3 Separation methods for impurities

According to the impurities source, it is a big challenge to completely remove the impurities in the medicine. In addition, the analysis method of impurities not only needs detect the known impurities of the drug, but also needs effectively detect the potential impurities in the impurity spectrum concept. Therefore, choosing appropriate analytical methods that accurately distinguish and quantify impurities is a key link in the quality control of drugs. Some detectors can detect impurities without separation. For example, quantitative Nuclear Magnetic Resonance Spectroscopy (qNMR) 34 has been described completely in the qualitative and quantitative methods section. However, it is not feasible for some detectors to directly perform qualitative and quantitative analysis of impurities in drugs. Through separation technology, a single compound can be obtained before detection to ensure the accuracy and authenticity of the detection result. Some separation methods are shown in Table 1.

3.1 Liquid Chromatography