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Standard reagents are those used in analytical chemistry that have known contents (or purities) or characteristic values; reagents whose amounts present and those consumed in reactions can be used as benchmarks for analytical measurements are referred to as standard reagents. In short, a standard reagent is a reference substance used to measure the chemical quantity of other substances. Although instrumental analysis is widely used today, most of the values obtained through this method are physical quantities; to convert them into chemical quantities, standard reagents (substances) are required. This shows its importance. As is well known, the quality of analyzed data is closely related to the quality of the standard reagents used. Therefore, standard reagents have higher reliability compared to other specifications. They are generally selected from guarantee reagents or JIS (Japanese Industrial Standard) reagents. However, standard reagents are not high-purity reagents; for standard reagents, strict control over the main component content is required, whereas for high-purity reagents, strict control over the impurity content is necessary. In our country, it is customary to refer to the standard reagents used in titrimetric analysis and those that correspond to IUPAC (International Union of Pure and Applied Chemistry) Grade C pH standard reagents as reference reagents, while calling the others standard reagents. Standard reagents and reference reagents are collectively referred to as standard reagents. There are many types of standard reagents; the commonly used ones in China include the following categories: Primary standards for titrimetric analysis (solid), Working standards for titrimetric analysis (solid), Standard solutions for titrimetric analysis (solution), Standards for organic element analysis (solid), pH standard reagents (solid), PD standard reagents (solid), Standards for ion-selective electrodes (solid), pH standard buffer solutions (solution), Standards for gas chromatography (liquid, solid), Standards for chromatographic analysis (solid), Standard solutions for impurity analysis (solution), Standard solutions for spectral analysis (solution), Standard solutions for oil analysis (solution), Standards for calorimetric analysis (solid), Standard solutions for clinical analysis (solution), Standards for pesticide analysis (solid), Standards for NMR analysis (solid), Standards for high-purity metals (solid). Note: The classification of chemical standards according to IUPAC: Grade A – Atomic weight standards. The reference material (Valid Standard) that is closest to Grade B and Grade A. Grade C is a standard reagent with a content of 100 ± 0.02 %. Grade D is a standard reagent with a content of 100 ± 0.05 %. Grade E refers to a purity obtained through comparative testing using Grade C or Grade D reagents, or to reagents with a purity equivalent to that, which is lower than the purity of Grade D. 1. Standard reagents for titrimetric analysis: Standard reagents used in titrimetric analysis serve as the benchmarks for stoichiometric measurements. They are not only essential standards for chemical analysis and instrumental analysis, but also fundamental reagents necessary for determining the standard values of reference substances. It is divided into two levels: First, titrimetric analysis of the first primary reagent. The specification requirement for the content of this first primary reagent in titrimetric analysis is 99.98–100.02%, and its testing is carried out by the National Institute of Metrology of China using the highly accurate \"coulometry\" method. Once approved, it is supplied to factories that produce standard reagents for titrimetric analysis, to serve as a benchmark for conducting titrimetric tests; therefore, this grade of reagent can be considered the \"standard of standards\". It is equivalent to IUPAC Grade C, and its English name is Primary Standard. The existing products include: potassium hydrogen phthalate, anhydrous sodium carbonate, sodium chloride, and potassium permanganate. Second, reference reagents for titrimetric analysis: The specified purity range for these reference reagents is 99.95–100.05 %. Manufacturers use the standard known as “Primary Reference for Titrimetric Analysis” and employ accurate gravimetric methods for determining their purity. Refer to GB-1253-1989 to 1260-1990 (Chemical Reagents: Reference Reagents, Volume 1), which are intended for users to calibrate standard solutions for titrimetric analysis, as shown in the table below. It is equivalent to Grade D as specified by IUPAC, and its English name is Working Standard. Uses of working standards in titrimetric analysis. Name of the working standard; Standard solution used for its calibration. **Standard number**: Sodium chloride – Silver nitrate standard solution, GB1253-1989; Sodium oxalate – Potassium permanganate standard solution, GB1254-1990; Anhydrous sodium carbonate – Hydrochloric acid, sulfuric acid standard solutions, GB1255-1990; Arsenic trioxide – Iodine standard solution, GB1256-1990; Potassium hydrogen phthalate – Sodium hydroxide, perchloric acid standard solutions, GB1257-1989; Potassium iodate – Standard solution prepared directly, GB1258-1990; Potassium dichromate – Sodium thiosulfate standard solution, GB1259-1989; Zinc oxide – EDTA disodium standard solution, GB1260-1990; Anhydrous p-aminobenzenesulfonic acid – Sodium nitrite standard solution, GB1261-1977; Potassium chloride – Silver nitrate standard solution, GB10736-1989; Ethylenediaminetetraacetic acid disodium salt – Zinc chloride standard solution, GB12593-1990; Potassium bromate – Sodium thiosulfate standard solution, GB12594-1990; Silver nitrate – Sodium chloride standard solution, GB12595-1990; Calcium carbonate – EDTA disodium standard solution, GB12596-1990; Benzoic acid – Sodium hydroxide standard solution, GB12597-1990. 2. Standard solutions for titrimetric analysis: Standard solutions are those with a precisely defined concentration, whose accuracy is 0.1%, and they are used in titrimetric analysis to determine the content of substances. The concentration of the standard solution is calibrated using a working reference reagent. The preparation and calibration of standard solutions shall be carried out in accordance with the provisions of **Standard GB601-88**. Such reagents are equivalent to IUPAC Grade E. China’s **standard 23 types of standard solutions are classified into 6 categories according to their uses: • Standard solutions of sodium hydroxide, hydrochloric acid, sulfuric acid, and sodium sulfate for acid-base titration. • Standard solutions for redox titration: sodium thiosulfate, potassium dichromate, potassium permanganate, ceric sulfate (or ammonium ceric sulfate), oxalic acid, ferrous sulfate, iodine, potassium iodate. • Standard solutions of silver nitrate, lead nitrate, sodium thiocyanate (or potassium thiocyanate), and sodium chloride for precipitation titration. • Standard solutions of disodium ethylenediaminetetraacetate, zinc chloride, and magnesium chloride for complexometric titration. • Perchloric acid standard solution for non-aqueous titration • Standard solutions of bromine, potassium bromate, and sodium sulfite for the determination of organic functional groups. 3. Standard reagents for organic element analysis: These reagents are used as standards for determining the elements in organic compounds. Equivalent to IUPAC Grade E. The specification for the elemental content of such reagents is to allow a variation of plus or minus 0.3%,; for example, the specification for carbon content in sucrose is 42.1 ± 0.3%. Abroad, the largest supplier is the British company BDH Chemicals, which offers 33 different varieties. There are currently over 20 varieties in our country: • Standard reagents for carbon and hydrogen elements, such as sucrose, anthracene, benzoic acid, etc. • Standard reagents for nitrogen, such as *** and p-***amine, etc. • Standard reagents for sulfur, such as sulfamic acid. • Standard reagents for chlorine, such as p-chlorobenzoic acid. • Standard reagents for bromine, such as p-bromobenzoic acid, etc. • Standard reagents for iodine, such as o-iodobenzoic acid, etc. 4. Impurity standard solution: An impurity standard solution is a solution that contains a precise amount of elemental ions or molecules per unit volume, and it is used as a standard for the determination of trace impurities. China’s **standard GB602-88 specifies the methods for preparing 83 types of standard impurity solutions. Abroad, such standards have more detailed regulations. American company Beckman Coulter offers impurity standards specifically for emission spectroscopy analysis, while the German company Immergut provides oil-soluble standard solutions, which are metal standards prepared from metal salts of organic acids. 5. PH reference reagent: The PH reference reagent is used as a calibration standard for pH meters. It is divided into two grades: • Grade 1 PH reference reagent, which is equivalent to IUPAC Grade C. After being produced by relevant reagent manufacturers commissioned by the National Institute of Metrology of China, they are tested by the institute; once approved, they are distributed to the various manufacturers as standard reagents for measuring pH. The pH value of this grade of reagent is determined using a dihydrogen electrode in a liquid-junction-free cell, with a method accuracy of ±0.005 pH units. It is commonly used for the calibration of PH reference reagents and the calibration of high-precision pH meters. • PH reference reagent is equivalent to IUPAC Grade D. Reagent manufacturers use first-class pH reference reagents as a standard, and determine the pH value with a hydrogen electrode equipped with a liquid junction cell; the accuracy of this method is ±0.01 pH units. It is used for the calibration of the pH meter. 6. PH standard buffer solutions: PH standard buffer solutions are a set of standard solutions with a pH range from 1.0 to 13.0; within the range of 1.0–10.0, there is one standard solution for every 0.1 unit increase in pH ； There is 1 standard solution at every 0.0 within the range of 10.0-13.0. The method for preparing such standard solutions is specified in China’s **standard GB604-88**. PH standard buffer solutions can be used as a standard for determining the PH value of a solution to be analyzed by colorimetry, as well as as a standard solution for determining the color change range of acid-base indicators. The accuracy of such standard solutions is ±0.03PH; it is not as accurate as pH reference reagents, so it is not suitable for calibrating pH meters. Furthermore, due to its low buffering capacity, it is also unsuitable as a buffer solution for constant-coordination titrations. 7. Gas chromatography standard reagents: Gas chromatography standards are abbreviated as “color standards”. Based on usage requirements and testing methods, color-coded reagents are divided into two categories: • Products tested using packed columns; the purity specifications vary among different manufacturers, being 99%, 99.5%, 99.9%, etc., with a moisture content specification of 0.05%. Used for the determination of general chromatographic retention values, the calculation of correction factors, the assessment of column polarity, and the measurement of resolution and tailing factors. • Products analyzed using hollow columns are mainly used in chromatographic research, for the determination of more accurate retention times and correction factors, as well as for the measurement of other chromatographic constants. The standards of Emek are commonly adopted by various manufacturers. 8. Clinical standard reagent solutions: Clinical standard reagents are used for clinical testing. Currently, China already has some standard solutions that are sold together with “reagent kits for clinical diagnosis”. For use by hospitals and research institutions. The concentration units of such standard solutions differ from those of ordinary chemical reagent standard solutions. For example: Product name, Unit – Glucose standard solution: 100 milligrams/100 milliliters; Urea standard solution: 5 milligrams/100 milliliters; Chlorine standard solution: 100 milliequivalents per liter. 4. Standard reagents for calorimetric analysis: These reagents are used to calibrate the constants of calorimetry instruments, that is, to determine the water equivalent. The heat released by their complete combustion is a constant value. The variety currently supplied in our country is benzoic acid. There are more varieties abroad than in our country. Our company mainly sells high-purity reagents: methanol, acetonitrile, propanol, and ethanol. We welcome customers to place orders! For more details, search for “Xin Lanjing” on Baidu to visit the company’s official website ； Or visit the Alibaba store: shop1437642211288.1688.com