Is it possible to create a solution with superoxide? I am not a chemist, and somehow I cannot find any material on this topic, so I decided to ask here.

I am looking to create a solution with a specified amount/concentration of superoxide ($\ce{O2^.-}$). Can you suggest some compounds that will enable me to "isolate" superoxide in a solution?
Potassium superoxide (Aldrich) and an equimolar
  amount of 18-crown-6 ether used to increase solubility were
  dissolved in dry DMSO.


Role of Hydrogen Bonding in the Active Site of Human Manganese Superoxide
Dismutase Biochemistry 2004, 43, 7038-7045