Lab 1 Identification of Analgesics Using TLC by: Brittani Summers

Purpose: To perform thin layer chromatography (TLC) analysis of unknown analgesics and determine: 1) the number of components in a mixture; 2) identify substances using Rf values; 3) determine the purity of the unknown analgesics

Introduction: This experiment will show the presence of certain drugs in a crime scene. The purity of the drugs is identified through the use of Thin Layer Chromatography by showing the possible presence of other substances in the mixture.

Materials:

• Unknown Sample 2 (1 % solution) prepared in ethanol, ethyl acetate and acetic acid



• Unknown Sample 5 (1 % solution) prepared in ethanol, ethyl acetate and acetic acid



• Iodine



• UV lamp



• TLC Plates



• Beaker with watch glass



• Ruler



• Calculator

Procedure:

1. A line was drawn 1 centimeter from the bottome of the TLC plate



2. A capillary tube was used to spot the TLC plate at the 1 centimeter line.



3. The TLC plate was then placed inside the beaker containing ethyl acetate and acetic acid and covered with a watch glass.



4. The mixture of ethyl acetate and acetic acid then began to absorb through the TLC plate. The TLC plate were then removed once the solvent reached approximately 1 inch from the top of the TLC plate.



5. The wet TLC plates were then left to dry.



6. The dried TLC plates were then observed under the UV lamp.



7. The plates were then placed in a beaker with solid iodine and the vapors from the iodine left more distinct marks on the TLC plates.



8. The TLC plates were then viewed again under the UV lamp and marks were made where the solution stopped flowing on the TLC plate.



9. With the ruler, measurements of where the solvent stopped and where the substance stopped were taken note of in centimeters.



10. The Rf values were then calculated by dividing the distance the substance traveled by the distance the solvent traveled.
    
    

• Rf= distance substance traveled/ distance solvent traveled

Results/Discussion/Conclusion:

Substance 2 had a Rf value of .613 Figures 1: Samples 2 & 5

Substance 5 had a Rf value of .565

The TLC plates showed several different spots in one line. Because there were several different spots in one line, it comes to a conclusion that the substance is not pure. Both substances 2 and 5 revealed several different spots so the conclusion was made that these two substances were not pure, therefore being mixed with something else.

Figure 2: Samples 2 & 5