why is calcium salt of EDTA an effective detoxicant for lead poisoning ??

Question

given the following Formation Constants(Kf) for
Kf ( Ca^+2 - EDTA ) = 5.0x10^10
kf ( Pb^+2 -EDTA ) = 1.1x10^18

Answer 1

EDTA or ethylenediaminetetra acetic acid is a methal chelator, and it binds heavy metals quite well. It has a higher affinity for Pb than for Ca, so that is why it is an effective detoxicant for Pb poisoning. The main reason the salt is used (and many times it is disodium salt) is to make the EDTA more soluble.

Answer 2

As EDTA has more tendency to bind with Pb than Ca.Hence Ca salt of EDTA is used as detoxicant for lead poisoning.

Answer 3

Because the formation of the lead Complex of EDTA is thermodynamically favored over the calcium complex. Hence, the lead complex will be formed, the toxic lead is fixated and can be removed from the body.
You can see that from the much higher formation constant of PbEDTA. Although you didn't give any units.... :)

Answer 4

I assume you want a more detailed answer than EDTA is used in chelating heavy metals because it binds so well. Can you get your hands on this article; it might be helpful?

Curr Med Chem. 2005 ;12:2771-94
[Pubmed] [Scholar] [Select] [Hide]
Chelators as antidotes of metal toxicity: therapeutic and experimental aspects.
Maja Blanusa, Veda M Varnai, Martina Piasek, Krista Kostial
The chelating drugs with worldwide application are dimercaprol (BAL), succimer (meso-DMSA), unithiol
(DMPS), D-penicillamine (DPA), N-acetyl-D-penicillamine (NAPA), calcium disodium ethylenediaminetetraacetate
(CaNa(2)EDTA), calcium trisodium or zinc trisodium diethylenetriaminepentaacetate (CaNa(3)DTPA, ZnNa(3)DTPA),
deferoxamine (DFO), deferiprone (L1), triethylenetetraamine (trientine), N-acetylcysteine (NAC), and Prussian blue
(PB). Several new synthetic homologues and experimental chelating agents have been designed and tested in vivo for
their metal binding effects. These include three groups of synthetic chelators, namely the polyaminopolycarboxylic
acids (EDTA and DTPA), the derivatives of BAL (DMPS, DMSA and mono- and dialkylesters of DMSA) and the
carbodithioates. Many factors have been shown to affect the efficacy of the chelation treatment in metal poisoning.
Within this context it has been shown in experiments using young and adult animals that metal toxicity and chelation
effects could be influenced by age.

Answer 5

I thought EDTA was put in anti-bacterial products.

Answer 6

I have referred your question to my doc for a clarification!