Certification procedures for sirius red F3B (CI 35780, Direct red 80)

Abstract

Sirius red F3B (CI 35780, Direct red 80) is a polyazo dye used principally in staining methods for collagen and amyloid. For certification by the Biological Stain Commission, a sample of the dye must exhibit an absorption spectrum of characteristic shape with a maximum at 528-529 nm, a small shoulder near 500 nm and narrow peaks at 372, 281-282 and 230-235 nm. Spot tests (color changes with addition of concentrated H₂SO₄ or HCl and subsequent dilution or neutralization) also are applied. The dye must perform satisfactorily in the picro-sirius red method for collagen by providing red staining of all types of collagen with yellow and green birefringence of fibers. Llewellyn's alkaline sirius red method applied to tissue known to contain amyloid must show red coloration of the products with green birefringence. Dye content, which does not influence significantly the staining properties of sirius red F3B, is not assayed.

Key words::

• amyloid staining
• Biological Stain Commission
• certified stains
• collagen staining
• Direct red 80
• sirius red F3B

Acknowledgments

We thank Matthew Frank, formerly of the Biological Stain Commission laboratory in Rochester, NY, for some of the earlier spectroscopic work. Bryan Llewellyn of Ladysmith, BC, Canada provided valuable advice about amyloid staining.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.