ENVE 202

Dr. Aslıhan Kerç

CHROMATOGRAPHY

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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

What is chromatography?

Chromatography (from Greek word for chromos for colour) is the collective term for a family of laboratory techniques for the separation of mixtures. It involves passing a mixture which contains the analyte through a stationary phase, which separates it from other molecules in the mixture and allows it to be isolated.

Which means ...

Chromatography is the physical separation of a mixture into its individual components.

http://members.shaw.ca/vict/chemistry_test3.htm

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All forms of chromatography involve 2 phases The Two Phases 1. stationary (absorbent) phase

o the material on which the separation takes place

2. mobile phase - the solvent transports the sample

Types of Chromatography - 5 of them

Separation

A sample is often a mixture of many components in a complex matrix.The components must be separated from each other so that each individual component can be identified by other analytical methods. The separation properties of the components in a mixture are constant under constant conditions.Once determined they can be used to identify and quantify each of the components. A mixture can be separated using differences in physical or chemical properties of the individual components.

In chromatography

A column holds the stationary phase, and the mobile phase carries the sample through it.

Sample components that partition strongly into the stationary phase spend a greater amount of time in the column and are separated from components that stay predominantly in the mobile phase and pass through the column faster.

Chromatograms

If a detector that responds to solute concentration is placed at the end of the column and its signal is plotted as a function of time, a series of symmetric peaks is obtained.

The positions of the peaks on the time axis is used to identify the components of the sample.

The areas under the peaks provide a quantitative measure of the amount of each species.

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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

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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)

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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

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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.

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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.

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Solve for Rf