GB/T 35799-2018 English PDF (GBT35799-2018)

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GB/T 35799-2018: Determination of sodium PCA in cosmetics -- High performance liquid chromatography
GB/T 35799-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.70
Y 42
Determination of Sodium PCA in Cosmetics -
High Performance Liquid Chromatography
ISSUED ON. FEBRUARY 6, 2018
IMPLEMENTED ON. SEPTEMBER 1, 2018
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Principle ... 4 
4 Reagents and Materials ... 4 
5 Instruments and Equipment ... 5 
6 Steps of Determination ... 5 
7 Result Calculation ... 7 
8 Recovery Rate and Precision ... 7 
9 Allowable Difference ... 7 
Appendix A (Informative) Chinese Name, English Name, INCI Name, CAS No.,
Molecular Formula, Relative Molecular Mass and Structural Formula of
Pyrrolidone Carboxylic Acid ... 8 
Appendix B (Informative) HPLC Chromatogram and DAD Spectrogram of
Pyrrolidone Carboxylic Acid Standards ... 9 
Determination of Sodium PCA in Cosmetics -
High Performance Liquid Chromatography
1 Scope
This Standard specifies the method of high performance liquid chromatography of
determining sodium PCA in cosmetics (counted by pyrrolidone carboxylic acid).
This Standard is applicable to the determination of sodium PCA (counted by
pyrrolidone carboxylic acid) in creamy, milky and liquid cosmetics.
In terms of sodium PCA (counted by pyrrolidone carboxylic acid), this Standard’s
detection limit is 0.003%; its limit of quantitation is 0.01%.
2 Normative References
The following documents are indispensable to the application of this Standard. In terms
of references with a specified date, only versions with a specified date are applicable
to this Standard. The latest version (including all the modifications) of references
without a specified date is applicable to this Standard.
GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods
3 Principle
Sample shall receive demulsification with saturated sodium chloride; mobile phase
ultrasonic extraction and centrifugation; filtration with 0.45 μm filter. Inject solution into
high performance liquid chromatograph; quantify with external standard method.
4 Reagents and Materials
Unless it is otherwise stipulated, all reagents shall be analytical purity. Water shall be
Grade-1 water that is stipulated in GB/T 6682.
4.1 Phosphate. excellent level of purity.
4.2 Sodium chloride.
4.3 Methanol. chromatographic purity.
4.4 Potassium dihydrogen phosphate.
4.5 0.02 mol/L potassium dihydrogen phosphate (pH=3.0). weigh-take 2.72 g of
potassium dihydrogen phosphate (4.4); add water to dissolve it; use phosphate (4.1)
to adjust pH to 3.0; add water to dilute to the constant volume of 1,000 mL. Use 0.45
μm filter to filter it.
4.6 Saturated sodium chloride. weigh-take 35.2 g of sodium chloride (4.2); add 97.8 g
of water; mix it, dissolve it for later usage.
4.7 Pyrrolidone carboxylic acid standards. purity shall be not less than 99.0%. Please
refer to Table A.1 in Appendix A for its Chinese name, English name, INCI name, CAS
No., molecular formula, relative molecular mass and structural formula.
4.8 Pyrrolidone carboxylic acid standard stock solution. accurately weigh-take 0.1 g of
pyrrolidone carboxylic acid standards, accurate to 0.0001 g; place it in a 100 mL
volumetric flask, then, use water to dissolve it to the constant volume. Thus,
pyrrolidone carboxylic acid standard stock solution (concentration. 1,000 mg/L) can be
obtained. Store it in a refrigerator at 4 °C; it shall remain valid within 1 week.
4.9 Standard working solutions. use 0.02 mol/L potassium dihydrogen phosphate (4.5)
to separately prepare the above-mentioned standard stock solution (4.8) into a series
of standard working solutions at the concentration of 0 mg/L, 2.0 mg/L, 10 mg/L, 50
mg/L, 100 mg/L and 200 mg/L; prepare it right before usage.
5 Instruments and Equipment
5.1 Liquid chromatograph, equipped with UV detector or diode array detector.
5.2 Analytical balance, division value. 0.0001 g.
5.3 Ultrasonic oscillator.
5.4 Centrifuge. rotating speed ≥ 10,000 r/min.
5.5 Filter membrane. aperture 0.45 μm.
5.6 Centrifuge tube. 10 mL.
5.7 Vortex oscillator.
6 Steps of Determination
6.1 Sample Processing
Weigh-take 0.2 g (accurate to 0.001 g) of sample, place it into a 10 mL centrifuge tube.
Add 1.0 mL of saturated sodium chloride (4.6), then, start vortex shaking for 1 min. Add
5.0 mL of 0.02 mol/L potassium dihydrogen phosphate (4.5). Start ultrasonic extraction