Chem 154 L16
Identifying Unknown Food Dye
50 mL Beaker
100 mL Beaker
Standard Dye Solutions:
1. Gather chromatography papers and pour 50ml of salt water in the 400ml beaker. Cover the beaker with watch glass.
2. Measure 1 cm from the bottom of the paper on both sides, and draw a light line (being careful not break the fibers of the paper) using PENCIL (not pen) across the paper. This line will serve as a reference point to spot your samples, and calculate your Rf values. Make a cross mark every 1.5 cm across the line. These will mark the positions of your spots.
3. At the top of the paper, above each mark, label the column with a color dye so that you know which spot is which sample or standard. Make sure you include all of the standards on each paper so that you can identify the components of the unknowns.
4. Using a clean toothpick for every standard, place a small spot of the dye on the cross mark of the paper in the appropriate column. Make sure the spot does not get too large, or your chromatogram may be streaky and difficult to read.
5. To prepare the food samples, use a small amount of water to dissolve the dye and use a clean toothpick to transfer the sample. It is important to make your food samples as concentrated as possible so that the dyes can be visualized after they have spread out during separation.
6. Let the paper sit until the spots are completely dry and staples the edge of