Quantitative Determination of Sugar Alcohols by the Komarowsky Reaction

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Abstract
SUMMARY: When heated in a reagent consisting of a cyclic aldehyde, thiourea, and concentrated sulfuric acid, the sugar alcohols, including glycerol and inositol, give orange, pink, or red colors whose intensities follow Beer's law. The reagent is stable for 6 weeks or more in an amber bottle under refrigeration. Of the aldehydes tested, p‐hydroxybenzaldehyde and p‐dimethylaminobenzaldehyde were the most sensitive. Generally, the reactivity of the sugar aleohols was as follows: sorbitol > dulcitol > mannitol > erythritol > xylitol > arabitol > ribitol > glycerol > inositol. Carbohydrates and other interferences were removed by acid hydrolysis followed by degradation with hot alkali and treatment with ion‐exchange resins. Hydrolysis, degradation, and removal of degradation products can also be done in a single operation with a mixture of ion‐exchange resins. Important factors for reproducible quantitative results are the concentration of acid, thiourea, and aldehyde in the reagent, the time and temperature of heating, and the particular aldehyde used. Recovery from complex milieu was good (95–101.8%).