Experiment Three: Separation and Identification of Food Dyes by Paper Chromatography

The mobile phase moves over a solid components

Species being analyzed, have to separate these species before analysis

does not involve chemical nature of the species that are to be separated, based on phys characteristics (sorting candy, based on color; how to do this for solubility)

what we are going to do in the lab, separate and identify the species in a mixture, chromatography

to resolve(separate) the components of a mixture, chemical compounds tend to partition (arrange and separate) based on polarity, capillary action

the preferential attraction of the components of a mixture for either a stationary or mobile phase. Affinity is based on attractive forces that exist between particles (molecs, atoms, ions), and the mobile and stationary phases. Differences in affinity for components of a mixture will result in separation

Component "A" will flow readily with mobile phase than "B" (it has an affinity for the mobile phase), A will travel farther

(Rf = Distance traveled by "A" / Distance traveled by solvent), out of 1

• Close to 0=stationary • Far from 0= mobile

Filter paper = stationary phase, several different mobile phases. Select mobile phase for which the dyes have the greatest difference in affinity. This will maximize the difference in retention factors and yield the most complete separation

First we extracted dye mixtures from assorted candy, by swirling it in acetic acid, then we added 5% ammonia to make the dye solution basic. Made 4 salt solutions (.1% salt, deionized water, ½ deionized, ½ ethanol; more ethanol than deionized water). Then we made 4 chromatography papers and labeled them with different dyes, then measured retention factors; saw which solution was the best, and then had a small drop of unknown, found out what was in there. Also analyze the color in the candy