EMS Catalog #16905
Imidazole is a liquid enhancing buffering agent that, when used with 4% osmium tetroxide solution as a post-fixation for tissue blocks, produces a prominent electron-opaque staining of lipid droplets with no evidence of diffusion.
Tissue is fixed by vascular perfusion with 1.5% glutaraldehyde in 0.1M cacodylate buffer (pH 7.4) containing 4% polyvinyl pyrolidone and 0.05% CaCl2. Sections about 50um thick are cut and placed in 0.2M Imidazole in which 4% aqueous OsO4 is added.
The final concentration of OsO4 is 2% and the pH is 7.5. Note that the tissue must first be placed in Imidazole buffer; then the OsO4 is added. This post-fixation is carried out for 30 minutes at room temperature.
Angermuller, S., Fahimi, H. Histochem. Journal 14, 823-35 (1982).