Optimization of capillary electrophoresis conditions for coupling to a mass spectrometer via a sheathless interface

When optimizing a capillary electrophoresis/electrospray ionization mass sp ectrometry (CE/ESI-MS) system, consideration has to be given not only to th e separation but also to the electrospray stability. Methods developed for CE/UV analysis of drugs and peptides were considered and modified to be sui table for a CE/MS system with a robust sheathless interface. Different conc entrations of the organic modifiers acetonitrile, methanol and 2-propanol w ere used in the separation buffer. The type and concentrations of these mod ifiers were also compared with reference to electrospray stability, sensiti vity and time of analysis. In addition, different ionic strengths in the bu ffers were evaluated with reference to electrospray stability, The repeatab ility was used for the estimation of electrospray stability. The degree to which these parameters influenced the separation and the ESI stability was studied using a nine-peptide standard mixture and the antibiotic drugs baca mpicillin and ampicillin as test substances. The analysis time and resoluti on were used as measures of the efficiency of the separation. A time-of-fli ght MS analyzer was used since it has the potential advantages of becoming a better fit for integration of CE with MS owing to the speed and sensitivi ty of this mass analyzer. The detection limit, i.e. 1 mu M, for bacampicill in was comparable to what could be achieved with CE/MS on a quadrupole inst rument using selected ion monitoring and sheath flow ESI, Copyright (C) 200 0 John Wiley & Sons, Ltd.