For the disodium salt, Sigma gives the solubility in water as 150 mg/ml, which is 0.59 M. So it may not be soluble enough to make a 1 M solution.

Hi Adam B Shapiro , my creatine phosphate sodium salt says its solubility is 10mg/ml in PBS from the spec sheet. Correct me if I am wrong, but this means 39 mM. However, for my reaction (total volume of 12 ul) I need 17 mM which would mean that creatine phosphate would take up almost half of the volume - my reaction has 13 components which need to be added. Is there any way to increase the concentration of creatine phosphate?

Thank you

It might help to neutralize the pH, or to use the disodium salt.

Why not just add your solutes first, creatine phosphate and the other 12 components, then bring it up to volume. Not sure how costly your other components are, but if you could increase your volume to say 100mL then you could more accurately weigh out your creatine. You would need around 433.7 mg creatine phosphate for 100 mL at 17 mM. Since some analytical scales can measure up to 0.1 mg accurately you might be able to get away with adding 4 mg and making a 1 mL solution along with your 12 other components.

https://cdn.caymanchem.com/cdn/insert/37803.pdf

At $82 bucks for 5 grams (Sigma), I'd stick to making a 1 mL solution. Also they advise not to store it for more than a day! Best of luck in your experiments Vanessa.