GB/T 26388-2011 PDF English
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Determination of dioxane residues in surfactants -- Gas chromatographic method
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GB/T 26388-2011: PDF in English (GBT 26388-2011) GB/T 26388-2011
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.40
Y 43
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
1 Scope
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
3 Principles
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.
4 Reagents
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
chromatographic analysis.
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 Programs
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):
where:
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
kilogram (mg/kg);
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 Detection
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.
11 Precision
11.1 Repeatability
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.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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