Determination of the most banned azo dyes analysis

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With the release of EU regulations on the prohibition of azo dyes and the implementation of China's mandatory national standard GB basic safety technical specifications for textile products, the detection methods of banned azo dyes have attracted more and more attention. The prohibition of azo dyes on textiles has become the most important monitoring index in the international and domestic production and trade of textiles and clothing

the basic branch of the National Technical Committee for textile standardization organized a standard drafting group. On the basis of summarizing the experience accumulated by many domestic experts in testing for many years and referring to the European Union standards, gb/t17592.1~17592 can be appropriately changed oil was completed in 2005 The revision of a series of national standards of "test methods for banned azo dyes in textiles". The revised version gb/t "determination of banned azo dyes in textiles" was issued and implemented in 2006. In order to ensure the accurate implementation of the standards, various testing institutions exchange experience in different forms, and enterprises are also learning and consulting the relevant contents of the standards. After discussion with relevant experts, the following explanations are made on the relevant issues involved in gb/t:

1 The main changes of the new standard

gb/t compared with the 98 version of the standard, mainly include the following changes:

- the original three parts are merged into a single standard, and the standard name is modified

- the standard is applicable to textile products processed by printing and dyeing while reducing carbon footprint

- the types of aromatic amines increased from 20 to 24

- the liquid-liquid extraction is canceled, and the pretreatment procedure for polyester product samples is added

- quantitative methods of hplc/dad external standard method and gc/ms internal standard method are added

- the practice of adding alkali to the reaction solution and adding hydrochloric acid to the ether extract is cancelled

2. Product scope of the standard

the scope of application of the 98 version of the standard is "applicable to textile products of cotton, wool, hemp, silk and viscose fibers". In fact, in addition to natural fibers and viscose fibers, there are also a large number of synthetic fiber products. Due to the narrow scope of application of the original standard, there is no basis for testing the azo dye content of these products. Therefore, the scope of gb/t clearly stipulates that "it is applicable to textile products after printing and dyeing". The textile products processed by printing and dyeing are: products dyed or printed with various colorants, including dyes, paints or pigments. Load specification for building structures GB 50009 (2) 001

3. Testing and sampling of products

gb/t stipulates that the test samples are "representative samples", which is in line with international standards. There is no sampling provision in most ISO standards for textile chemical analysis methods (such as formaldehyde and pH value). The reason for analysis may be that there are many kinds of textile products, which are ever-changing, and it is impossible to adopt a unified rule

for the detection of banned azo dyes, different sampling methods may lead to different test results, which may lead to missed detection or misjudgment. Therefore, it is necessary to clarify the sampling method. Here, for the testing and sampling of products, please refer to GB Implementation Guide - Classification and sampling examples of textile products (Continued), textile standards and quality, issue 5, 2006. For products with single color, uniform color mixing or similar effects, there are no special requirements for sampling in the test; For textile products composed of multiple components with different fibers or colors, each component is tested separately

for products with floral patterns (including printing and yarn dyed weaving), in principle, one of the color blocks is not tested as an independent component, and generally sampled according to the following methods:

- for regular small floral patterns, take at least one circular pattern or several circular patterns, cut them into pieces and mix them

- for patterns with large circulation or irregular patterns, samples shall be taken according to the proportion of the main hue as far as possible, and then mixed after cutting

- for (2) the local printing, independent printing and scattered pattern of the transmission range selection button on the white ground according to the required maximum torque, the sampling should include the main hue of the pattern. When the pattern is very small, it is not suitable to cut from multiple samples and then combine them into one sample. If these local flowers or scattered flowers are different in color, they should be sampled and tested separately. If it is only used for the inspection of internal production control or quality analysis of the enterprise, it is another matter. A single pattern or color can be taken for inspection

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