Introduction To Liquid Chromatography
Theory
Rate Theory (currently in use)
Plate Theory (older)
At each plate equilibrium of the solute between the mobile phase & stationary is assumed to take place
Developed by Martin & Synge in 1941
The partitioning of solute between the phase takes plate at each theoretical plate
Accounts for dynamic of separation
Describe the effect of elution band as well as its time of elution
Proposed by Van Deemter in 1956
Van Deemeter equation desribe the relation of height of theoretical plates,H and the average linear velocity of the mobile phase
Thus, the number of theoretical plate in the column is used as a measure of efficiency of column to separate the component from each other
The theory assume that column is divided into number of zones (N) called theoretical plate
Definition
Method of separation in which the component to be separated are distributed between two phase; stationary phase and mobile phase which move on stationary phase in a definite direction
The component of the mixture redistribute themselves between two phase by a process may be adsorption, partition, ion exchange or size exclusion
Phases
Mobile phase
Stationary phase
Can be gas or a liquid, which flows continously around the stationary phase
Can be solid or a liquid supported on a solid
Classification
Liquid Chromatography (LC)
Supercritical-Fluid Chromatography (SFC)
(Mobile phase : supercritical fluid)
Gas Chromatography (GC)
Stationary phase
Type of equilibrium
Specific method
a. Gas - liquid (GLC)
Liquid absorbed or bonded to a solid surface
b. Gas-solid
Solid
Adsorption
b. Liquid-solid, or adsorption
c. Ion exchange
a. Liquid-liquid, or partiton
d. Size exclusion
e. Affinity
Liquid absorbed or bonded to a solid surface
Solid
Ion-exchange resin
Liquid in interstices of a polymeric solid
Group specific liquid bonded to a solid surface
Adsorption
Ion echange
Partition/seiving
Partition between surface liquid and mobile liquid
Organic species bonded to a solid surface
Partition between supercritical fluid and bonded surface
Partition between gas and liquid
Partition between immiscible liquids
Resulted in a number of different equations
The Van Deemter Equation: H = A + B/u + u [Cm + Cs]
Specific method
Stationary phase
Type of equilibrium
Type of equilibrium
Stationary phase