Due to being extracted or refined from organic solvents, traditional Chinese medicine chemical reference materials generally have low moisture content. Therefore, in the absence of a specified moisture content, only high melting point traditional Chinese medicine chemical reference materials are required to be dried at 105 ℃ during calibration. Meanwhile, unstable reference materials can be dried in a silica gel or phosphorus pentoxide vacuum dryer before application. Strictly speaking, the reference substance should have a drying weight loss limit, and there should also be regulations for residual organic solvents.
According to experts, in the past, methods for determining the content of chemical reference materials and impurities generally included volumetric and gravimetric methods, as well as UV E value measurements. However, due to the development of modern science, especially the widespread application of spectral chromatography technology, the above-mentioned volumetric and gravimetric methods can only obtain the content of major total components such as total alkaloids and flavonoids. However, currently available high-performance liquid chromatography, thin-layer scanning methods, etc., not only have simple operating methods but also can obtain relatively accurate results
It is understood that the phase solubility analysis method mainly detects impurities including isomers, while the differential scanning calorimetry method measures the melting heat of substances. However, due to the presence of impurities, changes can occur. Although the purity of the reference substance can be measured, it cannot be used for substances that decompose during melting. In the content determination of traditional Chinese medicine chemical reference materials, some content determination methods use the identification standard materials included in the United States Pharmacopoeia. Purity and content inspection are conducted according to the requirements of the reference materials for content determination. However, in formulating standard limits, it is necessary to accurately understand the purity and content of the reference materials.