To DCHAS members.
Thank you so much for all who
responded to my question on Flash Chromatography and safety procedures
utilized in research to prevent glassware
breaking.
Enclosed are a few samples of answers
if you are interested in this
process.
Again, thank you for your help. You
are a terrific group, Have a great Summer!
. .
Yung
Morgan, MsPH
Laboratory Safety
Industrial Hygiene
Services
Environmental Health and Safety
117 Draper
hall
UMASS,Amherst MA 01003
phone (413)
545-2682
Fax (413) 545-2600
email : pmorgan**At_Symbol_Here**ehs.umass.edu
My Question :
Dear DCHAS group,
I was wondering if anyone had an idea
or can direct me to literature on =93Flash chromatography=94 whereby air
is directed the solvent column to speed up its elution of the compound
wanted. One of our researchers had gotten a cut from the glass column
breaking and cutting him on the arm.
Again, when asked, he said: everybody
uses this technique! Being an old analytical chemist, I did not remember
this method. However, an organic professor had informed me that this
method is also called =93Flash chromatography=94 and recommended the air
pressure to be no more than 20PSIG and to wrap the column in plastic
tapes to protect from breakage! . The lab in question use air spigots on
lab benches which runs more than 20PSI if fully
opened.
Any thoughts or comments you all have are welcome. Thank
you in advance and enjoy your
summer
I asked the safety
coordinator for our largest Chem research group, & his answer
is:
Flash
chromatography is best done in a fume hood because of potential exposure
to solvent vapors if done outside of a fume hood. We do use "house
air" but the spigot is not opened all the way. Just
enough to get the air flowing to the column. Flash chromatography column
should be wrapped with tape just in case of breakage due to stress
on glass or air pressure. To control the air flow, we use
a flow control adapter for chromatography that is available from
chemglass (Catalog # is CG-1195) which enable the control of air
flow and thus prevents column breakage due to excess air
pressure. If the control valve is use properly, column breakage is
rare. The columns should be inspected before each use and columns that
show any signs of stress on the glass should not be used.
Since, column breakage during use is always a possibility, gloves,
safety glasses or goggles and a lab coat should always be worn
when doing flash chromatography.
Kim Auletta
Lab Safety
Specialist
Hi Yung,
I remember this being called LPLC (Low Pressure Liquid
Chromatography) when I did my under grad research about 8-9 years a go
in organic research.
I used a glass column that looked
like the one in Figure 5 that in the Flash Chromatography PDF and also
packed it slightly differently. Our column was about 3ft tall, a
10 gram column. The top was tapered to a smaller opening to
fit a rubber stopper with a center hole., here we connected our
compressed air tubing from a cylinder. The stopper was held in
place with 2 rubber bands (one pass each, crisscrossed), which gave
enough flexibility for the stopper to blow out if too much pressure
built up in the column. At the air cylinders, we set the regulator
to 18 psi to control the pressure being delivered to the column.
To add additional solvent/mobile phase, their pressure was shut
off and the stopper was removed from the top and with a funnel, the
mobile phase was slowly added.
I do remember the columns,
even though a thicker glass, were extremely fragile and expensive.
They will break very easily, with the slightest bump,
over-tightening of the clamps, or too much pressure pumped in (though it
should be step with a way to relieve or avoid this). For some
protection, I have seen sleeves, plastic/poly- type material that slides
over the outside glassware to prevent flying glassware if it shatters or
explodes.
Chris
Suznovich
I'm an old chemist and used to do
tons of "flash chromatography". I don't ever remember reading about it,
just learned it from my lab mates in school but continued to use it in
industry in the late 80s. We used N2, not air. No regulator, just
whatever came out of the hood N2 tap. You could make it faster or slower
by changing the pressure. I never had one break but the rapid movement
of solvent through a glass column can build up quite a static charge -
enough to stand the hair on your arms on end and cause your solvent
stream coming out the bottom to veer towards your hand if you put
it near by. Scary when running ether columns. I always did mine in the
hood but many people did them on the bench top. (I
know, I'm really old.) I would wrap copper wire
around my column and attach it to the plumbing to help but since it was
insulated by the glass, it was of limited
value.
Now, as a safety person, I would
recommend plastic netting on the column and reservoir to contain
breakage, a regulator on the gas to control pressure and some method to
ground the whole thing. And,
of course, doing it in a hood.
Eventually,
we moved away from flash and began to use the automated fraction
collector chromatography systems like the Foxy sold by Isco (they may
have been sold again and sell under a different name). It is easier
since you didn't have to stand there and keep changing the collection
flask and refill the reservoir. Tell your guy to go buy one. I'm sure he
can find used ones if he doesn't want to buy
new.
Hi
Yung,
I believe that your researchers are
referring to the standard =93flash chromatography=94 used in organic
synthesis labs.
See the following link for a copy of
the technique as originally described by Clark Still of Columbia
University (Still, W.C., Kahn, M., Mitra, A., J. Org. Chem, Vol. 43, No.
14, 1978, p. 2923).
Many labs
have begun using automated medium pressure flash systems and pre-packed
silica gel columns in plastic cartridges (see Teledyne ISCO, Biotage,
and Interchim as example manufacturers of these systems), but the flash
column as originally described in 1978 still has significant utility
today.
In my experience, 10 psi is about the
practical limit for this technique, above which you may be putting
significant strain on the glass columns. Sometimes researchers are
tempted to put more pressure on the glass to elute the material faster,
or if plugs occur in the column. I would definitely recommend
pressure regulators be installed in the air
lines.
Steve
This is a very common
technique and most investigators that I know use compressed nitrogen
tanks with regulators that easily regulate the pressure down to a usable
level and you don=92t have to worry about contamination from house air
lines, i.e. water, dust, etc. Further, the compressed nitrogen
line is usually run through a oil bubbler
as a further
verification of low pressure. I have also seen some researchers
cut a small slit in the tygon tubing to prevent the pressure from
getting too high.
Hope this is
helpful,
Adam O.
Barden
Washington State University
Disclaimer/whatever: my
company is a Chemglass (now Chemglass Life Sciences)
distributor.
There are older
chromatography columns out there made out of standard wall tubing.
Flash chromatography first came into vogue the late 1970's, so
it's possible you may have some thinner wall ones circulating at your
organization. A true flash chromatography column should be
constructed out of medium wall tubing to provide an extra margin of
safety. Chemglass not only makes theirs out of medium wall
tubing, they are also available from the factory with a clear plastic
coating by special order (if anyone wants quotes on these, contact me
off list).
Many columns use a fritted
glass disc at the bottom. The maximum differential pressure rating
on those is 15 psi. So 15 or 20 psi should be established as the
safe working limit, yes.
Relatively safe pressure control on
columns can be achieved by making sure that the gas flow control adapter
at the top is not secured **too** tightly. A Keck clip or such is
more than enough to secure the adapter, but can still provide some
pressure relief. It is, of course, more reliable and
desirable to provide a pressure gauge and/or some sort of relief system
teed into the gas supply line so that researchers know exactly how much
pressure they are achieving. The best solution would be a
regulator can be used on the gas/air supply
line.
Your written SOP for
chromatography should include a discussion of the pressurization
hazards, "safe" pressure ranges, and how to mitigate the risks.
The SOP should also explain that proper PPE (lab coats with sleeves,
goggles) and engineering controls (fume hood sashes, blast shields etc.)
can also go a long way in minimizing any injury should an accident
occur.
Rob
Toreki
