This experiment was performed to discover if a food dye, Blue #1, was used to color a purple gumball. The purple gumball was submerged in different liquids to find which would dissolve the coating of the gumball. Water was found to be the quickest to dissolve this coating into liquid dye. The most concentrated solution of gumball dye was created and a small drop of the dye was put onto a piece of paper along with a small drop of Blue #1 on a separate piece of paper, both on the baseline. These two pieces of paper were then submerged in water up to the solvent line. The water dragged up different dyes at different speeds as it travelled up the paper. The blue colored dye from the gumball only had a had a Rf of .74 while Blue #1 had a Rf of 1.
Chromatography comes in many forms, but in general, it refers to a group of lab techniques using a mobile phase and a stationary phase to separate mixtures. The unknown mixture is placed in the stationary phase, and as the mobile phase moves by, it will carry different components of the mixture varying distances depending on the components affinity for the mobile and/or stationary phase. The ration of the distance a component moves over the distance the mobile phase travelled is known as the Rf value. For example, a molecule with a high affinity for the stationary phase wont be compelled to move very far, and will result in a low Rf value.
We chose water as the solvent because water was able to dissolve the outer coating of the gumball. Since water is polar, and like dissolves like, we were able to assume the dyes we would be testing would be polar molecules. This can also be assumed from the structures of the dyes, which contain positively charged sodium ions, as well as negatively charged lone pairs on various oxygen atoms. These unbalanced charges around the molecule make it polar. By using a polar solvent (water), we knew that the mobile phase could form dipole-dipole interactions, or even hydrogen bonds, with the dyes. This would carry the components of the mixture up the filter paper, allowing us to separate the unknowns.
1 Purple Gumball
1 Stir Stick
2 Paper Strips
Determine which solvents to use for the mobile phase and to dissolve the coating of the gumball.
Cut 2 strips of paper for stationary phase and draw a baseline.
Tape both strips side by side onto the stir stick.
Dab a small drop of the dissolved gumball coating (mixture of dyes) onto the baseline of the first strip.
Drop a miniscule amount of Blue #1 onto the baseline of the second strip.
Suspend the two strips inside a beaker using the stir stick so that the strips are submerged in water nearly up to the baseline.