GB/T 26388-2011 English PDF (GBT26388-2011)
GB/T 26388-2011 English PDF (GBT26388-2011)
GB/T 26388-2011: Determination of dioxane residues in surfactants -- Gas chromatographic method
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
Determination of dioxane residues in surfactants -
Gas chromatographic method
ISSUED ON: MAY 12, 2011
IMPLEMENTED ON: SEPTEMBER 15, 2011
Issued by: General Administration of Quality Supervision, Inspection and Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Principles ... 4
4 Reagents ... 4
5 Instruments ... 5
6 Preparation of standard solution ... 5
7 Sample preparation ... 6
8 Programs ... 7
9 Chromatographic evaluation ... 11
10 Presentation of results ... 11
11 Precision ... 13
12 Test report ... 13
Appendix A (Informative) How to find a linear regression equation ... 14 Determination of dioxane residues in surfactants -
Gas chromatographic method
This standard applies to the determination of trace amounts of 1,4-dioxane, in the surfactants, which are produced from ethylene oxide as raw materials, such as ethoxylated alkyl sulfates and polyethylene glycols. For the personal care products, which contain such surfactants, it may also refer to the method, which is determined by this standard, to determine the content of 1,4-dioxane. This standard applies to the determination of samples, which contain not less than 5 mg/kg 1,4-dioxane (using a hydrogen flame ionization detector) or 2.5 mg/kg 1,4-dioxane (using a mass selective detector). When the content of 1,4- dioxane exceeds 100 mg/kg, it is necessary to increase the concentration of the standard solution OR dilute or reduce the sample for determination. 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 13173-2008 Surface active agents - Detergents - Testing methods
Weigh the sample in the headspace vial. Then add the standard solution or solvent. Place the sealed vial in the headspace sampling instrument. Make it thermally equilibrated. The gas fraction in the vapor phase is separated by a temperature-programmed capillary column or packed column; it is used by the flame ionization detector, internal standard method or quantitative standard addition method.
Unless otherwise stated, only confirmed analytical grade reagents and distilled or deionized water or water of equivalent purity are used, in the analysis. 4.1 N,N-Dimethylformamide (DMF).
Note: DMF shall not interfere with the 1,4-dioxane and 4-methyl-1,3-dioxane peaks. 4.2 1,4-Dioxane: Purity ≥ 98% (ρ = 1.03 g/mL, 20 °C).
4.3 4-methyl-1,3-dioxane: Purity ≥ 98% (ρ = 0.98 g/mL, 20 °C), internal standard. 5 Instruments
Common laboratory instruments and the following.
5.1 Analytical balance, which has a sensitivity of 0.1 mg.
5.2 Gas chromatograph, which is equipped with programmed heating device and hydrogen flame ionization detector (FID) or mass selective detector (MSD). 5.3 Headspace sampler.
5.4 20 mL glass bottle, sealing gasket, sealing forceps, which are suitable for headspace equipment.
5.5 Chromatographic column: It is selected according to the type of detector, see 8.1 for specific requirements.
5.6 Volumetric flasks: 50 mL and 100 mL.
5.7 Gas-tight syringe: 1.00 mL ± 0.01 mL.
6 Preparation of standard solution
6.1 Standard stock solutions
Add about 40 mL of DMF to a 50 mL volumetric flask. Weigh 200 mg ± 1 mg of 1,4-dioxane. Use DMF to make the volume reach to the mark. Mix it uniformly. This solution contains 4 mg/mL of 1,4-dioxane.
6.2 Standard working solution
Pipette different volumes of standard stock solution (6.1), according to Table 1. Use DMF to make it reach the volume. Mix well. Prepare standard working solutions with different 1,4-dioxane concentrations, for quantitative
b) Add 1.00 mL ± 0.01 mL of standard solution D to the second bottle; seal it immediately; shake vigorously, until it is evenly mixed. This solution
contains 50 mg/kg of 1,4-dioxane added;
c) Add 1.00 mL ± 0.01 mL of standard solution E to the third bottle; seal it immediately; shake vigorously, until it is evenly mixed. This solution
contained 100 mg/kg of 1,4-dioxane added.
7.2.2 Internal standard method
For the specimens with known response factors and internal standard factors as described in 8.2, the following methods can be used:
Weigh 2.00 g ± 0.01 g of the specimen into a headspace vial. Add 1.00 mL ± 0.01 mL of standard solution A. Seal it immediately. Shake vigorously, until it is evenly mixed. Use it for chromatographic determination.
Note: When using the internal standard method for determination, 4-methyl-1,3- dioxane shall be used as the internal standard.
8.1 Chromatographic conditions
8.1.1 The choice of chromatographic conditions depends on the instrument used; the conditions given below can be modified, to provide suitable
separation conditions for the determination of the mixture.
a) The following conditions apply to gas chromatography-flame ionization (GC/FID) capillary column separation; Figure 1 is an example of a typical sample:
- Sample inlet temperature 200 °C;
- Chromatographic column: 50 m × 0.53 mm (i.d.) fused silica capillary
column (film thickness: 5.0 μm), with 5% phenyl silicone and 95%
methyl silicone as stationary phase or equivalent;
- Column settings are as follows:
1) Keep the initial temperature at 60 °C, for 3 min;
2) The initial heating rate is 4 °C/min to the intermediate temperature of 80 °C;
3) The final heating rate is 30 °C/min to the final temperature of 300 °C; The correlation response factor k is calculated by formula (1):
A1 - The peak area of 4-methyl-1,3-dioxane internal standard;
c2 - The concentration of 1,4-dioxane in the sample, in milligrams per
A2 - The peak area of 1,4-dioxane;
c1 - The concentration of 4-methyl-1,3-dioxane internal standard in the sample (if using the internal standard according to the instructions in Table 1, the concentration is 20 mg/kg), in milligrams per kilogram (mg/kg).
8.3.1 Standard addition method
Prepare the sample mixture, as described in 7.2.1. Place the sample vial into the headspace sampling device. Analyze it according to the chromatographic conditions given in 8.1.
8.3.2 Internal standard method
As the sample mixture described in 7.2.2, put the sample vial into the
headspace sampling device. Analyze it according to the chromatographic
conditions given in 8.1.
9 Chromatographic evaluation
Refer to Figure 1 or Figure 2, to determine the components in the specimen. Determine the peak area of 1,4-dioxane and 4-methyl-1,3-dioxane (if not using 4-methyl-1,3-dioxane, there is no corresponding chromatographic peak).
10 Presentation of results
10.1 Standard addition method
Taking the concentration of 1,4-dioxane as the independent variable AND the peak area as the dependent variable, the fitting curve equation is calculated by means of linear regression. The component concentration of 1,4-dioxane is calculated by substituting the peak area as zero, into the obtained equation (see sample (when using the internal standard according to the instructions in Table 1, the concentration is 20 mg/kg), in milligrams per kilogram (mg/kg); A1 - The peak area of 4-methyl-1,3-dioxane internal standard.
When the same test sample is determined by the same operator, in the same laboratory, through the same instrument and the same method, in a short period of time, the absolute difference between the two independent test results does not exceed the repeatability limit r; the situation where the repeatability limit r is exceeded is not more than 5%. Relative repeatability limits can be allowed as: When the concentration of 1,4-dioxane in the sample is < 20 mg/kg, it is 20%; When the concentration of 1,4-dioxane in the sample is ≥ 20 mg/kg, it is 15%. 11.2 Reproducibility
When the same test sample is measured, by different operators, in different laboratories, through different instruments and the same method, the absolute difference between the two independent test results does not exceed the reproducibility limit R; the case where the reproducibility limit R is exceeded does not exceed 5%. The relative reproducibility limit (calculated as a percentage of 1,4-dioxane concentration) can be allowed up to 45%.
12 Test report
The test report shall contain the following information:
a) All necessary information that can reflect the sample;
b) The method used;
c) The results and testing procedures used;
d) Not in accordance with this standard or other operational details
referenced in the standard, or other optional related operations and all annexes that may affect the results.