Paper chromatography, a method that can test the purity of substances and separate mixtures. It is a very convenient and useful analytical method because it can complete the analysis quickly and has few restrictions on materials. The separation principle of paper chromatography is the same as that of thin layer chromatography. The substance is distributed in a stationary phase and a mobile phase. The stationary phase is usually filter paper, and the mobile phase will flow with substances on it. This device will be separated according to the adhesion of different substances in the mixture to the stationary phase and the solubility of the mobile phase. When analyzing pigments, if there is more than one substance in pigments, the substances of different colors will be separated according to the polarity of solvents and solutes. This is because different molecular structures may have different polarity. These different polarities result in different solubility of the solvent, so that various solutes will precipitate at different positions of solvent diffusion and appear as spots on the stationary phase, which can be analyzed according to the location and size of the spots on the stationary phase.
Gas chromatography. Can be divided into gas-solid chromatography and gas-liquid chromatography. Gas solid chromatography refers to the chromatographic separation method in which the mobile phase is gas and the stationary phase is solid. For example, activated carbon and silica gel are used as stationary phases; Gas liquid chromatography refers to the chromatographic separation method in which the mobile phase is gas and the stationary phase is liquid. For example, the inert material diatomite coated with squalane can be used to separate and determine trace amounts of methane, acetylene, propylene, propane and other impurities in pure ethylene.
