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pumps in chemical experiments

pumps in chemical experiments - Chemistry Forum

pumps in chemical experiments - Chemistry Forum. Discuss chemical reactions, chemistry.


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  #1  
Old 01-14-2004, 08:57 AM
Otto Mation
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Default pumps in chemical experiments



>In a microscale lab, one uses very small quantities and small

I previously mentioned that analytical developments often precede
preparative developments. One of the things that drove down the
price of the septum vials for use in the UG lab was the growth of
automation, primarily for analytical instruments. First, roughly:

- collect samples and place in septum vials (10, 20, 100, ... 10^n);
- put septum vials in sample racks on autoanalyzer
- analyzer has septum piercing components that can add reagents
for pre-injection derivatization, sample removal, dilution, etc.
- inject samples
- analyze
- rinse, clean sampling probes, injectors, columns, etc.
- repeat

The analyzers can be HPLC, GC, MS, and other devices or coupled
devices (LC-MS. ...).

Here's another general website: [Only registered users see links. ]
(see the ALA Journal, too), but see also the manufacturers
of automated lab equip:
Hewlett-Packard
Perkin-Elmer
Beckmann
Applied Biosystems
Gilson
and I've barely scratched the surface with those.

Remove the analyzer portion and you have computer controlled
metering pumps, fluid reservoirs, sample changers, shaking
platforms, gas control, temp control and so on and you can
adapt that to do synthesis (sample derivatization IS synthesis).

But the synthesizer companies have already gone beyond that
and made sysnthesis specific improvements.

There are lots of cheap choices for tubing from stainless
steels (OK, not so cheap but cheap enough) to PE, PP or Teflon.
People are already using peristaltic, diaphragm, syringe and
piston driven pumps. High pressure compression fittings are
now made from plastic, not SS (e.g, [Only registered users see links. ]
"Request your 2003 [sic] catalog.") ... and have been for years.

Although I previously said that the field is in an intermediate
stage, it is certainly mature beyond the point of your Qs. Get
some free product literature, not textbooks. Even state of the
art journal articles might assume the reader knows a lot about
the 'standard' equipment: "A dual head Gizmo 2000 with sapphire
pistons was connected to Blocks A and B via a Doodad Splitter
Valve #22-2 controlled with a Whozy-Whatsis Model 47b
conductivity actuated probe ..."

If you can get yourself to an ACS or related meeting, some
exhibitors will provide a free pass to the Exhibit Hall
ONLY (not the meeting itself). See: [Only registered users see links. ]
--> Feb 2-4, San Jose, CA. "Do you know the way to San Jose?
I've been away so long, I may go wrong and lose my way."



I partially agree, ...


Almost anybody would welcome a volunteer who at least wasn't
destructive. If you're good in a machine shop (cf., chem lab)
you'd volunteer to do that part (make new stuff; modify off
the shelf stuff). Yep, volunteer at first; no pay. Academics
can be cheap SOBs. But after a few months of 4-10 hours a week
maybe they'll find some money for you if they like having you
around.

You should also ask in the local machine shops (chem dept,
physics dept, engineering depts) if they're doing any work
like that. Commercial shops will likely be working under
confidentiality and not tell you anything unless they hire
you and make you a confidant, too.

You tell us where you are NOT (MIT). Are you able to say
where you actually are, approximately?






--
Sent by xanadoof from yahoo subpart from com
This is a spam protected message. Please answer with reference header.
Posted via [Only registered users see links. ]
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  #2  
Old 01-14-2004, 04:19 PM
Mohammed Farooq
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Default pumps in chemical experiments

[Only registered users see links. ] (Otto Mation) wrote in message news:<[Only registered users see links. ].brandeis.e du>...


In another post Otto Mation wrote

GC. Manual HPLC Automated HPLC; etc.) I would argue that undergrads
NEED to

Would Otto Mation kindly explain what is meant by these two terms?
"Analytical development" and "preparative development"?
Thanks
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  #3  
Old 01-14-2004, 04:44 PM
Eppendorf
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Default pumps in chemical experiments

I would guess he's referring to how the advancement of a given analytical
procedure necessitates a change in the preparation of a given type of
sample. We've run into this before. A new instrument or method may be
incompatible with certain elements of a preparatory procedure. Of course,
this is just my take on Otto's post.

"Mohammed Farooq" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ] m...
news:<[Only registered users see links. ].brandeis.e du>...


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  #4  
Old 01-14-2004, 08:40 PM
Mark Thorson
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Default pumps in chemical experiments

Mohammed Farooq wrote:


Analytical HPLC is the use of HPLC to analyze the chemical
components of a sample.

Preparative HPLC is the use of HPLC to prepare purified
samples of those components.

Preparative HPLC equipment uses larger pumps and
larger diameter chromatography columns than those
used for analytical work.



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  #5  
Old 01-15-2004, 10:55 AM
Darren Rhodes
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Default pumps in chemical experiments


"Mohammed Farooq" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ] m...
news:<[Only registered users see links. ].brandeis.e du>...

Apologies for jumping into the thread at this point and not answering
Mohammed's question. Rather, returning to the subject of the thread.

A paper that may be of interest is: The Application of Micro Reactors to
Synthetic Chemistry, Chem Commun, 2001, 391-398. S J Haswell, R J
Middleton, B O'Sullivan, V Sketlon, P Watts and P Styring.

In the section on 'Chemical Control in Micro Reactors' it has 'Flow
Mechanics of Liquids in Micro Channels' in which it gives references to
researchers and their pumps eg "These pumps are typically based on a
piezoelectric driven one way valve to mobilise liquids<sup>27</sup>." The
paper criticises these sorts of pumps and goes on to discuss electro
osmostic flow (EOF) giving references and a brief description of the
process.

The paper also describes how to fabricate a reactor for your bench top and
where to buy one (if you don't want to buy one). The example they give
consists of two pieces of glass. One a glass block with three holes drilled
in it, the other piece of glass a flat plat of the same area as the block
(cube). They describe how to etch the glass plate (so that it has a capital
'T' shape etched into the surface) and how to join the two pieces of glass
together (they fit the etched plate onto the glass cube so that the holes
drilled into the cube align with the ends of the 'T' with the ends being at
the centre of the holes. A plan view would show the 'T' with three circles
above each of it's three ends). They describe how they can put reagent
solutions A and B into the wells (those drilled holes) that are above the
upper part of the 'T' etching and they get product C from the well that
rests over the bottom part of the 'T'. As for the 'pumping' - the system is
arranged so that there is solvent in the three wells and there are
electrodes placed in the wells. An electrical potential between starting
material wells and product well drives the reaction mixture to the product
well.

I think that this sort of thing fits into Allan Adlers original criteria
from his thought experiments. If he wishes he can begin experimenting with
neglible reagent inventory on his desk top. He would need some analytical
support eg tlc in order to determine whether or not his reaction has gone to
completion. By varying voltages the residence time of the reagents in the
reactor can be varied etc ... (The paper describes the apparatus necessary
and pc compatible software available).

The interesting part (for me) comes when you move away from the glass cube
to a metal cube (better at conducting heat). The 'cube' being prepared from
hundreds to thousands of plates. The reagents would be pushed through the
system under pressure; the metal cube would be attached to a heater/chiller.
Thus, if Allan got a process that worked with two of these metal plates and
gave 1 mg of product per hour then with a thousand plates ....

The other interesting part (for me) is - with a 'T' etch, one is constrained
to only two starting materials. What about a '+' shape where three starting
materials can meet in the centre simultaneously? What about a modified 'T'
shape where two reagents form a product half way down the vertical trunk and
there another channel has been etched to introduced a third starting
material (a sort of a superposition of a 'T' and an 'F'). In other words
one can telescope a two stage reaction. If one can telescope a two stage
reaction, one can also telescope a three stage reaction ... four stage etc
....

It gets even more interesting ... rather than just etching a groove some
researchers are depositing catalysts into the grooves. Others are using
gasses. (Forget about the Parr hydrogenator just swagelok that cube - the
one that has Raney Ni deposited in it's channels - into a hydrogen line and
pump a methanol solution of alkyne through it. Make sure that the
heater/chiller is set to the right temperature. Done it? Leak proof?
Exhaust gases safely vented and product under a bleed of nitrogen? OK, get
on with developing a process for another project we will strip the methanol
tomorrow to get our product). What about the hydrogenation block that
contains Duphos catalyst? The one that contains Binap?

Allan could do all of this work and not even move from his desk. Send me a
facs No Allan and I'll send you a copy of the paper. Darren.



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