We report the minimum amounts of polysaccharicles (6.5 ng) that can be studied using capillary electrophoresis-laser-induced flurescence (CE-LIF) and describe the separation of the various monosaccharides susceptible to occur in Sinorhizobium cell wall. On-gel hydrolysis of the polysaccharides is described. It allowed the easy and rapid determination of the monosaccharide composition of the excised lipopolysaccharides. The composition obtained fits with gas chromatography-mass spectrometry (GC-MS) results. This study underlines the simplicity of using CE-LIF, which remains an entirely "water medium" method, unlike GC-MS which is, in addition, less sensitive (at least 100-fold) than CE-LIF.