Background Information and Research:
1. Paper chromatography type of method that is used to separate mixtures of substances from a solution. 2. There are many uses for paper chromatography, especially concerning the fields of chemistry and biology. One use is to allow scientists to detect any sort of contaminants is rainwater. Another use is to identify clues at a crime scene such as blood, ink, or drugs. However, the more common use is to make sure food company’s processes are working correctly and that they are producing the correct product.
Research Sites:
http://jh399.k12.sd.us/Lab%20Activity/Chemistry/ch22chromatography.pdf http://www.discoveriesinmedicine.com/Bar-Cod/Chromatography.html#b http://www.chemguide.co.uk/analysis/chromatography/paper.html
Purpose
The purpose of this laboratory investigation is to observe how chromatography can be used to separate mixtures of a solution.
Materials
Four different markers, one being black
Rubbing alcohol or isopropyl alcohol
2 Coffee filters
2 Tall glasses or plastic cups
Pencil
Ruler
Tape
Table salt
Water
Measuring cups/spoons
Clean pitcher or 2-liter bottle
Procedure
Step 1. Take a coffee filter and cut it into a rectangle with the measurements of three cm by nine cm. Repeat once more, as two coffee filters in the shape of a rectangle will be needed. Step 2. Using a pencil, not a pen, draw a line one cm from the edge of one of the coffee filters.
Step 3. With a pencil, make four dots along the line just drawn about 0.5 cm apart.
Step 4. Use four different colored markers to draw a dot on each of the pencil marks on the coffee filter strip. Wait until the ink is dry, and then add more color to each of the dots.
Hints: 1. One of the colored markers should be black.
2. Restrain from using permanent markers.
Step 5. Make the salt solution by combining 1/8 teaspoon of salt and three cups of water in either a 2-liter bottle or a clean pitcher. Shake or stir the solution until all the salt has been dissolved. This solution will be one of 1% salt.
Step 6. Pour the salt solution in a clean glass so that the level of liquid is 0.5 cm.
Step 7. Now, tape the coffee filter to a pencil and rest the pencil on top of the glass so that the coffee filter hangs into the glass. Make sure that only the very end of the coffee filter, or chromatography strip, is touching the surface of the solvent solution. The colored dots must be above the surface of the liquid and have no contact with the liquid in the glass container.
Step 8. Capillary action will draw the salt solution up onto the paper. When the solvent passes through the dots, you will begin to see the separation of the dyes. When the saltwater is 0.5 cm from the top edge of the paper, remove the coffee filter strip from the glass and lay it down on a clean, flat surface in order for the strip to dry.
Step 9. Repeat steps through eight, using the second coffee filter strip and another clean glass, to test the same four colors using the alcohol instead of the saltwater solution at the bottom of the glass.
Data and Observations
Color of Ink
Salt Solution
Alcohol
Red
4.5 cm, pink pigment
3.0 cm
Black
3.75 cm, showed yellow, blue, and red pigment
1.5 cm, showed yellow, blue, purple, and red pigment
Purple
4.0 cm, blue and red pigments were mixed
2.0 cm
Blue
5.0 cm, a lighter blue pigment shown
3.5 cm
Discussion and Conclusion
While doing the lab, I realized that black is comprised of many colors. This was shown when the black ink was hit with the saltwater or alcohol solvent that different colors leaked through. Also the other pigments either had a more diluted version show through or the purple, for instance, had diluted colors mixed together of blue and red. Errors that could have occurred were being off just a little on the overall measurements of distance that the ink traveled by. For me, the saltwater separated the colors a lot better, and I think that is because it has more percentage of water in it which allows for the solvent to go up the coffee filter more easily. If I had not allowed the same amount of time I would not have seen some of the pigments that leaked out from the original four colors. Purple and blue traveled up the farthest for me during my lab experiment. Black traveled the least for both solvents.
