Extraction: Basic Principles

First of all, let me say it has been an extremely long time since I last posted, but nothing has changed. AFOAF still makes BHO regularly, and still knows all of the chemistry.

here are some basic concepts that may help both beginers, as well as the more advanced:


"Purifying" an alcohol solution or extract (removing impurities):


Many people believe that solvents like Ether, ethanol, isopropanol, MeOH, acetone, and a few others can be used to separate the cannabinoids from an impure alcoholic extract (which might contain impurities like chlorophyll, cellulose, and waxes)

they believe 1 of 2 things:

1) that some combination of these solvents will precipitate (cause to become solid) the impurities in the mixture

2) that a liquid/liquid extraction using some combination of these solvents can be used to isolate/separate the impurities from the cannabinoids.


the precipitation method will only work in the following way:

an isopropanol or ethanolic extract is mixed with an excess of a highly non-polar solvent that will mix (all of them will mix with those 2 alcohols).

this will make the solution non polar and cause any dissolved polar compounds to precipitate. that is the theory, though I have never tested it. some solvents work better than others in this regard. ether has a tendency to cause such compounds to precipitate, but ether is actually relatively polar in comparison to solvents like aliphatic hydrocarbons or aromatics, and may not work in the way desired.


On the liquid/liquid extraction method:

miscibility is the issue.

the only 2 solvents worth even considering in this situation are:

MeOH and Hexane

http://www.micronmr.com/download/fi...0_-_Solvent_Miscibility_&_Viscocity_chart.pdf

there are plenty of similar charts all over the web....


all common solvents will mix with ethanol, isopropanol, ethyl ether, chloroform, and dichloromethane. this renders them worthless for such a purification method.

the only option is to extract the plant material with, or dissolve a concentrated alcoholic extract in METHANOL, and then extract this solution using HEXANE. Look up "liquid liquid extraction" for explicit details on the process.

these are the only 2 solvents that will dissolve cannabinoids, have limited toxicity (yes, methanol is toxic, but not as toxic as DMF), and are relatively easily available (hexane is hard, but not impossible to find)


Next post addresses more issues

toxicity of solvents

hexane, butane, pentane, etc are aliphatic hydrocarbons. such chemicals do not have chemical reactivity necessary to damage the body's biochemistry.

molecules of these solvents cannot react with anything inside your body. Thus the only toxicity concerns are associated with ridiculously high levels of exposure.

most concerns are related to inhaling super high concentrations of the fumes (>>1000 PPM for extended periods), drinking the solvents, or complete immersion of the unprotected skin for long periods.


with that being said the small amount that remains in well purged BHO (or hexane, pentane, heptane extracts) is NOT toxic, and NOT dangerous. it is present in small enough quantities that it is completely safe to EAT or SMOKE.

I mentioned this to try to explain to people who are afraid of these solvents for fear of their supposed toxicity (rather than the dangers of the extraction itself).

yes. even the presence of branched alkanes in small concentrations are not dangerous (you breath them in at the gas station in higher quantities than are present in well purged BHO). Branched alkanes are more toxic than straight chain alkanes, but again this is only a concern when exposure is high (and it never is for this situation).


Aromatics are bad, no matter which one. Naptha is a mixture that contains aliphatic hydrocarbons as well as aromatics and should never ever be used in conjunction with an extraction like this (used for ingestion or inhalation).


Petroleum ether is also a mixture, but it is a mixture of PURE aliphatic hydrocarbons (no aromatics). it also typically a mixture of straight chain hydrocarbons, though some of the higher alkanes (hexanes or higher) cannot be separated from their branched isomers.

either way, Pet ether is a perfectly acceptable alternative to pentanes or hexanes (for the extraction, this will not work according to the above post's guidelines for a liquid/liquid extraction)


Isopropanol is toxic by ingestion (not skin exposure), and SUPER high vaporinhalation (you would basically need to breath it for hours at a ridiculously high concentration to be dangerous). it is used by medical professionals and in the food service industry. do not concern yourself with it.

Methanol toxic by ingestion, skin exposure, and vapor inhalation. has a much lower threshold for damage than isopropanol. limit use of methanol if you can. very dangerous.


Rossville anhydrous ethanol, sold in a red metal can is DENATURED. do not use this with an extraction.

rossville pure anhydrous ethanol (incredibly expensive, like >$50) comes in a BLUE metal can (not denatured)


butane should be "triple filtered" or "refined" or some other such designation. this has the simple meaning that it does not contain odorants for detection of leaks (ostensibly for the purpose of high performance jet lighters which might be damaged by the odorants)

common purchase location is a tobaccanacia store (cigar shop)

Impurities (I am not including oligo terpenoids that are not cannabinoids, as most are considered to be "good")

all life is composed mostly (weight percent) of carbohydrates (sugars and polymers of sugars), proteins (polymers of amino acids), and fatty acids and esters thereof (cell wall). chlorophylls are actually found in incredibly small (relative) concentrations in plants (cellulose makes up >40% of a average plant's dry mass), though they are responsible for the dark color of alcoholic extracts

alcohols will dissolve waxes (fatty acid esters, alcohols, and similar compounds), cellulose and smaller poly or mono saccharides, chlorophylls, and enzymes/amino acids.

basically, alcohols will dissolve any and all classes of chemicals inside a plant, though it will not dissolve all to the same degree.

aliphatic hydrocarbons (butane, pentane, hexane, and pet ether)

will dissolve waxes/fatty acids, very small amounts of cellulosic or sugar related chemicals, and a very very small number of amino acids, and a very small amount of chlorophyll related compounds (the red/gold color of BHO is NOT from the THC or other cannabinoids).

this is one of the main reasons for using these solvents, they are very selective for the specific chemicals that are the goal of the extraction


aromatics

aromatics are more polar than aliphatic hydrocarbons, but are still considered "non polar" they will dissolve everything the aliphatic solvents will, but will also dissolve more amino acids, and possibly more of the fatty acids and sugars

ethyl ether

the most "polar" non-polar solvent commonly used in this regard. it will dissolve the most sugars and amino acids, but less waxes and fatty acids (also less cannabinoids) than the above 2 solvent classes

relatively non toxic (can be ingested in small quantities)

For us non-chemists-
Can you further define the chemicals you are describing. I think we all know that ISO is isopropol alcohol, aka rubbing alcohol.
I thought that Napha was petrolum ether, aka PET. Am I totally confused?
Its been years since chemistery class!