Z-buffer (weights for 1 L)
Na2HPO4-7H20	0.06 M (16.1 g)
NaH2PO4-H20	0.04 M (5.5 g)
KCl	0.01 M (0.75 g)
MgSO4-4H20	0.001 M (0.25 g – use MgSO4-7H20)
β-mercaptoethanol	0.05 M (3.5 mL)
The pH of this solution should be 7.0. Raise pH by adding NaOH and lower it by adding HCl. Store at room temperature for up to 1 year.