[tcmbrendan]

I produce craft herbal medicines and for me extracting ALL of the constituents out of the herbs is really important, so the reflux process really caught my attention vs cold percolation/maceration etc.

However, I have run into a few stumbling blocks that really slow my progress down:



1.  The extractor only yields about 25g of material. Although the soxhlet extractor is capable of holding 500ml volume I can really only fit 25g or so worth of material in the apparatus at a time; I could have however potentially fit more but I am concerned that filling the chamber above the siphon arm would decrease the extraction process.

2. The process is time consuming. Although I know the entire process is built upon extracting the material until there is nothing left to yield, Is their a faster process?

So my questions are basically:

1A: Do they have an apparatus that is able to hold a larger quantity of material, say 100G of powdered herbs.

2A: Is there a more efficient (time wise AND total extraction) process for extraction of larger quantities of material than Soxhlet for the garage chemist?

Thank You!

[Archer]

You can buy larger soxhlet extractors, however these will only do so much. On a large scale (I used to go up to multi-kg scale for the production of fine chemicals from natural products) you can use the hot column method which needs a peristaltic pump to force hot (not boiling) solvent vertically up through a column of your material.

This feeds into a distillation vessel to recover your solvent which feeds into a collection vessel which is heated and this feeds the pump. The whole thing is a closed system but needs careful monitoring so that no vessel runs dry.

Or you can do batch hot extraction.

You will only recover 75-80% of your product in the first 3-4 extractions, after this your diminishing returns make it unfavourable but it is the only practical way. If you heat your material in a vessel of solvent with stirring for 20-30 mins then cool it, then filter (Buchner) followed by a cold wash. This is very heavy on solvent use but you can recover by distillation and reuse.
This method needs very efficient forced air ventilation and a spark free environment (there is enough static electricity in the human body to detonate solvent vapour if you are not careful.

[Arkcon]

Like Archer described, you can switch to hot extraction, if you can't find a large enough Soxhlet_extractor.  However, as you go to larger batch sizes, you have to think about what its meant for -- http://en.wikipedia.org/wiki/Soxhlet_extractor -- its meant to concentrate a minimally soluble extractables over time.  If you have a need for a particular component, you should: identify it, characterize it, determine the best solvent, and extract it specifically.

[tcmbrendan]

Thank you for the well thought out responses.. In regards to the "Hot Column Method" after scouring the web I stumbled upon a diagram that although not exact has similarities to the process you are talking about:



Is this similar to what you are describing?

If so, could one provide tips on how to go about manufacturing such a device for home/small laboratory use?

*Also, since I am not interested in refining down to individual constituents from the herbs but rather the overall contents of the plant matter I suppose I'm really just looking for a larger scale(in the hundreds of grams range) reflux method.

Thanks!

[curiouscat]

That looks like a generic distillation column.