The Sialic Acids

The Svennerholm resorcinol method for the quantitative determination of the sialic acids was modified by introducing a periodate oxidation step prior to heating with the resorcinol reagent. Sialic acid glycosides could be determined without acid hydrolysis. The glycosides gave chromogens stable to periodate oxidation at 37°, whereas free sialic acid gave chromogens that were destroyed at this temperature, but were stable at 0°. Using these properties, the periodate-resorcinol method was applied to the determination of total, free, or bound sialic acid. The periodate-resorcinol method was substantially more sensitive than the resorcinol procedure, was not affected by lipids, amino acids, or sugars, and could be used to detect free or glycosidically bound sialic acids on paper chromatograms.