The reaction between some dyes and synthetic hydroxyapatite. I. The uptake of dyes in relation to their structures.

Abstract

The uptake of dyes from dilute solutions by synthetic hydroxyapatite and other sparingly soluble calcium compounds has been determined. About 30 dyes, mostly azo-, dis-azo and anthraquinonoid types were used in 95% ethanol or 0.1 M tris buffer. Many had closely related configurations. Chemical groupings possibly responsible for the adsorption of particular dyes by hydroxyapatite have been deduced from an analysis of the results. The uptake of most dyes from alcoholic solutions was, linearly related to the surface area of hydroxyapatite. Calcium carbonate and secondary calcium phosphate took up less stain than hydroxyapatite of similar surface area. With the simpler anthraquinonoid dyes, the uptake was higher from aqueous than alcoholic solutions, but specificity for hydroxyapatite was much less. The increased uptake of dye by powdered bone or dentine when rendered anorganic was proportional to the increased surface area. It was found that several dyes in common use as stains for bone and calcified tissue were only poorly adsorbed by synthetic hydroxyapatite under the particular conditions of these experiments.