The recipe of DNase buffer is: 100 mM Tris-HCl (pH 7.5), 25 mM MgCl2, 1 mM CaCl2. You can make it in DEPC treated water to get rid of RNase. Hope it will help. Good luck.
Is that buffer concentration 10X or 1X????? Because the 1X buffer concentration of ThermoFisher is 10mM Tris HCl, 2.5 mM MgCl2 and 0.5 mM CaCl2and buffer PH-7.6 at 25o C