At least two thirds of domestic cats "enjoy" the effects of Nepeta, a.k.a. "catnip." But do they enjoy it enough? If humans were able to isolate the active ingredient in catnip, could we not use it to become omnipowerful CATGODS? Imagine the possibilities! What fool wouldn't want their own personal cat army? A massive fuzzy force with which to execute your every bidding? A united, unquestioning militia that requires nothing other than unfettered access to the super-powerful catnip products that give their adorable cuddly lives meaning?
Nepetalactone is the active ingredient in catnip.* Today we are going to isolate nepetalactone in its pure form through a steam distillation. The distilled liquid will be extracted with an organic solvent (toluene), refined, then evaporated to give the final product.
Now I know what you're thinking: is it safe for cats to be around such a concentrated extract of catnip? Hell yes! Within reason. And we're all reasonable people. Pure nepetalactone has been studied on cats extensively. In fact, "catnip oil" that is available from botanical stores is essentially just nepetalactone, and it is widely used in homeopathic medicine. More details later.
Nepetalactone is the active ingredient in catnip.* Today we are going to isolate nepetalactone in its pure form through a steam distillation. The distilled liquid will be extracted with an organic solvent (toluene), refined, then evaporated to give the final product.
Now I know what you're thinking: is it safe for cats to be around such a concentrated extract of catnip? Hell yes! Within reason. And we're all reasonable people. Pure nepetalactone has been studied on cats extensively. In fact, "catnip oil" that is available from botanical stores is essentially just nepetalactone, and it is widely used in homeopathic medicine. More details later.
- Note: pure nepetalactone will not enable you to create a cat army.
Step 1: Crash course in steam distillation
If you've taken any chemistry laboratory classes, or if you have a background in moonshine production, then you know a thing or two about distillation. Heat something up to boiling, then collect the vapors by condensing them into another container. Steam distillation is the same principal and uses the same equipment. The only difference is that you distill something in the presence of water. Steam serves to volatilize certain chemicals, such that they co-boil with the water and can be collected along with the steam when it condenses.
This is particularly useful for extracting plant matter, where the steam serves double duty, breaking open cell walls and releasing volatile oils like nepetalactone. A standard apparatus that you would use in a chemistry lab is shown in the first picture below. Of course, we'll be doing this at home without access to fancy science gadgets.
For this catnip extraction, I've constructed a much simplified apparatus shown in the second picture. The catnip and water goes in the bottom of a big pot, with a cup placed on top. The lid is really the key component here; by simply turning the lid of the pot upside down, the vapors will condense and drip down from the center, collecting in the cup below. By filling the top of the lid with ice water, the vapors are condensed very efficiently.
This is particularly useful for extracting plant matter, where the steam serves double duty, breaking open cell walls and releasing volatile oils like nepetalactone. A standard apparatus that you would use in a chemistry lab is shown in the first picture below. Of course, we'll be doing this at home without access to fancy science gadgets.
For this catnip extraction, I've constructed a much simplified apparatus shown in the second picture. The catnip and water goes in the bottom of a big pot, with a cup placed on top. The lid is really the key component here; by simply turning the lid of the pot upside down, the vapors will condense and drip down from the center, collecting in the cup below. By filling the top of the lid with ice water, the vapors are condensed very efficiently.
Step 2: Obtain the necessary materials
Cat armies don't come free.* It's time to go shopping. Here's our list:
-1 pound of catnip, available online for bargain basement prices. I paid $3.40/lb from the San Francisco Herb Co.
-1 turkey baster (this will be an improvised pipet)
-1 eye dropper, available from the drugstore
-1 nalgene bottle that you are willing to sacrifice to the cause. It will never be the same. A glass mason jar also works, and it would be more robust.
- toluene (available from the hardware store in the paint thinner section)
- a large pot with a glass lid. It's important that the tip/handle of the lid comes to a sharp point in the center, like this one.
- vegetable steamer
- salt
- baking soda
- coffee filters
- a funnel
- shot glasses and a glass cup
- plenty of ice (5 lbs or so)
-1 pound of catnip, available online for bargain basement prices. I paid $3.40/lb from the San Francisco Herb Co.
-1 turkey baster (this will be an improvised pipet)
-1 eye dropper, available from the drugstore
-1 nalgene bottle that you are willing to sacrifice to the cause. It will never be the same. A glass mason jar also works, and it would be more robust.
- toluene (available from the hardware store in the paint thinner section)
- a large pot with a glass lid. It's important that the tip/handle of the lid comes to a sharp point in the center, like this one.
- vegetable steamer
- salt
- baking soda
- coffee filters
- a funnel
- shot glasses and a glass cup
- plenty of ice (5 lbs or so)
- Note: pure nepetalactone will not enable you to create a cat army.
Step 3: Prepare the steam distillation
To start, load up your pot with about a 1/3 lb of the catnip. Add enough watter to get everything wet, stirring it up. This might take 1/2 gallon of watter. Remove the stem from the vegetable steamer and put it on top of the catnip mush, then put the glass on top of that. It's OK for the vegetable steamer to just sit on top of the catnip mush, without touching the bottom of the pan.
Place the glass lid on top of the whole assembly, upside down.
Place the glass lid on top of the whole assembly, upside down.
Step 4: Check the fit of the lid
Key to the success of this extraction is the properly assembly of your extraction apparatus. It's important that the handle of the glass lid be the right shape to facilitate the vapor collection. One that comes to a nice point will act as a "drip tip" and is perfect. It's also important that the drip tip has a little bit of clearance over the top of the glass, at least 1/2".
Before actually starting with the catnip, do a trial run by filling the pot just with water to make sure you can distill effectively.
Before actually starting with the catnip, do a trial run by filling the pot just with water to make sure you can distill effectively.
Step 5: Start distilling
Heat the pot up until the water starts boiling. Did I mention that you might want to do this outside? The catnip vapors don't smell bad, in fact it's a pleasant minty smell, but it's pretty strong and is likely to linger for a while. At least open up all the doors and windows.
Once the steam starts to condense on the lid, cover it with some of the ice. This will help condense the vapors more efficiently. To put some hard numbers on it, my distiller was able to condense ~10 mL in 15 min when I had the lid just cooled by air. But with ice on top, it condensed ~100 mL in 15 min.
The ice will melt as the steam condenses, hopefully collecting in the glass in the center of the pot. This is good.
Once the steam starts to condense on the lid, cover it with some of the ice. This will help condense the vapors more efficiently. To put some hard numbers on it, my distiller was able to condense ~10 mL in 15 min when I had the lid just cooled by air. But with ice on top, it condensed ~100 mL in 15 min.
The ice will melt as the steam condenses, hopefully collecting in the glass in the center of the pot. This is good.
Step 6: Collect the distillate
Once all the ice has melted, after 20 minutes or so, take off the lid and dump the water from the top (wear oven mitts for all of this). Take out the glass from the center of the pot and see how much you've collected. Hopefully you'll have around 100 mL. Pour this into the nalgene bottle, then put the glass back on top of the vegetable steamer inside the pot.
Add a little more fresh water to the mush to replace what you've just removed, put the lid back on, and cover it with a fresh round of ice.
Add a little more fresh water to the mush to replace what you've just removed, put the lid back on, and cover it with a fresh round of ice.
Step 7: Repeat steps 3 through 6
After replenishing the still with fresh water, repeat the distillation until you've collected another 100 mL of distillate (200 mL total). Then do it again; fresh water, fresh ice. After collecting 300 mL of distillate from the 1/3 lb catnip you originally put in, empty out the pot completely and add a fresh 1/3 lb catnip.
Cover that with water and extract exactly as before, obtaining 3 x 100 mL of distillate, to give you 600 mL total, combined with the first crop. Then do the procedure with the last 1/3 lb catnip, giving you 900 mL of combined distillate.
This procedure will take a few hours, but it's not very labor intensive. It basically involves checking on the operation every 20 minutes or so to collect the distillate; the perfect time interval to be watching TV, reading a book, or rounding up stray cats for your impending CAT ARMY*. Also, you can take a break and turn it off whenever you want.
Cover that with water and extract exactly as before, obtaining 3 x 100 mL of distillate, to give you 600 mL total, combined with the first crop. Then do the procedure with the last 1/3 lb catnip, giving you 900 mL of combined distillate.
This procedure will take a few hours, but it's not very labor intensive. It basically involves checking on the operation every 20 minutes or so to collect the distillate; the perfect time interval to be watching TV, reading a book, or rounding up stray cats for your impending CAT ARMY*. Also, you can take a break and turn it off whenever you want.
- Note: pure nepetalactone will not enable you to create a cat army.
Step 8: Extract out the organic material
What you have on your hands is about 900 mL of catnip-smelling water, which contains a very small amount of nepetalactone. Catnip contains about 0.3% of this volatile oil by weight, meaning the 1 lb you started out with (454 g) can yield at most 1.4 g of product.
To get that out, we're going to do an organic extraction. Nepetalactone is a non-polar molecule and is much more soluble in an organic solvent than in water. Toluene is convenient because you can get it at the hardware store, and it's not especially bad for you. You could also substitute something like diethyl ether, if you can get your hands on it.
First, add a large quantity of salt (about 1 cup) to the water and shake it up real well to dissolve it. This increases the ionic strength of the water, giving the nepetalactone even more reason to dissolve in the toluene. Add 1 shot glass worth of toluene to the solution. Close the nalgene bottle tightly and shake it really well for at least a minute. Allow it to stand for at least 15 minutes, until you can see two distinct phases in the liquid. It's not clear from this picture, but you should see a thin layer of toluene floating on top of the water. It may be a little murky but that's OK.
A side note, don't let this mixture stand for *too* long, because the toluene will start to degrade the plastic and fog the nalgene bottle. Not an issue if you're using a glass container.
To get that out, we're going to do an organic extraction. Nepetalactone is a non-polar molecule and is much more soluble in an organic solvent than in water. Toluene is convenient because you can get it at the hardware store, and it's not especially bad for you. You could also substitute something like diethyl ether, if you can get your hands on it.
First, add a large quantity of salt (about 1 cup) to the water and shake it up real well to dissolve it. This increases the ionic strength of the water, giving the nepetalactone even more reason to dissolve in the toluene. Add 1 shot glass worth of toluene to the solution. Close the nalgene bottle tightly and shake it really well for at least a minute. Allow it to stand for at least 15 minutes, until you can see two distinct phases in the liquid. It's not clear from this picture, but you should see a thin layer of toluene floating on top of the water. It may be a little murky but that's OK.
A side note, don't let this mixture stand for *too* long, because the toluene will start to degrade the plastic and fog the nalgene bottle. Not an issue if you're using a glass container.
Step 9: Separate the toluene layer
I bet you were wondering what the turkey baster was for, eh? Now is the time to put it to use. With a shot glass in one hand, turkey baster in the other, suck off the toluene layer from the top of the nalgene bottle and transfer it to a shot glass. If a little bit of water comes out with the toluene, that's fine. Use more than one shot glass if necessary.
Repeat by adding another "shot" of toluene to the catnip water in the nalgene bottle. Shake it up really well, let it separate, and use the turkey baster to suck off the top layer, placing it into shot glasses. When you're done you might end up like me with an array of shot glasses, mixed with toluene/water.
The mechanical action of transferring the liquid to shot glasses seems to help the layers separate further. The ultimate goal is to get rid of the water layer entirely, giving a clear toluene solution.
Repeat by adding another "shot" of toluene to the catnip water in the nalgene bottle. Shake it up really well, let it separate, and use the turkey baster to suck off the top layer, placing it into shot glasses. When you're done you might end up like me with an array of shot glasses, mixed with toluene/water.
The mechanical action of transferring the liquid to shot glasses seems to help the layers separate further. The ultimate goal is to get rid of the water layer entirely, giving a clear toluene solution.
Step 10: Refine the toluene extracts
Now it's time to get a little more precise. Set aside the turkey baster and grab the eye dropper, which we will use from now on. As I said, the objective is to obtain a clear toluene solution, which we will accomplish by washing with water and filtering.
Use the eye dropper to remove the top toluene layer from all of your shot glass mixtures, transferring it to a new shot glass. Avoid sucking up the bottom water layer as much as possible. You should now have a shot glass full of still-murky toluene. Add a little bit of fresh water and stir it up really well with a stick. This will hopefully wash out some of the stuff that causes the emulsion.
Now, remove and discard the bottom (water) layer with the eye dropper. What's left behind is a cloudy toluene solution that we will clarify in the next step.
Use the eye dropper to remove the top toluene layer from all of your shot glass mixtures, transferring it to a new shot glass. Avoid sucking up the bottom water layer as much as possible. You should now have a shot glass full of still-murky toluene. Add a little bit of fresh water and stir it up really well with a stick. This will hopefully wash out some of the stuff that causes the emulsion.
Now, remove and discard the bottom (water) layer with the eye dropper. What's left behind is a cloudy toluene solution that we will clarify in the next step.
Step 11: Dry the toluene solution
To get the last little bit of water and other insoluble junk out of the toluene, we're going to dry it and pass it through a filter. Add a small amount of table salt to the toluene and stir it up really well. This helps to sequester water and dry the toluene. In a chemistry lab, you would use magnesium sulfate for this purpose.* If you can get hold of that, even better.
- Have I mentioned that I am a MAN OF SCIENCE? Invest your tender faith in my finely honed skills!
Step 12: Filter off the salt
The last step in getting a clear toluene solution is to filter off the salt and other insoluble material. Cut a coffee filter into a circular disc about 4" in diameter. Fold it in half, then in half again. Pull out one of the quarters to make a cone-shaped filter. Place this in the middle of your funnel, over a collection vessel. I would recommend something made of glass that can withstand the toluene. I'm using a glass vial.
Use the eye dropper to put the toluene/salt/junk solution on the filter and let it all pass through. What comes through the other side may be tinted a little yellow or green, but it should be clear and water-free.
Use the eye dropper to put the toluene/salt/junk solution on the filter and let it all pass through. What comes through the other side may be tinted a little yellow or green, but it should be clear and water-free.
Step 13: Optional sodium bicarbonate wash
This step is optional but it's easy and will further increase the purity of your nepetalactone. When you steam distill catnip, one of the side reactions is that some of the nepetalactone gets hydrolyzed to nepetalic acid. Nepetalic acid is not harmful, but it has no effect on cats so it's considered an impurity. Separating it out is a piece of cake, by virtue of the fact that it is an acid. When it reacts with a base, like sodium hydroxide or sodium bicarbonate (baking soda) it turns into its sodium salt, which is water soluble. So all you have to do is wash your toluene extract with a solution of baking soda in water and the desired nepetalactone will be left behind in the toluene layer. See the third picture below for a schematic of what's going on.
Prepare a base solution by dissolving 1 tbsp of baking soda in 1 cup of water. Add a volume of this approximately equal to the amount of toluene you have. Stir it or shake it up really well for a minute, then allow the layers to separate. Use the eye dropper to remove the bottom water layer, which contains the impurities. Repeat the wash with a fresh portion of base-water and again remove the bottom layer.
The toluene solution that you're left with after this washing sequence now has a little bit of water in it, so we'll need to clarify it again, as in steps 11 and 12.
Prepare a base solution by dissolving 1 tbsp of baking soda in 1 cup of water. Add a volume of this approximately equal to the amount of toluene you have. Stir it or shake it up really well for a minute, then allow the layers to separate. Use the eye dropper to remove the bottom water layer, which contains the impurities. Repeat the wash with a fresh portion of base-water and again remove the bottom layer.
The toluene solution that you're left with after this washing sequence now has a little bit of water in it, so we'll need to clarify it again, as in steps 11 and 12.
Step 14: Re-clarify the toluene
Ok, we're almost done! Repeat steps 11 and 12 on your toluene solution. That is, add a little table salt (or better yet, magnesium sulfate if you have it), stir it up really well, then pass it through a new coffee filter. The container that you filter it into this time will be its final resting home. Again, I'm using a little glass vial.
Ultimately, you end up with a very clear liquid that contains nothing but toluene and nepetalactone.
Ultimately, you end up with a very clear liquid that contains nothing but toluene and nepetalactone.
Step 15: Evaporate the toluene
Put the container with the highly-refined toluene extract outside, under a fan, to blow off all the toluene. Toluene vapors are not toxic but they are quite flammable, so keep away from open flames. It takes a while to evaporate all of the solvent; overnight in my case.
Step 16: Admire your product
When all the toluene is gone and you can't smell it any more (it smells like rubber cement), you will be left with a tiny amount of greenish liquid in the bottom of your container that smells strongly of that familiar minty, catnip smell. I got 143 mg, which represents 0.03% of the 1 lb of catnip I started with. That may not sound like a lot, but it's not far off from the 0.3% theoretical maximum yield given the improvised apparatus. And a little goes a long way.
Furthermore, this material is extremely pure. I analyzed it using gas chromatography/mass spectrometry, and found it to be >99% nepetalactone (see the second image below). In the chromatogram, nepetalactone is the giant peak around 12 min with a molecular weight of 166, and it's the only peak that is visible. For comparison, a sample of "catnip oil" that I purchased online was only about 80% nepetalactone (third picture).
If your sample has any amount of solid material mixed in with the liquid, most likely that is nepetalic acid. You may see that if you chose to omit the base wash from step 13. It's OK and isn't going to harm anything.
Furthermore, this material is extremely pure. I analyzed it using gas chromatography/mass spectrometry, and found it to be >99% nepetalactone (see the second image below). In the chromatogram, nepetalactone is the giant peak around 12 min with a molecular weight of 166, and it's the only peak that is visible. For comparison, a sample of "catnip oil" that I purchased online was only about 80% nepetalactone (third picture).
If your sample has any amount of solid material mixed in with the liquid, most likely that is nepetalic acid. You may see that if you chose to omit the base wash from step 13. It's OK and isn't going to harm anything.
Step 17: Find a cat
Now it's time to build that cat army!* Find yourself a cat, uncap the vial, and let him/her get a good whiff. The effects are just the same as with catnip; immediately the critter will be propelled into a frenzied state of sniffing, scratching, rolling, cage fighting, you name it. Enjoy, and give yourself a pat on the back for completing a nice bit of kitchen chemistry.
A note about safety. Yes, it is safe to use this extract on cats. I have looked into it, and there are a number of studies (very interesting in their own right) using pure nepetalactone on cats in experiments trying to figure out why it causes them to go bonkers. The upshot is that it's pretty safe. In the last of the references below, the LD50 of nepetalactone was determined to be 1550 mg/kg (about the same as aspirin), meaning you would have to force feed your average 5 kg cat ~8 grams in order to cause it any harm. So as long as you are reasonable with the extract it should pose no harm.
If you are interested in learning more about the chemistry of catnip and nepetalactone, may I suggest the following primary references.
nepetalactone isolation and characterization:
J. Am. Chem. Soc. 1941(63), 1558-1563
J. Am. Chem. Soc. 1942(64), 1828-1831
J. Am. Chem. Soc. 1955(77), 1599-1605
behavior/metabolism/toxicology studies on cats
[http://dx.doi.org/10.1016/S0163-1047(85)91151-3 Behav. Neural. Biol. 1985(44), 38-46]
Science 1969(164), 1281-1282
Lloydia 1978(41), 367-374
Finally, I would like to acknowledge Dr. David C. for his kind donation of a GC/MS reference sample, laboratory helper Melissa A. and most importantly, Mer, the intrepid kitty with an appetite for catnip.
A note about safety. Yes, it is safe to use this extract on cats. I have looked into it, and there are a number of studies (very interesting in their own right) using pure nepetalactone on cats in experiments trying to figure out why it causes them to go bonkers. The upshot is that it's pretty safe. In the last of the references below, the LD50 of nepetalactone was determined to be 1550 mg/kg (about the same as aspirin), meaning you would have to force feed your average 5 kg cat ~8 grams in order to cause it any harm. So as long as you are reasonable with the extract it should pose no harm.
If you are interested in learning more about the chemistry of catnip and nepetalactone, may I suggest the following primary references.
nepetalactone isolation and characterization:
J. Am. Chem. Soc. 1941(63), 1558-1563
J. Am. Chem. Soc. 1942(64), 1828-1831
J. Am. Chem. Soc. 1955(77), 1599-1605
behavior/metabolism/toxicology studies on cats
[http://dx.doi.org/10.1016/S0163-1047(85)91151-3 Behav. Neural. Biol. 1985(44), 38-46]
Science 1969(164), 1281-1282
Lloydia 1978(41), 367-374
Finally, I would like to acknowledge Dr. David C. for his kind donation of a GC/MS reference sample, laboratory helper Melissa A. and most importantly, Mer, the intrepid kitty with an appetite for catnip.
- Note: pure nepetalactone will not enable you to create a cat army.
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"Heisenpurr."
"You're Goddamn right."
That's science being used for utterly important purposes. :) Seriously, most nerdy/crazy scientist/resource overkill statement I heard the whole year (as if distilling catnip wasn't already overkill)
Btw, I would do the same if I had a mass spectometer laying around. I'm just envious. :]
This statement says to me that you aren't fully grasping how much fun you can have being entertained by super happy high cats. Twice as much diethyl ether would be worth half of the fun of seeing a cat fight his nemesis, a stuffed animal from a claw machine...
But seriously, cats love this stuff...
you can try heptane
Just wondering whether you could omit this step by including some base in the initial salt-out. I guess the nepetalate salt might emulsify the mixture a bit more but it would save the extra step and the losses in washing & drying again if you could avoid the separate washing step.
Just a thought.
I highly appreciate how clear your instructions are; I would have expected instructions for a distillery to have possibly a few steps that left me guessing what I'm supposed to actually do. Other guides I'd read (not on this site,) about getting an extract had this tendency to assume, "Okay, now that step 2 is done, you do the usual thing, and then it's time for step 4!" which left me going "wtf what happened to 3."
So again, thank you for making such a concise intructable. I'm planing on growing my own catnip, and this guide is going to come in handy a few months down the road...!
BLASTED!
I just love this title; can't stop laughing at it. I just keep reading it over and over.
:P
TRI HOLER!