A line was drawn 1 CM from the bottom of each plate, and five small, evenly paced marks were made along those lines (see Figure 1). Each mark indicated where a substance would be spotted. All compounds used were in solutions of leg of each dissolved in 20 ml of a 50:50 mixture of methyl chloride and ethanol. The first plate made was the reference plate. Capillary microscopes were used to spot the first four marks with acetaminophen, aspirin, caffeine, and salicylic (in that order). (See figures 2-5 for chemical structures. ) The last mark was spotted with a reference solution of all four chemicals.
The second plate made was the sample plate. The first four marks were spotted with Niacin, Buffering, Exceeding, and Ethylene. The fifth mark was spotted with a reference solution of all four drugs. Figure 1. Prepared TTL plates Figure 2. Acetaminophen Figure 4. Caffeine Figure 3. Aspirin Figure 5. Salicylic A development container was created with a wide-mouthed screw jar. It was filled with the development solvent, which was . 5% glacial acetic acid in ethyl acetate, so that the solvent was approximately . 5 CM deep. The first TTL plate was then carefully placed into the development container.
Great care was taken to ensure that the plate went in evenly so that the solvent could rise evenly up the plate. Once the solvent front had reached approximately LLC from the top of the plate, the plate was removed, the solvent front was marked with a pencil, and the plate was allowed to dry. The second plate was then placed in the development chamber in the same manner as the first. Once the solvent front reached approximately LLC from the top of the plate, the plate was removed, the solvent front was marked with a pencil, and the plate was allowed to dry.
Each plate was then viewed under the UP light. Any spots that were seen were lightly circled with a pencil, and their color was noted. The orders of elution (RFC values) ere calculated by dividing the distance from the baseline to the center of the spot by the distance from the baseline to the solvent front. After all observations and calculations were made, the plates were placed in a jar containing iodine. The jar was warmed with hands so that the iodine vaporized. The plates were then removed from the jar and observed.
One problem that arose in this experiment was that the reference plate gave very similar RFC values for aspirin and salicylic and neither of them turned color after exposure to the iodine. This made it difficult to tell which compound was in Buffering. Salicylic and aspirin are similar compounds, so it would make sense for our tests to show them to have similar properties. The other problem encountered with the results was that aspirin did not spot n Exceeding or Niacin. There were two spots on the top left and right side of the sample plate and some coloration in between.
These things were all ignored and considered erroneous because they weren’t in line with the other spots. The two larger spots were in the approximate location of where the plate was handled, so this could be what created those spots. It could be that the aspirin was in the coloring between the two spots. If too much of the sample was applied, it could cause the aspirin to tail and not create defined spots. It could also be that too little sample was applied and no spots were created for the aspirin. The problem of not applying the correct amount of solvent could be resolved by using better capillary microscopes.
The ones used in this experiment were crudely made, and it was difficult to judge exactly how much sample had been applied. It would have been interesting to see if other methods of visualization showed other spots on the TTL plates. While we only used UP light and iodine, some other methods we could have used involve silver nitrate, sulfuric acid charring, and ferric chloride?just to name a few. In conclusion, the experiment was mostly successful because it correctly determined the composition of the sample rugs with the exception of the problems with aspirin.
Questions 1. Too much sample will cause the spots to tail and overlap. 4. The ink from a pen would rise up the TTL plate along with the development solvent and the chemicals being tested. This would make it very difficult to determine which spots belonged to the sample being tested. References 1. Sigma Aldrich. Http://BMW. Similarity. Com/safety-center. HTML Date accessed: August 31 2009. 2. Miriam Webster Online Dictionary. Http://dictionary. Reference. Com/browse [salicylic Date accessed: September 5, 2009.