pKa for EGTA

[scuzfly]

I'm trying to find the pKa for EGTA and google isn't helping much.

 

Wiki says it's 6.91

Another article says it's 8.8

 

I'm using EGTA to trap calcium and its in seawater which has about 0.1g of Calcium already in it. I'm trying to maintain a pH between 8-10 without losing the EGTA bound Calcium.

 

If someone could help me I'd greatly appreciate it. I'm trying to run the experiment asap.

[insane_alien]

wiki also says its 11.

 

the pkA is variable. you need to calculate it based on the conditions present.

[John Cuthber]

The stuff has 6 exchangeable protons so it has 6 different pKa values.

My guess is the pKas for this are similar to those for EDTA which are all in wiki.

[scuzfly]

So how would I know how much EGTA is deprotonated if I have 0.2M EGTA in solution with 0.2M Calcium?

 

 

I'm trying to find out how many EGTA I need to bind Calcium in seawater at a pH of 8.5 without losing the Calcium into seawater. I have immobilized the EGTA*Ca using alginate.