[IK]

Dear all,

if the salt label says salt hydrate with the formula C10H13N2Na2O8P · xH2O, as we do not know the amount of water molecules in the salt hydrate, how can the concentration be calculated? The salt label only gives the molecular weight of the anhydrous salt.

Best regards
Ik

[sjb]

How accurately do you need to know? Do you know what any other contaminants may be?

[IK]

Iam using the salt as a standard for HPLC analysis. So i think it needs to be accurate. No other contaminants. Just the salt and water.

[Arkcon]

You will have to find the information if you intend to use this as a standard.  They haven't reported it, because it is like highly variable.  You may have to dry it, according to a published method, or assay the water content.

What is the reagent?  When a carbon compound contains more than two or three carbons, the atomic formula tells us nothing.  Give us its name please.

[IK]

Thymidine 5′-monophosphate disodium salt hydrate

[Arkcon]

And if you google that name, you'll see the assay us likely the same as SigmaAldric reports, <= 14%.  If you need more accuracy, you will have to perform a Karl Fisher titration.

[IK]

Sigma states the assay>=99%.

http://www.sigmaaldrich.com/catalog/product/sigma/t7004?lang=en&region=GB

Does this mean it is 99% anhydous Thymidine 5′-monophosphate disodium salt ?

If that is the case, that accuracy is more than enough.

[sjb]

I

Sigma states the assay>=99%.

http://www.sigmaaldrich.com/catalog/product/sigma/t7004?lang=en&region=GB

Does this mean it is 99% anhydrous Thymidine 5′-monophosphate disodium salt ?

If that is the case, that accuracy is more than enough.

I'm not sure, I don't think so. Did you get a Certificate of analysis ( http://www.sigmaaldrich.com/united-kingdom/technical-services/c-of-a.html ) with the bottle?

If it's HPLC is this qualitative or quantitative? What will you be comparing it to?

[IK]

Hi no the bottles were already in the lab, purchased prior to me. On the sigma website it states Water (by Karl Fischer) < 20 % , Purity (HPLC) > 99 % and assay     ≥99%. HPLC quantitative.

[Arkcon]

Perhaps you're confused about how ~20% plus ~99% add up to a real percentage.

After you've accounted for the water, the rest of the sample is at 99%, is what they mean.

How you will find out how much water there is, just by asking the same question again, that ... that I can't help you with.