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What are the detection methods for leather formaldehyde?
Formaldehyde is a colorless gas with a strong special pungent odor. As a carcinogen, it is the key control object of many regulations. If people live in a room polluted by formaldehyde for a long time, it can cause diseases such as decreased immunity, infertility or fetal malformation, respiratory disease, mental depression, leukemia and cancer. The sources of formaldehyde in life: (1) The formaldehyde in the air mainly comes from industrial production and plastic parts, rubber products, urea-formaldehyde foam, automobile exhaust, etc.; (2) The indoor formaldehyde mainly comes from decorative materials, such as wood, Adhesives and wallpapers, etc.; (3) Formaldehyde can also come from cosmetics, preservatives, printing inks, paper, textile fibers, etc. Formaldehyde is widely used in synthetic resins, surfactants, plastics, rubber, leather, papermaking, dyes, pharmaceuticals, pesticides, photographic films, explosives, building materials, as well as in the process of disinfection, fumigation and anticorrosion. It can be said that formaldehyde is used. Formaldehyde is a generalist in the chemical industry, but the use of anything must be controlled in a limited amount and standard. Once the use exceeds the standard and limit, it will bring a negative side. Formaldehyde detection method: The chemical properties of formaldehyde are very active, so there are many methods for quantitative analysis of formaldehyde, which can be mainly classified into five categories: titration, gravimetry, colorimetry, gas chromatography and liquid chromatography. Among them, the titration method and the gravimetric method are suitable for the quantitative analysis of high-concentration formaldehyde, and the colorimetric method, gas chromatography and liquid chromatography are suitable for the quantitative analysis of trace formaldehyde. 1. Colorimetry Colorimetry is a classic method for the determination of formaldehyde, and it is also a standard method for the determination of formaldehyde in the environment. Using a UV-Vis absorption spectrophotometer (UV—VIS) analysis method has great advantages in analysis limit, accuracy and reproducibility. Just the operation is more complicated. The colorimetric method can be divided into: (1), acetylacetone method. The acetylacetone method uses an equimolar reaction between formaldehyde and acetylacetone in the presence of excess ammonium acetate to generate light yellow 2,6- Dimethyl-3,5-diacetylpyridine was measured colorimetrically at the maximum absorption wavelength of 412-415nm. The method has high precision, good reproducibility, stable color developing solution and less interference. (2) The sulfite fuchsin method (Schiff reagent method) The sulfite fuchsin method is to react fuchsin (rose red aniline) hydrochloride with acidic sodium sulfite and concentrated salt to generate magenta-acid sulfite. Then It reacts with acetylacetone formaldehyde under strong acid (sulfuric acid or hydrochloric acid) conditions to generate a rose-red (purple) salt, and the colorimetric determination is carried out at the maximum absorption wavelength of 552-554 nm. This method is easy to operate, but the sensitivity is low, the color developing solution is unstable, and the reproducibility is poor. It is suitable for quantitative analysis of higher formaldehyde content. (3) Phloroglucinol method Phloroglucinol method is to use formaldehyde and phloroglucinol to generate orange-red compounds under alkaline (2.5mol/L sodium hydroxide) conditions, and colorimetry is carried out at the maximum absorption wavelength of 460nm analyze. The advantages and disadvantages of this method are similar to the Schiff method. (4) The color-changing acid method The color-changing acid method is in the sulfuric acid medium, formaldehyde reacts with chromic acid (1,8-dihydroxynaphthalene-3,6-disulfonic acid) to form a purple compound, which has a maximum absorption wavelength of 568～ Colorimetric analysis was performed at 570 nm. This method has high sensitivity and good stability of the color developing solution, and is suitable for the determination of samples with low formaldehyde content. 2. Because the formaldehyde molecule is too small in chromatography, the peak is too fast when it is directly analyzed by GC, and there is no response in the FID detector; liquid chromatography also flows out at the same time as the solvent peak because the formaldehyde is too polar, and there is no UV Absorption cannot be detected. Therefore, when using chromatography to determine formaldehyde, formaldehyde is generally derivatized first, and then determined by GC or LC. 2,4-Dinitrophenylhydrazine is widely used in the chromatographic determination of formaldehyde as a relatively stable formaldehyde derivatizing agent. The reaction formula of formaldehyde and 2,4-dinitrophenylhydrazine is as follows. Then, the reaction product is extracted by liquid extraction or solid phase extraction with organic solvent. Because liquid-liquid extraction or solid-phase extraction not only increases the operation steps, but also causes the loss of derivatives. Usually, formaldehyde and 2,4-dinitrophenylhydrazine are directly reacted under weakly acidic conditions for liquid chromatography analysis, which does not require organic solvent extraction and avoids the loss of the extraction process. The method is applied to the determination of formaldehyde in actual samples, and the operation is simple and the result is accurate. The test of formaldehyde content is based on the requirements of the standard, and the operation methods are different. It should be comprehensively considered in combination with the test standard and the sample. If necessary, colorimetry and liquid chromatography should be used for comparison and verification to ensure the accuracy of the data. The test of formaldehyde content is a project with high technical requirements, which not only requires the operator to be proficient in the standard, but also requires the operator to have certain chemical professional knowledge and skills. Therefore, this project should attract more attention during the operation and implementation. More about Leather Testing Equipment: http://www.standard-groups.com/LeatherShoes/
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