[1] The stock solution for Karnovsky fixative is as follows:[1] Mix the paraformaldehyde with 25 ml of distilled water in a 125 ml Erlenmeyer flask.
When moisture forms on the sides of flask, add sodium hydroxide and stir until the solution clears.
Filter, add glutaraldehyde and 0.2M buffer, pH range 7.2 to 7.4.
Karnovsky's fixative solution is often modified for specialized applications.
[2][3] For example, 2% paraformaldehyde, 2.5% glutaraldehyde in 0.1 Molar sodium phosphate buffer (pH 7.4) has been used to study the ultrastructure of renal pelvis fragments.