How to make 10x Phosphate Buffered Saline, pH 7.4
(0.2 M phosphate, 1.5 M NaCl)

Materials
2.28 g NaH2PO4 (mw=120; 0.038M) or 2.62g NaH2PO4(H2O) (mw=137.99; 0.038M)
(Note: monobasic)
11.5g Na2HPO4 (mw=141.96; 0.162M)
(Note: dibasic)
43.84g NaCl

Make it up

Add NaH2PO4 and Na2HPO4 and NaCl to 450 ml dH2O.
Adjust pH to 7.4 by adding dilute (1N) HCl if necessary.
Bring the final volume to 500 ml with water.
Dilute 1:10 for final concentration.

Rb