CONTINUOUS-FLOW MALDI MASS-SPECTROMETRY USING AN ION-TRAP REFLECTION TIME-OF-FLIGHT DETECTOR

A continuous-flow probe has been used to directly introduce solutions of peptides into an ion trap storage/reflectron time-of-flight mass spectrometer for MALDI/MS analysis. The advantages of the trap, including the ability to operate efficiently at the elevated pressures required for direct liquid introduction into the trap, are demonstrated. It is shown that by using low-voltage auxiliary fields applied to the endcaps of the ion trap, the unwanted soh ent and matrix ions can be eliminated by resonance ejection, providing enhanced S/N for target peptide ions. Using this methodology, it is demonstrated that picomole level sensitivity can be routinely achieved with quantitation over 2 orders of magnitude for a mass range of > 5000 units, The conditions required to achieve a stable continuous liquid now and to optimize the liquid MALDI conditions are also discussed.