Chromatography

1. Chromatography Homogeneous mixtures of a solvent and one or more solutes (dissolved substances) are often separated by chromatography. Chromatography works to separate a mixture because the components of a mixture distribute themselves differently when they are in contact with a "two phase system". One phase is stationary and the other is moving or mobile. The stationary phase may be a solid packed in a tube or a piece of paper. The mobile phase may be liquid of gaseous. Food colorings are one example, a homogeneous mixture of a solvent and a single dye or combination of selected dyes that produce the desired color.

2. Chromatography This animation ( be sure to watch animation) shows what happens to a mixture of two dyes. The green and yellow dyes can be separated. The green dye moves along with the solvent better than the yellow dye. The mixture is separated into two "spots". There are two substances in the mixture. The Rffor the yellow dye is about 0.5 while the Rf for the green dye is about 0.8.The yellow dye moves half as far as the solvent front.Water can be used as a solvent but so can other liquids if need be.

4. Sample Rf determination The SOLUTE CAN NEVER LEAP AHEAD of the solvent. location of the solvent front 66mm distance traveled by fast dye 57 mm distance moved by the slow dye 32 mm