For 1 litre of 1x phosphate-buffered saline (1x PBS buffer) use:

8.00 g of NaCl
0.20 g of KCl
1.44 g of Na2HPO4
0.24 g of KH2PO4
Dissolve in 800 ml of distilled H2O
Adjust the pH to 7.4 with HCl or NaOH
Add distilled H2O to 1 liter
Autoclave (20 min, 121°C, liquid cycle).

For 1 Liter of 1x M9 Buffer use:

KH2PO4 3 g
Na2HPO4 6 g
NaCl 5 g
MgSO4 (1M) 1 ml
dH2O 1 L
Combine the above ingredients in large beaker or graduated cylinder using magnetic stir bar. Aliquot into appropriate sized bottles (I usually put 300mL in 500mL sized bottles), and then autoclave for 15 minutes.