Orthogonal injection of matrix-assisted laser desorption/ionization ions into a time-of-flight spectrometer through a collisional damping interface

摘要: Ions are produced from a conventional matrix-assisted laser desorption/ionization (MALDI) target by irradiation with nitrogen pulsed at 20 Hz. After being cooled collisions in an RF-quadrupole ion guide, the ions enter orthogonal-injection TOF mass spectrometer, already used for electrospray. The collisional cooling spreads out along axis of quadrupole to produce quasi-continuous beam, which is then into spectrometer repetition rate about 4 kHz. Approximately five each injection pulse, and these detected using single-ion counting registered TDC 0.5 ns resolution. The performance instrument similar that obtained ESI source. A uniform resolution 5000 (full width half maximum definition) routinely molecular weights up 6000 Da, accuracy around 30 ppm. sensitivity peptides low femtomole range. range currently limited energy (5 keV) detector, although cytochrome C (12 359 Da) have been detected. The competitive delayed-extraction MALDI usual axial geometry, but advantage mass-independent focusing conditions, simple two-point calibration procedure. However, most important advantages result nearly complete decoupling production measurement. In experiment must be carefully adjusted optimum performance, parameters depend on matrix method sample preparation. As decoupling, independent source conditions. This allows much greater flexibility different matrices, substrates (including insulating substrates), wavelengths, pulse widths fluences. Because design also convenient use both sources (and possibly others) same spectrometer. © 1998 John Wiley & Sons, Ltd.