In Vitro: Guidelines (Following is our recommended protocol. This protocol only provides a guideline, and should be modified according to your specific needs). 1. Prepare stock solution of Sorensen’s buffer: Solution A. Na2HPO4?2H2O (9.5 g/L); Solution B. KH2PO4 (9.1 g/L). 2. Cover the smear with Leishman stain for 2 min. 3. Add double volume of Sorensen buffer (6.8 pH) to the slide and mix gently for 15 min. 4. Wash off with running water and dry the smear (5 min).