Chromatography Forum

Hello. I'm a student and we currently are doing a project for our science class and we need your help.

We selected this project: paper chromatography. However, we have failed during our first and second trials. We are doing this so that we could identify the dyes that are present in a candy, locally and internationally manufactured. Well, we have based our experiment on an article we found on the internet. We followed it exactly the way it was elaborated, but we still failed. This is what we did:

1. We placed the candies in a test tube and filled it with vinegar so that the dyes from the candies would transfer to the vinegar.
2. After the dyes have been extracted, we dipped an undyed wool yarn into the vinegar with the extracted dyes, then waited.
3. The dyes then transferred the the undyed wool yarn. After, we placed the yarn into another test tube with ammonia solution, then we waited. After some time, the yarns became white, like its natural color before dipping it into the vinegar with the extracted dyes.
4. We heated the test tubes with the ammonia solutions and the extracted dyes, making the solution concentrated with the dyes alone and the ammonia solution evaporate.
* in this step, the ammonia solution didn't evaporate, and the result
didn't turn out to be the way it should be.
5. When we were about to do the "spotting" part of the experiment, we weren't able to 'spot' because when we were to place the candy dyes on the chromatography paper, we weren't able to see colors. It was only like water, colorless. Despite having gotten it from the test tubes which contained the extracted dyes from the candies.

Some of the things we thought we did wrong that made our experiment a failure are these (maybe it could help! ):
- we didn't really heat it directly above a bunsen burner.
- we didn't use a chromatography paper, which was supposed to be used. We used a filter paper instead, which we thought would yield the same and exact results as a chromatography paper would.

****How could we also identify the exact commercial dyes that were used? Like the colors with numbers (e.g. Red 10, Blue 4). We really need to find out the answer for this. Thank you very much.

THANK YOU VERY MUCH!

It might work if you just dissolve the candy completely in water, spot the solution on the paper, maybe dry the spot, and develop. Most likely you could get a better separation on chromatography paper.

It would probably be easier to start by working backwards.

The only way to identify compounds by any kind of chromatography is comparison with known reference standards. Which means obtaining samples of the pure dyes you are looking for (you might be able to obtain some of them in the form of food coloring from the grocery store).

Different types of paper will give different results, as will different solvents used to "develop" the chromatogram. You will probably have to do some experimentation to get the conditions just right. This is much easier to do with reference standards of the dyes, because you don't have to worry about interference from the sugar in the candy.

Once you have the chromatography running OK with the standards, you can run the standards through the preparation process with the vinegar and ammonia solutions. Many dyes are "indicators", which means that they change from colorless to colored as the pH changes (acid to base or vice versa); I don't know enough about the details of food dyes to know whether the ones you are looking for fall in that category.

Once you can make the entire process work with standards of the dyes, you can try it with the candy.

I suspect that the high sugar level in the candy would "gum up" the paper if you just dissolved the candy and spotted it directly on the paper.

Paper chromatography is one of those techniques that looks deceptively simple, but is actually complicated to do correctly (but it feels great when you finally get it to work!).

It might work if you just dissolve the candy completely in water, spot the solution on the paper, maybe dry the spot, and develop. Most likely you could get a better separation on chromatography paper.

Hello, HW Mueller. Thank you very much for your help. It meant a lot to us.

It would probably be easier to start by working backwards.

The only way to identify compounds by any kind of chromatography is comparison with known reference standards. Which means obtaining samples of the pure dyes you are looking for (you might be able to obtain some of them in the form of food coloring from the grocery store).

Different types of paper will give different results, as will different solvents used to "develop" the chromatogram. You will probably have to do some experimentation to get the conditions just right. This is much easier to do with reference standards of the dyes, because you don't have to worry about interference from the sugar in the candy.

Once you have the chromatography running OK with the standards, you can run the standards through the preparation process with the vinegar and ammonia solutions. Many dyes are "indicators", which means that they change from colorless to colored as the pH changes (acid to base or vice versa); I don't know enough about the details of food dyes to know whether the ones you are looking for fall in that category.

Once you can make the entire process work with standards of the dyes, you can try it with the candy.

I suspect that the high sugar level in the candy would "gum up" the paper if you just dissolved the candy and spotted it directly on the paper.

Paper chromatography is one of those techniques that looks deceptively simple, but is actually complicated to do correctly (but it feels great when you finally get it to work!).

Greetings, Mr. Tom Jupille! Thank you for the information you shared with us. We appreciated it very, very much. All these will surely be helpful in the further development of our project.