MALDI Produced Ions Inspected with a Linear Ion Trap-Orbitrap Hybrid Mass Analyzer

A MALDI source is interfaced to a modified LTQ Orbitrap XL instrument. This work gives insight into the MALDI Source design and shows results obtained with the MALDI source coupled to an accurate mass, high-resolution hybrid mass spectrometer. MALDI-produced ions and fragment ions thereof produced in the mass spectrometer may be analyzed and detected by the Orbitrap analyzer at a maximum mass resolution of 100,000 (FWHM) at m/z 400 with high mass accuracy. An accuracy of <= 2 ppm is achieved by internal mass calibration using lock mass functionality; using external mass calibration, an accuracy of <= 3 ppm is routinely obtained. External mass calibration of the hybrid mass spectrometer is performed using a standard calibration mixture of different peptides and matrix components. The instrumental capabilities are demonstrated for analytical methodologies Such as Protein ID using Peptide Mass Fingerprint (PMF) and MS/MS analyses of small molecule samples. Stability of mass accuracy and signal-to-noise ratio for low samples loads (on plates) are demonstrated as well as the experimental dynamic range using alpha-cyano-4-hydroxy cinnamic acid (CHCA) matrix. (J Am Soc Mass Spectrom 2009, 20, 1451-1463) (C) 2009 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry