This process aids in determining affinity. 3 The most polar compound is always the absorbent; however, the polarity of the compounds in the mixture in addition to the solvents found in the mixture differs in polarities. We use chromatography, or more specifically TLC, to determine the relative amounts of components in a mixture. Additionally TLC is utilized to determine the identity of two substances. When utilizing TLC, the ratio of distance traveled by the compound to the solvent is defined as Rf. 1 Column Chromatography, is used in this experiment to separate ? -carotene from a mixture.
Column Chromatography is utilized for purification of both solids and liquids. Primarily, CC is used to separate and isolate compounds. The similarities between TLC and CC include the utilization of a chamber and UV light to identify the affinity of the compounds. The steps found during a TLC can also be found in a CC. Differences include the extraction and purification procedure found in a CC. Results Thin Layer Chromatography Compound| Distance (cm)| Acetaminophen| 4. 7| Caffeine| 1. 5| Aspirin| 0| Ibuprofen| 0| Solvent front| 6. 5| Thin Layer Chromatography with unknown Compound| Distance (cm)|
Unknown| 1. 5| Thin Layer Chromatography comparison Compound| Distance (cm)| Residue| 0| Isolated ? -carotene| 0| Standard ? -carotene| 0| Calculations Rf = Distance traveled by the compound / Distance traveled by solvent Rf Acetaminophen = 4. 7cm / 6. 5cm = 0. 7 Rf Caffeine = 1. 5cm / 6. 5cm = 0. 2 Rf Aspirin = 0cm / 6. 5cm = 0 Rf Ibuprofen = 0cm / 6. 5cm = 0 Rf Unknown = 1. 5cm / 6. 5cm = 0. 2 Discussion The experimental results indicate that the identity of the unknown tablet was determined by measuring and comparing the distance traveled by the known standards to the unknown standard.
The Rf value of Caffeine was 0. 2 and of the unknown was also 0. 2 as shown by the calculations above, this proves that the unknown substance was Caffeine, given that the unknown substance traveled 1. 5cm and was equal to the distance traveled by Caffeine, showing that they were the same. Acetaminophen had a Rf value of 0. 7 with Aspirin having a Rf value of 0 and Ibuprofen also having a Rf value of 0. This shows that the unknown tablet was Caffeine. Yes, the column chromatography experiment was successful as the residue, isolated and standard ? carotene did not move from the baseline so all the three dots did not move. This shows that they must be similar, we could have used a better solvent than hexane to show reliable results. Conclusion The TLC successfully exhibited the different affinities of the analgesics. The Rf values were successfully obtained and due to the different affinities, the unknown standard was identified. However, the identity of the unknown standard was not easily attainable, there were complications with the experiment. The complications that could have hindered the results, include human error in measuring and observing.
Also, the tools used in this experiment may not have been sterile and the stock solutions may not have been pure solutions. For the column chromatography experiment, the isolated ? -carotene obtained was isolated from the solution, again human error in measuring and observing could have hindered these results. For isolating ? -carotene, the solvent used was hexane but that did not move the components so a better solvent could have been used to show more reliable results and to make the components move from the baseline.
After removing the TLC paper from the solvent, it would dry off very quickly so this could have caused errors in marking the solvent front, this is a human error and can be improved by reducing human error and improving accuracy with doing measurements. References: 1) Weldegirma, S. Experimental Organic Chemistry Laboratory Manual: CHM 2210l and CHM 2211L Fall 2011/ Spring 2012; Mason OH, 2010; pp 4-8. 2) Wikipedia. com Affinity. http://en. wikipedia. org/wiki/Affinity (accessed September 19,2011) 3) Wikipedia. com Elution. http://en. wikipedia. org/wiki/Elution (accessed September 19, 2011)