) Ultra pure iron powder: The sample is black in color, with high viscosity and easy aggregation. The reaction is weak when added to hydrochloric acid at room temperature and requires long-term low-temperature heating for dissolution. This sample should be iron oxide;

(3) After both were dissolved, there was a small amount of white precipitate, which may be a silicon-based substance. It can be filtered by constant volume and measured on the machine, and it should not affect the determination of other impurities.

4. Standard curve preparation (matrix matching method):

Matrix matching method:

The method of eliminating component interference by adding components with similar composition to the sample to the standard curve series concentration, in order to obtain the same or similar interference state as the sample.

Note: The added substance must be a high-purity substance that does not contain the element to be tested, or the composition of the substance to be tested is known.

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Ca in the sample

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Co in the sample

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Cr in the sample

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Cu in the sample

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K in the sample

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Mg in the sample

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Mn in the sample

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Na in the sample

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Ni in the sample

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Zn in the sample

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CAAM-2001E Six Lamp Flame/Graphite Furnace Atomic Absorption Spectrometer

The main interference in impurity detection in iron powder is the high content of iron ions, so it is only necessary to add iron content similar to the sample to the standard solution. The purity of the iron reference substance added in this test is 99.985%.

(1) Iron content W (mass fraction) of unknown sample iron powder: If the iron content is unknown, first measure the iron (conventional flame method) to obtain the mass fraction of iron;

Note: Iron testing must be prepared and diluted with 1% to 5% hydrochloric acid as the medium, otherwise the sample will be interfered with (different dilution ratios are not proportional). This test uses 2% hydrochloric acid as the medium.

(2) Add volume V to the background_x(ml): The final standard concentration is based on a constant volume of V₀Calculation, background addition amount V_x=(m₂×W×V₀×V₁)/(m₁×V₂）, in milliliters;

Note: After testing, the iron content of the sample is: 1. Reduced iron powder: 97%; 2. Ultra pure iron powder: 66%;

(3) If the standard series is calculated based on a fixed volume of 100, then:

① Reduced iron powder: The baseline addition amount is: (0.5 × 0.97 × 100 × 100)/(3.2 × 100)=15mL；

② Ultra pure iron powder: The baseline addition amount is: (0.5 × 0.66 × 100 × 100)/(3.2 × 100)=10mL；

5. Precautions:

(1) It is preferable for the added background iron powder to have an iron content of 99.9% or above, and to not contain the test substance or to have a known content of the test substance;

(2) If there is a substance to be tested, the concentration of the substance in the concentration series should be calculated based on the background addition amount, and the concentration value should be added when inputting the standard concentration at each point.

6. Test results:

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Beijing Haotianhui Instrument Co., Ltd. (hereinafter referred to as Haotianhui Instrument), founded in 1988, has been focusing on the research and manufacturing of spectral analysis instruments for more than 30 years. It was founded by Professor Wu Tingzhao, a well-known expert in China's atomic absorption analysis industry and the main researcher of early laboratory type atomic absorption spectrophotometers in China. It is a technology-based enterprise with independent intellectual property rights. Our main business covers the research and development, production, sales, and after-sales services of products such as atomic absorption spectrophotometers, atomic fluorescence spectrophotometers, UV visible spectrophotometers, flow injection hydride generators, and metal sheathed glass high-efficiency atomizers.

We have always adhered to the core concept of "focusing on instrument manufacturing and meeting customer needs", and have made unremitting efforts to continuously push the detection technology of domestic instruments to new heights, narrow the gap with foreign detection instruments, promote the development of domestic analytical instruments, and serve more customers.

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CAAM-2001H Eight Lamp Flame/Graphite Furnace Atomic Absorption Spectrometer

AFS-200 Fully Automatic Atomic Fluorescence Spectrometer

TS-5 dual beam UV visible spectrophotometer

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Beijing Haotianhui Instrument Co., Ltd