TheHomeScientist - 2010-04-10
Using Dragendorff Reagent to detect the presence of alkaloids at extremely low concentrations. Make up Dragendorff Reagent as follows: 1. Dissolve 0.4 g of bismuth subnitrate in about 10 mL of concentrated hydrochloric acid. 2. Dissolve about 5.0 g of potassium iodide in about 50 mL of distilled or deionized water. 3. Pour the bismuth subnitrate solution into the potassium iodide solution. 4. Make up the solution to 100 mL with distilled or deionized water and transfer to a storage bottle labeled Dragendorff Reagent. If you're unable to obtain bismuth subnitrate, you can use the following alternative procedure to make up a usable solution of Dragendorff's Reagent from Pepto-Bismol tablets or the generic equivalent. These tablets contain 262 mg of bismuth subsalicylate per tablet, which is equivalent in bismuth mass to about 212 mg of bismuth subnitrate. We can therefore substitute two Pepto-Bismol tablets for the 0.4 g of bismuth subnitrate. This alternative method isn't pretty, but it does use readily available materials and it does work. 1. Transfer two Pepto-Bismol tablets and about 20 mL of water to a beaker. 2. Swirl the beaker until the tablets have broken up into powder. Bismuth subsalicylate and the binders used in the tablets are both very insoluble in water, so don't be concerned if it looks as though none of the powder has dissolved. 3. Add about 10 mL of concentrated hydrochloric acid to the beaker. Swirl the beaker occasionally until foaming ceases. At this point, the liquid appears chalky white. 4. Allow the contents of the beaker to settle. Most of the solid matter precipitates, but enough remains suspended to give the liquid a cloudy white appearance. 5. Filter or carefully decant the liquid into a second beaker to remove as much as possible of the undissolved solids. 6. Dissolve about 7.0 g of potassium iodide in a few mL of water and transfer that solution to the beaker that contains the bismuth solution. The solution immediately assumes a yellow-brown, cloudy appearance. 7. Bring up the volume in the beaker to about 100 mL with distilled water, allow the solid material to settle, and then pour off the clear yellow-brown solution into a storage bottle labeled Dragendorff Reagent.
Hello.how can i extract ephedrins alkaloid from ephedra plants?thank you
very interesting stuff - I like the new intro, nice one KK and THS! :)
Great video,,and thank you for outlining the risks of performing such test@ home its better to be safe than sorry.
how do you do such a impress opening????
Thankyou sir
i want to show use of dragndorff as spry reagent in TLC IN SEPRATION OF ALKALOIDS THINKS
mostly you're just mumbling than explaining. please make clearer in terms of your speech
i would use lugol instead of KI(potassium iodide)
Did you say what volume of tonic water solution per 1 ml D reagent? Very useful video, thanks
As already mentioned, intro is too long
I'm interested in your comment, "These tablets contain 262 mg of bismuth subsalicylate per tablet, which is equivalent in bismuth mass to about 212 mg of bismuth subnitrate." Can you walk me through the math that leads you to that conclusion.
[0.262 g Bi subsalicylate / its molar mass (362.1 g/mol) ] * molar mass of Bi subnitrate
This is a nice video with a proper description, it does make sense what he is doing. Just a question: if you perform a test to check whether a plant contains alkaloids or not, would it not form a precipitate with phosphate or chlorides - like AgNO3 ?
no
30 second intro? Try for less than seventeen.
Great demo of Dragendorff Reagent. I wonder if I can use it to test comfrey herbal infusions for pyrrolizidine alkaloids. I have been assured that Symphytum uplandica x, a hybrid of comfrey species, does not contain these alkaloids, but I would like to reassure myself that the dried herb I am using is actually the hybrid and not the species. Would this reagent give me conclusive evidence, do you think?
It's 5 years ago, but anyway: yes that would be a good idea to give you an indication, it is used as a field test for alkaloids in plants. A crude outline, from most examples I have seen, is: they first made an extract using methanol or ethanol (macerating dried finely divided plant material for several days in the solvent), then they filter through cottonwool or kieselguhr (Buchner+vacuum, or use a large syringe). Usually they then distill off the solvent, weight the obtained extract, and dilute with 10x methanol before adding Dragendorff reagent.
It may be possible to do an even more sensitive test using a colorimetric analyzer, such as LaMotte's Smart colorimeter.
Having intros gets annoying when your watching alot ot vids
glenwoofit 6 years ago
@eveningniteshade I just tested the "84%" kavalactone paste from kona kava using dragendorff rgnt and regardless of weather it had pipermethystine it clearly did NOT react... mkes sense the kavalactones arent nitrogenous so i think you could. Also note: 84% kavalactone paste with Marquis: maroon/ brown with Froede is red to black
I wonder if you could used this method for testing for muscarine and muscimol in amanita muscaria?
Where does one acquire chemicals needed for this experiment that is not usually found in homes?
Ignore all the people telling you to shorten the intro, Microwave show has a pretty long intro and this one is cool, nicely edited as well keep up the good work, im no scientist but i enjoy watching your videos anways
im no chemist but lets say i wanted to extract alkaloids from the roots of a burdock plant for an anti inflammatory or say take the roots of a cannabis sativa and make a pain relief cream how would go by doing that, i know most alkaloids are poorly soluble in water but im guessing they dissolve more or less in a acidic solution. not sure what i would use though
I've heard that citric acid works well
Intro is a tad too long. 20sec would be better.
Aaron Harry - 2010-04-15
@eveningniteshade I dont know how you would seperate the various other Nious compounds from the root tho...