1. Distillation:

It uses the unit operation process of mixing liquid or liquid-solid system with different boiling points of each component to make the low boiling point component transpiration and then condense to separate the whole component. It is the combination of transpiration and condensation.

2. Recrystallization:

Recrystallization is the process of recrystallization from solution or melt after dissolving the crystal in solvent or melt. Recrystallization can purify impure substances or separate mixed salts from each other. Among them, it is the result of physical and chemical action.

3. Extraction:

Extraction is a unit operation that uses the different solubility of components in the system in the solvent to separate the mixture.

4. Chromatography:

It is also called column chromatography. According to the different distribution coefficients of each component in the sample mixture in the stationary phase and mobile phase, the groups are separated after repeated distribution.

The main methods of structure determination are:

1. UV spectrum:

The motion inside the molecule includes rolling, oscillation and electronic motion. The energy of the corresponding state (the eigenvalue of the state) is quantized, so the molecule has rolling energy level, oscillation energy level and electronic energy level. Generally, molecules are in the low-energy ground state, which can cause the transition of molecular energy levels after absorbing energy from the outside. The energy required for the transition of electronic energy levels is large, which is roughly between 1 and 20 ev (electron volts).

Valence electron transitions in many organic molecules must absorb light with wavelengths in the range of 200 ~ 1000 nm, just falling in the UV-vis region. Therefore, UV absorption spectrum is due to the transition of valence electrons in molecules, which can also be called electronic spectrum.

2. Infrared spectrum:

In organic molecules, the atoms that form chemical bonds or functional groups are constantly oscillating, and their oscillation frequency is equivalent to that of infrared light. Therefore, when organic molecules are illuminated with infrared light, the chemical bonds or functional groups in the molecules can be oscillatory absorbed. Different chemical bonds or functional groups have different absorption frequencies and will be in different positions in the infrared spectrum, so the information of what chemical bonds or functional groups are contained in the molecules can be obtained.

3. Mass spectrum:

Mass spectrometry analysis is an analysis method to measure the mass charge ratio (mass charge ratio) of ions. Its basic principle is to ionize each component in the sample in the ion source, generate charged ions with different charge mass ratio, and form ion beams through the action of accelerating electric field, which enter the mass analyzer. In the mass dissector, the electric field and magnetic field are used to make the opposite velocity dispersion, and they are gathered separately to obtain the mass spectrum, so as to confirm their quality.

4. Nuclear magnetic resonance:

Hydrogen atom is magnetic. For example, when the electromagnetic wave shines on the hydrogen nucleus, it can absorb the electromagnetic wave energy through resonance and make a transition. Nuclear magnetic resonance instrument can record relevant signals. Hydrogen atoms in different environments have different frequencies of absorbing electromagnetic waves when resonance occurs, and their positions on the spectrum are also different. This difference of various hydrogen atoms is called chemical shift. The chemical shift, peak area, integral value and coupling constant are used to infer its position on the carbon skeleton.

In the NMR hydrogen spectrum, the number of characteristic peaks reflects the variety of chemical environment of hydrogen atoms in organic molecules; The intensity ratio of different characteristic peaks (and the height ratio of characteristic peaks) reflects the number ratio of hydrogen atoms in different chemical environments.

Ginkgo isoflavone

Therefore, in the field of drugs, recrystallization and chromatography are commonly used for extraction and separation, while NMR and MS are commonly used for structure determination.