What is milli-q autoclaved water?

[Henrik Bendix Pedersen]

Hello out there, chemists!
I need your help!

As part of a physics project I needed some pure water.
I managed to get some autoclaved milli-q (=3Dmillipore?) water.

Now, my questions are:
How pure has the water become?
Exactly what happens with the water during the processes?
What more could I have done to make sure that the water was as pure as
possible?
What pH-value should I expect from the purified water?

If you know the answer to one or more of these questions, I would very
much appreciate your help!

Thanks in advance

Henrik Pedersen
Denmark

[Uncle Al]

Henrik Bendix Pedersen wrote:
>
> Hello out there, chemists!
> I need your help!
>
> As part of a physics project I needed some pure water.

> I managed to get some autoclaved milli-q (=millipore?) water.

>
> Now, my questions are:
> How pure has the water become?
> Exactly what happens with the water during the processes?
> What more could I have done to make sure that the water was as pure as
> possible?
> What pH-value should I expect from the purified water?
>
> If you know the answer to one or more of these questions, I would very
> much appreciate your help!
>
> Thanks in advance
>
> Henrik Pedersen
> Denmark

How much pure water? What does pure mean?

If you want it particle-free and sterile, run it through membrane filter
(no surfactant!). If you want it mostly pure, distill, leaving
non-volatiles behind (except for misting). If you want it REALLY pure,
multiple distillation or ion exchange (commercial still or ion exchange
loop) then a membrane filter polish and monitoring by resistance (18
megaohm is good stuff).

CO2 from the air will move the pH all over the map - vacuum degas or
purge with filtered nitrogen or argon. Ultrapure water cannot be
measured by a pH meter (electrode ion diffusion).

Would a gallon of chromatography water do it? A bottle of Perrier? (no
organics there, but inorganics and CO2 contaminate).

You could zone refine a column of ice.

The question is, what contaminants are objectionable?

If you want water and only water (what about isotope fractionation?)
think about multiple serial vacuum sublimations of ice in a unitary
glassblown fused quartz apparatus. Think "breakseal" and "flame off."

Note that ultrapure water is remarkably corrosive. It doesn't stay
ultrapure for long. Semiconductor fabs use dynamic purification systems
- the stuff never stops being purified. And even they have microbial
contamination problems (add a few ppm HF and
they go away.)

--
Uncle Al Schwartz
Uncl...@ix.netcom.com ("zero" before @)
http://pw2.netcom.com/~uncleal0/uncleal.htm
http://www.ultra.net.au/~wisby/uncleal.htm
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(Toxic URLs! Unsafe for children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?" The Net!

[hboyter]

There is no way of telling if you have pure water without establishing what
you mean by pure water. A Milli-q system is a general deionizing system
which removes ionic material. If it did not have an added organic
cartridge, you may still have organic contaminants depending on the feed
source. You test the ionic activity through its conductivity. You want at
least 18 M-ohm water. If you autoclaved the water to sterilize it, you
probably have to use it immediately. With water, you define what is pure,
there is no universal definition. As far as the pH, it will vary with age
after it is removed from the system, generally it will be acidic due to
taking up CO2 from the air.
--
Dr. Henry Boyter, Jr.
Ph.D. Chemist

The opinions of Dr. Boyter are provided for informational purposes only and
should not be used as advice. No warranty or expression of professionalism
is implied.

Henrik Bendix Pedersen <hen...@post4.tele.dk> wrote in article
<349179d4...@news.inet.tele.dk>...

Hello out there, chemists!
I need your help!

As part of a physics project I needed some pure water.
I managed to get some autoclaved milli-q (=millipore?) water.

Now, my questions are:
How pure has the water become?
Exactly what happens with the water during the processes?
What more could I have done to make sure that the water was as pure as
possible?
What pH-value should I expect from the purified water?

If you know the answer to one or more of these questions, I would very
much appreciate your help!

Thanks in advance

Henrik Pedersen
Denmark

----------

[Van de Weert]

Henrik Bendix Pedersen wrote:
>
> Hello out there, chemists!
> I need your help!
>
> As part of a physics project I needed some pure water.
> I managed to get some autoclaved milli-q (=millipore?) water.
>
> Now, my questions are:
> How pure has the water become?

That highly depends on the system, but even more importantly: it depends
on how you define purity. On this point I can't help very much, but IIRC
milli-q is called milli-q because it contains a very low amount of ions,
and thus has a very low conductivity.

> Exactly what happens with the water during the processes?

Dunno

> What more could I have done to make sure that the water was as pure as
> possible?

You could try some conductive measurements. IIRC, there are some limits
on the highest allowed conductivity of milli-q. Maybe you should browse
through some literature for that.

> What pH-value should I expect from the purified water?

Now this is a terrible one. You should expect 7, but unfortunately
milli-q has the tendency to take up carbon dioxide, resulting in
acidification. This is a fairly rapid process, and within an hour your
pH can be fairly stable around (IIRC again) 5

HTH,

Marco (replies to m.vand...@far.ruu.nl)