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GB/T 40231-2021 English PDF (GBT40231-2021)

GB/T 40231-2021 English PDF (GBT40231-2021)

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GB/T 40231-2021: Restricted substance in electrical and electronic products - Determination of hexavalent chromium - Ion chromatography method

This Standard specifies the ion chromatography method for the determination of hexavalent chromium in electrical and electronic products. This Standard is applicable to the determination of hexavalent chromium content in polymer materials for electrical and electronic products.
GB/T 40231-2021
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 31.020
L 10
Restricted Substance in Electrical and Electronic
Products - Determination of Hexavalent Chromium -
Ion Chromatography Method
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Principle ... 4
4 Reagents or Materials ... 5
5 Instruments and Equipment ... 6
6 Sample Preparation ... 7
7 Test Procedures ... 8
8 Result Calculation ... 11
9 Precision and Method Detection Limit ... 11
Appendix A (informative) Reference Working Conditions of Ion Chromatograph ... 12
Appendix B (informative) Ion Chromatogram of Hexavalent Chromium ... 13 Restricted Substance in Electrical and Electronic
Products - Determination of Hexavalent Chromium -
Ion Chromatography Method
WARNING 1: the personnel adopting this Standard shall have practical
experience in formal laboratory work. This Standard does not point out all possible safety issues. The user is responsible for taking appropriate safety and health measures and ensuring the compliance with the conditions stipulated by relevant national laws and regulations.
WARNING 2: all samples and reagents that may contain hexavalent chromium used in this Standard shall be handled with appropriate precautions. Solutions or wastes containing hexavalent chromium shall be properly disposed. For example, ascorbic acid or other reducing agents may be used to reduce
hexavalent chromium to trivalent chromium.
1 Scope
This Standard specifies the ion chromatography method for the determination of hexavalent chromium in electrical and electronic products.
This Standard is applicable to the determination of hexavalent chromium content in polymer materials for electrical and electronic products.
2 Normative References
The following documents are indispensable to the application of this document. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document. GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods 3 Principle
For soluble polymer samples of acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate (PC) and polyvinyl chloride (PVC) matrix, a suitable organic solvent may be used to dissolve the sample, then, use alkaline extraction solution to extract hexavalent chromium in the sample. For samples of antimony-free insoluble polymers 4.10 Sulfuric acid (H2SO4): density: 1.84 g/mL, 95% (mass fraction).
4.11 1,5-diphenylcarbazide.
4.12 Methanol.
4.13 Post-column derivatization solution: use a 500 mL volumetric flask; dissolve 250 mg of 1,5-diphenylcarbazide (4.11) in 50 mL of methanol (4.12); add 400 mL of water, then, add 14 mL of sulfuric acid (4.10). Use ultrapure water to dilute it to the scale, then, transfer and store it in a brown bottle. Before use, check whether the solution is discolored. If the solution is discolored, then, it shall be re-prepared. 4.14 Hexavalent chromium certified reference substance.
4.15 Molecular sieve (4A): CAS: 70955-01-0, desiccant.
4.16 Sodium bicarbonate (NaHCO3).
4.17 Ammonium sulfate [(NH4)2SO4].
4.18 Eluent: in accordance with the recommended working conditions of the instrument, the eluent may be composed of sodium carbonate (4.4), sodium bicarbonate (4.16) and ammonium sulfate (4.17) with appropriate concentrations; the eluent shall have a good degree of resolution. The systems and concentrations matching the anion exchange column may also be selected for preparation. Prepare it right before use. NOTE: the type and concentration of the eluent may be different depending on the instrument used.
5 Instruments and Equipment
5.1 Heating device: the heating temperature is controlled at 160 ??C ?? 5 ??C. 5.2 Ultrasonic water bath constant temperature oscillator: the temperature is controlled at 60 ??C ?? 2 ??C.
5.3 pH meter: pH value measurement range is 0 ~ 14, with an accuracy of ?? 0.03. 5.4 Analytical balance: accurate to 0.1 mg.
5.5 Temperature measuring device: for example, thermometer, which can measure up to 160 ??C.
5.6 Grinding machine.
5.7 Borosilicate glass or quartz beaker: with a volume scale of 150 mL, or equivalent. 7 Test Procedures
7.1 Sample Pre-treatment
7.1.1 Extraction of hexavalent chromium in soluble polymers (ABS, PC and PVC) The extraction of hexavalent chromium in soluble polymers (ABS, PC and PVC) shall be carried out in the following steps:
a) Accurately weigh-take 0.1 g of sample, then, put it into the glass bottle with a screw mouth (5.9).
NOTE: for samples, whose concentration of hexavalent chromium may be extremely low or extremely high, other sample sizes may be used.
b) Pour 10 mL of NMP (4.2) into the glass bottle with a screw mouth (5.9); tightly fasten down the cap of the container.
c) Shake the sample container by hand for about 10 s, so as to suspend the insoluble particles. Then, at a temperature of 60 ??C, use the ultrasonic water bath constant temperature oscillator (5.2) to conduct treatment for 1 h. Before proceeding to the next step, the sample shall be completely dissolved.
d) Shake the glass bottle with a screw mouth (5.9) by hand to mix it well, then, add 200 mg of MgCl2 (4.6) and 0.5 mL of 0.5 mol/L phosphate buffer solution (4.7) to each glass bottle with a screw mouth (5.9). Re-shake the glass bottle with a screw mouth (5.9) to mix it well.
e) Use a measuring cylinder (5.8) to measure-take 20 mL of the extraction solution (4.8) and slowly pour it into the glass bottle with a screw mouth (5.9); mix it well.
f) Place the sample solution prepared in Step e) in the ultrasonic water bath constant temperature oscillator (5.2); at a temperature of 60 ??C, conduct ultrasonic treatment for 1 h. When the ultrasonic treatment reaches 0.5 h, shake the glass bottle with a screw mouth (5.9) by hand to evenly mix the liquid.
g) Transfer the sample solution processed through Step f) into a 150 mL beaker (5.7); constantly stir it up and monitor the pH value. Meanwhile, dropwise add HNO3 (4.3) to the beaker. Adjust the pH value of the solution to 7.5 ?? 0.5. h) Pour the sample solution into a 100 mL volumetric flask; use pure water (4.1) to reach a constant volume to the scale. Use the 0.45 ??m filter membrane or filter syringe (5.12) and the RP solid phase extraction column (5.13) for purification.
i) Take an appropriate volume of the filtered sample and dilute it by 10 times; reserve it for the later test.
7.1.2 Extraction of hexavalent chromium in antimony-free insoluble polymers / unknown polymers and electronic parts
The extraction of hexavalent chromium in antimony-free insoluble polymers / unknown polymers, and electronic parts shall be carried out in the following steps: a) Accurately weigh-take 0.15 g of sample, then, pour it into the microwave digestion tank equipped by the microwave digestion apparatus (5.14).
NOTE: for samples, whose concentration of hexavalent chromium may be extremely low or extremely high, other sample sizes may be used.
b) Use the measuring cylinder (5.8) to respectively measure-take 10 mL of the extraction solution (4.8) and 5 mL of toluene (4.9); add it to the microwave digestion tank.
c) Add 400 mg of MgCl2 (4.6) and 0.5 mL of 0.5 mol/L phosphate buffer solution (4.7); mix it well.
d) Use the microwave digestion apparatus (5.14) or the heating device (5.1) to heat the sealed microwave digestion tank to 160 ??C; maintain it for 1.5 h. Then, cool the sample to room temperature.
e) Use the separatory funnel (5.11) to separate the organic phase from the container and discard it. Filter the inorganic phase through the 0.45 ??m filter membrane or filter syringe (5.12). Use water to rinse the filter and the microwave digestion tank for 3 times. If clogging occurs when using the 0.45 ??m filter syringe, large-pore-size filter papers may be used to filter the sample. f) Use water to rinse the inside of the filter bottle and filter pad; transfer the filtrate and rinsing fluid into a clean 150 mL beaker (5.7).
g) Constantly stir it up and monitor the pH value, meanwhile, dropwise add HNO3 (4.3). Adjust the pH value of the solution to 7.5 ?? 0.5.
7.2 Drawing of Standard Working Curve
Use the pipette (5.10) to transfer-take an appropriate amount of the hexavalent chromium certified reference substance (4.14). Use water (4.1) to dilute it to standard solutions with different concentrations. The specific concentrations are shown in Table 1. Generate a standard working curve of the standard solution series concentrations through linear regression; the correlation coefficient of the curve shall be not less than 0.999. The standard solution should be prepared right before use.

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