Protein analysis by packed capillary liquid chromatography with electrospray ionization and time-of-flight mass...

Packed capillary liquid chromatography (LC) has been interfaced on-line to electrospray (ES) ionization with time-of-flight (TOF) mass spectrometry (MS) detection for the separation and identification of standard proteins. Using this system, as little as 2.5 fmol of cytochrome c could be detected with a 0.1 mm I.D. column. The effect of column size on sensitivity has been investigated using various column diameters and a sensitivity increase of 428-fold has been observed between the 0.10- and 2.1 mm I.D. columns. Although the TOF-MS can ultimately record data at up to 100 mass spectra/s, the peak widths for these particular separations require only 1 spectra/s. Finally, the sensitivity obtained is a function of both the reduced diameter LC column and the high ion duty cycle of the TOF-MS.