GB/T 20975.17-2020 PDF English
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Methods for chemical analysis of aluminium and aluminium alloys - Part 17: Determination of strontium content
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| GB/T 20975.17-2008 | English | 279 |
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Methods for chemical analysis of aluminium and aluminium alloys -- Part 17: Determination of strontium content -- Flame atomic absorption spectrometric method
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GB/T 20975.17-2020: Methods for chemical analysis of aluminium and aluminium alloys - Part 17: Determination of strontium content
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT20975.17-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.10
H 12
GB/T 20975.17-2020
Replacing GB/T 20975.17-2008
Methods for chemical analysis of aluminium and aluminium
alloys - Part 17: Determination of strontium content
ISSUED ON: SEPTEMBER 29, 2020
IMPLEMENTED ON: AUGUST 01, 2021
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 Terms and definitions ... 6
4 Flame atomic absorption spectrometry ... 6
5 Na2EDTA titration ... 11
6 Test report ... 15
Methods for chemical analysis of aluminium and aluminium
alloys - Part 17: Determination of strontium content
WARNING -- Personnel using this Part shall have practical experience in regular
laboratory work. This Part does not address all possible safety issues. Users are
responsible for taking appropriate safety and health measures and ensuring
compliance with the conditions specified in relevant national regulations.
1 Scope
This Part of GB/T 20975 specifies the determination of strontium content in aluminum
and aluminum alloys by flame atomic absorption spectrometry and Na2EDTA titration.
This Part applies to the arbitration determination of strontium content in aluminum and
aluminum alloys. The determination range of flame atomic absorption spectrometry:
0.020 % ~ 12.00 %; the determination range of Na2EDTA titration: 3.00 % ~ 22.00 %.
NOTE: When the strontium mass fraction is > 3.00 % ~ 12.00 %, Na2EDTA titration is used as
the arbitration method.
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 8005.2 Terms of aluminium and aluminium alloys - Part 2: Chemical analysis
GB/T 8170-2008 Rules of rounding off for numerical values & expression and
judgement of limiting values
3 Terms and definitions
For the purpose of this document, the terms and definitions defined in GB/T 8005.2
apply.
4 Flame atomic absorption spectrometry
4.1 Method summary
Dissolve the sample with hydrochloric acid and hydrogen peroxide, measure the
absorbance of strontium using air-acetylene rich flame at the wavelength of 460.7 nm
of a flame atomic absorption spectrometer, to determine the strontium content.
4.2 Reagents
Unless otherwise stated, only reagents and laboratory grade 2 water confirmed to be of
analytical grade are used in the analysis.
4.2.1 Pure aluminum (wAl ≥ 99.99 %, wSr ≤ 0.001 %).
4.2.2 Hydrogen peroxide (ρ = 1.10 g/mL).
4.2.3 Hydrofluoric acid (ρ = 1.14 g/mL).
4.2.4 Nitric acid (ρ = 1.42 g/mL).
4.2.5 Hydrochloric acid (1 + 1).
4.2.6 Lanthanum chloride solution (200 g/L): WEIGH 100 g of lanthanum chloride
(LaCl3 · 6H2O), DILUTE to a 500 mL volumetric flask with water.
4.2.7 Aluminum solution A (20 mg/mL): WEIGH 20.00 g of pickled pure aluminum
(4.2.1) and PLACE it in a 1000 mL beaker, COVER it with a watch glass, and ADD a
total of 200 mL of hydrochloric acid (4.2.5) in portions. After the violent reaction stops,
ADD a few drops of hydrogen peroxide (4.2.2), HEAT slowly until completely
dissolved, and COOL down. TRANSFER the solution into a 1000 mL volumetric flask,
DILUTE to the mark with water, and MIX well.
4.2.8 Aluminum solution B (2 mg/mL): PIPETTE 50 mL of aluminum solution (4.2.7)
into a 500 mL volumetric flask, DILUTE to the mark with water, and MIX well.
4.2.9 Strontium standard storage solution: WEIGH 1.6850 g of strontium carbonate
(wSrCO3 ≥ 99.99 %) and DISSOLVE it in an appropriate amount of hydrochloric acid
(4.2.5), HEAT to boil, COOL down, DILUTE to 1000 mL with water, and MIX well. 1
mL of this solution contains 1.0 mg of strontium.
4.2.10 Strontium standard solution A: PIPETTE 50.00 mL of strontium standard storage
solution (4.2.9) into a 200 mL volumetric flask, DILUTE to the mark with water, and
MIX well. 1 mL of this solution contains 0.25 mg of strontium.
4.2.11 Strontium standard solution B: PIPETTE 50.00 mL of strontium standard storage
solution (4.2.9) into a 500 mL volumetric flask, DILUTE to the mark with water, and
MIX well. 1 mL of this solution contains 0.1 mg of strontium.
4.3 Instruments and equipment
Atomic absorption spectrometer with strontium hollow cathode lamp. The instrument
shall meet the following conditions:
- Characteristic concentration: in a solution consistent with the matrix of the tested
sample solution, the characteristic concentration of strontium shall not be greater
than 0.25 μg/mL;
- Precision: use the highest-concentration standard solution to measure the
absorbance 10 times, the standard deviation shall not exceed 1.0 % of the average
absorbance; use the lowest-concentration standard solution (not a “zero”
concentration solution) to measure the absorbance 10 times, the standard deviation
shall not exceed 0.5 % of the average absorbance of the highest-concentration
standard solution;
- Working curve linearity: divide the working curve into five equal segments
according to concentration. The ratio of the absorbance difference of the highest
segment to the absorbance difference of the lowest segment shall not be less than
0.7.
4.4 Sample
Process the sample into chips with a thickness of no more than 1 mm.
4.5 Analysis steps
4.5.1 Sample
Weigh the sample (4.4) with a mass (m0) of 0.50 g, accurate to 0.0001 g.
4.5.2 Parallel test
Carry out two tests in parallel and take the average value.
4.5.3 Blank test
Weigh pure aluminum (4.2.1) according to Table 1 to replace the sample (4.5.1), and
carry out a blank test along with the sample.
4.5.4 Determination
4.5.4.1 PLACE the sample (4.5.1) into a 250 mL beaker, ADD 15 mL of hydrochloric
acid (4.2.5), after the violent reaction stops, ADD 3 ~ 5 drops of hydrogen peroxide
(4.2.2), BOIL and STEAM until salt precipitates, COOL down slightly, ADD 3 mL of
hydrochloric acid (4.2.5), HEAT until the salts are dissolved, then REMOVE the beaker
and COOL down.
4.5.4.2 If there is insoluble matter, filter and wash. PLACE the residue together with
the filter paper in a platinum crucible, ASH it (do not burn the filter paper). BURN at
5.2.3 Ammonia water (ρ = 0.89 g/mL).
5.2.4 Hydrochloric acid (1 + 1).
5.2.5 Hexamethylenetetramine solution (250 g/L).
5.2.6 Copper reagent solution (50 g/L): WEIGH 5 g of copper reagent (sodium diethyl
aminothiocarbamate) and DISSOLVE it in 25 mL of absolute ethanol (5.2.2), DILUTE
to 100 mL with water. (Prepare before use.)
5.2.7 Ammonia-ammonium chloride buffer solution (pH ≈ 10): WEIGH 54 g of
ammonium chloride and DISSOLVE it in 200 mL of water, ADD 350 mL of ammonia
water (5.2.3), and DILUTE to 1000 mL.
5.2.8 Zinc standard solution (c' = 0.02 mol/L): WEIGH 1.3076 g of zinc (wZn ≥ 99.9 %)
and PLACE it in a 300 mL beaker, ADD 20 mL of hydrochloric acid (5.2.4), HEAT to
dissolve completely and then EVAPORATE to 10 mL, COOL down, TRANSFER to a
1000 mL volumetric flask, DILUTE to the mark with water, and MIX well.
5.2.9 Magnesium standard solution (0.02 mol/L): WEIGH 0.4861 g of metallic
magnesium (wMg ≥ 99.9 %) and PLACE it in a 300 mL beaker, ADD 30 mL of
hydrochloric acid (5.2.4), HEAT to dissolve completely, COOL down, TRANSFER into
a 1000 mL volumetric flask, DILUTE to the mark with water, and MIX well.
5.2.10 Na2EDTA standard titration solution (c1 ≈ 0.02 mol/L):
- Preparation: WEIGH 7.4 g of disodium ethylenediaminetetraacetate
(C10H14N2O8Na2 · 2H2O) and DISSOLVE it in 200 mL of hot water, COOL down,
TRANSFER into a 1000 mL volumetric flask with water, and MIX well.
- Calibration: PIPETTE 20.00 mL (V') of zinc standard solution (5.2.8) into a 250
mL Erlenmeyer flask, ADD 50 mL of water and 15 mL of ammonia-ammonium
chloride buffer solution (5.2.7), ADD 4 ~ 5 drops of chrome black T indicator
(5.2.11), TITRATE the solution with Na2EDTA standard solution (5.2.10) until the
solution turns pure blue, which is the end point, and RECORD the volume (V) of
the Na2EDTA standard titration solution (5.2.10) consumed. CALIBRATE three
copies in parallel, and the difference in volume between the two calibration copies
shall not be greater than 0.10 mL.
- Calculation: CALCULATE the concentration of Na2EDTA standard solution
according to formula (2):
where:
c' - the concentration of zinc standard solution, in moles per liter (mol/L);
V' - the volume of the zinc standard solution pipetted, in milliliters (mL);
V - the volume of the Na2EDTA standard titration solution consumed, in milliliters
(mL).
The calculation results retain four significant figures, and rounding off of numerical
values is performed in accordance with 3.2 and 3.3 of GB/T 8170-2008.
5.2.11 Chrome black T indicator: WEIGH 0.2 g of chrome black T and DISSOLVE it
in 10 mL of ammonia water (5.2.3) and 40 mL of absolute ethanol (5.2.2). After
complete dissolution, store it in a brown dropper bottle.
5.3 Sample
Process the sample into chips with a thickness of no more than 1 mm.
5.4 Analysis steps
5.4.1 Sample
Weigh the sample (5.3) with a mass (m) of 0.20 g, accurate to 0.0001 g.
5.4.2 Parallel test
Carry out two tests in parallel and take the average value.
5.4.3 Determination
5.4.3.1 PLACE the sample (5.4.1) into a 250 mL beaker, ADD 6 mL of hydrochloric
acid (5.2.4), ADD a few drops of hydrogen peroxide (5.2.1), HEAT, after the sample is
completely dissolved, COOL down.
5.4.3.2 DILUTE to about 20 mL with water, NEUTRALIZE with ammonia water (5.2.3)
until the pH of the solution is about 6 (precision pH test paper), ADD 15 mL of
hexamethylenetetramine solution (5.2.5), CONTROL the pH of the solution to 6. 5 ~
7.5, HEAT and BOIL for 1 min, then COOL down to room temperature. ADD 10 mL
of copper reagent solution (5.2.6) while stirring, TRANSFER it to a 200 mL volumetric
flask (V5), DILUTE to the mark with water, and MIX well. LET STAND for 30 min
and carry out dry filtration.
5.4.3.3 PIPETTE 50.00 mL of filtrate (V6) into a 250 mL Erlenmeyer flask, ADD water
to approximately 100 mL, ADD 10 mL of ammonia-ammonium chloride buffer solution
(5.2.7), ADD 10.00 mL (V0) of magnesium standard solution (5.2.9), ADD 3 ~ 5 drops
of chrome black T indicator (5.2.11), TITRATE with Na2EDTA standard titration
solution (5.2.10) until the color change nears the end point, ADD 7 mL to 8 mL of
absolute ethanol (5.2.2), continue to TITRATE until the solution turns pure blue, which
is the end point. RECORD the volume of Na2EDTA standard solution consumed (V4).
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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