Funkerman23
Hazard to Others
Posts: 416
Registered: 4-1-2012
Location: Dixie
Member Is Offline
Mood: No Mood
|
|
chromatography column?
For the members here who work in Organics: how often do you find a Chromatography column useful for your personal work? That is, outside of class or
the company lab how often is a Chrom. column used? Just trying to get a general consensus on this as I may be able to get one soon and I am on a bit
of a budget( among other factors). comments, critiques and replies are always appreciated.Thank you.
" the Modern Chemist is inundated with literature"-Unknown
|
|
|
Endimion17
International Hazard
Posts: 1468
Registered: 17-7-2011
Location: shores of a solar sea
Member Is Offline
Mood: speeding through time at the rate of 1 second per second
|
|
It's not used exclusively for organic chemistry. Chromatography columns are used a lot in inorganic nuclear chemistry when you have to deal with
minute quantities of substances that are easy to detect because they eject subatomic particles.
small columns = small capacity = small quantities = application in analysis
If you want to use such columns for making reagents in useful quantities, you have to use very large columns (and I mean very large indeed) and a lot
of solvent. In conclusion, I don't find that neccessary to buy one. If I want to goof around with plant matter analysis, I can use a burette, too.
They're basically the same thing.
|
|
|
Nicodem
Super Moderator
Posts: 4230
Registered: 28-12-2004
Member Is Offline
Mood: No Mood
|
|
It depends on what the product is. For crystalline solids you can often get away without chromatography, but if it is an amorphous, resinous, oily or
otherwise non-crystalline and non-volatile organic compound, chromatography is the first choice. For amateur chemistry, preparative chromatography is
best avoided, because it consumes lots of solvents and lots of silicagel just to get a gram or two of a product (you can easily waste 1 L of solvents
and 100 g silicagel for that much of a product). It is expensive and time consuming. And unnecessary, because an amateur can chose the chemistry to
do, and so all you need to do, is to chose something that is easily isolable.
On the other hand, analytical chromatography, TLC in particular, is the best friend for an amateur interested in organic chemistry.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
|
|
|
BromicAcid
International Hazard
Posts: 3247
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
It depends on the chemist  In my experience most chemists will shy away from
using a column entirely because it does not scale up well, it's labor intensive, and time consuming. Solvents in the industrial world are pretty
cheap so that's not a major factor.
Still there are other chemists that use column chromatography as their go-to purification if they're having issues because it can be very effective.
And it CAN be scaled if needed, we have a column at work, 25 ft long, 1.5 feet in diameter that we use for those processes that were developed that
can only be purified by column chromatography.
Point being you can probably get away without it, but it can be very useful.
|
|
|
Ozone
International Hazard
Posts: 1269
Registered: 28-7-2005
Location: Good Olde USA
Member Is Offline
Mood: Integrated
|
|
A straight condenser + glass wool + some end-pieces + creativity = jacketted chromatography column. I work out chromatographic conditions on TLC
before scaling-up to a column.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
|
|
|
chemrox
International Hazard
Posts: 2961
Registered: 18-1-2007
Location: UTM
Member Is Offline
Mood: LaGrangian
|
|
Everybody was right in his own way. The amateur chemist may want to use a column to clean up a messy product before investigating the
recrystallization parameters. I like flash for this. I have one 5 cm X 900 mm column for that. I use the cheapest hardware store solvents I can
find and distill them when needed. TLC is a good way to check the feasibility of doing that kind of cleanup. TLC is great for working chemists as
well as amateurs. I use it all the time. I buy precoated glass plates and have them cut at the window shop. There some expensive software that can
be used to quantify spots. I wish someone here would post it somewhere....I'll look it up and post the ref back here so we can all look for it.
[Edited on 30-10-2012 by chemrox]
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
|
|
|
Funkerman23
Hazard to Others
Posts: 416
Registered: 4-1-2012
Location: Dixie
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by chemrox  | Everybody was right in his own way. The amateur chemist may want to use a column to clean up a messy product before investigating the
recrystallization parameters. I like flash for this. I have one 5 cm X 900 mm column for that. I use the cheapest hardware store solvents I can
find and distill them when needed. TLC is a good way to check the feasibility of doing that kind of cleanup. TLC is great for working chemists as
well as amateurs. I use it all the time. I buy precoated glass plates and have them cut at the window shop. There some expensive software that can
be used to quantify spots. I wish someone here would post it somewhere....I'll look it up and post the ref back here so we can all look for it.
[Edited on 30-10-2012 by chemrox] |
Unless I am very much mistaken flash chromatography requires preloaded
"cartridges" and unique columns to use.useful no doubt but not financially appealing( that and I haven't found anyone selling these things to
individuals either.. but suggestions here are very much appreciated) I asked as I know chromatography is used to separate organics that otherwise are
a pain to purify.. But.. a few grams of product for all that work& supplies needed isn't very appealing.I had hoped that greater yields where
possible..hmmmmm
" the Modern Chemist is inundated with literature"-Unknown
|
|
|
Funkerman23
Hazard to Others
Posts: 416
Registered: 4-1-2012
Location: Dixie
Member Is Offline
Mood: No Mood
|
|
Pardon the dumb question but in lieu of a C.column what other methods do you recommend for separating organics like the ones mentioned( resinous, non
volatile,etc)? | Quote: Originally posted by BromicAcid | It depends on the chemist In my experience most chemists will shy away from
using a column entirely because it does not scale up well, it's labor intensive, and time consuming. Solvents in the industrial world are pretty
cheap so that's not a major factor.
Still there are other chemists that use column chromatography as their go-to purification if they're having issues because it can be very effective.
And it CAN be scaled if needed, we have a column at work, 25 ft long, 1.5 feet in diameter that we use for those processes that were developed that
can only be purified by column chromatography.
Point being you can probably get away without it, but it can be very useful. |
" the Modern Chemist is inundated with literature"-Unknown
|
|
|
Nicodem
Super Moderator
Posts: 4230
Registered: 28-12-2004
Member Is Offline
Mood: No Mood
|
|
Indeed, you are very much mistaken. Flash chromatography is one of the separation techniques that requires the less equipment. All you need is a glass
tube with a stopcock at one end. You will also need some cotton, some sand, the stationary phase (most commonly silicagel) and the mobile phase (for
example, ethyl acetate and petroleum ether). It is not the glassware that is the problem for the amateur, because it can be improvised and built from
other purpose equipment (see Ozone's reply). It is the amount of solvent per gram of isolated product that is the annoying non-amateurish part of the
process. Silicagel can eventually be recycled, and so can the solvents be, but then it becomes too much of a fuss for too little product.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
You'd also need a source compressed air/nitrogen/argon. Also, columns can be bought on eBay easily, so there's no need to improvise. I agree that the
problem lies in the silica gel and massive amounts of solvents used. If one has good routines and equipment for redistilling solvents and silica gel I
think it's doable, though.
This just in: 95,5 % of the world population lives outside the USA
Please drop by our IRC channel: #sciencemadness @ irc.efnet.org
|
|
|
Dr.Bob
International Hazard
Posts: 2734
Registered: 26-1-2011
Location: USA - NC
Member Is Offline
Mood: No Mood
|
|
For flask chromatography, the general rule of thumb is that you use 10-100 times as much silica gel as crude product. For tough separations or where
you need very high purity, 100 is generally good or overkill. But for many separations, especially if the product is not very dirty or the
separation is easy (removing baseline material from product), then using 10 x is often sufficient. That may seem like a lot, but for a gram of
product, 10-20 gram of silica gel is often enough to get it clean enough to then crystallize, which will then improve the purity even more.
For example, recently I made ~10 grams of a crude material, which would not crystallize, but after running it through a 80 gram silica gel column, I
was able to go from about 60% purity to 90% or better, which was enough to allow it to then crystallize, which brought the purity to over 99%.
Another example are amide couplings, which often contain acid SM, amine SM, HOBT, TEA, and other coupling agent byproducts. But if the amide is
non-polar, it can often be pushed through a "plug" of silica (maybe 4 grams for a 400 mg reaction) to remove the baseline (on TLC) materials to give
clean amide product. The main cost is in solvent, but if you can find simple cheap solvents, and/or reuse them by distillation, then the cost is not
too bad. And while silica gel is not cheap, you can buy small amounts of it on ebay (even preloaded columns) or elsewhere for prices that are not
too bad.
|
|
|
wiccanchemist
Harmless
Posts: 2
Registered: 1-11-2012
Member Is Offline
Mood: No Mood
|
|
use of c column
In my lab at University I used a lot of times column croma because is more expensive to use HPLC in cantitative separation.
I use c. croma to separete my product from reactants then send the sample to NMR and x-ray diffraction to confirm the structure. For example I
synthetized a product that have 2 close related structures and i separated them with c croma by gradient elution all of the work was done by close
analysis of TLC.
Learn Chemistry and understand the Nature.
|
|
|
malford
Hazard to Others
Posts: 116
Registered: 17-6-2013
Member Is Offline
Mood: No Mood
|
|
Chroma Column for Addition
Any reason a chromatography column wouldn't work well for drop addition? They seem to be much more plentiful on the secondary market that addition or
dropping funnels.
|
|
|
adamsium
Hazard to Others
Posts: 180
Registered: 9-4-2012
Location: \ƚooɿ\
Member Is Offline
Mood: uprooting
|
|
Although this was already addressed, I just wanted to add that it seems you are thinking of automated flash chromatography systems such as the Biotage
Isolera and similar. These are horrendously expensive (for an amateur, anyway), as are their pre-loaded cartridges. They are just amazing, though.
See: http://www.biotage.com/DynPage.aspx?id=58261
In finding that link, I found that they now make a model with integrated MS. 
*I want one*
|
|
|
smaerd
International Hazard
Posts: 1262
Registered: 23-1-2010
Member Is Offline
Mood: hmm...
|
|
Can do flash with an aquarium pump for small diameter columns. Peristaltic pump to add eluent.
If its for basic analysis a pastuer pipet column can be used for a microscale column and eluted with a rubber bulb.
I'm pretty surprised at just how affordable a small isocratic used HPLC system could be had by an amateur. Not for preparative separations but for
analysis it'd be fine.
I have yet to master home made TLC plates but thats my next adventure. I think there are simple ways to make the process a lot easier and
reproducible. It's an art I'd like to see resurrected.
Preparitive TLC doesn't look too bad for small quantities of compound as well. Applicators can be made relatively easy.
Some people have had good results performing chromatrography with flint glass dust from pottery supply stores of the appropriate mesh size. Probably
rinsing it first and drying it. That helps cut the cost but we can't kid ourselves the surface chemistry isn't the same as commercial silica gel.
I like the idea of reverse phase media as it uses polar solvents for elution. Polar solvents in general are cheaper and available in quantity locally.
It'd be nice to see a OTC fix for that. Most are modified stationary phases though.
There are all kinds of tricks around running columns it's pretty hard to say which is best or more applicable. I think we have yet to find the best
way. In my opinion it really all boils down to work up. Can the compounds be separated with a Liquid Liquid Extraction, crystallization, distillation,
solid phase extraction, and or do I need to run a column.
|
|
|
Dr.Bob
International Hazard
Posts: 2734
Registered: 26-1-2011
Location: USA - NC
Member Is Offline
Mood: No Mood
|
|
I will agree with many of your hints, but for most solvents (other than maybe water), an aquarium pump is NOT going to work or be safe (if flammable).
A Peristaltic pump may work if right tubing is used, but many of those are not designed for organics either.
If people are looking for columns, I still have a pretty wide variety of glass columns (1/2" - 4+" diameter) as well as a few small pre-loaded silica
gel cartridges for various older systems around. I have some photos but not of all of them. But I have them in most every size and style
available, plus some accesories for them (reservoirs, flash flow controllers, etc)
|
|
|
smaerd
International Hazard
Posts: 1262
Registered: 23-1-2010
Member Is Offline
Mood: hmm...
|
|
The aquarium pump is for air pressure not moving solvents. Should have been more explicit. I am a proud owner of several of Dr. Bob's columns,
definitely a great person to do transactions with.
|
|
|
Dr.Bob
International Hazard
Posts: 2734
Registered: 26-1-2011
Location: USA - NC
Member Is Offline
Mood: No Mood
|
|
So sorry, I just wanted to make sure that someone did not think of using the pump with the solvent.
I mostly use pumped solvent driven columns now, so I am biased towards thinking of the solvent being pumped, not the air. But for pressuring a flash
column, an aquarium pump might be ideal, as it won't generate too much pressure.
For home use, I really like the air pressured 2 tank gradient formers, a company called Elution Solutions made a nice, simple, inexpensive, one for a
while until they were bought out by a bigger company and closed. You just put A and B into 2 vessels, then pump air into A, which forces it into
tank B, where it mixes well, hopefully, and then it is pushed into the column. Very simple way to make a gradient, but dependent on good mixing.
Best for small columns.
|
|
|
Dr Lauren
Harmless
Posts: 2
Registered: 10-8-2013
Location: NC, USA
Member Is Offline
Mood: Curious
|
|
Chromatography Column Use
I use the following depending on the scale, cost, and availability:
Liquid, Liquid Extraction, Solid Phase Extraction, TLC, Chromatotron, and then Column Chromatography. Some of those pertain more to product isolation
rather than purification.
Best to buy a large top reservoir to fit onto your column, if it is glass. A large separatory funnel (w/stopcock) could be mounted above the column
and opened to allow loading of the column and then application of the various eluents/solvents to elute the purified target compound.
I once had an industrial scale stainless steel column for purification of proteins. The thing was 36 inches in diameter and over six feet tall. It
had its own packing system otherwise we never would have loaded the thing with an even layer of solid phase material. It took 75 kilograms of silica
gel slurry to pack the column. As you can imagine the solvent use cost a small fortune. The yield was 45% of a 99.2% pure product, so that made it
all worthwhile! If i have an old picture I will post it sometime.
<hr width="90%" />
Have you ever heard of a Chromatotron? http://www.harrisonresearch.com/chromatotron/
It can be rigged to recover purified product after it has passed through a separating/purifying layer of solid phase material (silica or alumina
depending on how you choose to set yours up). A large chromatography column may well be more trouble than it is worth. Try to explore liquid-liquid
extraction methods to pre-isolate as much of your target product as possible and then use only as large of a chromatography column as you can pack
manually. Get sand and clean the heck out of it and also buy some glass wool.
Also, the purity of your eluents/solvents is critical and you will use quite a bit if you plan on cleaning and recycling the solid phase material. I
know a supplier of bulk silica gel in Morrisville, NC and you can pick your sieve size/porosity. He only communicates via email, but if you decide to
buy a column, you can obtain the necessary silica gel in bulk at a fair price. Note that I am not affiliated with that company however I have bought
from them many times and have no complaints other than ordering via phone would be convenient.
You probably already do, but before running the product through a prepared column, perform TLC to make sure you have the right eluent mixture to
separate and purify your target product. I recommend that you make your own TLC plates and try using a variety of eluents having near-identical
polarity and pH to see if a cheaper one will accomplish the separation. For a quick TLC plate I make my own using microscope slides, plaster of
paris-silica gel-solvent slurry, and an warm oven. You can find multiple videos or tutorials online for making TLC plates and also preparing and
packing a column.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: merged
sequential posts]
[Edited on 10.8.13 by bfesser]
"Education is what remains after one has forgotten everything he learned in school." -Albert Einstein
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
<strong><a
href="viewthread.php?tid=10030">Chromatotron - radial chromatography.</a></strong>
Please edit your existing post to append any additional comments, rather than posting another reply. Thank you.
[Still not sure how you posted two in such quick succession (1 min.)—must have been copy-paste.]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
