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Alt 27.11.2009, 15:25   #9   Druckbare Version zeigen
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Beitrag AW: Suche Aromatische Kohlenwasserstoffe (Xylole)

Step 2: De-Fatting
Once cooled, the next step is to de-fat the solution. This step will remove the fats and many other non-alkaloidal plant matter. Make sure the solution is acidic (pH 4 is good) before doing this. If the solution is acidic, the alkaloids will be in a salt form which is soluble in water but not in xylene. Pour the solution into a glass jar (or separatory funnel, if available). Add 25-50% of the solution volume in xylene. For example, if you have 200ml of solution, add 50-100ml of xylene. Put the lid on the jar and gently turn the jar over 50 to 100 times. Do not shake the mixture vigorously as this could result in emulsions that will be difficult to separate. (If you do end up with an emulsion layer, which looks like a thin layer of poorly separated bubbles, bathing the jar in hot water can help separate the emulsion. If the emulsion layer is thin enough, you may wish to just discard it rather than taking the time to let it separate.) Once mixed, let the jar sit and separate out into the different layers. When this is done, you will have a top layer of solvent, a middle fatty layer, and a bottom layer containing the acidic aqueous solution (and the alkaloids).
If you are using a separatory funnel, drain out the bottom aqueous layer and throw away the top two layers. Alternatively, use a turkey baster to siphon off the top two layers and discard them. (Make sure you dispose of all solvents safely! Do not flush it down the toilet if you have a septic tank. If pouring it down a sewer-connecting drain, make sure to wash it down with large amounts of water.) You will likely find that the turkey baster only gets off most of the solvent and fat layers. To get the thin layer that the turkey baster can't get, try this trick. Siphon off all of the remaining solvent and fat layers, as well as some of the top of the aqueous layer. Put this liquid into a tall thin glass container (a graduated cylinder or test tube, for example), and let it separate back into layers. Then, use an eye dropper to get off the solvent and fat layers, then add the remaining aqueous solution back to the main jar.
There is one other possibile approach to separating the layers. Because xylene freezes at -47.7 degrees Celsius, a separation can be done in the freezer. Put the container in the freezer and let it sit for a few hours until the water has frozen solid. The xylene can then be poured off and discarded. I do not know if this will work for defatting, as I do not know the freezing point of cactus fats. If the fats freeze at freezer temperatures, it may not be possible to pour them off with the xylene. This freezing technique can certainly be used later on in steps 4 and 5 to separate the xylene and water layers, however.
Repeat the de-fatting process two more times, or until you no longer get a fatty layer after separation. Make sure that you have good ventilation through the whole de-fatting process (or any time you are working with xylene). If you begin to feel light-headed or nauseous, or get a headache, go outside immediately and breathe fresh air until you feel better. Also, make sure there are no open flames or sparks as xylene is quite flammable.
Step 3: Basification
After de-fatting, slowly add sodium hydroxide to the aqueous solution until the pH is up around 10. Rather than adding dry sodium hydroxide, it may be wise to prepare a solution of sodium hydroxide in water, and add this. Be careful when mixing the sodium hydroxide and water, as the mixture will cause an exothermic (heat producing) reaction. Do not prepare the mixture in heat-sensitive containers. When working with sodium hydroxide, remember that it is a highly caustic material and can burn you badly. Avoid contact, especially with the yes, and if any gets on you wash the spot immediately with plenty of water. It is highly recommended that you wear protective gloves and goggles when working with sodium hydroxide or other hazardous chemicals.
Be aware that once you do this step, you need to continue the extraction at least up through the xylene extraction because leaving the alkaloids in a strongly basic solution will cause them to start breaking down after several hours. Making the solution basic turns the alkaloids into their free base forms, which are soluble in xylene.
Step 4: Extraction of Free Bases
Once the solution is basic, xylene using the same ratio as used during the de-fatting process. Again, mix the solution thoroughly but gently to avoid emulsions. Let the solution sit, and it will separate out into two layers. On the bottom will be a basic aqueous solution, and on the top will be a xylene layer which now contains the alkaloids. Using either a separatory funnel or a siphoning process, collect the xylene layer and set it aside. Since there will still be significant alkaloids in the aqueous layer, repeat this process two more times. Combine all the xylene and discard the remaining aqueous solution.
If you are using a separatory funnel, gas may be formed when adding xylene to the basic solution. To prevent pressure from building up and potentially leading to an explosion, vent the separatory funnel occasionally. If you are using a jar, you should remove the lid.





sooo das wäre der Text, den ich nicht 100% übersetzten kann.....




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