1/18 Objective: Explain the purpose and process of chromatography. DMA: What is the definition of chromatography? (you can look this up on your phone/book/etc.)

Chromatography Chromatography A means of separating and identifying the components of a mixture.

Chromatography Molecules that have a preference for the moving phase will slowly pull ahead and separate from those substances that prefer to remain in the stationary phase.

How do mixtures separate? Need two “phases” to separate a mixture of molecules: mobile phase (solvent) stationary phase.

How do mixtures separate? The stationary phase is more POLAR than the mobile phase The more polar component (of the mixture) interacts more strongly with the stationary phase The more polar component moves more slowly. The non-polar component moves more rapidly.

Thin-Layer Chromatography: A Two-Component Mixture s o l v e n t f r o n t Less polar! c o m p o n e n t B s o l v e n t f r o n t c o m p o n e n t B More polar! c o m p o n e n t A c o m p o n e n t A mixture o r i g n o r i g i n o r i g i n s o l v e n t f r Increasing Development Time

Paper Chromatography Mobile phase is solvent used. Stationary phase is water bound to surface of paper. Advantage : its cheap!

Thin-Layer Chromatography: Determination of Rf Values Rf of component A = dA dS Rf of component B = dB The Rf value is a decimal fraction, generally only reported to two decimal places

This number is usually expressed as a decimal Calculating Rf Values Rf value is a ratio of the distance a component sample moves to the distance the solvent moves This number is usually expressed as a decimal bsapp.com

Practicing Calculating Retention Factor (Rf)

Paper Chromatography Pick up a round filter paper. Fold the edges of the paper down about 1 cm. Have them cut off three out of the four edges. Students will fold the remaining flap over a glass rod and tape.

Paper Chromatography Draw a straight line (IN PENCIL) between 1-2 cm from the bottom of the filter paper. On the pencil line, spot 5 different pens and/or pen colors. These should be equal distance apart. Not too big or too small! Allow to dry (1 minute) Fill a 600 mL beaker to 300 mL of water Place the chromatography paper into the water.

Paper Chromatography Wait until the water has moved at least ¾ up the paper, then pull out the paper Draw a pencil line at the place where the water stopped moving. In pencil, mark the center of each color range (so the place with the most concentrated area of color). Measure the distance (in cm) from the starting line to each color. Calculate the Rf Values

Important Concepts in Paper Chromatography Capillary Action – the movement of liquid within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension. The liquid is able to move up the filter paper because its attraction to itself is stronger than the force of gravity. Solubility – the degree to which a material (solute) dissolves into a solvent. Solutes dissolve into solvents that have similar properties. (Like dissolves like) This allows different solutes to be separated by different combinations of solvents. Separation of components depends on both their solubility in the mobile phase and their differential affinity to the mobile phase and the stationary phase.

Stationary Phases Alumina Silica Cellulose Acidic: -Al-OH Neutral: -Al-OH + -Al-O- Basic: -Al-O- Silica Cellulose

Mobile Phases Could be lots of things: Ethanol Acetone Benzene Water etc

Some Types of Chromatography Liquid Column Chromatography High Pressure (performance) Liquid Chromatograph (HPLC) Paper Chromatography Thin-layer Chromatography (TLC) Gas Liquid Chromatography

Review Paper and TLC https://www.youtube.com/watch?v=J8r8hN05xXk

Chromatography Gas Chromatography is a means of separating and tentatively identifying the components of a mixture.

Gas Chromatography In GC, the moving phase is actually a gas called the carrier gas, which flows through a column.

Gas Chromatography The written record of this separation is called a chromatogram. The time required for a component to emerge from a GC column is known as retention time.

Gas Chromotography https://www.youtube.com/watch?v=0m8bWKHmRMM https://www.youtube.com/watch?v=q0pM-k0SvOQ

Mass Spectrometry https://www.youtube.com/watch?v=mBT73Pesiog Practice Calculations http://www.austincc.edu/biocr/1406/laba/tlc/