Certification procedures used by the Biological Stain Commission for eriochrome cyanine R (C.I. 43820, Mordant blue 3)

ABSTRACT

Eriochrome cyanine R (C.I. 43820, Mordant blue 3), also known as chromoxane cyanine R and solochrome cyanine R, has been used as a biological stain since 1957. In conjunction with ferric ions, it provides selective blue coloration of the nuclei of cells in methods procedurally similar to commonly used progressive or regressive hemalum (aluminum-hematoxylin) stains. Eriochrome cyanine R also is used to stain the myelin sheaths of axons in nerve tissue; the results are visually similar to those in sections stained with luxol fast blue MBS (C.I. 74180, solvent blue 38) with selective blue coloration of myelin and erythrocytes. Eriochrome cyanine R is an article of commerce with many uses in industrial coloration and analytical chemistry; it can be used instead of either hematoxylin or luxol fast blue MBS, especially in the event of a shortage of either of the latter compounds. The Biological Stain Commission (BSC) will certify batches of eriochrome cyanine R that meet the criteria set out in this document. The criteria include satisfactory UV/visible spectra at pH 4 and pH 12 − 13, a dye content not less than 40% and not greater than 52% (calculated as the color acid; equivalent to 46 − 59% of the trisodium salt), and satisfactory performance in three staining methods: regressive for nuclei, progressive for nuclei and regressive for myelin.

KEYWORDS:

• certified dyes
• certified stains
• chromoxane cyanine R
• eriochrome cyanine R
• hematein substitutes
• hematoxylin
• hematoxylin substitutes
• luxol fast blue
• myelin stain
• solochrome cyanine R

Acknowledgments

A grant in aid of research from the Biological Stain Commission to JAK is gratefully acknowledged. We thank Drs. R.W. Dapson, R.W. Horobin and the late Thomas Wickersham for helpful comments on the manuscript.

Disclosure statement

The authors report no conflict of interest.