In the Paper Chromatography experiment, known and unknown ions were placed on a chromatography sheet and then placed in an eluting solution, for seventy-five minutes and then sprayed with an activator to determine how far the ions had traveled. Doing so allowed us to figure out what the unknown ions consisted of. Focusing on the known and unknown ion spots that were placed on the chromatography sheet, the reason that they moved up the sheet, when placed in the eluting solution is because the solution acted as a solvent and the higher the solution moved, the more the ions moved, depending on their densities. The denser the ion, the shorter the distance they moved. The reason that the solvent moved farther than the ions themselves is because it had a much lighter density than the ions did.
When the least dense ion had fully dissolved into the chromatography paper, the solution kept going because there was also a continuous flow of it from the bottom of the container. Known ions, as opposed to unknown ions, were used in this experiment because they allowed us to determine what the unknown ions consisted of. Being careful about how big the spots were was a big deal because if the spots differed in size, then there would be a greater amount of the ions present on the page which would cause the spot to move farther than it is supposed to and would have skewed the results at the end of the lab. In this lab, Rf values for the ions were calculated using the following equation: Rf= distance ion moveddistance solvent movedWhat this means is that the distance, in centimeters, was measured from the original spot of application to the final spot the ion moved, as well as to the farthest point that the solvent, or eluting solution, moved. The ion distance was then divided by the solvent distance in order to achieve the Rf value for each ion tested.
The reason that the Rf values were calculated was to help compare the values from the known ions with the values from the unknown ions to determine what the unknown ions closely matched with. In order to see the distances travelled, a staining reagent was sprayed on the chromatography paper to help better see where the ions had moved. Without the reagent, the ion spots were almost hidden on the paper making it impossible to tell how far they had travelled so Rf values could not be determined.
In order to determine the unknown ion, the distance travelled and Rf values for the known and unknown ions were compared to see which ones matched, or were close enough to match, so that the name of the unknown ions could be determined. For some, this may not have worked properly for a few reasons. This could have been because of a foreign liquid getting onto the chromatography paper, the eluting solution being shaken during the rising process, or even the size of the spots not being consistent enough. This method can be used in real life such as in a police lab to help compare different bloods found at the scene, or different liquids that could have been potential poisons, or even to see if any drugs were involved at the scene. In industry, this method can be used to help companies try to steal ingredients from other companies such as in Pepsi® from Coke® or vice-versa.
