A Simple Assay Procedure for Mixtures of Hematoxylin and Hematein

A simple and rapid method for the simultaneous quantitative analysis of mixtures of hematoxylin and hematein uses the molar extinction coefficients of the pure substances calculated by Lalor and Martin (1959). Absorbance measurements of the samples dissolved in methanol are made at wavelengths of 292 nm and 445 nm, the wavelengths of maximum absorption of hematoxylin and hematein respectively. The hematoxylin absorbance at 292 nm is corrected for the presence of hematein.

Using this method it was found that of 12 commercial samples labelled “hematoxylin” all contained at least 90% of the compound. Hematein contents of these samples fell in the range 0.1% to 6.8%. In 9 commercial samples labelled “hematein” the hematein contents fell in the range 1.2% to 90.7%. The hematoxylin contents of these samples fell in the range of 1.0% to 82.7%.

This paper describes also a chromatographic method for the identification of hematein and its oxidation products.