OFF-LINE COUPLING OF CAPILLARY ELECTROPHORESIS AND MATRIX-ASSISTED LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY

An automated fraction collection interface is used in conjunction with matrix-assisted laser desorption/ionization (MALDI) time-of-flight ma ss spectrometry to analyze material isolated by capillary electrophore sis (CE), CE fractions are deposited directly on the MALDI probes so t hat individual peaks from the electropherogram are associated with a s ingle sample spot on the probe. MALDI matrices with high acid concentr ations afford enhanced tolerance of electrophoresis buffers. The utili ty of this hybrid instrument is demonstrated by separation and mass an alysis of a tryptic digest of cytochrome c and synthetic mixtures of f our proteins. Mass assignments corresponding to the protonated molecul ar ions are in good agreement with those predicted from molecular stru cture. Miniaturization of the interface affords enhanced sensitivity, with good-quality spectra from separations of as little as 25 fmol of protein.