GB/T 35952-2018 (English Version)

Standard No.: GB/T 35952-2018
Language: Chinese, Available in English version
Release Date: 2018
Published By: General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
Latest: GB/T 35952-2018

Scope: This standard specifies the gas chromatography determination method for undecylenic acid and its zinc salt in cosmetics (creams, lotions, toners) and hand sanitizers. It is applicable to the determination of undecylenic acid and its zinc salt in cosmetics (creams, lotions, toners) and hand sanitizers.

Introduction

1. Standard Overview

This standard specifies the gas chromatography determination method for undecylenic acid and its zinc salt in cosmetics (creams, lotions, toners) and hand sanitizer products. It is applicable to the quantitative detection of undecylenic acid and its zinc salt in the above products, with a detection limit of $12~\mathrm{mg/kg}$ to $0.002\%$.

2. Determination Principle

Undecylenic acid and its zinc salt are methylated with sulfuric acid methanol solution, and the resulting undecylenic acid methyl ester is extracted with n-hexane. The n-hexane layer is filtered through a $0.45~\mu\mathrm{m}$ filter membrane and injected into a gas chromatograph for detection, and the external standard method is used for quantification.

3. Reagents and Instrument Requirements

Category	Name	Specifications	Remarks
Reagents	Methanol	Chromatographic grade	For methyl esterification reaction
Instrument	Gas Chromatograph (GC-FID)	Equipped with hydrogen flame ionization detector	HP-5 capillary column is recommended

4. Determination Procedures

Standard working solution treatment:Take the standard solution of undecylenic acid at various concentrations, add sulfuric acid methanol solution, and react in a $65~^{\circ}C$ water bath for $1~\mathrm{h}$. After cooling, add n-hexane, vortex mix and add saturated sodium chloride solution. After standing and stratification, wash the organic layer, take the upper organic layer, filter and inject.

Sample treatment:Accurately weigh $0.25\mathrm{~g}$ sample, add sulfuric acid methanol solution, and ultrasonically extract for $10\mathrm{min}$. The methylation step is the same as the standard working solution.

Chromatographic conditions: - Chromatographic column: HP-5 capillary column $(30.0~\mathrm{m} \times 0.25~\mathrm{mm} \times 0.25~\mu\mathrm{m})$ or equivalent polarity chromatographic column - Temperature program: initial temperature $100~^{\circ}\mathrm{C}$, maintain for $2\mathrm{min}$, increase the temperature to $240~^{\circ}\mathrm{C}$ at $15~^{\circ}\mathrm{C}/\mathrm{min}$, maintain for $5\mathrm{min}$ - Inlet temperature: $250~^{\circ}\mathrm{C}$, detector temperature: $260~^{\circ}\mathrm{C}$

Result calculation: The mass fraction $X_i$ of undecylenic acid or undecylenic acid zinc salt in the sample is calculated as follows: $$ X_{i} = \frac{m_{i}}{m \times 10^{3}} \times 100 $$

5. Standard Comparison and Application Suggestions

Dimensions	GB/T 35952—2018	Comparison standards (such as ISO XYZ)	Advantages
Detection Range	$12~\mathrm{mg/kg}$ to $0.002\%$	-	Wide applicability, covering low-content detection needs

6. Implementation recommendations

To ensure the accuracy and reliability of the test results, it is recommended that:

Strictly control the methyl esterification reaction conditions (such as sulfuric acid concentration, water bath temperature)
Use high-purity reagents to avoid interference from impurities
Regularly calibrate the instrument and verify the linear range of the standard curve
Operators must undergo professional training

GB/T 35952-2018 history

2018 GB/T 35952-2018 Determination of undecylenic acid and zinc undecylenate in cosmetics—Gas chromatography