While doing this experiment I learned many things about chromatography and food dyes. I learned how different things affect the results of the chromatography. I also learned about different ways chromatography is being used in the world today. I also learned things I did not previously know about food dyes. Also, I was able to learn which colored Easter candy shells of the leading candy bit contain FD& C Yellow dye #5.
Through contacting many scientists, I was able to learn why and how chromatography is used today in the real world. For example, I did not know that detectives used chromatography to analyze fibers found at a crime scene or that, besides using dogs, gas chromatography is a common way to identify explosives in airports. Chromatography is used by food producers to test food to make sure that it is good. It is also used in high schools to preform drug screening. Such a simple process of separating compounds is used in many serious criminal cases to prove whether someone is guilty or innocent. I did not know that chromatography had such a serious impact on our world today.
While doing this project, I also learned many things about food dyes. There are only seven certified and approved dyes for food, drug, and cosmetic use. All the colors we have in our food and cosmetics are from seven main colors. I was not aware that, before 1938, food dyes caused serious health problems because food producers used such poisons as arsenic and dyes meant for textiles. Dyes and colors have been around since the Ancient Egyptians, but it has been only a short time that they have been used in a safe manner.
Besides learning which candy shells contained FD & C Yellow #5, I learned that many different things can affect the results of the chromatography tests. The kind of chromatography paper and the solvent can make a huge difference. Also, there are two different ways of determining a result from the chromatography test. There is a qualitative way in which you look at how the colors separated and compare them to controls to find out which colors are contained in the unknowns. There is also a quantitative way where your determine the Rf values and compare you results with controls.
I received many suggestions from e-mails and sources as to what solvents to use. I chose four different solvents to use with my chromatography paper and coffee filters and I used the solvent that came with my thin-layer chromatography kit. These four solvents made a large difference in the way in which they separated the colors. The four different solvents that I used were distilled water, household ammonia, household white vinegar, and a 5% NaCl solution with distilled water.
After doing my controls using liquid and paste food colors I found that each solvent had a different effect on each of the colors and how they separated. The ammonia was the best at separating the reds and yellows. The vinegar did the best job of separating the blues and the yellows. The 5% NaCl solution did the most consistent job of separating the colors. The distilled water did not do a very good job of separating any of the colors. The tests that I did with the distilled water did not have very clear results and were not very consistent.
The different types of paper used when doing the paper chromatography tests also made a difference. The two different types of paper that I used were coffee filters and purchased chromatography paper. The coffee filters gave no good separations with any of the colors. This probably happened because they were not long enough. There was only a ten centimeter traveling distance which made it hard to measure the Rf values. Also, the results that I got using the coffee filters were not consistent.
The results I obtained using the chromatography paper were a little better than those obtained using the coffee filters. The chromatography paper had a longer stationary phase so the solvent could travel further and the colors separated better. Since the stationary phase was longer, sometimes when the solvents reached a certain point they would start evaporating as fast as they were moving. This caused some inconsistency with the results, even though these results were more consistent that the results from the coffee filters. When using the chromatography paper, the solvents made more of a difference in the color separation than they had on the coffee filters. Still, some of the colors did not separate very well.
The thin-layer results were the best from all of the tests I preformed. These had the best separations and were the most consistent. I only used the solvent that came with the kit because it was suggested to me that changing the solvent might cause the tests not to work. The results I got from these tests were very clear and well separated. When the results are well separated, then it is easier to make qualitative as well as quantitative analyses. This is why I used thin-layer chromatography to test the candy dyes.
One color that did not separate very well was the paste food color Red Red. When doing a test with this color, the result was always a poor separation and it was very difficult to get the Rf values. This was probably because there are four different FD&C colors in this one food dye color. This was the most F.D.&C. colors in any of the food dyes I used. Since there are four different colors in one dye there are probably very small concentrations of each color and therefore it was difficult to get them to separate. The results of this test generally looked like one long red streak along the stationary phase.
From all of my tests on the candy shells there was one FD&C color listed on the label that I never saw. This was Yellow #6. I am not sure this dye never showed up in any of my test results. I think it might have been that there was too small a concentration of it in the sample I took from the candy shell for it to show up. Also, perhaps the solvents that I was using had no affect on this color and did not separate it.
To extract dye from the candy shell, I first dissolved the candy coating in a small amount of distilled water. I applied this solution to the chromatography paper and coffee filter paper and, when they were put into the solvents, the dyes just faded away on the papers. This probably happened because the concentration of dye was not high enough, or maybe the solution contained sugars or other substances that interfered with the separation. From one of my web sources, I found another method that extracted the dye only. This method provided a very small amount of dye. Since the results from the thin layer chromatography using the controls were so good and reproducible, I only used the dye with the thin layer chromatography.
Even though the results from the candy dye were light, I could still see which dyes were in which colored candy shell. I found that all of the different colored Easter candy shells, except for the pastel blue one, contain FD&C Yellow #5. For people who are allergic to Yellow #5, tartrazine, they can only eat the blue candy without worrying about the possibility of an allergic reaction.
I hope that my experimenting will help someone who is allergic to Yellow #5. Now they do not have to steer clear of all Easter candy bits. They can still enjoy the blue ones.
If I was going to continue this project I would experiment with other
solvents with the thin-layer kit and see if I could find Yellow #6 which never
showed up in any of the tests I did. I would also try and find a way to separate
the paste food dye Red Red into it's four different colors.
Project researched and
documented by Ann VanBlaricum
Disclaimer: These pages were written in 1997 while the author was a sophomore in high school taking AP Chemistry. Hence, the author is not an expert on this subject, she cannot vouch for the accuracy or currency of these data or the links.