Science Buddies: "Ask an Expert"

I am in the research phase of my science project and I need to find out how to crystallize cholesterol. What would be an appropriate solvent to use? I need to make relatively small crystals so how can I achieve that? I am using a powdered form of cholesterol. I need this question answered as soon as possible so I can continue working on my research. Thank you!

Hi,

I did a search for cholesterol crystallization and found a 2006 paper that describes one method: http://onlinelibrary.wiley.com/doi/10.1 ... 280906/pdf

The cholesterol powder is placed into a glass container (they used a graduated cylinder but a plain glass dish should work OK) and applied heat using a heat gun until the cholesterol melted into a clear liquid. They don't say how hot it has to be. Maybe a hair drier on high heat would work.

As the melted cholesterol cools it forms crystals and turns milky colored. They said it took about 15 minutes for the cholesterol to crystallize completely.

Try it and let me know what happens. I assume you want to use the crystals in some experiment, so you will need to be able to remove them and weigh them. The crystals in their figures look pretty large so i don't know if this will work for you. Maybe if you cooled the cholesterol melt more quickly by placing the dish in cold water, the crystals would not have time to grow very big.

I'm sure there are solvents that would dissolve cholesterol and allow you to form crystals by evaporation, but such solvents are highly toxic or flammable [http://lxsrv7.oru.edu/~alang/onsc/solub ... holesterol] , so the melt technique is the best for you if it works.

Let me know how it works and if you have any specific questions, please repost to this thread.

Scibee

Hello,

Thank you so much for your response. The paper was a great help. I am using the crystals in a way that requires them to be transported, not just grown in a test tube or beaker, so I am looking to make spherical and dense(not brittle) crystals. Using the information posted earlier, I melted the cholesterol (at about 150 degrees Celsius) until it was a clear liquid then I poured it, in small drops, into a beaker of cool water. Upon hitting the water, the cholesterol hardened immediately.
However due to surface tension of the water, the cholesterol crystallized into small disk shapes that were fairly brittle. I tried dropping the liquid cholesterol in alcohol, since it is less dense than water, but the crystals that formed broke as I attempted to remove them from the alcohol.
So now my question is, how can I get a more spherical and less delicate shape (something more dense)?
Would melting a significant amount of cholesterol and then running a string through the liquid cholesterol and allowing it to cool provide a more crystal shape? Or would using very warm water (almost boiling) instead of cool water slow down the hardening process and allow it to crystallize into a more spherical and condensed shape? Please let me know any ideas you have regarding a method.
Thank you!

Hi,

I've never tried to crystallize cholesterol, but i know in general that fast cooling results in smaller crystals than slow cooling. Did you try putting the beaker containing the melted cholesterol into the water (NOT the cholesterol itself)? You could try different water temperatures from 4 degrees C up to 20C, just make sure you have a large enough volume of water so the temperature doesn't change when you swirl the beaker in the water.

The other way to make crystals is to dissolve the solid in a suitable liquid solvent, then evaporate the liquid until the crystals form. Here's a list of solvents for cholesterol: http://lxsrv7.oru.edu/~alang/onsc/solub ... holesterol
Most of them are highly toxic and flammable and I would not use them unless you have access to a lab with a fume hood and someone to supervise your experiments. You could try dissolving the cholesterol in denatured ethanol or isopropanol then let the liquid evaporate outdoors in the open so the vapors could dissipate. This would take several days, however.

I would stick with the melting method and just vary the cooling rate till you get crystals of the right size and sturdiness. Keep checking the literature on cholesterol chemistry. There may be another method that gives uniformly small crystals. You can always call a chemical supply company like Sigma-Aldrich and ask them. They are always helpful and have loads of experience working with organics.

Good luck! We'll be here to help you again when you need us.

Best wishes,

Sybee

Hi,

I have a similar query on cholesterol crystal making with the exception that I have liquid form of cholesterol instead of crystals. So please guide me on how to make cholesterol crystals from cholesterol solution.

Please let me know urgently.