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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.