Concentration calculation of disodium salt standard

[arobles]

Hi

I am analyzing ATP by reverse phase HPLC. I want to calculate the concentration of ATP in a sample using as reference the calibration curve of the standard (ATP disodium salt). My question is the following: Do I have to subtrac the sodium weight from the molecular weight of the standar? before to calculate the ATP concentration of the samples.

Thanks!

[JGK]

use a correction factor based on MW

Factor = MW ATP/MW sodium salt

weight of sodium salt X factor will give you the weight of ATP present (assuming 100% purity)

[arobles]

thanks a lot!

[lmh]

things like that I prefer to express on a molar basis (which often makes a lot more sense anyway. Who has ever quoted the Km of an enzyme in mg/mL??). That way I can calculate the molar concentration of my standard based on whatever salt I buy, and my reader (assuming anyone reads anything I write) can't get it wrong...