There is a 15 minute shake which is sufficient
This method is simplistic with advantages. Identify your goal...whether it's quick&easy, inexpensive, max recovery, uniqueness, safety.... Sonication with ethanol is quicker and will result in greater yields. There is the drawback of expense: not everyone has one in their shed and they'll put ya back a few.
let....your solution sit for an additional few hours
Time is in your favor as long as your container is sealed, to prevent evaporation. Ethanol-soluble desireables come in 2 extremes: those compounds highly soluble in EtOH, and those barely soluble in EtOH. Let's focus on the barely soluble ones for a moment. Hours or days could be necessary for complete equilibrium to be reached with these compounds, so don't be in a hurry.
Liquid extraction has to do with the physical desire for a compound to leave it's happy home, like my ex bailing out of bed for cleaner air after i release some mayan death cloud. The pressure of seeking an easier way, like out of the room, gets to a point where it just happens, like a survival thing. With liquid-solid extraction, "enough" time is just
necessary. Match up a good solvent and most of the desireables dissolve out each time an additional extraction is performed. There always remains some desireables in the solid phase due to physical barriers originally present in the plant structure. Rinsing washes away already-dissolved desireables which are in solution but hanging up in and around the crannies. Targeting the remaining desireables not yet in the EtOH phase is where appreciation of good extraction technique begins.
Leave a window open long enough and eventually all the bad gas goes out leaving only a few molecules in that room. Extractions are quite different. Many physical barriers are present in the nature of the plant structure. As you come to understand there are differing solubility factors of interferents present in the plant, you will like myself conclude that extraction time is truly in your favor. T
Liquid-liquid extractions will reach 100% equilibrium, but try to extract from within a complicated plant matrix? Never gonna happen at standard temperatures and pressures without first creating super fine powder or adding a second solvent phase which is beyond an entrepeneur w/o a lab. I have years of experience with matrices including shellfish and placenta, & i can tell ya proteins can b a bitch.
Each time additional EtOH is used a new bracket of equilibrating factors comes to play. Remember the compounds barely soluble? Each chemical has a particular solubility factor in EtOH. Compounds barely soluble have a knack of needing many extractions, when for example the extraction is limited to using low temperatures and atmospheric (low) pressure. Increase the temperature and pressure, and solubility factors multiply. On a side-note: often visual indicators of the progress of an extraction, such as color depth, is misleading. Chlorophyl has its' own solubility factor. So don't read too much into what it looks like, unless your ability to consistently reproduce results is associated w/ your prediction of complete extraction, all other variables being the same.
there is another cycle with fresh ethanol
I suggest using a smaller amount of solvent for the secondary & tertiary extractions. Also, 150mL sounds excessive for the first. Way excessive. I'd use a much smaller amount each time and add additional extraction(s) w/ plenty of time inbetween. Let the extraction occur in a jar, like a babyfood jar, and cap it tight. Keep it warm...hot if you can get away with it not leaking. Consider the waiting time as incubation.
polar compounds........waxes and oils
Some of them will go into the EtOH preferentially during extraction. EtOH is polar. The
concentration of these substances in each (150mL) of the extracts could be low, so overall there's not much of them to end up in the combined extracts. Cool the extract down, and these compounds "come out of solution." They stick to the glass, the spoon...anything&everything, because their solubility in EtOH is so low in the first place. There's bound to be some non-polar oils too. They're like cooking oil, practically insoluble in EtOH/H2O. These non-polar oils act like condoms, wrapping themselves around prize granules, blocking the solvent from reaching them. Implement additional techniques I will address in my next non-pyrotechnic post
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