[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: EDTA and light

On Tue, 18 Mar 1997 Aquatic-Plants-Owner at ActWin_com wrote:
> From: toado <toado at ihug_co.nz>
> Date: Tue, 18 Mar 1997 21:02:31 +1200
> Subject: Re: EDTA and light.
> > > to 1 ratio.
> > > One other point, EDTA degrades in the presence of light so should be kept
> > > in a dark bottle.
> > 
> > Iron:EDTA degrades in the presence of light due to photchemical
> > reactions.  Sodium salts of EDTA are perfectly stable in the light.
> > 
> Uhm, Sodium Edetates do degrade appreciably if you chuck a little UV
> light at 'em. Lab suppliers package the stuff in opaque plastic or amber
> glass bottles for this reason. 

Sorry, Don't think so.  Sodium EDTA is very stable in light.  There is no 
chromophore absorbing anywhere near the visible region, so I see no 
mechanism for it to undergo a photochemical transformation with any 
light that you are reasonably going to have indoors.  If you put it 
under a UV lamp, sure, it will probably degrade.  Many suppliers sell 
EDTA in natural polyethylene containers.

Yes, light is pumping redox chemistry in the case of Fe:EDTA.

Relevance to planted tanks:  PMDD and other solutions containing Fe:EDTA 
should be stored in the dark, or at least in amber containers.  If chem 
whiz kids on this list make a stock of sodium EDTA, it is perfectly 
stable in clear glass or plastic, at room temp, in the light.  Solutions 
of EDTA and any transition metal should be stored in the dark.