Chromatography is a method of physically separating mixtures of gases, liquids, or dissolved substances. Chromatography can be used to identify drugs, poisons and many other substances. Separation is determined by the molecular size and/or charge
All forms of chromatography involve 2 phases • The Two Phases • 1. stationary (absorbent) phase • the material on which the separation takes place • 2. mobile phase - the solvent transports the sample • Types of Chromatography - 5 of them
Gas Chromatography Gas Chromatography • a gas separates the components • they are then ionized and an electrical signal is recorded • mobile phase - carrier gas • stationary phase - thin film of liquid
HPLC • High Performance Liquid Chromatography (HPLC) • - done at room temp. - advantageous for chemicals that are heat sensitive or volatile - example LSD • - a liquid (mobile phase) is pumped through a column containing fine particles (stationary phase)
TLC • Thin - Layer Chromatography (TLC) • -A plate is coated with a granular gel - usually silica gel or aluminum oxide (stationary phase) • - the substance to be separated is carried up the plate by capillary action - the substance with most affinity for the plate will rise the farthest. • 4. Paper chromatography • Same as TLC but paper • is used as stationary phase
Electrophoresis • Electrophoresis • - Similar to TLC but the substance is separated through a gel by electric current • - Due to different size and charge substances will move across the plase at different speeds.
Paper Chromatography of Ink Two samples of black ink from two different manufacturers have been characterized using paper chromatography.
Retention Factor (Rf) • A number that represents how far a compound travels in a particular solvent • It is determined by measuring the distance the compound traveled and dividing it by the distance the solvent traveled.