Jenks
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Building an Analytical System for Plant Alkaloids
I am starting a project in a few weeks that has been on my mind for most of my adult life - there needs to be a robust, open-source system that a
hobbyist or growing professional can put together for themselves to provide analytical services. I know this sounds very general, but the specific
application I have in mind could be applied to an extremely wide variety of common problems.
In this particular case, there are a few factories that have been set up to extract voacangine from the bark of the Voacanga africana tree that has
habitat in many African countries, isolate it and have it converted into ibogaine, which is used primarily in the treatment of addiction to opiates
and stimulants. I have spent much of my life developing these processes and openly publishing the manufacturing procedures. But the process is
hampered by the lack of an easily available analytical tool to assess the amount of voacangine or ibogaine present in intermediate stages of the
manufacturing process.
So in two weeks I intend to go to Ghana and try to cobble together an analytical system using parts I have mostly amassed through eBay, mostly from
the Chinese factories that seem to have down producing electronic and related high-tech parts.
I am following the obvious course of using a low pressure chromatography column of some sort, feeding the effluent from that into a flow cell made of
quartz, passing through it a beam of ~250nm UV from a UV LED, detecting it with one of the specific UV sensors I have bought, and getting the signal
from that into a computer where I will process it in a Linux operating system environment, hopefully taking advantage of existing open-source software
to present the analytical results in a convenient format. Hopefully TSA will allow my suitcases stuffed with these supplies to pass through security
as they have graciously done in the past.
The specifics of this system are where I can use all the help I can get. I have tried to guess the best technologies to put in these bags, but,
although I have a PhD in organic chemistry I'm not even a practicing chemist and need a lot of help. I will try plain silica of course but neutral or
basic alumina seems like a good option for these alkaloids based on the literature and past experience, but there are also functionalized media that I
don't understand very well and the idea of ion exchange chromatography of the cations seems promising. Then there is GC, which has worked with these
alkaloids despite their mass. I don't have time to investigate everything. I have only five weeks in Ghana to get this together, so I need to center
on the best ideas quickly to offer the best working system to everyone when I am done. Thank you for any recommendations you find to share.
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Sulaiman
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Not my area at all, but may I suggest that someone in Ghana orders equipment and supplies for traditional wet chemical quantitative analysis as backup
/ reference.
Hopefully to arrive about the same time as you.
I guess that you have better info.
(and some members here have real expertise)
https://www.google.com/url?sa=t&source=web&rct=j&...
https://www.orientjchem.org/vol29no2/qualitative-and-quantit...
etc.
CAUTION : Hobby Chemist, not Professional or even Amateur
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leau
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This document might be helpful:
https://www.researchgate.net/publication/257907428_Analysis_...
as chromatography is almost certainly your best choice.
[Edited on 3-7-2024 by leau]
Attachment: Analysis_of_alkaloids_from_different_chemical_grou.pdf (2.5MB)
This file has been downloaded 21 times
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Anthracene
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The system you describe would take care of separation and detection
/quantification at once, pretty neat but also complex.
How about a two step approach?
First separation on a column, maybe there is a suitable SPE column solvent combination that works. You could build this from a syringe, some cotton
and a suitable stationary phase.
Then in a second step UV detection in a cuvette, like measuring OD600 of a culture.
Of course it is more tedious and requires more time to do, but it is a lot simpler to set up.
Even simpler would be a specific reagent to mix directly with the sample and then measuring the absorbance at a specific wavelength. I am thinking of
something like ferrozine for iron(II) or o-toluidine for glucose.
Edit:
Actually, looking at the molecules, they might have some unique absorption bands as they are. Maybe just putting them in a photometer might do the
trick. I did not find any good spectra with 5 min of googling but they might be published. If not, I have two spectrophotometers and could provide
them given a sample. If the goal is an open source device this might be accomplished with LEDs of specific wavelength and photoresistors. Can you
describe what kind of sample you are looking at? Raw plant material will require extraction of course.
[Edited on 3-7-2024 by Anthracene]
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bnull
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Quote: Originally posted by Anthracene  | | If the goal is an open source device this might be accomplished with LEDs of specific wavelength and photoresistors. |
You can even use LEDs in place of the photoresistors.
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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Jenks
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Thanks for the article suggestion - it does look relevant, and it is even accessible! I will check it out.
My work in this area has focused on making technology more accessible in terms of price, otc availability of parts and materials and making the
system easily understandable to set up and use. Past work was on ibogaine extraction or manufacture, but I tested conditions for GC and HPLC for others to reproduce and also to put some numbers behind the production processes.
While I could make a manual process to extract and isolate voacangine and ibogaine from a sample and then quantity it spectroscopically, I imagine a
more elaborate system that would allow convenient, ongoing sample analysis compatible with the needs of the few ibogaine factories in operation today.
These tend to be run by individual chemists or small teams who have dedicated their careers to this work, and I imagine the analytical chemist being a
full time part of such a team and hopefully collaborating with other teams to meet their analytical needs.
I had to pick between gas and liquid chromatography to develop for this project, and I picked liquid mainly out of familiarity, and hopefully I won't
regret it. GC is promising for these alkaloids because I have seen it work, and it may be very selective because many of the alkaloids needing to be
separated are dimeric or of higher molecular weight.
I envision this system delivering solvent at a known, controlled flow rate, either utilizing a pump such as a peristaltic or syringe pump or by measuring the flow rate, perhaps by counting drops optically, and using something like a solenoid valve to control the flow.
The procedure I remember using to prepare samples for HPLC was to weigh 10-20 mg of plant or solid alkaloid mixture directly into each of three 10 mL
volumetric flasks, fill with methanol, sonicate, filter through a syringe filter disk, then dilute to the proper analytical concentration using a
micropipetter and another volumetric flask.
Since this chromatography would operate close to or at atmospheric pressure, the column would be larger than an HPLC column and the injected volume to
be analyzed would be around 0.1-1 mL, which might be measurable using a standard hypodermic syringe, provided that the plastic it is made of is
compatible with the solvent injected. Perhaps it could be injected through a rubber septum into the line leading to the column, or even into a rubber
tube carrying the solvent.
The column could be a small conventional column or a prepackaged one. For the detector I bought a Gilson 111 UV detector, but I plan to compare that with building a flow cell detector using a 1mm quartz flow cell with a 250 nm UV LED, comparing various detectors such as this photodiode or a UV detector module. Since these alkaloids absorb UV longer than 254 nm because of their bicyclic indole system, a 270 nm UV LED and detector can
be added to the same flow cell and may allow some distinction of which alkaloid is passing through. I plan use a Raspberry Pi to process and integrate
the signal from the detector since I am familiar with using them, and that same Pi can be used to manage solvent flow rate and any other automated
features of the system.
The quartz flow cell is expensive, so although I sprung for one I would still like to try my original idea of fabricating one by cutting the bottom
off a 1mm quartz cuvette and attaching tubes to the ends, or even just using quartz tubing itself.
Finally, I am playing with the idea of automatically recycling the solvent by continuous distillation, perhaps using a Peltier module and a pair of CPU cooling blocks to distill eluent from the hot side of the module to the cold side.
[Edited on 4-7-2024 by Jenks]
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Anthracene
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I looked at your homepage and I am really impressed. It is fascinating how dedicated you have been over the years and how much research you have done
for this cause. I see now that you are dealing with quite complex mixtures of alkaloids, so you definitely will need a chromatography step.
For the pumps I think a syringe pump is the best option. Both peristaltic and syringe pumps are theoretically suited but especially the cheap
peristaltic pumps produce fluctuating pressure. You could try to get away really cheap with a big syringe actuated by a spring or rubber bands.
The idea to use UV LEDs and UV index detector modules is great, potentially this could be a ridiculously cheap UV detector. Are you sure that the 2 mm
path length is enough though? I am sure you have some actual data on how well these molecules absorb in the given wavelength. During my lunchbreak
today I found out that quartz discs can be purchased for a small price, maybe a chamber resembling a commercial UV detector module could be
fabricated? Basically a tube with a quartz disc and a rubber seal on either side. This way you could get a path of an inch or more.
The idea of recycling solvents is great, but it seems to me that collecting over a bunch of samples followed by simple destillation is more straight
forward than an automated continuous system.
I wish the best of luck to you and your project in Ghana!
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Jenks
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Thank you, Anthracene, for your feedback and encouragement - it goes a long way. I bought two rather heavy Tecan Carvo syringe pumps. If I can figure
out how to get them working, I agree with you that they should at least be designed to provide a more measured flow rate. The potential problems are
that neither these nor the peristaltic pumps are designed to pump organic solvent - the peristaltic pumps being only as compatible as the probably
silicone tubing they came with - so I am on my own to assess compatibility. And while syringe pumps are the technology that provide continuous,
measured, high-pressure flow for HPLC, those have two syringes pumping in tandem to accomplish that. Since my repurposed pumps have only single
syringes, it is not physically possible for them to provide continuous flow unless I employ a buffering system, but then that system would require the
actual flow per minute to be calibrated.
As for the flow cell path length, these are actually 1mm, not 2mm, which I selected to reduce the size of column needed to have the peaks of interest
be contained within the volume of the flow cell. But in case the path length is inadequate, I bought several standard 1cm quartz cuvettes I can cut
the bottoms off to fabricate 10mm path length flow cells. I also have a sheet of UV filter glass I can cut up to fabricate flow cells the shape I want. I don't know why that sheet is much cheaper per unit area than the quartz
disks you mention, or why any quartz on eBay seems much more expensive than oven door window material, unless I am missing something.
My main constraint seems to be having few choices of chromatography media to test. Even the pre-packaged amine-functionalized medium I linked to above was lost by the seller and refunded, so all I have to test are silica gel and some neutral alumina I can bring. I should have
invested in some C18 cartridge but I didn't see anything at a reasonable price when I had the chance, and the point of my system is to bring the price
of it within reach of us mere mortals.
I have to agree that for an analytical system, maybe it adds unnecessary complexity to recycle solvent automatically. Two more reasons I want to do
this are that it would allow time to leach off any crud on the column that might be detectable so that the column can be used as long as it keeps its
ability to separate components. The other thing is that I would like to be able to use this same technology to automate production chromatography,
using the aforementioned solenoid valves for sample collection. I suppose with only six weeks to work I must be dreaming, but if I can sufficiently
inspire an apprentice, maybe they can fulfill the vision after I am gone.
[Edited on 5-7-2024 by Jenks]
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