A Brief Description of HPLC
High-performance Liquid Chromatography is abbreviated as HPLC. Because of the different separation mechanism, there are five types of HPLC. They are liquid-solid adsorption chromatography,liquid-liquid partition chromatography ( normal-phase and reversed phase),ion-exchange chromatography, ion-pair chromatography, and exclusion chromatography.
First, liquid-solid adsorption chromatography is to isolate the components from the determined by solid absorbents, which are usually made from silica gel or alumina. The components are separated according to the different adsorbability from the stationary phase in the chromatographic column. This method usually is used for separating isomers.
Second, the basic principle of liquid-liquid partition chromatography is the components’different solubilities in mobile and stationary phases. The liquid-liquid partition chromatography is divided into NPC and RPC. NPC is often used to separate compounds of medium polarity or strong polarity. And RPC is the most popular method of HPLC, accounting for 80% of the application.
Third, ion-exchange chromatography. The principle of this method is related to the action between the ion exchange group and the compositional ions, pH values and ion strengths.
Fourth, ion pair chromatography is a branch of liquid-liquid chromatography, which mainly used to separate acidic and alkaline substances with strong ionic strength.
And the last is exclusion chromatography. We also called it ERC. This method uses the differences of the exclusion capacities to separate the components which have already filtered by the molecular sieves.