Lab Conclusion: Cholesterol Egg Extraction Experiment – Brandon Skenandore
Cholesterol Egg Extraction Experiment
The purpose of this lab experiment was to isolate and purify cholesterol from egg yolks using distillation, funneling, refluxing, separation, and recrystallization. This experiment used many, if not all, techniques used in lab and therefore was very extensive. This experiment was done over the course of two weeks.
At the end of the first day, crude cholesterol was obtained and placed in a capillary tube for melting point obtaining. This crude cholesterol was a deep yellow color and rather powdery. From here, the cholesterol was recrystallized from methanol, and once this was funneled, it was a light yellow and had larger crystals. A portion of this cholesterol was placed in a capillary tube for melting point measurement as well.
The second day, the recrystallized cholesterol was weighed and a percent composition of cholersterol in egg yolks was found. This percent composition was 0.543%. However, this cholesterol most likely still contained impurities, so the actual percent composition of cholesterol in egg yolks was most likely even smaller.
After 100 mg of the recrystallized cholesterol was purified again using bromination, the purified cholesterol was a white color. However, only 11 mg of purified cholesterol was obtained from the original 100 mg. The final melting point range for the crude cholesterol was 125º C – 132º C. The melting point range of the recrystallized cholesterol was 136º C – 142º C. The melting point range of the final purified cholesterol was 146º C – 149º C. Using these numbers and given that the literature melting point for cholesterol was 148.5º C, this shows that the cholesterol was indeed further purified. Difference in altitude can account for the lower melting point range observed. Not only did the melting points help conclude that the cholesterol was purified, but the cholesterol itself was whiter than the recrystallized cholesterol, which was whiter than the crude cholesterol. Obviously having a whiter color means less egg yolk product, which means more purified cholesterol. Therefore, the experiment was successful.