MNK - 28-5-2008 at 06:05
extraction:
- plant material blended in methanol
- left to sit for one week
- filtered into a wide based dish
- evaporated to +/- 20% of the original volume of liquid
- liquid refiltered and placed into a new smaller pyrex dish
at this point (during evaporation) i often find a yellowish/light brownish residue accumulating on the surface of the pyrex dish underneath the
liquid. Id like to know if this residue is merely an accumulation of microscopic remnants of plant material or could it contain a large portion of the
alkaloids which i am attempting to extract.
Pls note that i am not referring to the final product, as in the goo usually seen once all methanol has been evaporated. I am referring to the build
up at the base of the pyrex dish that occurs while the alkaloids should (theoretically) still be suspended in the not-yet-evaporated methanol.
Also note that i am using lab filters, not coffee filters. After filtering twice the vast majority of plant material (excluding water, oils, fats and
alkaloids) should have been eliminated.
Of the 10 or so different plant materials i have extracted from in my life, i have always encountered this situation. This is also the reason why i
feel it unneccesary to speak of any specific plant. I prefer to ask the question more generally.
What is this residue?
Thank u guys
Sauron - 28-5-2008 at 08:05
There are books on the alkaloids available for free in the forum library.
Please consult them.
There is no single general procedure.
The books and the chemical literature are the place to search for specific procedures.
I further suggest that you studt chromatography.
Klute - 28-5-2008 at 09:39
It could also be plant fats, thta are slightly soluble in MeOh, and crash out whne part of it has been evaporated. Or microscopic plant material
agglomerating too.
You could try performing an A/B extraction on the extract to remove these, or at least a solvent (the ideal solvent needs to be determined) boil on
the alkaoid salts.
MNK - 28-5-2008 at 22:34
Thanks Klute. I agree. Much appreciated.
MNK - 28-5-2008 at 22:42
Sauron - where would i fnd this library...every place i try to enter that resembles a library ends up requiring a password
Why remove water from plant material before extraction?
MNK - 28-5-2008 at 22:46
Why is it necessary to dry plant material before extraction with an organic solvent? Is it simply that it further removes impurity from the final
product or is there more to it?
Sauron - 29-5-2008 at 06:17
@MNK
A reasonable question.
If you go to the root url for this site
http://www.sciencemadness.org/
You will find a manu, one item is LIBRARY
for which the direct url is
http://www.sciencemadness.org/library/index.html
THE PLANT ALKALOIDS, in 2 volumes, id down the page.
You can right click the link and do a Save Target As.
Once for each volume. You will need Adobe Reader or one of the free DjVu readers described in the header at top of Library page.
I don't rememberwhich file format these are in but it is one of these or the other (PDF or DJVU).
My advice is to install both types of reader.
Have fun!
Klute - 29-5-2008 at 06:59
I would think completly drying tyhe plant material would able any organic solvent to soak up inside the plant cells easily. If the plant is still wet,
there might just be an interface between the water containe din the material, and the solvent outside, without any good diffusion/aborption.
MagicJigPipe - 29-5-2008 at 10:54
I would think drying a plant material before extraction would be a MUST. Is it desirable to have wet material before extraction of some plants? I
suppose I will have to look through the Plant Alkaloids book.
MNK - 29-5-2008 at 23:26
Magic - why exactly do u say a must? based on logic alone i would fully agree, but i would like to hear your justification for your statement.
Sauron and Klute - thanks guys, youve helped me out a great deal. much apprecited.
Sauron - 29-5-2008 at 23:54
I have done a lot of "extractions" of herbs with relatively concentrated aqueous ethanol ("macerations") followed by distillation (simple
distillation, with added water) to produce herbal liqueurs. I am very familiar with the way that this was and is done industrially in the production
of the same liqueurs and liquors, such as gin and absinthe. I can tell you that in every instance I know of, the herbs are dried in special drying
sheds prior to maceration or steeping in alcohol, or percolating with alcohol. The dried leafy material is shredded before extraction, and woody herbs
such as star anise are milled in a herb mill.
These herbs do not contain alkaloids but rather essential oils.
The alkaloids of course by definition are nitrogenous bases and this the utility of acid-base extration as a method of isolation ought to be clear.
The importance of drying the plant material if not adequately explained in the alkaloid books, might be further elucidated in the essential oils
book(s) also to be found for free in forum library.
There is also a slim volume specifically on ephedrine, which may or may not happen to be of interest to you; it is anyway an alkaloid.