ghetto soxlet for plant extractions

loki · guinea pig

While messing around with my ghetto coldfinger, I rigged it up as a basic coldfinger/distillation rig, and looking at it gave me a whole heap of thoughts...

let's say swim has a large quantity of herb to extract. The conventional method of constructing a soxlet doesn't really lend itself well to large scale at all, a kilo sized soxlet is probably about the top end of capacity with the conventional soxlet apparatus.

What about doing the whole thing inside a large stockpot. I think, since the main concern here is not purity but conserving solvent and energy (from not evaporating large amounts of solvent), a large aluminium stockpot, maybe a 10L size one. The lid does not need to be a tight fit, there is expected to be some amount of vapour loss in this, but it is not that significant.

First, one gets a quantity of aluminium or copper piping. Fill the copper pipe with salt to stop kinks, then bend it into a flat coil of a suitable diameter that allows the maximal amount of the lid to be used. Once the coil is made, soak it in hot water to remove the salt. The lid has two holes cut in it to accept the in and out feeds of the coil, and metal hose clamps could be used to retain the coil in place on the lid. silicone hose (for heat resistance) is attached to each end of the condenser, i'd say that feeding the water in at the edge is probably the best way to go to ensure that the coldest part is at the region where the most vapour loss is likely to occur, to reduce that loss.

A quantity of alcohol (denatured is probably the safest, health-wise), say about 2 inches deep at the bottom of the pot. A sheet of cotton is placed in the pot set up so that it's about 1-2 inches above the surface of the solvent at the bottom, and retained at the edge of the pot with wire. The herb is then loaded into the cloth part, right to the top. The coil should be able to sit comfortably on the top of the plant material then, ideally there should be contact so that a maximal amount of spread of the solvent condensation across the top surface is created. The lid is placed on top, and probably it is a good idea to put a weight on the lid to make it sit not tightly, but not too loose.

Then, one heats the pot, runs cold water through the condenser, and the solvent vapourises, condenses on the cool herb and the condenser at the top of the pot, and refluxes down through the herb. After an hour or two, most of the useful material will have been extracted out of the herb, and the alcohol at the bottom will contain a fairly concentrated alcoholic extract, but of a dramatically smaller volume than if one had done an immersive extraction.

loki · guinea pig

Here's photos of the first prototype of it. It's been tested with water being boiled underneath and the condensate drips from all around the coil. I think it probably will need to be run with periodic rotation of the pot underneath to ensure that the condensate is dropped over the entire top surface of the herb.

jackoozzi · specialist

What is this certificate try to install when i view this thread

loki · guinea pig

it's my non-third party ssl certificate, i don't think it installs it, unless you ask, but it is asking you whether to accept it.

ok, been doing more thinking, and i've come up with a few things to further improve the operation of this device.

At the top, just below the condenser, some kind of loose felt/fluff type material would help ensure that the solvent is properly distributed evently throughout the top surface of the plant material

At the bottom, a cake cooling tray, circular with mesh, should be sewn into the retaining cloth so that one can maximise the amount of plant material that goes into the device by making a flat bottom surface, and allows it to be placed as close to the top of the solvent at the bottom as possible.

bio · Working Bee

Having built a couple similar purpose units what was found is that the even distribution of the solvent is a major problem due to channelling etc.

Of course there are many ways to do this adequatley but what I found thru the trials and tribulations was that a tall vertical vessel with a distributor arrangment solves most of it (with occasional rapping). At least 3:1 better 5:1 height to width. Either condensed reflux from the top or pumped liquid from the bottom. In practice what worked best was pumped thru the distributor from the bottom for lighter than water solvent (dry plant) with overflow to suction.

With alcohol from the refluxed in from the top maybe a percolator type arrangement would work well as the distributor plate and riser tube are already built in. Those 100 cup coffee percolators with built in element would work and your cooling coil could go right into the basket.

If this is only a once in a while thing then what you have should do just fine with a little tweaking. I even saw a glass percolator with plastic internals recently for smaller batches. Take a look in Kimble or Corning at the "percolators", really quite simple but effective.

loki · guinea pig

i was thinking that making the part of the bag holding the plant material slower dripping might be good, so it pools up a bit. the heat from underneath will cause a lot of nice refluxing action too, moving things downwards as the condensate moves upwards. Another solution to channelling would be to periodically give the plant material a bit of agitation, scoop up from underneath, turn it all over.

yeah i figured it should be decently effective, and definitely with some tweaking as you describe. I feel that the reflux/condensation thing would help a lot with reducing solvent volume needed and holdup of solutes in the plant material, and i don't see why, within practical limits of solubility of the solutes in the solvent, one could process larger amounts in consecutive runs with the same batch of solvent, the juice squeezed out of the plant material at the end. The advantage of using condensation/reflux is that the solvent that contacts the plant material is always pretty much pure, with nothing dissolved in it, meaning it does not leave anything behind once it has happened enough.

Another idea that comes to mind is some kind of non-corroding metal stuff at the top, pushed against the condenser would dramatically reduce channelling, by broadening the surface of condensation. Maybe retained with a metal mesh.

stratosphere · Sun Jul 03, 2005 12:38 pm

just out of curiosity what did you use to drill the holes in the lid?

another possible improvement would be to solder a perforated circular plate to the coil.