一. The origin of chemical reagent classification: Why are there grades?
Core logic: Purity and impurity control affect the success or failure of experiments
The Industrial Revolution promotes standardization: The chemical industry developed explosively in the 19th century, and the purity requirements of laboratories for reagents diverged. For example, synthetic dyes need to control metal impurities, and pharmaceutical preparations need to limit toxic substances.
Error chain theory: Impurities in reagents will affect experimental results through the "error amplification effect". For example, 0.1% of water will cause the result to deviate by more than 5% when measuring water by the Karl Fischer method.
Economic principle: The cost of high-purity reagents may be more than 10 times higher than that of ordinary reagents. Reasonable selection can reduce scientific research funds by 30%~50%.
二. In-depth analysis of the purity of chemical reagents
1. Primary Reagent (PT)
Label color: dark green
Level positioning: Primary reagent is the "king" of reagents, with extremely high purity, usually reaching more than 99.95%. Its impurity content is extremely low and its stability is excellent. It lays a precise foundation for the entire experiment, and its accuracy directly affects the reliability of subsequent experimental results.
Typical applications: used to directly prepare standard solutions or calibrate the concentration of other solutions, etc.
2. Guaranteed Reagent (GR)
Label color: dark green
Level positioning: The purity of guaranteed reagents is also quite high, generally reaching more than 99.8%. This type of reagent has a low impurity content and is widely used in scientific research. In high-end chemical analysis experiments and precision instrumental analysis, guaranteed reagents are the first choice for researchers.
Typical applications: detection of ppb-level heavy metals in atomic absorption spectroscopy (AAS), etc.
3. Analytical Reagent (AR)
Label color: Golden red
Level positioning: Analytical reagents are the most common in laboratories, with a purity of about 99.7%. They can meet the needs of most conventional chemical analysis experiments. Whether it is general qualitative analysis or titration, colorimetry and other experiments in quantitative analysis, analytical reagents can show their skills and are the first choice for cost-effectiveness.
Typical applications: routine titration in university laboratories (such as acid-base neutralization experiments), etc.
4. Chemical Pure (CP)
Label color: medium blue
Level positioning: Chemically pure reagents have a slightly lower purity, generally around 99.5%. Although the purity is not as high as the previous types, chemically pure reagents are fully capable of some basic chemical experiments that do not require high standards, such as simple material preparation, property verification, etc.
Typical applications: Bisphenol A used in the preparation of industrial synthetic epoxy resins, middle school chemistry experiments, etc.
5. Laboratory Reagent (LR)
Label color: yellow
Level positioning: The purity of laboratory reagents is relatively low, and they are mainly used in some experiments that do not require high purity, such as general cleaning, auxiliary experimental steps, etc. Laboratory reagents can play their role in some simple testing links in industrial production, or in large-scale, low-cost experimental demonstrations in school laboratories.
Typical applications: laboratory equipment cleaning reagents, preliminary pH testing of water quality in factories, etc.
三. Other common reagent levels
1. Chromatographic purity (HPLC)
Technical indicators: HPLC grade acetonitrile absorbance at 190nm ≤ 0.01, 0.22μm membrane filtration, etc.
2. Biological reagent (BR, Biological Reagent)
Technical indicators: Purity requirements vary depending on the specific purpose, but usually require strict control of impurities that affect biological activity.
3. Biological stain (BS, Biological Stain)
Technical indicators: The purity requirements of this type of reagent focus on specific staining properties and extremely low toxicity to ensure that the morphological structure of cells or tissues can be clearly presented during the staining process, while not affecting the activity and normal physiological function of biological samples.
Reagents of different purities each play an important role in the field of chemistry. From high-end scientific research to basic teaching, from precision analysis to general experiments, they each perform their duties and jointly promote the development of chemical science. When choosing reagents, we need to comprehensively consider multiple factors such as experimental purpose, requirements and cost to ensure that the most appropriate reagents are selected so that every chemical experiment can bloom with its due brilliance.