Question

In our Thin-Layer Chromatography Lab, we were asked to determine the components of Excedrin by analyzing the development of aspirin, acetaminophen, and caffeine on a TLC plate and compare it to Excedrin's development. Pure ethyl acetate was used as the solvent, and each analyte was mixed with 95% ethanol.

Unfortunately, our professor suspected that our TLC plates were old/deteriorated as every group was unable to detect CAFFEINE or ASPIRIN with a UV lamp, but ACETAMINOPHEN and EXCEDRIN were easily detected and traveled the same distance along the solvent front. Obviously, I know that Excedrin is supposed to be composed of all three analgesics, but I am unsure why acetaminophen would appear and caffeine and aspirin would not.

Because the lab was mostly a failure, we were asked to find the reason why acetaminophen and Excedrin would show up on the TLC plate, but caffeine and aspirin would not.

Answer 1