Posted by Jim Wilkins on May 30, 2011, 1:15 pm
> Jim,
> >If you have good instructions and can weigh samples to 1 part in
> >2000 or better precision you should be fine.
> I don't have good instructions, I'm winging this as I go, it all
> stemmed from that spread-sheet I wrote based on math the beer, wine,
> and spirits folks use to calculate output ethanol from the amount of
> fermentable sugar present.
> ...
> Curbie
An example:
http://www.hc-sc.gc.ca/fn-an/res-rech/analy-meth/chem/index-eng.php
I suggested looking for a pre-1960's lab manual because it won't
assume you have an Atomic Absorption Spectrophotometer, just simple
equipment. The 'wet' analytical techniques for foods are over a
century old. I found manuals for petroleum and medical lab techs, not
for food.
A general chemistry book may explain how to perform the procedures but
is unlikely to give specific instructions for all the tests you need.
It's such a broad field that we could learn only enough to understand
the explanations when we entered any branch of industry.
jsw
Posted by Jim Wilkins on May 30, 2011, 2:53 pm
> ...
> I suggested looking for a pre-1960's lab manual because it won't
> assume you have an Atomic Absorption Spectrophotometer, just simple
> equipment. The 'wet' analytical techniques for foods are over a
> century old. ...
> jsw
This describes the considerations for starch and sugar assay, though
it uses an optical photometer to make measurements:
http://treephys.oxfordjournals.org/content/24/10/1129.full.pdf
The writing style and jargon are standard for chemical literature. A
lab tech's manual should be easier to follow.
jsw
Posted by Curbie on May 30, 2011, 4:15 pm
Jim,
>This describes the considerations for starch and sugar assay, though
>it uses an optical photometer to make measurements:
>http://treephys.oxfordjournals.org/content/24/10/1129.full.pdf
I downloaded this, because there seems to math in here that might
provide a cross-check.
Thanks,
Curbie
Posted by Jim Wilkins on May 30, 2011, 2:13 pm
> ...
> I doubt my scale with a precision of 0.1g or refractometer or
> hydrometer are going to get me 1 part in 2000 but I hoping to get an
> idea within a couple of % and if I get anything interesting, I'll
> spring $0 on a lab report.
> ...
> Curbie
The ratio between full capacity and one division sets your potential
accuracy. More sensitive scales permit smaller samples. We aimed for
~1 in 2000 in each step because the errors accumulated with every
measurement. In your case that would mean trying for at least 200g of
algae after drying.
The tare weight of containers is a problem, also transferring -
everything- from one container to another. You can make sample dishes
for drying and weighing from heavy duty aluminum foil, then re-weigh
the amount of it that you transfer into glassware.
jsw
Posted by Curbie on May 30, 2011, 4:17 pm
Jim,
>The ratio between full capacity and one division sets your potential
>accuracy. More sensitive scales permit smaller samples. We aimed for
>~1 in 2000 in each step because the errors accumulated with every
>measurement. In your case that would mean trying for at least 200g of
>algae after drying.
>The tare weight of containers is a problem, also transferring -
>everything- from one container to another. You can make sample dishes
>for drying and weighing from heavy duty aluminum foil, then re-weigh
>the amount of it that you transfer into glassware.
This makes sense, thanks.
Curbie
> >If you have good instructions and can weigh samples to 1 part in
> >2000 or better precision you should be fine.
> I don't have good instructions, I'm winging this as I go, it all
> stemmed from that spread-sheet I wrote based on math the beer, wine,
> and spirits folks use to calculate output ethanol from the amount of
> fermentable sugar present.
> ...
> Curbie