GB/T 40275-2021 English PDF (GBT40275-2021)

This Standard specifies high performance liquid chromatography (HPLC) method to determine the content of restricted preservatives - sorbic acid and benzoic acid - in toothpaste. This Standard is applicable to the determination of the content of restricted preservatives - sorbic acid and benzoic acid - in toothpaste. The method detection limit of this Standard is 0.5mg/kg.

GB/T 40275-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.01
CCS W 04
Textiles - Quantitative Analysis of Bicomponent Fiber -
Melting Microscopy Method
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Principle ... 4
5 Instruments, Equipment and Materials ... 5
6 Test Procedures ... 5
7 Calculation and Result Expression ... 7
8 Test Report ... 8
Appendix A (informative) Cross-sectional Morphology of Sheath-core Type, Paralleling Type, Fibril Matrix Type and Split Type of Bicomponent Fibers ... 9 Appendix B (informative) Volume Density and Melting Point of Conventional Components in Bicomponent Fiber ... 11
Appendix C (normative) Determination of Coefficient of Variation, Allowable Error Rate and Number of Increased Test Fibers ... 12
Bibliography ... 15
Textiles - Quantitative Analysis of Bicomponent Fiber -
Melting Microscopy Method
1 Scope
This Standard describes the method of adopting the melting microscopy method for the determination of the mass fraction of each component in the bicomponent fiber. This Standard is applicable to bicomponent fiber identifiable by melting and textile products with unchanged appearance.
NOTE: for samples that can be tested by both the chemical dissolution method and this Method, the chemical dissolution method is preferred.
2 Normative References
The content of the following document constitutes indispensable clauses of this document through the normative references in the text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document.
FZ/T 01101-2008 Textile Test Method - Fiber Content - Quantitative Physical Analysis 3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Bicomponent Fiber
Bicomponent fiber refers to a fiber composed of two high polymers with different chemical or physical structures.
NOTE: bicomponent fibers include four types of structures: sheath-core type, paralleling type, fibril matrix type and split type, etc.
4 Principle
After using a microscope to observe and collect the cross-sectional images of the bicomponent fiber. In accordance with the different characteristics of melting point, morphology, polarity and solubility, determine the corresponding fiber component; collect images at 12 different positions; ensure that the images are not repeatedly collected on the fibers. Among the 12 collected images, there shall be at least 120 fibers with clear cross-sections.
If the bicomponent is relatively approximate in morphology and size, it may cause relatively significant interference to the quantitative determination. Collect 1 clear image, then, at the same position, take the polarized image to assist the quantitative determination.
6.3 Qualitative Analysis of Fiber Components
6.3.1 At a rate of 3 °C/min ~ 4 °C/min, raise the temperature of the fiber specimen on the heating table. When a certain component melts, immediately transfer it to the heat preservation state; record the melting temperature.
6.3.2 Fine-tune the digital metallographic stereo-microscope (5.5); magnify by 500 ~ 1,000 times to observe the melting process of the low-melting component in the fibers. After most of the component is melted, collect the post-melting image; continue to raise the temperature; determine and record the melting point of the other component. Combine the melting image, or supplemented by the difference of the polarized image, determine the morphology of the bicomponent fiber (see Appendix A) and the distribution position of each component in the clear image.
6.3.3 In accordance with the melting point of each component, conduct the qualitative analysis; determine the corresponding volume density (see Appendix B).
NOTE: if the determined melting points of the bicomponent are relatively close, then, refer to FZ/T 01057, supplemented by other qualitative methods to conduct the identification.
6.4 Quantitative Determination of Fiber Components
6.4.1 Determination of cross-sectional area ratio of bicomponent
6.4.1.1 Method A: determination by digital fiber analysis software
Respectively import the 60 clear fiber cross-sectional images collected in 6.2 into the digital fiber analysis software matching the digital metallographic stereo-microscope (5.5). In accordance with 7.2.1.2 in FZ/T 01101-2008, determine the number of pixels corresponding to the cross-sectional area of the bicomponent in each fiber; calculate the ratio of the two; the result shall retain two decimal places.
6.4.1.2 Method B: determination by micro-projector
Respectively import the 60 clear fiber cross-sectional images collected in 6.2 into the micro-projector (5.6). In accordance with 7.2.1.1 in FZ/T 01101-2008, determine the cross-sectional area of the bicomponent in each fiber; calculate the ratio of the cross- Appendix C
(normative)
Determination of Coefficient of Variation, Allowable Error Rate and Number of Increased Test Fibers
C.1 Calculation of Coefficient of Variation
The coefficient of variation shall be calculated in accordance with Formula (C.1) and Formula (C.2). The calculation result shall retain two decimal places; the third decimal place is rounded when it is non-zero.
Where,
S---the standard deviation of the mass fraction of a certain component in the fiber, expressed in (%);
X1i---the mass fraction of a certain component of the ith fiber, expressed in (%); X1---the average mass fraction of a certain component in the fiber, expressed in (%); N---the total number of test fibers;
CV---the coefficient of variation of the mass fraction of a certain component in the fiber, expressed in (%).
C.2 Calculation of Allowable Error Rate
A large number of n test values are in approximately normal distribution. Under the confidence level of 95%, the true value will fall within the interval of the arithmetic mean value X ± C of the test result of the specimen. This interval is known as the confidence limit. The half-width value C and the allowable error rate of the confidence interval shall be calculated in accordance with Formula (C.3) ~ Formula (C.5):