silica gel and separation by gravity column chromatography

[stevenjang]

I am doing a high school science project regards gravity column chromatography. The problem is no separation occurred when food color mixture injected into my column chromatography.

I have followed the procedure according to the following web site for high school science project. “http://www.juliantrubin.com/encyclopedia/forensicscience/strawchromatography.htmlâ€

[chromatographer1]

I don't know what kind of silica gel you purchased or its size but the effect of the dyes indicates that the retention of the silica gel is too weak or your solvent is too strong, OR BOTH.

Of course it could be that your dye is not the right type of dye.

If at first you don't succeed.......................

try something different: silica gel, dye, mesh size, water, etc.

I have never seen the silica gel you described at any local store.

It is most likely the primary cause of your issue.

Good luck,

Rod

[danko]

Hi Stevenjang,

You can try calcium carbonate for stationary phase. It should be the easiest material to acquire - especially at school
Remember to grain it to the smallest possible particles and you’re ready to go.

Good luck

P.S. The graining thing goes for the silica as well. Maybe the particle size was the problem with your first trial?

[stevenjang]

Hi Stevenjang,

You can try calcium carbonate for stationary phase. It should be the easiest material to acquire - especially at school
Remember to grain it to the smallest possible particles and you’re ready to go.

Good luck

P.S. The graining thing goes for the silica as well. Maybe the particle size was the problem with your first trial?

From Steven:

Thanks a lot for the reply from Rod and Danko.
I got another Silica Gel (30-60 mesh) from school and did the experiments again last night. The separation is a bit better. For green color, I can see very little yellow cames out first, then a few green color (not separated), thereafter a lot of blue color. Theoretically, I should only get the yellow color first and then the green color.

I also tried other solvent such as rubbing alcohol, vinegar. The results are not that good neither. Vinegar is the best among the three solvents.

I then tried to grain the silica gel and redid the experiments. However, I grained it too fine that the water even can not flow down. I am going to try more tonight.

I want to thank you all the advices that make me feel more confortable and ensure me that I have not done something very wrong.

[chromatographer1]

You may have trapped air in the grained silica gel. Push out the air (pull it out) and then see if you can get flow.

Or use a less fine material.

You are really learning about making column the old fashioned way!

DIY

have fun,

Rod

[tom jupille]

for green color, I can see very little yellow cames out first, then a few green color (not separated), thereafter a lot of blue color.

That means that you are getting a separation, but it's not "complete" (by the way, this happens to professional scientists, too!).

One additional possibility is that you may be overloading your column. Try a much smaller drop of food coloring (or try diluting the food coloring 1/10 with water first) and see if things improve.