> There are two Vitamin C on the market: (+) and (-). Which is the correct
> one to use?
> i think the + one is ever with another salt like calcium or sodium
> my lab fluka don't put - before the other one L-Threoascorbic acid
> 50-81-7 cas
I'm guessing a bit, but imagine that the (+) and (-) designations refer to
stereo isomers of ascorbic acid (levorotatory and dextrorotatory). This
refers to the physical structure of the molecule, and specifically to the
structural symmetry. Quite often when analyzing molecular structure you
find that it is possible to combine two sets of the same atoms in such a
way that you get two molecules that are physically mirror images of each
other. Our hands are a good example of such symmetry. They are
fundamentally the same yet distinctly different. You can't put your
right glove on your left hand for instance.
Stereo isomers are distinguished by how they rotate the plane of polarized
light passing through them. If the plane is rotated to the right or
clockwise it is dextrorotatory and if the rotation is counter clockwise or
to the left it is levorotatory. My guess is that the (+) or (-) sign you
mention indicates the sign of the rotation vector.
The "handedness" of the molecule can sometimes affect the chemical
reactions that it participates in. I don't know about the affect this has
on developer chemistry. My guess is that it probably won't have much if
any affect, but again that is only a guess. (It has been over 10 years
since I studied any stereo chemistry.)
This reply is not intended to be any kind of definitive answer. I do hope
that it gives you an idea about where or what to look for to get a good
answer to your question.
- Wayde
(wallen@boulder.nist.gov)