Evaluation of 1,10-phenanthroline as a reagent for sialic acid determinations.

Use of o-phenanthroline as a reagent for determination of sialic acids was proposed by a previous investigator. This method was based on an increase in absorbance at 307 nm that occurred when solutions of o-phenanthroline and various sialic acids were mixed. It was postulated that the increased absorbance was a result of formation of specific complexes. Using N-acetylneuraminic acid, we found no evidence for complex formation. Our results indicate that the observations of the previous investigator resulted from shifts in the pH of the medium rather than from formation of specific complexes. Therefore o-phenanthroline is not a specific reagent for sialic acids and its use is not recommended.