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GB/T 20975.28-2019: Methods for chemical analysis of aluminium and aluminium alloys - Part 28: Determination of cobalt content - Flame atomic absorption spectrometry
GB/T 20975.28-2019
Methods for chemical analysis of aluminium and aluminium alloys--Part 28. Determination of cobalt content--Flame atomic absorption spectrometry
ICS 77.120.10
H12
National Standards of People's Republic of China
Aluminum and aluminum alloy chemical analysis method
Part 28. Determination of cobalt content
Flame atomic absorption spectrometry
Part 28.Determinationofcobaltcontent-
Published on.2019-06-04
2020-05-01 implementation
State market supervision and administration
China National Standardization Administration issued
Foreword
GB/T 20975 "Aluminum and Aluminum Alloy Chemical Analysis Methods" is divided into 31 parts.
--- Part 1. Determination of mercury content;
--- Part 2. Determination of arsenic content;
--- Part 3. Determination of copper content;
--- Part 4. Determination of iron content - Orthophenanthroline spectrophotometric method;
---Part 5. Determination of silicon content;
---Part 6. Determination of cadmium content by flame atomic absorption spectrometry;
---Part 7. Determination of manganese content - Potassium periodate spectrophotometric method;
---Part 8. Determination of zinc content;
---Part 9. Determination of lithium content by flame atomic absorption spectrometry;
--- Part 10. Determination of tin content;
--- Part 11. Determination of lead content;
--- Part 12. Determination of titanium content;
-- Part 13. Determination of vanadium content - Benzoylphthalide spectrophotometric method;
--- Part 14. Determination of nickel content;
---Part 15. Determination of boron content;
---Part 16. Determination of magnesium content;
---Part 17. Determination of hydrazine content by flame atomic absorption spectrometry;
---Part 18. Determination of chromium content;
---Part 19. Determination of zirconium content;
---Part 20. Determination of gallium content - butyl rhodamine B spectrophotometric method;
---Part 21. Determination of calcium content by flame atomic absorption spectrometry;
--- Part 22. Determination of bismuth content - yy chrome cyanide R spectrophotometric method;
--- Part 23. Determination of bismuth content - Potassium iodide spectrophotometric method;
--- Part 24. Determination of total rare earth content;
---Part 25. Inductively coupled plasma emission spectrometry;
--- Part 26. Determination of carbon content by infrared absorption method;
--- Part 27. Determination of content of ruthenium, osmium and osmium by inductively coupled plasma atomic emission spectrometry;
---Part 28. Determination of cobalt content by flame atomic absorption spectrometry;
---Part 29. Determination of molybdenum content by thiocyanate spectrophotometric method;
---Part 30. Determination of hydrogen content Heating extraction heat conduction method;
--- Part 31. Determination of phosphorus content - Molybdenum blue spectrophotometric method.
This part is the 28th part of GB/T 20975.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part was proposed by the China Nonferrous Metals Industry Association.
This part is under the jurisdiction of the National Nonferrous Metals Standardization Technical Committee (SAC/TC243).
This section drafted by. Guangdong Industrial Analysis and Testing Center, Nonferrous Metals Technology and Economic Research Institute, National Standard (Beijing) inspection and certification limited
Company, Hebei Sitong New Material Co., Ltd., Northeast Light Alloy Co., Ltd., Guizhou Research and Analysis Institute, Changsha Mining Research Institute
Research Institute Co., Ltd.
Drafters of this section. Huang Portuguese, Xiong Xiaoyan, Xi Huan, Chen Xiongfei, Zhao Weitao, Wang Zhengqiang, Yi Jia, Zhou Bing, Li Yuhong, Zhang Xiao, Liu Fei, Wang Wenhong,
麴 Dafang, Yang Lin.
Aluminum and aluminum alloy chemical analysis method
Part 28. Determination of cobalt content
Flame atomic absorption spectrometry
Cautions - Personnel using this section should have hands-on experience in formal laboratory work. This section does not point out all possible security questions.
question. It is the responsibility of the user to take appropriate safety and health measures and to ensure compliance with the conditions set by the relevant national regulations.
1 Scope
This part of GB/T 20975 specifies a method for the determination of cobalt in aluminum and aluminum alloys by flame atomic absorption spectrometry.
This section applies to the determination of cobalt content in aluminum and aluminum alloys, aluminum-cobalt intermediate alloys. Measuring range. 0.005%~12.0%.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article.
Pieces. For undated references, the latest edition (including all amendments) is used in this document.
GB/T 6682 Analytical laboratory water specifications and test methods
GB/T 8170-2008 Numerical rounding rules and the representation and determination of limit values
3 method summary
The sample was dissolved with hydrochloric acid or nitric acid. In a dilute acid medium, at an atomic absorption spectrometer wavelength of 240.7 nm, measured by air-acetylene flame
The absorbance of cobalt is used to determine the cobalt content.
4 reagents
Unless otherwise stated, only analytically pure reagents and secondary water in accordance with GB/T 6682 are used in the analysis.
4.1 Aluminum [w (Al) ≥ 99.99%, w (Co) < 0.001%].
4.2 Hydrochloric acid (ρ = 1.19 g/mL).
4.3 Nitric acid (ρ = 1.42 g/mL).
4.4 Hydrofluoric acid (ρ=1.14g/mL).
4.5 Hydrochloric acid (1 1).
4.6 Nitric acid (1 1).
4.7 Aluminum solution (20mg/mL). Weigh 10.00g of pickled aluminum (4.1) in a 1000mL beaker, cover the table, add the total
The amount of hydrochloric acid (4.5) was.200 mL, and after the violent reaction was stopped, it was slowly heated to complete dissolution. Remove and cool. Move into 500mL capacity
Dilute to the mark with water and mix well.
4.8 Cobalt standard storage solution. Weigh 0.5000g of metal cobalt [w(Co) ≥ 99.99%] in a 250mL beaker, add 20mL of nitric acid
(4.6), after the dissolution is complete, transfer to a 500mL volumetric flask, add 40mL of nitric acid (4.6), dilute to the mark with water, and mix. This solution
1 mL contains 1 mg of cobalt.
4.9 Cobalt standard solution. Pipette 25.00mL of cobalt standard storage solution (4.8) into a 250mL volumetric flask, add 25mL of nitric acid (4.6), use
Dilute the water to the mark and mix. 1 mL of this solution contained 100 μg of cobalt.
5 instruments
Atomic absorption spectrometer with cobalt hollow cathode lamp. Under the best working conditions of the instrument, the atomic absorption spectrometers that meet the following indicators are
be usable.
--- Characteristic concentration. In the solution consistent with the measurement solution matrix, the characteristic concentration of cobalt should be no more than 0.03 μg/mL.
---Precision. 10 times of absorbance measured with the highest concentration of standard solution, the standard deviation should not exceed the average absorbance
1.0%; measure the absorbance 10 times with the lowest concentration of standard solution (not a "zero" concentration solution), the standard deviation should not exceed
The highest concentration standard solution has an average absorbance of 0.5%.
---Working curve linearity. The working curve is divided into five segments according to the concentration, and the difference between the absorbance difference of the highest segment and the absorbance of the lowest segment is
The ratio should be no less than 0.80.
6 sample
The sample was processed into chips of no more than 1 mm.
7 Analysis steps
7.1 Samples
A sample having a mass (m) of 0.20 g (see Chapter 6) was weighed to the nearest 0.0001 g.
7.2 Number of measurements
The measurements were performed twice independently and averaged.
7.3 Blank test
0.20 g of aluminum (4.1) was weighed instead of the sample (7.1), and a blank test was carried out along with the sample.
7.4 Determination
7.4.1 Place the sample (7.1) in a 100 mL beaker and add 10 mL of hydrochloric acid (4.5). After the violent reaction is stopped, heat until the sample dissolves.
A few drops of nitric acid (4.6) were added dropwise, and the nitrogen oxides were boiled and cooled. Transfer to a 100mL volumetric flask, dilute to the mark with water, and make up to volume (V).
Mix well.
Note. If there is insoluble matter, filter, wash. The residue was placed in a platinum crucible together with filter paper, ashed (do not burn the filter paper), fired at about 550 ° C, and cooled. Join
5 mL of hydrofluoric acid (4.4), and hydrochloric acid (4.5) was added dropwise to the solution to be clear, heated to dryness, and calcined at 700 ° C for several minutes, and cooled. Use as little as possible
Hydrochloric acid (4.5) dissolves the residue. This filtrate was combined in a stock solution.
7.4.2 Take the test solution according to Table 1 in a suitable volumetric flask, add hydrochloric acid (4.5), dilute to the mark with water, mix, and test.
Table 1 Dividing the volume of the test solution, adding the amount of hydrochloric acid and dispensing the volume of the test solution
Cobalt mass fraction w(Co)/% fractionation test solution volume/mL supplemental hydrochloric acid (4.5)/mL fractionation test solution volumetric volume/mL dilution factor (T)
0.005~0.10 - - 100 1
>0.10~1.0 10.00 9 100 10
>1.0~12.0 10.00 24 250 25
7.4.3 Using an air-acetylene flame at the wavelength of 240.7 nm of the atomic absorption spectrometer, simultaneously with the series of standard solutions, zero with water, measuring
The absorbance of the blank test solution and the sample solution, the mass concentration of cobalt in the blank solution (ρ0) and the quality of cobalt in the test solution were determined from the working curve.
Volume concentration (ρ). Simultaneous determination with a series of standard solutions.
7.5 Working curve
7.5.1 Preparation of series standard solutions
7.5.1.1 When the cobalt content is 0.005%~0.10%. remove 0mL, 0.10mL, 0.20mL, 0.50mL, 1.00mL, 1.50mL,
2.00mL cobalt standard solution (4.9), respectively placed in a set of 100mL volumetric flask, each adding 10mL aluminum solution (4.7) and 6mL hydrochloric acid
(4.5), dilute to the mark with water and mix.
7.5.1.2 When the cobalt content is >0.10%~1.0%. remove 0mL, 0.10mL, 0.20mL, 0.50mL, 1.00mL, 1.50mL,
2.00mL cobalt standard solution (4.9), respectively placed in a set of 100mL volumetric flask, each adding 1mL aluminum solution (4.7) and 9.6mL hydrochloric acid
(4.5), dilute to the mark with water and mix.
7.5.1.3 When the cobalt content is >1.0%~12.0%. remove 0mL, 0.80mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL,
10.00 mL of cobalt standard solution (4.9) was placed in a set of 100 mL volumetric flasks, each adding 0.4 mL of aluminum solution (4.7) and 9.8 mL of salt.
Acid (4.5), dilute to the mark with water and mix.
7.5.2 Drawing of the working curve
Under the same conditions as the test solution, zero the water, measure the absorbance of the series of standard solutions (7.5.1), subtract the series of standard solutions.
The absorbance of the "zero" concentration solution is plotted on the abscissa with the mass concentration of cobalt and the ordinate on the ordinate.
8 Calculation of analysis results
8.1 The cobalt content is calculated by the formula (1) based on the mass fraction w(Co) of cobalt.
w(Co)=
(ρ-ρ0)VT×10-6
m ×100%
(1)
In the formula.
ρ --- The concentration of cobalt in the test solution is obtained from the working curve, and the unit is microgram per milliliter (μg/mL);
Ρ0---Check the mass concentration of cobalt in the blank solution from the working curve in micrograms per milliliter (μg/mL);
V --- test solution volume to volume, in milliliters (mL);
T --- dilution factor;
m --- The mass of the sample in grams (g).
8.2 When the cobalt content is < 0.10%, the calculation result is expressed to three decimal places; when the cobalt content is ≥0.10%, the calculation result is expressed to the decimal point.
Two. The numerical repair is performed according to 3.2 and 3.3 of GB/T 8170-2008.
9 precision
9.1 Repeatability
The measured values of two independent test results obtained under repetitive conditions, within the average range given below, the results of the two test results
The absolute difference does not exceed the repeatability limit r, and the case where the repeatability limit r exceeds 5%. Repeatability limit r is linearly interpolated according to the data in Table 2.
The law is obtained.
Table 2 Repeatability limits
w(Co)/% 0.005 0.050 0.52 2.00 12.00
r/% 0.0005 0.0031 0.028 0.11 0.20
9.2 Reproducibility
The measured values of the two independent test results obtained under reproducibility conditions are within the average range given below, the results of the two test results
The absolute difference is not greater than the reproducibility limit R, and the case where the reproducibility limit R is exceeded does not exceed 5%. The reproducibility limit R is linear within the data of Table 3.
Interpolation.
Table 3 Reproducibility limits
w(Co)/% 0.005 0.050 0.52 2.00 12.00
R/% 0.0006 0.0036 0.030 0.20 0.21
10 Quality Assurance and Control
For analysis, check with a standard or control sample, or check the analytical method with at least a standard or control sample each year.
Times. When the process is out of control, you should find out why. After correcting the error, recheck it.
11 test report
The test report should at least give the following aspects.
a) the number and name of this part;
b) all necessary information regarding the identification of samples, laboratories, date of analysis, date of reporting, etc.;
c) express the test results in an appropriate form;
d) anomalies that occur during the test;
e) any operations that are not explicitly stated or optional in this section that may affect the results;
f) The signature of the person responsible for the test, audit, etc.
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