I have tried a number of solvents and even tried to spike with non polar solvents and still could not dissolve nickel attached to ATP and other biological components.
If you mean nickel ion, it's fairly soluble in water, but the problem with solubility probably arises from the ATP and other biological components.
However, ATP should be soluble in water as well, if you have problems with high concentrations, try something like DMSO (dimethylsulfoxide), MeOH or water/MeOH
Thank you, I will try those and perhaps even mixing if the individual solvents do not work. I did try water, DMSO and ethanol. Could it be the result of contamination that it does not dissolve as easily as it should?