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Simply put, analytical purity is slightly higher than chemical purity, but analytical purity does not necessarily have to reach a certain number of nines; it is classified according to national standards based on the specific reagent. The purity of chemical reagents in China is currently classified as follows: National standard reagents: These reagents are specified by China’s standards and are suitable for testing, identification, and analysis. Reference reagents (JZ, green label): Used as reference materials for calibrating standard solutions. Ultra-pure (GR, green label) (Grade 1): It has a very high content of the main component and high purity, making it suitable for precise analysis and research work; some of it can be used as reference materials. Analytical grade (AR, red label) (grade 2): It has a high content of the main component, high purity, and very low levels of interfering impurities; suitable for industrial analysis and chemical experiments. Chemically pure (CP, blue label) (Grade 3): High content of the main component and relatively high purity, with the presence of interfering impurities; suitable for chemical experiments and synthetic preparations. Experimental grade pure (LR, yellow label): High content of principal components, lower purity; impurity levels are not specified. Suitable only for general chemical experiments and synthetic preparations. Teaching reagents (without labels): A type of reagent that can meet the teaching needs of students without causing deviations in chemical reactions. Designated grade (ZD): These reagents are chemical substances tailored for specific users, in accordance with the quality control standards specified by those users. High-purity reagents (EP): including ultra-pure, special-pure, high-purity, and spectroscopically pure grades, used for preparing standard solutions. The quality of such reagents is evaluated based on the level of impurities that may cause deviations in analysis results during specific analytical methods, as well as those impurities that can interfere with component analysis or content determination; however, no high requirements are placed on the main component content. Chromatographically pure (GC): intended for gas chromatography analysis. The quality criteria focus on impurities that interfere with gas chromatography peaks. High content of principal components. Chromatographically pure (LC): A standard material for liquid chromatography analysis. The quality criteria focus on impurities that interfere with the peaks in liquid chromatography. High content of principal components Indicator (ID): Used to prepare indicator solutions. The quality indicators are the color change range and the sensitivity to color change. It can replace CP and is also suitable for organic synthesis. Biochemical reagents (BR): Used for preparing solutions for biochemical tests and biochemical synthesis. Quality indicators focus on bioactive impurities. Alternative indicators that can be used in organic synthesis. Biological stains (BS): used to prepare staining solutions for microbial specimens. Quality indicators focus on bioactive impurities. Alternative indicator, usable in organic synthesis. Spectrally pure (SP): used for spectral analysis. Suitable respectively for spectrophotometer standards, atomic absorption spectroscopy standards, and atomic emission spectroscopy standards. Electronic grade (MOS): Used in electronics manufacturing, with an extremely low content of electrical impurities. Equivalent reagents (3N, 4N, 5N): The main component content is over 99.9%, 99.99%, and 99.999% respectively. Electrophoresis reagents: The quality specifications focus on controlling the content of electrical impurities. In addition, there are special reagents whose production volume is extremely low; they are manufactured on demand, and their quantity and quality are generally specified by the user.