Principles of Chromatography

Process by which one separate compounds from one another by passing a mixture through a column that retains some compounds longer than others.

Chromatography

Column Eluent

In

Eluate

Out

Mobile phase = solvent moving through the column. Stationary phase = substance that stays fixed inside the column. Eluent = fluid entering the column. Eluate = fluid exiting the column.

Gas Chromatography = gas carrier Liquid Chromatography = liquid mobile phase

Types of Chromatography

How We Describe a Chromatogram?

Chromatographic Separations

Planar

Column

Gas Chromatography

Column separation (gas-liquid, gas-solid) used for separating and analyzing compounds that can be vaporized without decomposition.

Separations based on differences in boiling points!

Liquid Chromatography

Column separation (liquid-liquid, liquid-solid) used for separating and analyzing compounds based on differences in their interaction with a stationary phase.

Adsorption, partition, ion exchange, molecular exclusion and affinity

Gas and Liquid Chromatography

Why Do Bands Separate and Broaden with Time on Column?

Efficiency of Separation

Multiple Flow Path Term

H = L/N Small plate height = narrow peaks = better separation

Zone Broadening Terms

A term = Eddy Diffusion

Bterm = Longitudinal Diffusion

C term = Stationary Phase Mass Transport

Why Do We Care About Flow Rate?

N (efficiency) = L/H N α Rs

Flow Velocity (cm/s) = Flow Rate (cm3/s)/Cross sectional area (cm2)

Van Deemter Eq.