February 28, 2020, 07:38:47 PM
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Topic: Testing purity of caffeine?  (Read 206 times)

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Offline Mati

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Testing purity of caffeine?
« on: January 26, 2020, 05:18:17 PM »
In my chemistry class we are doing our projects and my project is extracting caffeine from energy drinks.
I am using Dichloromethane to remove the caffeine from the drink after dissolving some Ca(OH)2 and NaCl in it.
Afterwards I am using anhydrous CaCl2 to remove any water.
I then decant the dichloromethane and leave it to evaporate under a fume hood.

The way I determine the mass I extracted is by weighing the evaporating basin empty and then again after all the dichloromethane has evaporated, however during my first run a small amount of the energy drink go into my dichloromethane and because I was in a hurry I couldn't leave it to dry any longer.
This completely threw off my results as now the caffeine is highly impure.

So my question here is, is there a way I can easily test the purity of caffeine I have to get a final mass of pure caffeine in the sample?
Would it just be easier redoing the experiment?

Offline Corribus

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Re: Testing purity of caffeine?
« Reply #1 on: January 26, 2020, 09:26:16 PM »
So my question here is, is there a way I can easily test the purity of caffeine I have to get a final mass of pure caffeine in the sample?
Yes, of course, but:

Quote
Would it just be easier redoing the experiment?
Given the resources likely available to you: probably.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Mati

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Help with purification of caffeine.
« Reply #2 on: February 13, 2020, 10:22:17 AM »
I've already posted about my project multiple times and here I go again.

Basically now that I have managed to isolate caffeine from energy drinks I am trying to purify it.

This is my method:
The crude caffeine is washed with 1 ml portions of a 1:1 mix of hexane and diethylether.
The liquid is removed using a pipette.
The caffeine is dissolved in 2 ml of dichloromethane.
This is filtered through a thin layer of cotton into a test tube and the dish is washed a couple times with small portions of dichloromethane.
The test tube is placed in a  water bath at 50-60°C
After the solvent evaporates isopropyl alcohol is added drop wise till the caffeine dissolves.
The test tube is removed from the water bath and allowed to cool to room temperature.
1 ml of hexane is added to the test tube causing the caffeine to crystallise.
The liquid is removed using a pipette and the caffeine is washed with small portions of a 1:1 mix of hexane and diethyl ether. This is removed using a pipette.
The caffeine is left to dry.

Everything goes pretty well for the most part, When adding the isopropyl alcohol I could see some nice crystals of caffeine, however, after it dissolves and the hexane is added very little crystallises.
Is this due to something I'm overlooking or is it better to stop the purification a bit earlier like just before adding isopropyl alcohol?
I am generally quite inexperienced so I would not be surprised if it's something very simple.
Thank you.

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