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(do others have problems too with fitting long titles?)
this article was digged up for you by lugh. (thanks!) it compares the
steam volatility of pervitine, benzedrine and ephedrine. this might be
very interesting for those steaming their reaction mixture. i redded
the key sentence for the ADD/ADHDers amongst us  . but this might
also be of interesting for those trying to steam ephedrine out of plant
material. check it out...
as usual: if the pix don't appear, try it again in an hour or two.
note: anytime you see "amphetamine" in this text, the original says
"weckamine". but i believe that "weckamines" means only
amphetamine and methamphetamine. OTOH on google i found that "weckamine"
is also a general term for stimulants. maybe a knowledgeable german speaking
bee can clear this up?
From the Institute of Forensic
Medicine of the Humboldt-university in Berlin
Director: weiland Prof. Dr. med.
H. Anders
On the steam volatility of
Pervitine, Benzedrine and Ephedrine
by R. HÜNEMOHR and E. SCHEIBE
(1)
For the isolation of amphetamines and related compounds, as well in small as
in big scale, besides extraction, steam distillation from basic solution is
used since long, because those compounds are usually volatile with steam.
Also in recent time, this method of isolation of amphetamines from biological
material, resp. purification of obtained reaction mixtures, was recommended
for example by Griebel, Vidic and Scheibe. D. Richter on the other hand
believes to be able to isolate amphetamines without steam distillation,
whereas Mc. Nally emphatically recommends the use thereof.
With this method it is possible to separate amphetamines from alkaloids and
biogenic amines (especially decomposition products of proteins), as long as
those are not volatile. However according to our experiences, presence of
adrenaline derivates in the biological material can make troubles during the
detection of amphetamines in the steam distillate. According to Vidic these
troubles can be circumvented by using his method of detection with platinum
chloride reagent. He explicitly mentioned that using his method, no
interferences by adrenaline derivates or biogenic amines are to be expected.
Because of these unclarities, it seemed advisable to verify the steam
volatility of pervitine, benzedrine and similar compounds in a number of
experiments. To achieve this goal, it was necessary to characterise the
behaviour of the amphetamines benzedrine and pervitine in steam distillation.
At the same time it should be clarified if a quantitative isolation of those
amphetamines from aqueous medium is possible. As comparison substance only
ephedrine was used.
According to the available literature (Graf), the amphetamine bases should be
separable from the ephedrine base. But unpublished experiments (Scheibe)
showed that a certain amount of this base is found in the distillate, when
steam distilling from basic solution. That's why pervitine hydrochloride,
benzedrine sulfate and ephedrine hydrochloride were steam distilled from
basic solution and the distillate collected in sulfuric acid in multiple
fractions. Thus it was possible to get an idea of the course of the steam
distillation. We will describe the details of this method below.
The preparation of the solutions was the same for all the compounds, namely
pervitine hydrochloride, benzedrine sulfate and ephedrine hydrochloride. All
solutions were made up with distilled water, the measurement thereof was
performed in officially calibrated graduated flasks, resp. pippetes. All
glassware was thoroughly washed and degreased.
The substance to be analysed was dried for 24h in an evacuated dissicator.
Then exactly 25 mg were weighed on a microscale, dissolved in a little water,
transfered into a 100 ml graduated flask and the flask filled up exactly to
the 100 ml mark. Series of different concentrations were then prepared from
this stock solution containing in each case 5, 10, 20, 50, 100, 200, 250, 300
and 400 ug substance in 2 ml. The individual solutions and the stock solution
were kept at +4°C in the fridge if they couldn't be used right away. However
it is not advisable to use the solutions for more than 10 days, because after
this time the concentration on substance starts to decline drastically.
2 ml of an exactly adjusted solution were then made basic in a separatory
funnel with 2 drops 30% sodium hydroxide solution and extracted two times
with 2 ml pure chloroform. The extracts were transferred into a little
measuring flask with a 5 ml mark. Then the solution was extracted a third
time with 2 ml chloroform, but only so much of the chloroform was transferred
into the measuring flask so that the volume of the extract was exactly 5 ml.
The contents of the measuring flask were filtered through filterpaper
(moistened with chloroform) into a test tube and treated with 3 drops 2%
picric acid in chloroform. Pervitine- (Benzedrine-, Ephedrine-) picrate was
thus obtained, giving the solution a more or less intense yellow colour,
depending on the concentration.
The extinction of those solutions was measured with a Pulfrich-photometer
using 1 cm layer thickness against pure chloroform with a S42 filter. The
extinctions, each determined by 6 readings, were plotted against a coordinate
system, using the usual method. In order to determine the blank value, 2 ml
aqua dest were recorded. The thus obtained extinction coefficient was never
higher than 0.03 (0.02 - 0.04).
The calibration curves were linear for all substances below an absolute
amount of 300 ug of pure substance, whereas at higher amounts, the increase
of the extinction was not proportional to the increase of concentration
anymore (see curves). The effect of time on the extinction (after addition of
picric acid) was also determined by repeated measurement. Here it appeared
(as opposing to statements by D. Richter) that about 5 minutes after the
addition of picric acid the extinction does not change for the next 24 h.
The steam distillation was performed using the common Parnas-Wagner (Schott
& Gen., Jena) apparatus for nitrogen determination. 2 ml of the to be
analysed solution and then 2 ml 30% sodium hydroxide were introduced into the
distillation flask. Three times about 2 ml water were used to wash the last
bit of substance into the flask. For every solution five graduated separatory
funnels where filled with 10 ml 4N sulfuric acid; for ephedrine up to 15
separatory funnels were necessary per sample. The steam flask was heated with
a triple bunsen burner. The lower end of the condenser was slightly immersed
into the sulfuric acid in the separatory funnel. The distillation was
executed until 10 ml of distillate were collected, then the receiver was
quickly changed until no more base could be detected. When changing the
receiver care was taken not to lose a single drop. The content of every
separatory funnel was then treated with 30% sodium hydroxide until clearly
basic. Then the solution was extracted, filtered and measured like described
above.
When steam distilling between 5 and 500 ug pervitine, the bulk of the base
could already be found in the first fraction. In the case of ephedrine on the
other hand, the base came considerably slower. The steam distillation had to
be extremely forced in this case. The bulk of the base (especially when using
bigger amounts) was nearly evenly distributed in the first 10 fractions. Even
when using solutions of low concentration, the base could be detected more or
less noticeably in the 6th up to the 10th fraction. The amount of base in the
first 5 fractions was considerably lower than in the case of pervitine or
benzedrine. Benzedrine seems to behave like pervitine in steam distillations,
but the former seems to be more volatile with steam (see pic. 2).
Pic 2. Percental distribution of the recovered amines in the different
fractions of the steam distillation. - The lowest section gives the amount in
the first fraction, the second from bottom the amount in the second fraction
and so on.
1 = 100 ug Pervitine HCl
2 = 500 ug Pervitine HCl
3 = 100 ug Benzedrine sulfate
4 = 500 ug Benzedrine sulfate
5 = 100 ug Ephedrine HCl
5 = 500 ug Ephedrine HCl
On the basis of the performed experiments, one notes that pervitine and
benzedrine are very volatile with steam and are to be expected in the first
fractions. This is in accordance with relevant publications. Amphetamines can
easily be separated from less volatile bases by steam distillation.
If it was to be desired that already the first fraction contains an as big as
possible amount of ephedrine, then the used steam had to be very powerful and
the distillation had to be assisted by direct heating of the distillation flask.
While the qualitative detection of ephedrine gave only a very weak positive
result when slowly distilling, using a strong stream gave considerably more
base. Even though not always 100% of the bases could be recovered in the
experiments, no bases could be detected in the distillation flask. This can
possibly be attributed to the destruction of the amines after longer heating
in strongly alkaline solution - see for example Griebel (manual entry)! -
Strangely Vidic found with his microbeaker experiments that the main part of
the pervitine base was to be found in the second fraction (in the
second condensation). Our experiments clearly show that Vidic's results are
only valid for the microbeaker method (this is also true for the Griebel
method) and must not be generalised.
A
separation of ephedrine from the amphetamines seems possible if a steam
distillation as mild as possible is used to isolate the amphetamines. Then a forced steam
distillation can be used to separately collect the ephedrine.
For the analysis of biological material, it rests to find out if the steam
distillation is better done before or after the extraction of the main groups
of pharmaceuticals etc. As is generally known, distillation from alkaline
medium sets free an abundance of biogenic amines through basic reaction,
which can appear in the distillate and interfere with the analysis of the
amphetamines. Of course the results of the measurements are the more
doubtable, the more of those interfering substances etc. are in the distillate.
Especially with thoroughly dried ether and chloroform extracts this seems not
to be that much of a problem as with untreated material, so it seem
purposeful to perform the steam distillation only after extraction with
organic solvents.
Summary
In order to obtain exact fundamentals for the isolation of amphetamines, the
steam volatility thereof was examined. The following results were obtained:
1. Pervitine and benzedrine are fairly volatile.
2. They can be isolated nearly quantitatively from aqueous alkaline solution
by steam distillation.
3. An separation from ephedrine can only be achieved by steam distillation
when special experimental conditions (slow distillation) are adhered to.
Notes)
1) According to experimental results by R. HüNEMOHR
couch
terrorist
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