EDTA



EDTA stands for ethylene-diamine-tetraacetic acid. It chelates divalent cations and is therefore used in many buffers. Its relative EGTA has a higher affinity for calcium than for magnesium ions.

Purpose

 * EDTA is a synthetic amino acid and chelating agent for divalent metals.


 * Most enzymes that synthesize or modify nucleic acids (e.g. polymerases, ligases, kinases, nucleases) are Mg2+-dependent. The addition of EDTA is a convenient way to stop these reactions.


 * EDTA is a component of many buffers used to store DNA, such as TE buffer, where the EDTA removes the metal cofactors (typically Mg++ required for activity of DNAses and other DNA damaging enzymes.

Procurement

 * Usually sold as the disodium salt (CAS 6381-92-6) (Sigma E1644).

Use

 * Molecular Weight, disodium salt dihydrate: 372.24


 * EDTA is essentially insoluble in water, and will only dissolve when neutralized with sodium hydroxide to a pH = 8.0


 * Standard stock solutions are 0.5M at pH 8.0. A 1M solution cannot be made.  Autoclave.


 * Making the standard solution from disodium EDTA (the typical form sold) requires approximately 1 molar equivalent of NaOH


 * pK1 = 1.99
 * pK2 = 2.67
 * pK3 = 6.16
 * pK4 = 10.26

0.5 M EDTA stock

 * 18.61 g EDTA (Sodium Salt)
 * dH2O to 90 ml
 * adjust pH to 7.0
 * adjust volume to 100 ml

0.5M 500ml pH 8.0 with NaOH pre-calculated

 * 93.05g of Na2.EDTA (FW 372.2)
 * 10.14g of NaOH (FW 40)
 * 500 ml dH2O

Storage and stability

 * store at room temperature
 * stable for years

Interesting facts

 * Here's an article that speaks of the wonders of EDTA and how it can help treat Aunt Edna's cardiovascular disease, enhance your enjoyment of the Friday night happy hour, and act as a "get out of jail free" card.


 * EDTA can prolong the life of your motorcycle battery!


 * EDTA helps you determine the hidden contents of your hard water.

Safety
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