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 H. Hall, M.D.
> 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 ,
> 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
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