Capillary electrophoresis for the simultaneous separation of selected carboxylated carbohydrates and their related 1,4-lactones

A capillary electrophoresis method has been developed for the separation of acidic monosaccharides and their corresponding 1,4-lactones in a single run without derivatisation. The controlled changes of the concentration in borate and the pH of the buffers allowed good selectivity in the separation of the 18 studied compounds and of two isosaccharino-1,4-lactone isomers. Best separations were at neutral pH to avoid the saponification of the 1,4- lactones to the acidic carbohydrates, and with high borate concentration to form the negatively charged bidentate borate esters (BL^-, 1:1 complexes). The BL^- complex formation could be modeled and the corresponding measured association constants could be calculated; the selective controlled association of borate ions to specific 1,2- and 1,3-diol structures can be a useful tool in the selectivity of the separation of known carbohydrate-type mixtures.