ANALYTICAL CHEMISTRY IN THE SEPARATION, PURIFICATION, CHARACTERIZATION AND QUANTIFICATION OF RAMNOLIPIDS

Abstract

The term rhamnolipids represents a mixture of congeners of widely varying composition and ratio. The homologues contain one (mono-rhamnolipid) or two (di-rhamnolipid) rhamnose units covalently linked to one or two β-hydroxy acid chains. The structural diversity of these molecules determines that the analytical techniques used consider chemical reactions of homogeneous and heterogeneous equilibria. Within the homogeneous equilibrium, the formation of complexes stands out, while acid precipitation, solvent extraction and chromatography are methods based on the heterogeneous equilibrium. Likewise, the use of the instrumental methods molecular absorption spectrophotometry, infrared spectroscopy and nuclear magnetic resonance, and liquid or gas chromatography-mass spectrometry hybridization allow reaching a complete characterization of these glycolipids. In the present work, the different methods most commonly used in the analytical determination of rhamnolipids are reviewed and explained, specifying the analysis of rhamnolipids AT10, ORA9 and Y3B1A. The main physicochemical detection and characterization methods are also mentioned. Molecular absorption spectrophotometry and HPLC-mass hybridization are the most applied analytical methods of quantification and characterization; while acid precipitation is chosen as the separation method