Zenker's fixative is a rapid-acting fixative for animal tissues. It is employed to prepare specimens of animal or vegetable tissues for microscopic study. It provides excellent fixation of nuclear chromatin, connective tissue fibers and some cytoplasmic features but does not preserve delicate cytoplasmic organelles such as mitochondria. Helly's fixative is preferable for traditional dye staining of mitochondria.
Zenker's fixative contains mercuric chloride ("corrosive sublimate"), potassium dichromate, sodium sulfate, water, and acetic acid. Fixatives containing mercuric chloride or potassium dichromate are toxic, making disposal as hazardous waste costly. Mercuric chloride can be replaced with the same weight of less toxic zinc chloride but the resulting "zinc-Zenker" may not give the same quality of fixation as the original mixture.
This fixative is named after Konrad Zenker, a German histologist, who died in 1894 (Baker 1958).
Before use, 5 ml glacial acetic acid is added to 100 ml of the solution. Both the stock solution and the complete Zenker fixative are stable for many years.
If the glacial acetic acid is replaced by 5 ml of formalin (37–40% formaldehyde), the resulting solution is Helly's fixative, also sometimes called "formol-Zenker". Helly is stable for only a few hours because the formaldehyde and dichromate components react, producing formic acid and chromium(III) ions; the orange solution becomes greenish.
- Barszcz CA (1976) Use of zinc chloride in Zenker-type fixatives. Histo-Logic 6: 87.
- Baker JR (1958) Principles of Biological Microtechnique. London: Methuen, p. 344.
- Gabe M (1976) Histological Techniques (Transl. E. Blakith and A. Kavoor). Paris: Masson.
- Kiernan JA (2008) Histological and Histochemical Methods. 4th ed. Bloxham, UK: Scion. p. 40–41.
- Lillie RD & Fullmer HM (1976) Histopathologic Technic and Practical Histochemistry. 4th ed. New York: McGraw-Hill. p. 54–57.