A method for determining trace selenium in zinc arsenide based on selenium arsenic coprecipitation separation

Abstract

The application discloses a method for determining trace selenium in zinc arsenide based on selenium-arsenic co-precipitation separation, which comprises the following steps: decomposing a zinc arsenide sample by using an acid mixed reagent to obtain a sample solution; adding a co-precipitation carrier and a reducing agent into the sample solution, and heating to make selenium ions and arsenic ions in the solution be co-reduced into elemental substances and form a precipitate; dissolving the precipitate by using an oxidizing acid to obtain a to-be-tested solution; and determining the selenium content in the to-be-tested solution by using a spectrophotometry method. The application effectively eliminates the interference by means of selenium-arsenic co-precipitation separation pretreatment, and solves the technical problems that the zinc arsenide matrix contains a very high amount of arsenic and seriously interferes with the determination of selenium. The method is simple in operation, low in cost, high in precision and accuracy (RSD is less than 6%, and the recovery rate is 90.8%-106.2%), and is suitable for popularization in production enterprises and conventional laboratories.

Description

Technical Field

[0001] This invention relates to the field of analytical detection technology, and specifically to a method for determining trace selenium in zinc arsenide based on selenium-arsenic coprecipitation separation. Background Technology

[0002] Zinc arsenide is an important raw material or intermediate for the preparation of compound semiconductor materials such as gallium arsenide and indium arsenide. The selenium content significantly affects the electrical properties and doping effect of semiconductor materials, thus requiring accurate measurement. Currently, the main methods for selenium detection include instrumental analysis methods such as inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrometry (AFS). While these methods offer high sensitivity, the equipment is expensive, operation and maintenance costs are high, and sample pretreatment is complex, making them unsuitable for production process control or small to medium-sized laboratories. Spectrophotometry, due to its readily available equipment, ease of operation, and low cost, has better applicability. However, in zinc arsenide samples, the matrix arsenic content is extremely high (typically greater than 99%), while the selenium content is extremely low (trace levels). The presence of arsenic severely interferes with selenium determination, for example, by producing similar light absorption in the colorimetric reaction of selenium, leading to significant deviations in results. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for determining trace selenium in zinc arsenide based on selenium-arsenide coprecipitation separation, which can effectively eliminate the interference of high-content arsenic matrix and other impurity elements and achieve accurate and stable determination of trace selenium in zinc arsenide using a spectrophotometer.

[0004] The technical solution of the present invention is as follows: A method for determining trace selenium in zinc arsenide based on selenium-arsenic coprecipitation separation includes the following steps: S1. Decompose the zinc arsenide sample with an acidic mixed reagent to obtain a sample solution; S2. Add a coprecipitant and a reducing agent to the sample solution, and heat the solution to reduce the selenium ions and arsenic ions to their elemental form and form a precipitate; S3. Dissolve the precipitate with an oxidizing acid to obtain the test solution; S4. The selenium content in the test solution was determined by spectrophotometry.

[0005] Furthermore, in step S2 of the present invention, the coprecipitation support is a copper salt solution, and the reducing agent is sodium hypophosphite.

[0006] Further, in step S4 of the present invention, the determination step specifically includes: S41. Add a masking agent to the test solution and adjust the pH to 2-3; S42. Add chromogenic agent 3,3'-diaminobenzidine to carry out a complexation reaction to generate a selenium-chromogenic agent complex, and then add an organic solvent to extract the complex; S43. Measure the absorbance of the extract at a wavelength of 420 nm using a spectrophotometer.

[0007] Furthermore, in step S1 of the present invention, the acidic mixed reagent is a mixed solution of nitric acid and sulfuric acid in a volume ratio of 2:1 to 10:1, and is heated until white sulfuric acid fumes are emitted and maintained for 1 to 2 minutes.

[0008] Furthermore, in step S3 of the present invention, the oxidizing acid is aqua regia.

[0009] Furthermore, in step S2 of the present invention, the sodium hypophosphite is added in two parts: 2-3g is added first, stirred and dissolved for 5 minutes, and then another 2-5g is added.

[0010] Furthermore, the masking agent described in this invention is a sodium ethylenediaminetetraacetate solution with a mass concentration of 0.5-5%; when adjusting the pH, m-cresol purple is used as an indicator, and the pH is first adjusted to purple with ammonia water, and then adjusted to pH 2-3 with formic acid solution.

[0011] Furthermore, the organic solvent used in this invention is toluene, and the extracted organic phase is dehydrated with anhydrous sodium sulfate to remove trace amounts of water entrained in the organic phase.

[0012] Compared with the prior art, the advantages of the present invention are as follows: 1. This invention utilizes selenium-arsenic coprecipitation to reduce and precipitate trace amounts of selenium together with the main element arsenic from the solution, effectively separating selenium from other non-reducing interfering elements in the zinc arsenide sample. Simultaneously, in a subsequent step, the selenium and arsenic are redissolved in aqua regia, transferring them back into the solution for subsequent spectrophotometric determination. This avoids severe spectral interference from a high-arsenic matrix on selenium measurement, filling a gap in this field.

[0013] 2. This invention further eliminates the interference of residual trace metal ions through EDTA masking, precise pH control, and selective extraction steps. The relative standard deviation (RSD) is less than 6%, and the spiked recovery rate is between 90% and 107%, which meets the analytical requirements for trace selenium.

[0014] 3. The reagents used in this invention are all commonly used analytical grade reagents, which reduces the detection cost and is suitable for promotion in manufacturing enterprises and routine laboratories. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the embodiments.

[0016] I. The instruments and reagents used in Examples 1 and 2 are as follows:

[0017] 1. Spectrophotometer: Visible spectrophotometer (equipped with a 1cm cuvette).

[0018] 2. Preparation of selenium standard stock solution (100 μg / mL): Accurately weigh 0.1000 g of metallic selenium (purity ≥99.99%) into a 100 mL beaker, add 10 mL of nitric acid, heat at low temperature until completely dissolved, cool, transfer to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. When using, serially dilute this solution to prepare a 1.0 μg / mL selenium standard working solution.

[0019] 3. Other main reagents: nitric acid, sulfuric acid, hydrochloric acid, formic acid, and ammonia were all of analytical grade; toluene, sodium hypophosphite, copper sulfate, and disodium ethylenediaminetetraacetate (EDTA): analytical grade, prepared as a 5% (w / v) aqueous solution; 3,3'-diaminobenzidine (DAB): analytical grade, prepared as a 0.5% (w / v) aqueous solution before use, and prepared fresh each time; m-cresol purple indicator: 0.1% (w / v) aqueous solution; water was deionized water or distilled water of equivalent purity.

[0020] II. Establishing Standard Operating Curves

[0021] Accurately transfer 0 mL, 1.0 mL, 2.0 mL, 5.0 mL, 10.0 mL, 20.0 mL, and 40.0 mL of selenium standard working solution (1.0 μg / mL) into a series of 125 mL separatory funnels, corresponding to selenium masses of 0 μg, 1 μg, 2 μg, 5 μg, 10 μg, 20 μg, and 40 μg, respectively. Add water to each separatory funnel to a volume of approximately 50 mL. Then, perform the same procedures as described in section III, starting with acidity adjustment and masking (i.e., from the addition of EDTA solution to the final determination). Using the zero standard tube (0 μg) of extract as a reference, measure the absorbance of each standard tube at 420 nm using a spectrophotometer. Plot a standard curve with selenium mass (μg) on ​​the x-axis and absorbance on the y-axis. The correlation coefficient R² of this standard curve should be no less than 0.999.

[0022] III. Operating Procedures

[0023] A method for determining trace selenium in zinc arsenide based on selenium-arsenic coprecipitation separation includes the following steps: S1. Sample Decomposition: Weigh 0.2000 g to 0.5000 g (accurate to 0.0001 g) of zinc arsenide sample into a 100 mL beaker. Add 10 mL to 15 mL of nitric acid and 5 mL of sulfuric acid, cover with a watch glass, and heat on a hot plate at a low temperature (approximately 120 to 150 °C) until the sample is completely decomposed and the solution is clear. Remove the watch glass, increase the temperature, and continue heating until white fumes of sulfuric acid are emitted. Maintain this temperature for 1 to 2 minutes to remove any remaining nitric acid. Remove the beaker and cool to room temperature. Add 30 mL of water and heat to boiling to completely dissolve the soluble salts. After cooling, add 15 mL to 20 mL of hydrochloric acid, rinse the beaker walls with a small amount of water, controlling the final solution volume to be within the range of 50 to 100 mL, mix well, and obtain the sample solution.

[0024] S2. Selenium-Arsenic Coprecipitation Separation: Add 2 mL of 10% (w / v) copper sulfate solution to the above sample solution and stir until homogeneous. Add sodium hypophosphite as a reducing agent in portions: first add 2-3 g and stir to dissolve; after standing for 5 minutes, add another 2-5 g and stir until completely dissolved. Heat the solution to a gentle boil, at which point a large amount of black precipitate (elemental selenium and elemental arsenic) will appear in the solution; maintain a gentle boil for 1 minute. Then, place the beaker in a boiling water bath and keep it warm for 30-60 minutes to allow the precipitate to fully coagulate and age. Remove the beaker and cool to room temperature. Filter with slow-speed quantitative filter paper, wash the precipitate and the inner wall of the beaker 3-5 times with a 5% (v / v) hydrochloric acid solution containing 2% (w / v) sodium hypophosphite, and then wash the precipitate 3-5 times with water to remove adsorbed impurity ions.

[0025] S3. Dissolve the precipitate with an oxidizing acid: Transfer the precipitate and filter paper back to the original beaker, add 10 mL of aqua regia (hydrochloric acid to nitric acid volume ratio of 3:1), and heat at low temperature until the precipitate is completely dissolved. Filter with defatted cotton, collect the filtrate in a 125 mL separatory funnel, wash the beaker and defatted cotton with a small amount of water, and control the final volume of the test solution to be approximately 50 mL.

[0026] S41. Acidity Adjustment and Masking Add 5 mL of 5% EDTA solution to the test solution in the separatory funnel and shake well to mask any trace metal ions (such as Cu) that may co-precipitate. 2+ Fe 2+ Zn 2+ Add 2 drops of 0.1% m-cresol purple indicator; the solution will turn red due to the acid content. Neutralize with (1+1) ammonia solution dropwise, shaking constantly, and observe the solution color change from red to purple (the pH is approximately 7-8 at this point). Then carefully adjust with (1+9) formic acid solution until the solution color changes from purple to orange-red (the pH is approximately 2-3 at this point).

[0027] S42. Complexation and Extraction Add 3 mL of 0.5% 3,3'-diaminobenzidine (DAB) solution to the separatory funnel, shake immediately, and allow to stand at room temperature in the dark for at least 30 minutes (preferably 40 minutes) to allow for complexation. Remove the separatory funnel and adjust the solution color to purple again with (1+1) ammonia. Accurately add 10.0 mL of toluene, tightly seal the separatory funnel, and shake vigorously for 1 minute to completely extract the selenium-DAB complex into the organic phase. Allow to stand until the two phases completely separate (approximately 5-10 minutes), and discard the lower aqueous phase. Add approximately 0.2 g of anhydrous sodium sulfate to the upper organic phase, and gently shake to remove any trace amounts of water entrained in the organic phase, yielding a clear and transparent extract for testing.

[0028] S43. Measurement and Calculation Transfer the extract to a 1 cm cuvette. On a spectrophotometer, measure the absorbance of the extract at 420 nm, using the extract of a blank solution (without sample added) that underwent the same procedure as the sample as a reference. Based on the measured absorbance value, find the corresponding selenium mass M (in μg) from the standard curve. Calculate the selenium content ω in the zinc arsenide sample using the following formula. Se (%)

[0029] In the formula: M — The mass of selenium obtained from the standard working curve, in micrograms (μg); m — The mass of the sample taken, in grams (g). Example 1

[0030] This embodiment uses the same method as the above-described steps (III) to determine the zinc arsenide sample with batch number HX26003.

[0031] Sample weight: 0.2000 g; Coprecipitation conditions: First addition of 2.5 g of sodium hypophosphite; second addition of 2.5 g; boiling water bath incubation for 40 minutes; Combination time: 40 minutes.

[0032] Eleven independent determinations were performed on the sample, and the results (%) were: 0.0029, 0.0027, 0.0024, 0.0026, 0.0027, 0.0028, 0.0028, 0.0027, 0.0025, 0.0029, and 0.0026. The calculated average value was 0.0027%, and the relative standard deviation (RSD) was 5.87%. The accuracy was verified using the spiked recovery method. 5 μg, 10 μg, and 15 μg of selenium standard solution were added to the sample, and the total selenium content was determined and the recovery rate was calculated. The results are shown in Table 1.

[0033] Table 1. Spiked recovery test results of Example 1 (sample HX26003)

[0034] The results show that this method has good precision and accuracy. Example 2

[0035] This embodiment uses the same method as the above-described steps (III), but adjusts only some parameters to determine the zinc arsenide sample of another batch number HX26006.

[0036] Sample weight: 0.3000 g; Sample decomposition: Add 15 mL of nitric acid and 5 mL of sulfuric acid; white fumes are emitted after 2 minutes. Coprecipitation conditions: Add 3 g of sodium hypophosphite for the first addition, and 4 g for the second addition; keep in a boiling water bath for 60 minutes; Combination time: 40 minutes. Eleven independent measurements were performed on the sample, and the results (%) were: 0.0048, 0.0053, 0.0050, 0.0051, 0.0052, 0.0053, 0.0052, 0.0050, 0.0049, 0.0051, and 0.0049. The calculated average value was 0.0051%, and the relative standard deviation (RSD) was 3.31%. The results of the spiked recovery experiment are shown in Table 2.

[0037] Table 2. Spike recovery test results for Example 2 (sample HX26006)

[0038] The results show that this method has good precision and accuracy.

[0039] The method provided by this invention can accurately and stably determine the trace selenium content in zinc arsenide samples, with relative standard deviations (RSDs) all less than 6%, meeting the requirements for trace analysis. Spiking recovery experiments showed recoveries between 90.8% and 106.2%, indicating good accuracy and the absence of systematic positive or negative biases. The method of this invention can quantitatively recover selenium, and subsequent EDTA masking and pH adjustment effectively eliminate residual interference. All embodiments were performed using conventional hot plates, water baths, and spectrophotometers, requiring no special or expensive instruments. The operational steps are clear and easy to implement in ordinary laboratories.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining trace selenium in zinc arsenide based on selenium-arsenic coprecipitation separation, characterized in that, Includes the following steps: S1. Decompose the zinc arsenide sample with an acidic mixed reagent to obtain a sample solution; S2. Add a coprecipitant and a reducing agent to the sample solution, and heat the solution to reduce the selenium ions and arsenic ions to their elemental form and form a precipitate; S3. Dissolve the precipitate with an oxidizing acid to obtain the test solution; S4. The selenium content in the test solution was determined by spectrophotometry.

2. The determination method according to claim 1, characterized in that, In step S2, the coprecipitation support is a copper salt solution, and the reducing agent is sodium hypophosphite.

3. The determination method according to claim 1 or 2, characterized in that, In step S4, the determination step specifically includes: S41. Add a masking agent to the test solution and adjust the pH to 2-3; S42. Add chromogenic agent 3,3'-diaminobenzidine to carry out a complexation reaction to generate a selenium-chromogenic agent complex, and then add an organic solvent to extract the complex; S43. Measure the absorbance of the extract at a wavelength of 420 nm using a spectrophotometer.

4. The determination method according to claim 1, characterized in that, In step S1, the acidic mixed reagent is a mixed solution of nitric acid and sulfuric acid in a volume ratio of 2:1 to 10:1, and is heated until white sulfuric acid fumes are emitted and maintained for 1 to 2 minutes.

5. The determination method according to claim 1, characterized in that, In step S3, the oxidizing acid is aqua regia.

6. The determination method according to claim 2, characterized in that, In step S2, the sodium hypophosphite is added in two parts: first, 2-3g is added, stirred and dissolved for 5 minutes, and then another 2-5g is added.

7. The determination method according to claim 3, characterized in that, The masking agent is a sodium ethylenediaminetetraacetate solution with a mass concentration of 0.5-5%. When adjusting the pH, m-cresol purple is used as an indicator. First, ammonia water is used to adjust the pH to purple, and then formic acid solution is used to adjust the pH to 2-3.

8. The determination method according to claim 3, characterized in that, The organic solvent is toluene, and the extracted organic phase is dehydrated with anhydrous sodium sulfate to remove trace amounts of water entrained in the organic phase.

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