oxygen water stability 1%

Dentists and orthodontists all now require solutions of 1% oxygen water as a pre-treatment.
I'd stabilize with disodium monohydrogen phosphate. I have 2 questions:
*What concentration of the stabilizer should I add (same quantity as at 3% or only 1/3?)
*How long would this solution remain stable? Some dentists ask 5l

Thank you very much,

Jeroen