I emailed Sigma a couple weeks ago asking about the D content of their D2O. Here is their response:

Thank you for contacting Sigma-Aldrich Technical Service. Product 151882 is pure deuterated water with the deuterium content a minimum of 99.85% of the total hydrogen content. Although it’s not normally reported as ppm, there would be 201,198 ppm deuterium in pure deuterium oxide. Product 151882 is prepared to the chemical purity indicated, but is not sterile filtered or tested for endotoxins or nucleases, so a direct comparison with molecular biology grade water can’t be made.

 

Is it just me, or is the ppm of Deuterium a bit low? Theoretically, if there is only deuterium and oxygen in D2O then the deuterium should be 2/3 of the total molecules and so that should be something like 666,666ppm. If there is 0.15% Hydrogen that should be about 1500ppm. So if my theoretics are wrong, then I’ve become worse at math than I thought and I should return my BS in Mathematics.

But if not, then this begs the question, what else is in the water?