Determination of Pyrrole Derivatives and Hydroxyproline with 4-(Dimethylamino)benzaldehyde in a Micellar Medium

Abstract The spectrophotometric determination of pyrrole derivatives and hydroxyproline with 4-(dimethylamino)benzaldehyde (Ehrlich's reagent) in a sodium dodecyl sulphate micellar medium is studied. Pyrrole and pyrrole-2-carboxylic acid were used as model compounds for the optimization of the procedure. In the micellar medium with 0.2 M HCl at 90° C, pyrrole reacts in 15 min, whereas a HCl concentration larger than 5 M is required in the absence of the surfactant. The sensitivity increases from 1.3 to 5.6-fold with respect to the use of a non-micellar medium, for some pyrrole derivatives. The procedure is applied to the determination of hydroxyproline in meat samples.