Citrate buffer contains:
0.1 M Citric acid 21.01 gm in 1 L distilled water (DW)
0.1 M Sodium citrate 29.41 gm in 1 L DW
Add 80 of citric acid to 920 ml sodium citrate. To make
a working solution, adjust the pH to 5.9-6.0. Store at room
temperature. Solution will last for 1 year.