GB/T 35952-2018 PDF in English
GB/T 35952-2018 (GB/T35952-2018, GBT 35952-2018, GBT35952-2018)
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Determination of undecylenic acid and zinc undecylenate in cosmetics -- Gas chromatography
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Standards related to (historical): GB/T 35952-2018
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GB/T 35952-2018: PDF in English (GBT 35952-2018) GB/T 35952-2018
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.70
Y 42
Determination of Undecylenic Acid and Zinc
Undecylenate in Cosmetics - Gas Chromatography
ISSUED ON: FEBRUARY 06, 2018
IMPLEMENTED ON: SEPTEMBER 01, 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 ... 5
6 Determination steps ... 5
7 Result calculation ... 7
8 Recovery and precision ... 7
9 Allowable difference ... 8
Appendix A (Informative) Standard substance information of undecylenic acid
and zinc undecylenate ... 9
Appendix B (Informative) Gas chromatogram of methyl esterification of
undecylenic acid standard solution ... 10
Determination of Undecylenic Acid and Zinc
Undecylenate in Cosmetics - Gas Chromatography
1 Scope
This Standard specifies the gas chromatographic method for the determination
of undecylenic acid and zinc undecylenate in cosmetics (creams, emulsions,
lotions) and hand sanitizers.
This Standard applies to the determination of undecylenic acid and zinc
undecylenate in cosmetics (creams, emulsions, lotions) and hand sanitizers.
The detection-limit of this method for undecylenic acid and zinc undecylenate
is 12 mg/kg (0.001 2%), and the quantitation-limit is 40 mg/kg (0.004%) (both
in terms of acid).
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
GB/T 6682, Water for analytical laboratory use. Specification and test
methods
3 Principle
After the undecylenic acid and zinc undecylenate are methylated by the sulfuric
acid-methanol solution, use n-hexane to extract the produced methyl
undecylenate; filter the n-hexane layer through a 0.45 μm filter; then, inject it
into the gas chromatograph for detection; use the external standard method to
quantify.
4 Reagents and materials
Unless otherwise specified, all the reagents are analytical reagents, and the
water is grade-1 water which is specified by GB/T 6682.
4.1 Methanol: chromatographic pure.
(4.2); vortex and mix well; add 2 mL of saturated sodium chloride solution (4.8);
vortex and mix well; let stand for layering; add 2 mL of distilled water to wash
the organic layer; let stand; take the upper organic layer for filtering and injection.
6.2 Sample treatment
Accurately weigh 0.25 g of sample; add 5 mL of 5% sulfuric acid-methanol
solution (4.7); perform ultrasonic extraction for 10 min. The methyl esterification
steps are the same as 6.1.
6.3 Determination
6.3.1 Chromatographic conditions
The chromatographic conditions are shown as below:
a) chromatographic column: HP-5 capillary column (30.0 m × 0.25 mm × 0.25
μm) or a column of equivalent polarity;
b) heating procedure: keep the initial temperature of 100°C for 2 min; rise the
temperature to 240°C at 15°C/min; then, keep it for 5 min;
c) temperature of the injector: 250°C; temperature of the detector: 260°C;
d) carrier gas flow velocity: 1 mL/min.
e) injection volume: 1 μL;
f) split ratio: 30:1.
6.3.2 Drawing of the standard working curve
Inject the undecylenic acid standard working solution (6.1) into the gas
chromatograph; detect it according to the chromatographic conditions of 6.3.1;
respectively take the chromatographic peak area of the undecylenic acid methyl
ester as the ordinate, and the total content of undecylenic acid in the system
before methyl esterification as the abscissa to draw the standard working curve
of undecylenic acid. See Figure B.1 in Appendix B for the gas chromatogram of
methyl esterification of undecylenic acid standard solution.
6.3.3 Sample determination
Inject the sample solution (6.2) into the gas chromatograph; measure according
to the chromatographic conditions of 6.3.1. The peak area of the
chromatographic peak can be used to determine the total undecylenic acid
content from the standard curve; the response value of the measured
substance in the sample solution shall be within the linear range of the standard
curve. When the content of the measured substance is higher than the upper
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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