DEPC-treated (ribonuclease free) water can be prepared as decribed below:
Add 1 mL DEPC per L of H2O
Shake until DEPC has dissolved in the water
Let sit for 1 h
Autoclave
Buffers containing Tris cannot be DEPC-treated (Tris inactivates DEPC by binding to amino groups). To prepare a Tris buffer, the water should be DEPC-treated and autoclaved before adding Tris. After addition of the Tris, the solution should be autoclaved again.