Liquid Chromatography

Liquid chromatography is one of the most important methods for microanalysis of current constituents. The two phases in the chromatographic analysis refer to a stationary phase having a large specific surface area and a mobile phase carrying a mixture to be separated flowing through the stationary phase. A liquid phase liquid using a liquid as a mobile phase. Liquid chromatography is also known as "liquid chromatography." A chromatographic method in which the mobile phase used is a liquid. Since the liquid in the column is more resistant to gas than the gas, in order to increase the analysis speed, a high pressure infusion method is usually used, so it is also called "high pressure liquid chromatography". According to the different stationary phases, it can be divided into liquid-solid chromatography and liquid-liquid chromatography; depending on the type of equilibrium between the stationary phase and the mobile phase, it can be divided into adsorption chromatography, partition chromatography, ion exchange chromatography and gel chromatography. Used for separation and analysis of organic, inorganic and polymeric liquids. [A brief history] The Russian botanist MSTswett first used column chromatography to separate plant pigments in 1906. It is the oldest one in liquid chromatography and has developed into various kinds in the past 30 years. Chromatographic separation is an important part of analytical chemistry. 1 Classical liquid chromatography: the mobile phase flows downward from the upper end of the column tube by its own gravity, and the effluent is collected one by one at the outlet of the lower part of the column, and then measured by other methods, the analysis speed is slow and the efficiency is low; 2 thin layer chromatography : Appeared around the 1940s, easy to operate, improved analysis speed, but poor repeatability, quantitative difficulty; 3 high performance liquid chromatography: in the early 1960s, JCGidelings modified the gas chromatography theory for Liquid chromatography lays the foundation for its modernization. Since then, high-pressure pumps, high-efficiency stationary phases and high-sensitivity detectors have been used in technology, and developed into high-performance liquid chromatography with fast analysis speed, high separation efficiency and automatic operation. In 1971, RAHenry et al first used it for pesticide analysis. [High Performance Liquid Chromatography] High performance liquid chromatography is one of the most important separation methods in modern analytical chemistry. It originated from the classical liquid chromatography method. The basic method is to use a single solvent with a certain polarity or a mixed solution of different proportions as the mobile phase, and pump the mobile phase into the column with the filler, and inject it into the test. After the product is taken into the column by the mobile phase for separation, the components are successively entered into the detector, and the chromatogram or data processing is recorded by a recorder or a data processing device to obtain a measurement result. Due to the application of various characteristics of particulate filler and pressurized liquid mobile phase, the method has the characteristics of high separation performance and fast analysis speed. High performance liquid chromatography is suitable for the analytical determination of pharmaceuticals that can be separated on a specific filler column, especially for the determination of multi-component drugs, impurity inspection and determination of macromolecular substances. Some drugs need to be derivatized before or after chromatographic separation to be separated or detected. Commonly used column packing agents are: silica gel for normal phase chromatography; chemically bonded stationary phase, which can be used for reversed phase or normal phase chromatography depending on the bonded groups; ion exchange packing for ion exchange chromatography; Large pore packing for exclusion chromatography. High performance liquid chromatography consists essentially of pumps, injectors, columns, detectors, and chromatographic data processing systems. The most commonly used detectors are variable wavelength ultraviolet and visible light detectors, and other detectors such as refractive index detectors and evaporative light scattering detectors. The collection and processing of chromatographic information is often performed using an integrator or data workstation. Gradient elution can be achieved by two pumps or a single pump plus a proportional valve.