Stability of EDTA solution?

[satoshi]

Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?

Making EDTA solution is a pain in buck. If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often. Satoshi

[Farooq W]

Post by satoshi
Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?
Making EDTA solution is a pain in buck.

This begs a question "Why"? Do you use the pure acid or the disodium
salt for making its solutions.

Post by satoshi
If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often.

I guess a period of one year is too high for something as reactive as
EDTA. Using glass containers you can imagine that a blue solution of
Eriochrome dye (an indicator for complexometric titrations) turns red
in few hours indicating that calcium in glass has begun to form a
complex with it.

[satoshi]

I prepare from disodium salt. But titration and dissolving with NaOH
solution is a messy operation.

Post by Farooq W
EDTA. Using glass containers you can imagine that a blue solution of
Eriochrome dye (an indicator for complexometric titrations) turns red
in few hours indicating that calcium in glass has begun to form a
complex with it.

I store EDTA in plastic bottle. It seems that we should store EDTA in
plastic bottle rather than in glass bottle.
BTW, I am not familiar with Eriochrome dye stuff. I do not have Merck
Index here but in my office. I will check that tomorrow. So I am under
the impression that if EDTA solution turns red with Erichrome dye, that
means that I got to prepare EDTA solution again. Please advise if I am
wrong. Satoshi

Post by Farooq W

Post by satoshi
Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?
Making EDTA solution is a pain in buck.

This begs a question "Why"? Do you use the pure acid or the disodium
salt for making its solutions.

Post by satoshi
If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often.

I guess a period of one year is too high for something as reactive as
EDTA. Using glass containers you can imagine that a blue solution of
Eriochrome dye (an indicator for complexometric titrations) turns red
in few hours indicating that calcium in glass has begun to form a
complex with it.

[Farooq W]

Post by satoshi
I prepare from disodium salt. But titration and dissolving with NaOH
solution is a messy operation.

Do you need to add sodium hydroxide to dissolve EDTA? Do you slightly
heat the solution e.g. a temperature controlled magnetic stirrer would
really help.

Post by satoshi

Post by Farooq W
EDTA. Using glass containers you can imagine that a blue solution of
Eriochrome dye (an indicator for complexometric titrations) turns red
in few hours indicating that calcium in glass has begun to form a
complex with it.

I store EDTA in plastic bottle. It seems that we should store EDTA in
plastic bottle rather than in glass bottle.
BTW, I am not familiar with Eriochrome dye stuff. I do not have Merck
Index here but in my office. I will check that tomorrow.

I don't know your specific application niether I have data on the
stability of EDTA solutions what I wanted to point out that even the
glass container can contaminate the reagents.

Post by satoshi
So I am under
the impression that if EDTA solution turns red with Erichrome dye, that
means that I got to prepare EDTA solution again.

Nope. Eriochrome is simply a dye used as indicator in complexometric
titration of many metal ions. The original color of the dye solution at
pH~10 is blue, when it forms a complex with a metal ion it turns red.
Adding EDTA to that solution "snatches" the metal ion from
Eriochrome-metal complex and sets the dye free which makes the solution
blue again.

If you keep (blue) Eriochrome solution at pH~10 in ordinary glass it
slowly turns pink with time indicating that metallic (e.g. Ca) ions
"from" glass are reacting with the dye.

Post by satoshi
Please advise if I am
wrong. Satoshi

Post by Farooq W

Post by satoshi
Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?
Making EDTA solution is a pain in buck.

This begs a question "Why"? Do you use the pure acid or the disodium
salt for making its solutions.

Post by satoshi
If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often.

I guess a period of one year is too high for something as reactive as
EDTA. Using glass containers you can imagine that a blue solution of
Eriochrome dye (an indicator for complexometric titrations) turns red
in few hours indicating that calcium in glass has begun to form a
complex with it.

[Bob]

Post by satoshi
I prepare from disodium salt. But titration and dissolving with NaOH
solution is a messy operation.

Why not buy some tetra-sodium EDTA. Make up both the Na2 and Na4, at
desired concentration. Then mix as desired to get the pH you want, but
any mix still has the same [EDTA]. That may be easier than NaOH
titration.


As to leaching... depends what you are using the EDTA for. For much
routine biology work, it is there simply to keep ions in solution, and
a little leaching is of no concern. OTOH, for some analytical work, it
would be serious. So you need to judge that, for your application.

bob

[satoshi]

My question for this thread was about the stability of EDTA solution, not
about how to make solution.
Satoshi

Post by Bob

Post by satoshi
I prepare from disodium salt. But titration and dissolving with NaOH
solution is a messy operation.

Why not buy some tetra-sodium EDTA. Make up both the Na2 and Na4, at
desired concentration. Then mix as desired to get the pH you want, but
any mix still has the same [EDTA]. That may be easier than NaOH
titration.
As to leaching... depends what you are using the EDTA for. For much
routine biology work, it is there simply to keep ions in solution, and
a little leaching is of no concern. OTOH, for some analytical work, it
would be serious. So you need to judge that, for your application.
bob

[Bob]

Post by satoshi
Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?
Making EDTA solution is a pain in buck. If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often. Satoshi

It's stable.

But if it is not sterile, things might grow in it over time.

bob

[satoshi]

Bob,
I know it is stable but how long?
Do you have an idea how long 0.5M EDTA could be stable when kept at room or
4oC temperature?
My question is whether it is a year or two or more? Advise me. Satoshi

Post by Bob

Post by satoshi
Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?
Making EDTA solution is a pain in buck. If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often. Satoshi

It's stable.
But if it is not sterile, things might grow in it over time.
bob

[Bob M]

Store in a high density natural (non pigmented) poly ethylene bottle.
I preserve mine with 500 ppm of phenylcellosolve (phenoxyethanol)
0.1N seems to be stable well over a year.
In any case you can also keep on hand primary standard CaCO3 in HCl
reference soln this is stable almost indefinitely kept in the above
bottle.
If in doubt about your edta just do a restandardisation.
The only time I have ever found any deterioration was be for I used the
above preservative.

BobM

[satoshi]

Thanks Bob,

Post by Bob M
I preserve mine with 500 ppm of phenylcellosolve (phenoxyethanol)
0.1N seems to be stable well over a year.

2-Phenoxyethanol 99% solution is available from commercial source. I might
add this stuff to EDTA (0.5M) solution for storage.

I am a bit surprised to see that EDTA with (phenoxyethanol) is stable just
over a year. Do you store at room temperature or in refrigerator?

In fact, I called a company which sells concentrated EDTA solution. I was
told that it is stable for 2 years at room temperature.
Since the commercial EDTA solution was maintained at pH 8.0 for the obvious
reason, I am wondering how EDTA could be stable that long at alkaline pH.
I assume that the commercial solution was prepared without phenylcellosolve.
That's why I raised this question.

Satoshi

Post by Bob M
Store in a high density natural (non pigmented) poly ethylene bottle.
I preserve mine with 500 ppm of phenylcellosolve (phenoxyethanol)
0.1N seems to be stable well over a year.
In any case you can also keep on hand primary standard CaCO3 in HCl
reference soln this is stable almost indefinitely kept in the above
bottle.
If in doubt about your edta just do a restandardisation.
The only time I have ever found any deterioration was be for I used the
above preservative.
BobM

[Bob M]

My stock solutions in the lab are M/10 and M/100 They are stored at
room temp. I use disodium EDTA to make them up and standardise using
Precipitated calcium carbonate in HCl. as my primary standard.

I know solutions are stable in xs of a year but they are normally used
up a long time before the year is finished.
Bob M

[r***@hotmail.com]

Post by satoshi
Does anybody know how stable is EDTA solution at pH 8.0 at room or cold
temperature (4oC)?
Making EDTA solution is a pain in buck. If I know the approximate
stability duration of EDTA solution (say, one or two year), I do not have
to make it so often. Satoshi

This has actually come up once before. You can say its come up more
than once for various slow to dissolve chemicals -- do a google groups
search for TRIS stability as an example.

I've yet to find a comprehensive guide to chemical solution stability.
But various labs do have rules they stick to, and if they're university
labs, will publish them in text books or online, so its worth googleing
on that. But that info is just fitness for their application -- if a
hydroponics lab says calcium edta solution is good for 6 months, that
could mean Jack Schmit to a lab using it as a standard for a trace
metal analytical instrument. If you're looking for commercial
standards, well, those are trade secrets, and you won't find them
anywhere.

Basically, it is up to you to determine how long you can store a
reagent solution and still have it be useful for your application, so
you can take all variables into consideration. You've already been
told that chemicals that complex calcium can leach it out of a glass
bottle rapidly. What effect can other bottles have on your solutions?

Here's an opinion. Take it for what its worth. NOTHING lasts a year.
Now wait, allow me to explain:

Many reagents are adequtely chemically stable for a year. 'Tho I'd put
my money on an inorganic salt before a large organic molecule. But if
you fill a bottle and put it on the shelf, what'll happen? People will
take a aliquoit from time to time, sometimes leaving the cap off or
using a dirty transfer pippette - your reagent ends up contaminated.
The tape/adhesive/lettering on the label/bottle will wear off over
time. At some time before the years up, the label will be lost or just
look ratty and someone will toss it out.

Basically, as a chemist its your job to prepare reagents, as needed, to
the appropriate quality standard for your application. You're not
trying to get yourself replaced by a machine and some semi-skilled
labor, are you?

[labrat]

Disodium EDTA is soluble to the extent of approximately 0.25mol/L at
room temperature (25C here). I use 1mol/L (tetrasodium) EDTA in
thermometric titrations. I make it from disodium EDTA and a slight
stoichiometric excess of NaOH. I don't find it a hassle to make up,
whipping up a batch in a matter of minutes. I've never worried about
long-term stability since I only make up what I intend to use over the
coming month or so. Obviously it should be stored in a plastic bottle.

[muha]

maybe he wants to start selling the stuf :) Anyway, Sigma offers the
solution in a polycarbonate plastic bottle, unstabilised, which can be
stored on the shelf without refrigeration, for years.

If you look up the chemical structure, you will understand why there is
nothing to worry about EDTA in terms of stability. If you want to be
100% sure, you can fill your botle with near-boiling solution and close
them while hot - that should keep them sterile.