GB/T 20975.22-2020Methods for chemical analysis of aluminium and aluminium alloys—Part 22:Determination of beryllium content (English PDF)

4.1 Method summary

The sample is dissolved in hydrochloric acid and nitric acid, and disodium edetate and sodium tartrate are used as masking agents, and the pH value is 9.5 ammonia-ammonium nitrate buffer In the solution, beryllium forms a ternary complex with chrome cyanide R (SCR) and cetyltrimethylammonium bromide (CTMAB), which is measured in a spectrophotometer.

The absorbance at 560.0nm is measured to determine the content of beryllium.

4.2 Reagents

Unless otherwise stated, only reagents and laboratory secondary water confirmed to be analytically pure are used in the analysis.

4.2.1 Sulfuric acid (rho=1.84g/mL).

4.2.2 Nitric acid (rho=1.42g/mL).

4.2.3 Hydrofluoric acid (rho=1.14g/mL).

4.2.4 Ammonia (rho=0.90g/mL).

4.2.5 Hydrochloric acid (1 1).

4.2.6 Disodium ethylenediaminetetraacetic acid (Na2EDTA) solution (100g/L), need to be filtered.

4.2.7 Sodium tartrate solution (1mol/L), need to be filtered.

4.2.8 Solochrome cyanine R (Solochrome cyanine R, SCR) solution (2g/L). weigh 0.500g SCR in a 250mL beaker, Add 2mL nitric acid (4.2.2), stir well with a glass rod, then add about 150mL water to dissolve it completely, and transfer it into a 250mL volumetric flask. For turbidity, filter, dilute to the mark with water, and mix well.

4.2.9 Cetyltrimethylammonium bromide (CTMAB) solution (4g/L). Weigh 1.000g CTMAB in a 250mL beaker and add About 150mL of water, 10mL of ethanol, stir, warm to make it completely dissolved, transfer to a 250mL volumetric flask, dilute to the mark with water, and mix. (If crystals appear during use, it can be warmed to clear).

4.2.10 Ammonia-ammonium nitrate buffer solution. Weigh 51.8g of ammonium nitrate and dissolve in about 400mL of water, add 65mL of ammonia (4.2.4), shake uniform. Adjust to pH 9.5 with ammonia (4.2.4) or nitric acid (1 1) (measured by pH meter), transfer it into a 500mL volumetric flask, and dilute with water to Scale and mix well.

4.2.11 Aluminum solution (20mg/mL). Weigh 20.00g pure aluminum (wAl>=99.99%) in a.2000mL beaker, cover with a watch glass, and divide Add 600mL of hydrochloric acid (4.2.5), slowly heat until completely dissolved, remove, cool, transfer to a 1000mL volumetric flask, dilute with water Release to the mark and mix well.

4.2.12 Beryllium standard storage solution. use a certified standard solution to prepare. This solution 1mL contains 0.1mg beryllium.

4.2.13 Beryllium standard solution A. Pipette 25.00mL beryllium standard stock solution (4.2.12) into a 500mL volumetric flask, add 167mL salt Acid (4.2.5), dilute to the mark with water, mix well (prepared when used). 1mL of this solution contains 5µg of beryllium.

4.2.14 Beryllium standard solution B. Pipette 20.00mL beryllium standard solution A (4.2.13) into a 100mL volumetric flask, add 33mL hydrochloric acid (4.2.5), dilute to the mark with water, and mix well (prepared when used). This solution 1mL contains 1µg beryllium.

4.2.15 Beryllium standard solution C. Pipette 20.00mL beryllium standard solution A (4.2.13) into a 500mL volumetric flask, add 83mL hydrochloric acid (4.2.5), dilute to the mark with water, and mix well (prepared when used). This solution 1mL contains 0.2µg beryllium.

4.2.16 P-nitrophenol solution (2g/L).

4.3 Apparatus

4.3.1 Spectrophotometer.

4.3.2 pH meter or ion meter.

4.4 Sample

Process the sample into chips with a thickness of not more than 1mm.

4.5 Analysis steps

4.5.1 Sample

According to Table 1, weigh the sample (4.4) of the corresponding mass (m1) to the nearest 0.0001g.

4.5.2 Parallel test

Do two tests in parallel and take the average value.

4.5.3 Blank test

Pipette 5.0mL aluminum solution (4.2.11) in a 50mL volumetric flask, and operate according to 4.5.4.4 and 4.5.4.5 below.

4.5.4 Determination

4.5.4.1 Place the sample (4.5.1) in a 250mL beaker, add 10mL of water, and slowly add 30mL of hydrochloric acid in batches (4.2.5), cover with a watch glass, after the violent reaction stops, add 2mL of nitric acid (4.2.2), heat until the sample is completely dissolved, and remove. According to Table 1, Filter with medium-speed quantitative filter paper in the corresponding volumetric flask (V1), wash the beaker with hot water and precipitate 7 to 8 times, and cool. When the sample is silicon When the amount fraction is >=1.00%, place the precipitate and filter paper in a platinum crucible after filtration, burn it at 700°C for 30min, take it out, cool it, and add 2mL sulfuric acid (4.2.1), 5mL hydrofluoric acid (4.2.3), dropwise add nitric acid (4.2.2) to make the solution clear, heat to volatilize the silicon, remove, cool, and add dropwise A small amount of hydrochloric acid (4.2.5) to dissolve the residue (if turbidity needs to be filtered), the solution is combined in the above sample solution.

4.5.4.2 Dilute the sample solution (4.5.4.1) to the mark with water and mix well. Transfer the corresponding volume (V2) to a 50mL volumetric flask according to Table 1. In, and add aluminum solution (4.2.11).

4.5.4.3 Add 1.5mL sodium tartrate solution (4.2.7) and shake well. Add 15.00mL Na2EDTA solution (4.2.6), add immediately Add 1 drop of p-nitrophenol solution (4.2.16), and adjust the solution from colorless to light yellow with ammonia (4.2.4) under constant shaking, then add 2.00mL ammonia (4.2.4); add 5.00mL ammonia-ammonium nitrate buffer solution (4.2.10), shake well; add 4.00mL CTMAB solution (4.2.9), shake slowly, and place for about 5 minutes. It should not be placed after adding Na2EDTA solution, and the subsequent steps should be carried out continuously.

4.5.4.4 According to Table 1, add SCR solution (4.2.8), dilute to the mark with water, and mix.

4.5.4.5 Move part of the sample solution (4.5.4.4) into the quartz absorption cell, take the blank test (4.5.3) as the reference, and set it at the wavelength of the spectrophotometer. Measure the absorbance at 560.0nm, and find out the corresponding mass of beryllium (m2) from the working curve.

4.5.5 Drawing of working curve

4.5.5.1 According to the mass fraction of beryllium, the preparation of the working curve series standard solution is divided into the following two types.

a) When the mass fraction of beryllium is 0.0001%~0.0050%. add 5.0mL aluminum solution to a set of 50mL volumetric flasks (4.2.11), sequentially add 0mL, 0.50mL, 2.50mL, 5.00mL, 7.50mL, 10.00mL beryllium standard solution C (4.2.15). Add 1.5mL sodium tartrate solution (4.2.7), shake well. Add 15.00mL Na2EDTA solution (4.2.6), immediately add 1 drop of p-nitrophenol solution (4.2.16), and adjust the solution with ammonia (4.2.4) under constant shaking. The color changes to light yellow, then add 2.00mL ammonia (4.2.4); add 5.00mL ammonia-ammonium nitrate buffer solution (4.2.10), shake Evenly; add 4.00mL CTMAB solution (4.2.9), shake slowly, and place for about 5min. Add 2.00mL SCR solution (4.2.8), dilute to the mark with water, and mix well. It should not be placed after adding Na2EDTA solution, and the subsequent steps should be continuous get on.

b) When the mass fraction of beryllium is >0.0050%~0.40%. add 5.0mL aluminum solution to a set of 50mL volumetric flasks (4.2.11), respectively add 0mL, 0.50mL, 2.50mL, 5.00mL, 7.50mL, 10.00mL beryllium standard solution B (4.2.14). Add 1.5mL sodium tartrate solution (4.2.7), shake well. Add 15.00mL Na2EDTA solution (4.2.6), immediately add 1 drop of p-nitrophenol solution (4.2.16), and adjust the solution with ammonia (4.2.4) under constant shaking. The color changes to light yellow, then add 2.00mL ammonia (4.2.4); add 5.00mL ammonia-ammonium nitrate buffer solution (4.2.10), shake Evenly; add 4.00mL CTMAB solution (4.2.9), shake slowly, and place for about 5min. Add 3.00mL SCR solution (4.2.8), dilute to the mark with water, and mix well. It should not be placed after adding Na2EDTA solution, and the subsequent steps should be continuous get on.

4.5.5.2 Transfer part of the series of standard solutions (4.5.5.1) into the quartz absorption cell, and use the reagent blank solution (without beryllium standard solution) as the reference In comparison, the absorbance was measured at a wavelength of 560.0nm with a spectrophotometer, the mass of beryllium was used as the abscissa and the absorbance was the ordinate, and the working curve was drawn.

4.6 Processing of test data

The content of beryllium is calculated by the mass fraction of beryllium wBe, calculated according to formula (1).

When the mass fraction of beryllium is less than 0.0010%, the calculation result retains a significant number; when the mass fraction of beryllium is >=0.0010%, the calculation result is retained Two significant digits. The rounding of values shall be implemented in 3.2 and 3.3 of GB/T 8170-2008.

4.7 Precision

4.7.1 Repeatability

The measured values of two independent test results obtained under repeatability conditions, within the average range given below, these two test results The absolute difference does not exceed the repeatability limit r, and the case of exceeding the repeatability limit r does not exceed 5%. The repeatability limit r is within the linear range according to the data in Table 2. Obtained by interpolation or extension.

4.7.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions, within the average range given below, these two test results The absolute difference does not exceed the reproducibility limit R, and the case of exceeding the reproducibility limit R does not exceed 5%. Reproducibility limit R is linear according to the data in Table 3 Obtained by interpolation or extension.

5.1 Method summary

The sample is dissolved in hydrochloric acid, and disodium edetate and sodium tartrate are used as masking agents, and the pH value is 9.5 ammonia-ammonium nitrate buffer solution Among them, beryllium forms a ternary complex with chrome cyanide R (SCR) and cetyltrimethylammonium bromide (CTMAB), which is at the wavelength of the spectrophotometer.

The absorbance is measured at 560.0nm to determine the content of beryllium.

5.2 Reagents

Unless otherwise stated, only reagents and laboratory tertiary water confirmed to be analytically pure are used in the analysis.

5.2.1 Nitric acid (rho=1.42g/mL).

5.2.2 Ammonia (rho=0.90g/mL).

5.2.3 Hydrochloric acid (1 1).

5.2.4 Sodium tartrate solution (200g/L), need to be filtered.

5.2.5 Disodium ethylenediaminetetraacetic acid (Na2EDTA) solution (100g/L), need to be filtered.

5.2.6 Cetyltrimethylammonium bromide (CTMAB) solution (4g/L). Weigh 1.000g of CTMAB into a 250mL beaker and add About 150mL water, 10mL ethanol, stir and warm to dissolve them completely, transfer them into a 250mL volumetric flask, dilute to the mark with water, and mix (make If crystals appear during use, it can be warmed to clear).

5.2.7 Solochrome cyanine R (Solochrome cyanine R, SCR) solution (2g/L). weigh 0.500g SCR into a 250mL beaker, Add 2 mL of nitric acid (5.2.1), stir with a glass rod, then add about 150 mL of water to dissolve it completely, and transfer it to a 250 mL volumetric flask. For turbidity, filter, dilute to the mark with water, and mix well.

5.2.8 Ammonia-ammonium nitrate buffer solution. Weigh 51.8g of ammonium nitrate and dissolve in about 400mL of water, add 65mL of ammonia (5.2.2), and mix. Use ammonia (5.2.2) or nitric acid (1 1) to adjust the pH to 9.5 (measured by a pH meter), transfer it into a 500mL volumetric flask, and dilute with water to Degree, mix well.

5.2.9 Beryllium standard storage solution. use a certified standard solution to prepare. This solution 1mL contains 0.1mg beryllium.

5.2.10 Beryllium standard solution D. Pipette 10.00mL beryllium standard stock solution (5.2.9) into a 500mL volumetric flask, add 167mL hydrochloric acid (5.2.3), dilute to the mark with water, mix well (prepared when used). This solution 1mL contains 2µg beryllium.

5.2.11 P-nitrophenol solution (2g/L).

5.3 Apparatus

5.3.1 Spectrophotometer.

5.3.2 pH meter.

5.4 Sample

Process the sample into chips with a thickness of not more than 1mm.

5.5 Analysis steps

5.5.1 Sample

Weigh a sample (5.4) with a mass (m3) of 0.250g, accurate to 0.0001g.

5.5.2 Parallel test

Do two tests in parallel and take the average value.

5.5.3 Blank test

Do a blank test with the sample (5.5.1).

5.5.4 Determination

5.5.4.1 Place the sample (5.5.1) in a 250mL beaker, add 20mL of hydrochloric acid (5.2.3) in batches, cover with a watch glass, and wait After the strong reaction stops, heat to dissolve the sample completely, cool it, and transfer it to a 250mL volumetric flask (V3) (if insoluble matter needs to be filtered), dilute with water To the mark, mix well.

5.5.4.2 The pipetting volume (V4) is 5.00mL sample solution (5.5.4.1) in a 250mL volumetric flask (V5), and 20mL hydrochloric acid is added (5.2.3), dilute to the mark with water, and mix well.

5.5.4.3 Pipette the volume (V6) 5.00mL sample solution (5.5.4.2) into a 50mL volumetric flask.

5.5.4.4 Add 1.0mL sodium tartrate solution (5.2.4) and shake well. Add 2.0mL Na2EDTA solution (5.2.5), add immediately 1 drop of p-nitrophenol solution (5.2.11) and adjust the solution from colorless to light yellow with ammonia (5.2.2) under constant shaking, then add 2.00mL Ammonia (5.2.2). Add 5.0mL ammonia-ammonium nitrate buffer solution (5.2.8), shake well. Add 4.0mL CTMAB solution (5.2.6), slowly Shake well, place for about 5 minutes, add 3.00mL SCR solution (5.2.7), dilute to the mark with water, and mix. After adding Na2EDTA solution Should be placed, and the subsequent steps should be performed continuously.

5.5.4.5 Move part of the sample solution (5.5.4.4) into the absorption cell, take the blank test (5.5.3) as the reference, and set the wavelength of the spectrophotometer at 560.0nm Measure the absorbance at each place, and find out the corresponding beryllium mass (m4) from the working curve.

5.5.5 Drawing of working curve

5.5.5.1 Pipette 0mL, 1.50mL, 2.00mL, 2.50mL, 3.00mL, 3.50mL beryllium standard solution D (5.2.10) into one Group 50mL volumetric flask, add water to dilute to 10mL, the following operations are performed according to 5.5.4.4.

5.5.5.2 Move part of the series of standard solutions (5.5.5.1) into the absorption cell, take the reagent blank solution as a reference, and set it at the wavelength of the spectrophotometer. The absorbance was measured at 560.0nm, the mass of beryllium was taken as the abscissa and the absorbance was the ordinate, and the working curve was drawn.

5.6 Processing of test data

The content of beryllium is calculated by the mass fraction of beryllium wBe, calculated according to formula (2).

The calculation result is expressed to two decimal places. The rounding of values shall be implemented in 3.2 and 3.3 of GB/T 8170-2008.

5.7 Precision

5.7.1 Repeatability

The measured value of two independent test results obtained under repeatability conditions, within the average range given below, these two test results The absolute difference does not exceed the repeatability limit r, and the case of exceeding the repeatability limit r does not exceed 5%. Repeatability limit r is close to the data in Table 4 Data utilization ratio is obtained.

5.7.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions, within the average range given below, these two test results The absolute difference does not exceed the reproducibility limit R, and the case of exceeding the reproducibility limit R does not exceed 5%. Reproducibility limit R is close to The data is calculated using the ratio.