chromotography Flashcards
chromotography
technique commonly used to seperate mixtures of similar substance
how does chromotography work
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.
what factors cann affect distance and speed substance moves up chromotograph
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
how can chromotography be quantified
using a measurment called
retardation factor (Rf)
Rf
distance travelled by spot/ distance travelled by solvent
what do you need to use of susbtance is colourless
techniques such as staining or ultraviolet light to show up the spots
absorption chromotography techniques
gas-solid chromotography
liquid column chromotogrphy
high performance chromotography
thin layer chromotography
explain gas solid chromotography
type of absorption= absorption chromotography
mobile phase= gas
stationary phase= solid
stationary phase support= column
explain liquid column chromotography and high performance liquid chromotography
type of absorption= absorption chromotography
mobile phase= liquid
stationary phase= solid
stationary phase support= column
explain thin layer chromotography
type of absorption= absorption chromotography
mobile phase= liquid
stationary phase= solid
stationary phase support= planar layer
polar and non polar solvents
polar substances are soluble in polar solvents non polar susbtance are soluble in non polar solvents
ion dipole forces
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
what solvent is used for paper chromotography of amino acids
eluent= mobile phase
what must be used for paper chromotography of amino acids
locating agent eg. ninhydrin
