Dansylation of hydroxyl and carboxylic acid functional groups

Fluorescent labeling of primary and secondary amines using dansyl chloride has been widely used in the past. Its application provides an extremely sensitive means to detect amine functional groups to amounts of less than 1 microg of material. This work describes a method for the dansylation of hydroxyl (-OH) and carboxylic acid (-COOH) functional groups. This technique is demonstrated with ethanol, gamma hydroxy butyric acid (GHB), benzoic acid, and p-chloroaniline. Sensitivity of detection for all compounds are microgram or microliter. For the compounds ethanol and GHB which are liquids at room temperature, as little as 1 microl quantity can be detected. Benzoic acid and p-chloroaniline which are solids at room temperature can be detected at levels of 1 microg. Fast thin layer chromatography was accomplished using acetone as the resolving solvent, which resulted in good differentiation of analytes for R(f) measurement. The dansylation reaction performed similarly at pH 11, 10 and 9.6 and uses 2 molar Na(2)CO(3).