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GB/T 20975.28-2019 PDF English


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GB/T 20975.28-2019English90 Add to Cart 0-9 seconds. Auto-delivery. Methods for chemical analysis of aluminium and aluminium alloys -- Part 28: Determination of cobalt content -- Flame atomic absorption spectrometry Valid
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GB/T 20975.28-2019: PDF in English (GBT 20975.28-2019)

GB/T 20975.28-2019 NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 77.120.10 H 12 Methods for chemical analysis of aluminium and aluminium alloys - Part 28: Determination of cobalt content - Flame atomic absorption spectrometry ISSUED ON: JUNE 04, 2019 IMPLEMENTED ON: MAY 01, 2020 Issued by: State Administration for Market Regulation; Standardization Administration of the People's Republic of China. Table of Contents Foreword ... 3  1 Scope ... 6  2 Normative references ... 6  3 Method summary ... 6  4 Reagents ... 7  5 Apparatus ... 7  6 Sample ... 8  7 Analysis steps ... 8  8 Calculation of analysis result ... 10  9 Precision ... 10  10 Quality assurance and control ... 11  11 Test report ... 11  Methods for chemical analysis of aluminium and aluminium alloys - Part 28: Determination of cobalt content - Flame atomic absorption spectrometry WARNING - The personnel using this Part shall have practical experience in formal laboratory work. This Part does not address all possible security issues. It is the responsibility of the user to take appropriate safety and health measures and to ensure compliance with the relevant national regulations. 1 Scope This Part of GB/T 20975 specifies the method of flame atomic absorption spectrometry to determine cobalt content in aluminium and aluminium alloys. This Part is applicable to determination of cobalt content in aluminum and aluminum alloy, aluminum-cobalt intermediate alloy. Determination range: 0.005%~12.0%. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 6682, Water for analytical laboratory use - Specification and test methods GB/T 8170-2008, Rules of rounding off for numerical values & expression and judgement of limiting values 3 Method summary Use hydrochloric acid, nitric acid to dissolve test material. In dilute acid medium, at the wavelength of 240.7nm of atomic absorption spectrometer, in air- acetylene flame, measure absorbance of cobalt so as to determine cobalt content. standard deviation shall not exceed 0.5% of average absorbance of highest-concentration standard solution. - Working curve linear: Divide working curve into five segments according to concentration. The ratio of difference between absorbance of the highest segment and absorbance of the lowest segment shall be not less than 0.80. 6 Sample Process sample into chips of no more than 1mm. 7 Analysis steps 7.1 Test material Weigh a sample of which mass (m) is 0.20g (see Clause 6), to the nearest of 0.0001g. 7.2 Number of determination Perform two determinations independently. Take the average value. 7.3 Blank test Weigh 0.20g of aluminum (4.1) to replace test material (7.1). Carry out blank test with test material. 7.4 Determination 7.4.1 Place test material (7.1) into a 100mL beaker. Add into 10mL of hydrochloric acid (4.5). After violent reaction stops, heat until test material is dissolved. Add few drops of nitric acid (4.6). Boil to remove nitrogen oxide. Cool. Move into a 100mL volumetric flask. Use water to dilute to scale. Set volume (V). Mix well. NOTE: If there is insoluble matter, filtrate and wash. Place residue together with filter paper in a platinum crucible. Perform ashing (do not let filter paper burn). Burn at about 550°C. Cool. Add 5mL of hydrofluoric acid (4.4). And add into hydrochloric acid (4.5) drop by drop till solution is clear. Heat to evaporate to dry. Burn at 700°C for several minutes. Cool. Use hydrochloric acid (4.5) as little as possible to dissolve residue. Combine this filtrate in stock solution. 7.4.2 According to Table 1, distribute test solution in a suitable volumetric flask. Add into hydrochloric acid (4.5). Use water to dilute to scale. Mix well for testing. 8 Calculation of analysis result 8.1 Cobalt content is calculated in mass fraction of cobalt w(Co). Calculate according to formula (1): Where, ρ - Mass concentration of cobalt in analysis solution found on working curve, in micrograms per milliliter (μg/mL); ρ0 - Mass concentration of cobalt in blank solution found on working curve, in micrograms per milliliter (μg/mL); V - Set volume of test solution, in milliliters (mL); T - Dilution factor; m - Mass of test material, in grams (g). 8.2 When cobalt content is < 0.10%, calculation result is expressed to three decimal places. When cobalt content is ≥0.10%, calculation result is expressed to two decimal places. Numerical rounding-off is carried out according to 3.2 and 3.3 in GB/T 8170-2008. 9 Precision 9.1 Repeatability Obtain measured values of two independent test results under repeatability conditions. Within the range of average values given below, the absolute difference between two test results does not exceed the repeatability limit r. When it exceeds the repeatability limit r, it shall not exceed 5%. Repeatability limit r is obtained by linear interpolation according to data in Table 2. Table 2 -- Repeatability limit 9.2 Reproducibility ......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.