Decomplexing madder lakes using oxalic acid: A novel method coupled with microwave or ultrasound processes

Publication date: Available online 27 April 2019Source: Comptes Rendus ChimieAuthor(s): Jean-Baptiste Mazzitelli, Carole Mathe, Cathy VieillescazesAbstractThe aim of the present study was to establish a mild extraction and universal method to characterize madder lakes of Rubia tinctorum by liquid chromatography coupled with a photodiode array detector . To analyze the lakes, anthraquinone molecules must be decomplexed of metal links. To this end, two processes, one ultrasound and the other microwave, were improved in association with two solutions, an oxalic acid solution (0.5 M in MeOH/H2O 50/50) and an acetic acid buffer solution (1 M). First, the decomplexation of an alizarin experimental lake was optimized in comparison with a reference method using a strong acid. The microwave process used oxalic acid and increased the decomplexation yield of alizarin (71%) compared with the reference method (31%). Second, different madder experimental lakes, which were prepared using different metal salts, were decomplexed. The obtained results suggest that the use of microwave associated with oxalic acid solution is the most universal method providing a decomplexation of anthraquinones from lakes without hydrolysis of glycosidic compounds occurring.RésuméLe but de cette étude est d’établir une méthode universelle et non dénaturante pour caractériser les laques de garance par chromatographie en phase liquide (CLHP/UV–Vis.). Pour les analyser, les molécules anthraquinoniques ...
Source: Comptes Rendus Chimie - Category: Chemistry Source Type: research