What metal ions does EDTA react with?

Question

This is for a chemistry assignment and I've done an experiment with mineral water; determining the concentration of calcium and magnesium ions...
BUT!
I've researched a little about EDTA and many sources say it reacts with "metal ions", so I'm thinking not just calcium and magnesium?
As we would know, mineral water contains more than just calcium and magnesium ions, such as potassium, strontium and sodium ions. (depending on which brand)
Soooooo does anyone know if EDTA would react with any of these and therefore producing a slightly inaccurate reading in the experiment? Or does it leave these metal ions alone and my search for something more to talk about in my scientific report is in vain?
Much appreciated :)

And if anyone feels like telling me a bit of the science behind mineral water; how the minerals are beneficial to the body and whatnot, that'd be helpful too. :D

Answer 1

1) EDTA is a chelating (complexation) agent.

It chelates metal ions.



And, YES, it can chelate other metal ions present in the solution and thus, cause interference. This can result in a higher than normal value or a lower value.



This is why during EDTA-complexometric titrations, MASKING agents are used.

Masking agents are certain substances/solutions that are used to nullify the effect of the atoms/ions present in solution causing interference.

They have a preferential affinity for the interference.

They do this by reacting with the interference and thus leaving it in a form in which it cannot react with EDTA leaving the ion/atom of interest (analyte) free for chelation.



Demasking agents are used to nullify the effect of the masking agents.



Some common examples of interference are K in Ca-determination [ ur example ].

In this case, Na-citrate is usually used as a masking agent.



2) Mineral water is good because it provides necessary minerals for the body. E.g.

Na, K, Mg, Ca, Mg, Chlorides, Nitrates etc among others.

Some other imprtant minerals include Fe, Co etc.



Na and K are responsible for the transmission of messages/responses in the neurones in the Nervous system.

Ca, as we know, is the major mineral component of bones. Ca keeps our bones strong and enhances repair of broken bones.

Chlorides are mostly present as NaCl and HCl [ which is a digestive fluid in the stomach (gastric juice) maintaning the pH of the stomach ]

Co, Cobalt, is the central metal atom in the complex of Vitamin B12.

Fe is the central metal atom of the Fe[Hb]2 complex in the blood [ Hb = haemoglobin ] that makes up the red blood cells.



Sorry, this is all I can think of now.

E-mail me later if u get stuck:

[e-mail]

Answer 2

EDTA does not form cmplxs with monovalent metal ions such as Na^+ and K^+ only divalent and trivalent M^n+ ions. I doubt that there is any detectable amount of Sr^2+ in mineral water. Fe^2+?

[1] http://www.coldcure.com/html/stability_constants.html

[2] http://openwetware.org/wiki/EDTA

Answer 3

The hardness of water is defined as the total concentration of alkaline earth metals present. This is usually determined by measuring the total amount of magnesium and calcium that is present, since these two make up the majority of metals present. The accepted practice for reporting the hardness of water is by milligrams of calcium carbonate. EDTA is used as a titrant since it forms a complex with metal ions, thereby measuring the amount of calcium and magnesium present. The amount of EDTA used in the tirtation is proportional to the amount of calcium and magnesium present. Once you know the volume of EDTA used for the titration, this value can be converted into milligrams of calcium carbonate or PPM (part per million) calcium carbonate, therefore determining the hardness of water. EDTA: ethylenediaminetetraacetic acid, a chelating agent that can donate electrons, Lewis Base usually prepared by dissolving disodium EDTA in water

Answer 4

Edta Reactions