Experiment 4

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Feb 20, 2024

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Experiment 4: Thin – Layer Chromatography Analysis of OTC Analgesics Components Alexander Filosa Department of Chemistry, Binghamton University, Binghamton, NY, 13902 October 23, 2022 Post Lab Exercise: 1) What is the purpose of adding a small amount of acetic acid to the developing solvent?  By adding a small amount of acetic acid to the developing solvent, it will help correct streaking with acids. What it does is that it increases the polarity of the solvent and in such, will lead to a lesser amount of attraction that polar compounds tend to have within their stationary phase. 2) Suppose you carry out a column separation of acetaminophen and phenacetin on silica gel using ethyl acetate. Which compound would elute first?  If the experiment were to be carried out using a column separation of acetaminophen and phenacetin on silica gel using the ethyl acetate, phenacetin would have a lesser amount retained. In contrast, acetaminophen would have a greater amount retained. 3) Describe the possible cause/effect of the following experimental situations: a. You cannot determine the solvent front on a TLC plate. b. The horizontal spots line is below the solvent level in the developing chamber. c. Spots have Rf values of 75% and above.  If you cannot determine the solvent front on a TLC plate, one cannot find the Rf value of each compound that is placed on the plate. Although you can find the relative retention, it is still not much of usable data. An idea to be used is to use the end of the plate as the end of elution. In the case that the horizontal spots line is below the solvent level, some of the points would dissolve in the mobile phase. The plate would be dripping and the Rf value would be hard to calculate. If the spots have Rf values 75% or greater, there is no issue with it. You can run another test to make with a lesser polarity in the mobile phase to confirm that each of the spot on the plate is different. 4) Assuming that the active ingredients of the tablet whose spots you identified entirely dissolved in ethanol/methylene chloride solution, what was the solid that remained behind? 5) If the active ingredients of the tablet whose spots entirely dissolved in the ethanol/methylene chloride solution, the solid that was remained is either starch or any pill coating substance. Although starch binds the tablet together, it is an ingredient that is inactive and will not dissolve. 6) Describe one or more simple chemical tests that would distinguish acetaminophen and ibuprofen.  One simple chemical test that would distinguish acetaminophen and ibuprofen from each other would be the melting point since acetaminophen’s melting point is 169-

172 and ibuprofen’s is 75-78. An NMR spectroscopy could also work by counting the number of protons there. 7) Another common OTC analgesic Aleve contains sodium salt of naproxen as its active ingredient. a. What is the systematic name and structure of naproxen? b. The physiological effects of naproxen are very similar to one of analgesics analyzed in this experiment. Which one do you think it is? Justify.   naproxen  The IUPAC name for Aleve is (2 S )-2-(6-methoxynaphthalen-2-yl)propanoic acid. Naproxen (Aleve) is use to treat both pain conditions as well as inflammation. Its used for management of pain; management of primary dysmenorrhea; signs and symptoms of tendonitis, bursitis and acute gout. It is similar to ibuprofen since it is also an anti-inflammatory drug and used for inflammation and as well as pain.  ibuprofen

Analysis: To whom these concerns, the lab result has come back. It was to be said that a patient had overdosed on an over-the-counter (OTC) drug, and the container it was in was not to be found, and family members did not know what drug it was. The patient urine sample (#8) was taken to be screened as soon as possible to figure out what drug had been ingested, and through the method of thin-layer chromatography, we were able to figure out the drug’s compound. By extracting the active ingredients of each OTC drug and placing it in organic solvent(s). The pure active ingredients must be chromatographed to be used as the Rf standard for the extracted solution. The Rf values that were found are as follow acetaminophen (.25), acetylsalicylic acid (.464), Ibuprofen (.631), Phenacetin (.423), Salicylamide (.538), and Caffeine (.115). The Rf values for each drug are as follows: Advil (.585), Anacin (.451), Aspirin (.439), Excedrin (.360), and Tylenol (.384). And for the patient urine sample (#8), it was .407, .432, and .420. By comparing the Rf value, it was determined that the drug, Aspirin, was consumed with the phenacetin compound. Both Rf values correspond to the Rf value found in the patient’s urine sample. Through thin-layer chromatography, these results answer the problem of finding out what drug and compound of the drugs were consumed to treat the patient. To further back up the test results, a second trial could be run to confirm that it is the correct compound and drug existing in the urine sample. Reference: Lehman, J. W.; Multiscale Operational Organic Chemistry: A Problem-Solving Approach to the Laboratory Course.; Prentice-Hall, Inc, 2002; pp 123-127.

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