QB/T 5291-2018 English PDF (QBT5291-2018)

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QB/T 5291-2018: Determination of hexavalent chromium in cosmetics
QB/T 5291-2018
LIGHT INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.70
Classification No.: Y42
Filing No.: 65903-2018
Determination of hexavalent chromium in cosmetics
ISSUED ON: OCTOBER 22, 2018
IMPLEMENTED ON: APRIL 01, 2019
Issued by: Ministry of Industry and Information Technology of PRC
Table of Contents
Foreword ... 3 
Introduction ... 4 
1 Scope ... 5 
2 Normative references ... 5 
3 Method 1 -- Diphenylcarbazide spectrophotometry ... 5 
4 Method 2 -- Ion chromatography-inductively coupled plasma mass spectrometry ... 8 
Appendix A (Informative) Reference conditions of instrument ... 12 
Appendix B (Informative) Ion chromatography-mass spectrograms of standard
solutions and samples ... 13 
Determination of hexavalent chromium in cosmetics
1 Scope
This standard specifies the methods for the determination of hexavalent chromium in
cosmetics, by diphenylcarbazide spectrophotometry and ion chromatography-
inductively coupled plasma mass spectrometry.
This standard applies to the determination of hexavalent chromium in cosmetics. When
the sample weight is 2 g, the detection limit of diphenylcarbazide spectrophotometry is
0.25 mg/kg, the quantification limit is 0.83 mg/kg; the detection limit of ion
chromatography-inductively coupled plasma mass spectrometry is 0.010 mg/kg, the
quantification limit is 0.033 mg/kg.
2 Normative references
The following documents are essential to the application of this document. For the dated
documents, only the versions with the dates indicated are applicable to this document;
for the undated documents, only the latest version (including all the amendments) is
applicable to this standard.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
3 Method 1 -- Diphenylcarbazide spectrophotometry
3.1 Principle
After the sample is extracted by the alkaline leaching solution, the hexavalent
chromium in the leaching solution reacted with diphenylcarbazide in an acidic solution,
to form a purple-red complex, which was determined by spectrophotometry, at a
wavelength of 540 nm.
3.2 Reagents
Unless otherwise specified, the reagents are of analytical grade. The water is the first
grade water, which is specified in GB/T 6682.
3.2.1 Nitric acid (ρ20 = 1.42 g/mL), excellent grade.
3.2.2 Sulfuric acid (ρ20 = 1.84 g/mL), excellent grade.
3.2.3 Sodium hydroxide.
3.2.4 Anhydrous sodium carbonate.
3.2.5 Dipotassium hydrogen phosphate.
3.2.6 Potassium dihydrogen phosphate.
3.2.7 Diphenylcarbazide.
3.2.8 Acetone.
3.2.9 Activated carbon powder (75 µm ~ 177 µm): If the background of activated
carbon powder interferes with color development, use water to wash it 2 ~ 3 times.
Place it in an oven, at 110 °C ~ 120 °C, to dry for 10 hours. Prepare for use.
3.2.10 Nitric acid solution (5 mol/L): Measure 31 mL of nitric acid (3.2.1). Add it to 69
mL of water. Mix well to prepare for use.
3.2.11 Sulfuric acid solution: Measure 5 mL of sulfuric acid (3.2.2). Add it to 100 mL
of water. Mix well to prepare for use.
3.2.12 Extraction solution: Weigh 20 g of sodium hydroxide (3.2.3) and 30 g of
anhydrous sodium carbonate (3.2.4). Use water to dissolve them. Transfer them to a
1000 mL volumetric flask. Dilute to the mark. Mix well. Transfer it into plastic bottles
for storage.
3.2.13 Buffer: Dissolve 8.71 g of dipotassium hydrogen phosphate (3.2.5) and 6.80 g
of potassium dihydrogen phosphate (3.2.6) in water. Pipette it to a 100 mL volumetric
flask. Use water to dilute it to the mark (this buffer solution has a pH = 7).
3.2.14 Hexavalent chromium standard solution: 1000 mg/L.
3.2.15 Standard stock solution of hexavalent chromium (c = 5.0 mg/L): Pipette 0.50 mL
of standard stock solution (3.2.14) into a 100 mL volumetric flask. Use water to dilute
it to the mark. Mix well to prepare for use.
3.2.16 Diphenylcarbazide developer: Weigh 0.5 g of diphenylcarbazide (3.2.7).
Dissolve it in 100 mL of acetone (3.2.8). Store it in a brown bottle.
3.3 Instruments
3.3.1 UV-Visible spectrophotometer.
3.3.2 Ultrasonic generator: Constant temperature (60 ± 1) °C.
3.3.3 Acidity meter.
3.3.4 Analytical balance: Sensitivity 0.0001 g.
3.3.5 Graduated centrifuge tube (polyethylene or polypropylene): Specification 50 mL.
3.4 Analytical procedures
3.4.1 Sample processing
Accurately weigh (0.5 g ~ 2 g, accurate to 0.0001 g) of the sample into a 50 mL
graduated centrifuge tube. Add 20.0 mL of extract (3.2.12) and 0.5 mL of buffer (3.2.13).
Completely submerge the sample in the extract. Shake well. Carry out ultrasonic
extraction, at 60 °C for 20 min. Take it out. Cool to room temperature. Use water to
make its volume reach to 25.0 mL. Add 2.0 g of activated carbon powder. Shake well.
Use filter paper to filter it. Discard the first 1 mL of filtrate. Collect 20 mL of filtrate in
a clean 50 mL graduated centrifuge tubes. Add 5 mol/L of nitric acid (3.2.10) dropwise.
Use the acidity meter (3.3.3), to control the pH of the solution at (7.5 ± 0.5).
3.4.2 Color developing
Add 2.0 mL of diphenylcarbazide developer (3.2.16) to the filtrate (3.4.1). Mix well.
Add the sulfuric acid solution (3.2.11) dropwise, to make the pH of the filtrate reach
2.0 ± 0.5. Then transfer all the solution into a 50 mL volumetric flask. Use water to
dilute it to the mark. Mix well. Prepare for test, after color development for 10 min.
At the same time, do a reagent blank test. When the sample background has an influence
on the measurement results, the background absorbance of the sample needs to be
measured. Use 2.0 mL of acetone (3.2.8), to replace the diphenylcarbazide color
developer (3.2.16). The sample size and treatment steps are the same as the sample
determination. Take the determination result as the sample blank.
3.4.3 Preparation of standard curve solution
Pipette 0 mL, 0.5 mL, 1.0 mL, 2.0 mL, 4.0 mL, 6.0 mL of chromium standard solution
(3.2.15), respectively. Place them in 50 mL graduated centrifuge tubes, respectively.
Add 25 mL of water. Add 2.0 mL of color developer (3.2.16). Mix well. Add sulfuric
acid solution (3.2.11) dropwise, to make the pH of the filtrate reach 2.0 ± 0.5. Transfer
it to a 50 mL volumetric flask. Use water to dilute it to the mark. Mix well. Prepare for
test, after color development for 10 min. The concentrations of the standard series are:
0 mg/L, 0.050 mg/L, 0.10 mg/L, 0.20 mg/L, 0.40 mg/L, 0.60 mg/L.
3.4.4 Determination
Use a 1 cm absorption cell, to measure the standard curve solution, blank, specimen
solution sequentially, using an ultraviolet-visible spectrophotometer, at an absorption
wavelength of 540 nm.
3.5 Result calculation
Unless otherwise specified, the reagents are of analytical grade. The water is the first
grade water, which is specified in GB/T 6682.
4.2.1 Nitric acid (ρ20 = 1.42 g/mL): excellent grade.
4.2.2 Ammonia.
4.2.3 Sodium hydroxide.
4.2.4 Anhydrous sodium carbonate.
4.2.5 Dipotassium hydrogen phosphate.
4.2.6 Potassium dihydrogen phosphate.
4.2.7 Activated carbon powder (75 µm ~ 177 µm): If the background of activated
carbon powder interferes with color development, use water to wash it 2 ~ 3 times.
Place it in an oven, at 110 °C ~ 120 °C for 10 h, to prepare for use.
4.2.8 Extraction solution: Weigh 20 g of sodium hydroxide (4.2.3) and 30 g of
anhydrous sodium carbonate (4.2.4). Use water to dissolve it. Transfer it to a 1000 mL
volumetric flask. Dilute it to the mark. Mix well. Transfer ...