Why alumina adsorbent for column chromatography?
In column chromatography, the stationary phase, a solid adsorbent, is placed in a vertical glass column and the mobile phase, a liquid, is added to the top and flows down through the column by either gravity or external pressure. Column chromatography is generally used as a purification technique: it isolates desired compounds from a mixture. Silica gel (SiO2) and alumina (Al2O3) are two adsorbents commonly used by the organic chemist for column chromatography. Alumina is more typically used in column chromatography and is quite sensitive to the amount of water which is bound to it: the higher its water content, the less polar sites it has to bind organic compounds.
