Tri or mono sodium citrate for making iron citrate

UK_Pete · Nov 26, 2014

Hi Randy, having read your synthesis of iron citrate, I am unclear the type of sodium citrate required.

Wiki states that sodium citrate can exist in 3 forms, mono, di and tri sodium citrate. Mono sodium citrate is mentioned as being a strong sequestrant, but the common form of sodium citrate I can find on ebay is tri sodium citrate. I just wanted to confirm which form Randy uses in his iron citrate synt. I guess mono, but would like to confirm. Tri would be easier as theres no extra step (I can buy it rather than make it) but would it work?

I have sodium carbonate, citric acid (easily available), and can get ferrous sulphate on ebay, so I guess these starting chemicals are all thats required? (the only iron tabs I can find in the shops here contain lots of excipients like calcium phosphate and glycerine, in unknown concentrations, so I prefer to steer clear of them).

Thanks, Pete

UK_Pete · Nov 26, 2014

Also, I just noticed you seem to be adding the 2 components with almost a 2:1 ratio of citrate to iron, either way (mono or tri citrate) - is this right? (IE monosodium citrate dihydrate, if it exists, is 250g / mol, and trisodium dihydrate is 294g / mol, which means 0.2 mol for the tri and 0.17 mol for the mono citrate, versus 25g of the ferrous sulfate heptahydrate, which is 0.09 mol). From what I read today I think iron citrate is 1:1 molar. Have I missed something, or is a decent excess of the citrate the right thing to do to ensure good chelation?

Thanks, Pete

Randy Holmes-Farley · Nov 26, 2014

FWIW, I presently use and recommend ferrous gluconate, which is available from the Pharmacy (in the US) as Fergon tablets.

I believe that what I used was trisodium citrate dihydrate at about a 2:1 ratio to the iron. My quick review of ferrous citrate structures in water suggested it might be more complex than a simple 1:1 so I added enough citrate to form other structures as well. But I don't know if that was necessary.

These show the complexity for Fe+++ (ferric):
Journal of the Brazilian Chemical Society - Ion-Selective Electrode for the Determination of Iron(III) in Vitamin Formulations

Iron(iii) citrate speciation in aqueous solution - Dalton Transactions (RSC Publishing)

UK_Pete · Nov 26, 2014

Thanks very much Randy, if it worked for you at 2:1 then I will use that too.

Re gluconate, although its available here in tablets, none of them have the simple excipient list that fergon has - one thing that specifically worries me is the sugar and glycerine, which I guess would both be carbon sources, in undisclosed amounts on the bottles. Thats what I found the the versions I looked for in local pharmacies anyway, hence the decision to go with the citrate.

Not sure if this is your area, but its worth asking in case you know - if I was to try to eliminate a dosing tube and mix this in with something else (the iron citrate that is), I imagine a few things would cause it to precipitate almost completely in the bottle. I guess mixing it with carbonate, for instance, would precipitate quickly, because of the alkalinity? Do you think it would be compatible with vinegar, though, with its low pH? And since I am already dosing vodka, could you hazard a guess as to its compatibility with vodka?

Thanks, Pete