When the reagent is added, alkaloids show a characteristic color. Tertiary amines can give yellow, orange and red to brown colors. Among other things, it is used in thin layer chromatography (TLC) as a spray or immersion reagent, for example for drug analysis .
The reagent is made up of bismuth oxide nitrate (bismuth subnitrate), tartaric acid and potassium iodide . A potassium tetraiodobismuthate complex is formed. Basic aliphatic amines are protonated (by the tartaric acid), the formation of an ion pair of the form [BiI 4 ] - [HNR 3 ] + which can no longer be solvated occurs .
The Dragendorff reagent was developed by the pharmacist Georg Dragendorff (1836–1898) and first published in 1872.
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