chromotography

technique commonly used to seperate mixtures of similar substance

a small amount of a sample mixture is placed on a “stationary phase”, eg. paper, while a ‘mobile phase”such as a solvent like water or hexan, moves through the stationary phase or soacks up the piece of paper in the case of paper chromotography. As it does so sample also moves and distance it mves will depend on difference between attracton to stationary phase and to mobile phase. Molecules more attracted to mobile phase will move faster and further from starting point and vice versa.

size of molecule, polarity, shape, presence of ionic groups will all affect how far a molecule moves and since most molecules have different combinations of these factors a mixture containing a range of different molecules will be seperated into a series of seperate spots

using a measurment called retardation factor (Rf)

distance travelled by spot/ distance travelled by solvent

techniques such as staining or ultraviolet light to show up the spots

gas-solid chromotography liquid column chromotogrphy high performance chromotography thin layer chromotography

type of absorption= absorption chromotography mobile phase= gas stationary phase= solid stationary phase support= column

type of absorption= absorption chromotography mobile phase= liquid stationary phase= solid stationary phase support= column

type of absorption= absorption chromotography mobile phase= liquid stationary phase= solid stationary phase support= planar layer

polar substances are soluble in polar solvents non polar susbtance are soluble in non polar solvents

ion dipole forces occur between water molecules and ions in acqueos solutions when an ionic comound dissolves in water ion-dipole forces occur between the ions and the oppositely charged dipoles of the water molecules\the water molecules surround the ion forming a hydration shell

eluent= mobile phase

locating agent eg. ninhydrin