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

• Published in: Journal of the American Society for Mass Spectrometry 2009-08, Vol.20 (8), p.1451-1463
• Main Authors: Strupat, Kerstin, Kovtoun, Viatcheslav, Bui, Huy, Viner, Rosa, Stafford, George, Horning, Stevan
• Format: Article
• Language: English
• Subjects: Accuracy; Analytical biochemistry: general aspects, technics, instrumentation; Analytical Chemistry; Analytical, structural and metabolic biochemistry; Bioinformatics; Biological and medical sciences; Biotechnology; Calibration; Chemistry; Chemistry and Materials Science; Cinnamic acid; Exact sciences and technology; Focus: The Orbitrap; Fundamental and applied biological sciences. Psychology; Ions; Mass spectrometry; Organic Chemistry; Peptides; Proteomics; Spectrometric and optical methods; Stability analysis
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/j.jasms.2009.04.013

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 α-cyano-4-hydroxy cinnamic acid (CHCA) matrix. A MALDI source is combined with an ion trap-Orbitrap hybrid analyzer via a collisional cooling interface. The interface is shown here; MALDI-produced ions are collected in the shown quadupole q00 according to a previously measured prescan (AGC). Both, AGC scan and analytical scan derive from the identical spot location; for the analytical scan an ion package meeting the AGC criteria is sent to the ion trap or Orbitrap mass analyzer.