Staining, Histochemistry and Histotechnology
(Frequently Asked Questions)
Dr. John A. Kiernan
Department of Anatomy
and Cell Biology
The University of Western Ontario
Does anyone have a recipe for Saccomanno fixative (a cytology fixative) which gives the molecular weight of the Carbowax (polyethylene glycol) in the solution? Thanks in advance!
This formula is from Koss. Roughly equal volumes of Saccomanno's fixative can be added to liquid cytologic specimens such as sputum, urine, bronchial washings, and pleural and peritoneal fluids to stabilize them at room temperature until they can be prepared as filter or cytocentrifuge preparations or cell blocks, and it also works fairly well for small biopsy specimens. It is not suitable for Thin Prep preparations, for which a special fixative is required.
Saccomanno's fixative is 50% alcohol which contains approximately 2% of Carbowax 1540 (Union Carbide Corporation, UCAR). Carbowax 1540 is solid at room temperature, with a melting point of 43 to 46 C. To avoid having to melt it whenever the fixative is prepared, a stock solution can be propared by melting of Carbowax (melted in an incubator or hot air oven at 50 to 100 C) and adding it to an equal volume of water or 50% alcohol. The mixture will not solidify. Saccomanno's fixative can then be prepared with 430 mL of water, 530 mL of 95% ethanol, and 40 mL of the stock Carbowax solution. Some light green SF or fast green FCF can be added to color the fixative. Koss warns that the denaturants in reagent alcohol may cause excessive hardening of mucus.
I suppose that the 1540 is the molecular weight, but basically it's a catalog number for a long series of these UCAR products that range from thin liquids to dense paraffin-like waxes.
From Leopold G. Koss, Diagnostic Cytology and Its Histologic Bases, 3rd ed., Lippincott 1979, page 1192 I don't have the current edition of this venerable tome. I have never tried to make Saccomanno's fixative, but those who have rank it right up there with hanging wallpaper as a good way to wind up screaming.