Sensitivity Improvement of disaccharide analysis by Capillary Electrophoresis/ Electrospray Ionization Mass Spectrometry Using Nonvolatile Borate Buffer

Due to the interaction between borate anion and diols of the disaccharides, borate became a popular buffer in the analysis of disaccharides especially for isomer separation. Borate buffer offers good separation efficiency, however, it was found to be incompatible with CE-ESI-MS due to ion suppression. Using ammonium salt instead of sodium salt could improve sensitivity; however, the problem of borate anion suppression still exists. In order to alleviate the problem resulting from non-volatile borate buffer, capillary coating was employed to reduce the electroosmotic flow (EOF). Under a low EOF, borate anion stays on liquid junction reservoir. However, analytes still migrate toward the ESI source, so borate would not interfere with the signal generated by analytes. This strategy was applied to a liquid junction-low flow interface. With the proposed approach, which maintaining a good separation efficiency, the interference due to borate can be reduced.