The D.O. Filling solution recipe is a proprietary recipe owned by our electrode manufacturer. We do not have that recipe and are not able to distribute it to customers.
The probe manufacturers feel strongly that people making up their own solutions would render their warranty invalid. We can tell you that the solution contains KCl and other ingredients, but we do not know the concentration.
We do sell bottles made by the manufacturer as:
DO Filling Solution, 125 mL (FS)