A DUAL VACUUM CHAMBER FOURIER-TRANSFORM MASS-SPECTROMETER WITH RAPIDLY INTERCHANGEABLE LSIMS, MALDI, AND ESI SOURCES - INITIAL RESULTS WITHLSIMS AND MALDI

A design is presented involving two separate vacuum chambers to provid e nearly simultaneous capabilities of liquid secondary ion mass spectr ometry (LSIMS), matrix-assisted laser desorption/ionization (MALDI), a nd electrospray ionization (ESI) in an external source Fourier transfo rm mass spectrometer. The instrument consists of two vacuum chambers, one with five stages of differential pumping for ESI and another with two stages of differential pumping for a combined LSIMS/MALDI source, The chamber dedicated to ESI was formerly a three-stage chamber with L SIMS and electron ionization. Two additional stages were added with th e ESI source, LSIMS and MALDI have similar vacuum requirements and wer e moved to a newly built chamber with two stages of pumping. We presen t our first results obtained on the new vacuum chamber, Data presented for the MALDI source show that, with only two stages of pumping, and with shorter radio frequency-only quadrupole rods for ion injection, s pectra comparable to those obtained on the formerly three-stage instru ment can be obtained, Characterization of the MALDI source and data on linear, cyclic, and branched oligosaccharides are given, Finally, the design of the second chamber is proposed as a low-cost prototype for an external source FTMS instrument.