Thin Layer Chromatography of Analgesics Essay

Thin-Layer Chromatography of Analgesics Abstract: In this experiment thin-layer chromatography (TLC) was used to determine the composition of an unknown mixture of analgesics given five references of AC, ASP, CAF, IBU, SAL, an unknown consisting of a mixture of three of the references, and two unknowns (6,23) containing a single reference compound. The composition of the unknown mixture and two single unknowns were determined by spotting the reference compounds and the unknown compounds on two TLC plates. Placed them in a developing chamber that contained 0. % acetic acid in ethyl acetate solvent and observed the TLC plates under UV light after the TLC plates were taken out of the developing chamber. The known reference compounds portrayed spots and calculated Rf values that the unknown compounds matched to. This suggests that the composition of the unknown mixture is SAL, and ASP fused with AC and that unknown compounds 6 and 23 are compositions of AC and CAF. Conclusion: The composition of the unknown mixture and single unknown’s #6, and #23 were determined by contrasting them with the spots generated from the 5 reference compounds.

Resulting in the unknown mixture consisting of reference compounds SAL, ASP, and AC. Measuring on the TLC plates at 6. 0 cm, 4. 0 cm, 5. 0 cm and calculated Rf values of 0. 80, 0. 67, and 0. 53. In contrast SAL is measured at 6. 5 cm with Rf value 0. 93, ASP measured at 4. 0 cm with Rf value 0. 53 and AC measured at 5. 0 cm with Rf value 0. 67. Portraying how closely related or even exact these measurements at Rf values are. The second spot on the TLC plate is a fusion of ASP and AC due to them unable to separate during the eluting process and the third spot is merely a contamination streak.

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Unknown sample #6 is identified to be AC due to having the same distance and Rf value of 5. 0 cm and 0. 67. Lastly, unknown sample #23 is identified to be CAF because of it consisting of relatively the same distance and Rf value of 0. 27 and distance of 2. 0 cm. Where CAF is actually measured at 2. 5 cm and has Rf value of 0. 33. The distance and Rf value for unknown compound #23 is only closely related to CAF than any other reference compounds. Questions: 1.

Cis-2-pentene and trans-2-pentene are very similar in structures; therefore they travel at the same rate on the TLC plate so it is difficult to distinguish. 2. The problem in regards to the if the level of the developing solvent in the chamber is higher than the level at which a spot is applied to the TLC plate would result in the spot dissolving off of the TLC plate into the solvent pool rather than eluting up the plate, thus giving inaccurate results. 3. If the TLC plate was left in the developing chamber too long, it is expected that nothing will be seen when the TLC plate is observed under the UV light.

This is due to the solvent would elute too far up the plate and eluting the samples off of the plate which will also make it impossible to calculate the Rf value. 4. If too much compound on the TLC plates are spotted then not all of them will travel at the same rate which will cause a long streak observed under the UV light. 5. Ibuprofen is the analgesic that contains a chiral center. Enantiomers are isomers that are mirror images of each other. The ibuprofen has an (S)-(+) enantiomer that is more effective at reducing pain than the other (R)-(-) enantiomer because it is inactive.

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