Borek,
Thank you for the help,
To be more specific, I am looking at the anti-coagulation of whole blood vs saline-diluted blood, wherein anti-coagulation of the saline-diluted blood with citrate-based anticoagulant does not work well for some reason. (don't worry, biochemistry shouldn't be much of an issue here).
I would like to rule out the saline as a possible reason, therefore the questions in the original post.
I am using citrate phosphate dextrose anticoagulant with the diluted blood, in the same ratio (1:7) as whole blood. (unknown how diluted the blood is)
The mechanism of action seems basic- citrate in the anticoagulant solution chelates the Ca2+ ions in blood, which are critical to the coagulation cascade.
Ca2+ exists in blood in the concentration "6.7-10.7 ... (mg/dL) or 1.90-2.75 ... (mmol/L)", and blood pH is around 7.4
The anticoagulant contains 15.5mmol/L citric acid and 89.9mmol/L trisodium citrate. (2.99g @ 192.124 g/mol (anhydrous) and 26.3g @ 294.10 g/mol (dihydrate), for citric acid and trisodium citrate (sodium citrate (dihydrate), respectively, per liter).
Therefore, combined in the recommended 1:7 ratio, this means 15.5mmol citric acid and 89.9 mmol trisodium citrate per 13.3-19.25 mmol Ca2+ in blood (for whole blood). There should be even less Ca2+ for diluted blood.
Seems more than enough, unless the the Na+ from the saline somehow had more of an effect... (Na2+ concentration would be 154mmol/L for 0.9% saline (9g NaCl into 1 litre).
(Na+ concentration in blood is "136-145 ... (mEq/L) or 136-145 ... (mmol/L)" which is not too different.)
I am still searching for stability constants, as they are difficult to find for sodium, calcium, and citrate...
A previous forum post on an unrelated subject (difficulty finding now) mentioned something about "I know that Na+ doesn't [affect] chelation" but I'm not sure if it applies in this case.
(I suppose there could be other factors involved as well too, I am looking into these)
Therefore, the questions in the original post.
Any help or thoughts would be appreciated, again, thanks in advance.