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Previous by Date: Subject: Re: Science Education & Safety - Follow-up Date: Mon, 11 Oct 2010 11:48:03 -0500 Author: "Koster, Sandra" |
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Paul et al,
I won't debate the solvents issue. However, dichloromethane (a.k.
a. methylene chloride) is a general anesthetic agent which used to be used
clinically and which is also metabolized in the liver to carbon monoxide.&n
bsp; I doubt it's likely to result in either effect as used in the caffei
ne extraction experiments described here, but product process substitutio
n is generally a good idea.
For the "teratogen" issue, I'd suggest you attend the upcoming "Ask Dr. S
afety: Reproductive Hazards in Laboratories" workshop which will be
presented at the spring meeting in Anaheim (Neal Langerman, Harry
;Elston, and myself). There are no good answers. The Ca
lifornia Prop 65 reproductive hazards list might be helpful. There
will also be a new ATSDR Case Study in Environmental Medicine docume
nt on Reproductive and Developmental Hazards which I helped revise c
oming out in the near future. Also, there are some databases of i
nterest as part of NLMs TOXNET series of databases. Just go
to www.nlm.nih.gov, on the left ha
nd sidebar you can click on something about environmental, and the
n choose from the list. Then there are standard references such as
Shepard's. The TERIS service from the University of Washington is e
xcellent, but it is a subscription service. Reprotox is another s
uch database.
Overall, however, there are no right answers. Workplace standar
ds have never been set with protection of pregnant women and their fetuses
in mind.
Alan
Alan H. Hall, M.D.
Medical Toxicologist
> Date: Sun, 10 Oct 2010 00:14:59 -0400
> From: pharriso**At_Symbol_Here**UNI
VMAIL.CIS.MCMASTER.CA
> Subject: Re: [DCHAS-L] Science Education &a
mp; Safety
> To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
>
> Collea
gues:
>
> I have an undergrad. lab experiment that uses di
chloromethane to extract caffeine, but hadn't thought of changing the sol
vent. This interesting discussion raises the question of whether there is a
"safety series" of solvents, much like the elutropic series. What exactl
y is the problem with DCM? Is it safer or more environmentally friendly (no
t necessarily the same thing) to replace 1 mL of one solvent with xx mL of
another? What about volatility? Should David replace the hexane in his frie
s experiment with e.g. heptane, as we have done in the research lab? Does
price enter into the "value" of a solvent?
>
> On another
note, I have recently been involved in assessing chemicals around a preg
nant student. I googled "teratogen" and found many sites that quoted ethano
l and dilantin and a few other prominent examples. Does anyone know if ther
e is a more complete list?
>
> Lastly, I was surprised t
o find dilantin on the list, especially since we have another experiment
in this class in which students make dilantin which has run for years uneve
ntfully (ignorance is bliss). Does anyone know what level of exposure to di
lantin is required to exert an effect? Should I worry about the (remote but
not inconceivable) possibility that a student in this class is pregnant? M
y feeling is that the chances of successful synthesis X pregnancy likelihoo
d X likelihood of actually absorbing an adequate dose is pretty remote, w
hen compared to e.g. alcohol exposure for students. I can certainly warn st
udents, but do not want mass hysteria. I would appreciate any expertise.<
BR>>
> I look forward to continuing to read the excellent pos
ts to this list: keep up the great work!
>
> Best wishes
,
>
> Paul
> On Sat, 9 Oct 2010 07:41:52 -070
0
> DAVID KATZ <dakatz45**At_Symbol_Here**MSN.COM> wrote:
> >
I did a quick and dirty web search for a caffeine extraction that does not
use dichloromethane. I found this https://teach.lanecc.edu/thompsonj/CH241
/laboratory/Caffeine%20Extraction.pdf<about:blank> It is by John
Thomson at Lane Community College, Eugene, Oregon
> >
> > I have not tried this procedure and I would be curious to kno
w how well it works.
> >
> > I do not know the s
cale at which the class at your university performs this experiment, macr
oscale, small scale, semi-micro, or micro. That will also affect the
extraction solvent used. For semi-micro scale or microscale procedures, I
agree with Ernie Lippert that students must learn how to work with chemica
ls such as dichloromethane safely. That includes the generation of only sma
ll quantities of waste product.
> >
> > In anot
her experiment, I have my class extracting the fat from potato chips and
French fries. Starting with 5 g of chips or 10 g of French fries in a 125-m
L flask, I have switched the solvent from dichloromethane to hexane and u
se several rinsings of 10 mL or less. The solvent is disposed of in a waste
bottle and the chips or fries which are only slightly damp with solvent,
in the flask, are dried in a water bath under the hood. The fat content
is determined by the loss in mass. We get good results.
> > > > David
> >
> > __________________
_______________________________________________________
> > > > David A. Katz
> > Chemist, Educator, Expe
rt Demonstrator, Science Communicator, and Consultant
> >
Programs and workshops for teachers, schools, museums, and the publi
c
> > 133 N. Desert Stream Dr. * Tucson, AZ 85745-2277 * USA
> > voice/fax: (520) 624-2207 * email: dakatz45**At_Symbol_Here**msn.com<
mailto:dakatz45**At_Symbol_Here**msn.com>
> > Visit my web site: http://ww
w.chymist.com<http://www.chymist.com/>
> > _________
________________________________________________________________
>
> Paul Harrison
> Associate Professor of Chemistry
>
; Department of Chemistry and Chemical Biology
> McMaster Univers
ity
> 1280 Main St. W., Hamilton, ON, L8S 4M1, Canada
&g
t; Phone: (905)525-9140 ext. 27290; FAX: (905)522-2509
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