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Improved PSD and CID on a MALDI TOFMS
Andrew J Hoteling1, Kevin G Owens
1Imaging Materials and Media, R&D, Eastman Kodak Company, Rochester, New York, USA.
Journal of the American Society for Mass Spectrometry
|March 30, 2004
Summary
Optimizing instrument parameters significantly improved mass accuracy and resolution in matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) post-source decay (PSD) and collision-induced dissociation (CID) experiments, enabling more reliable peptide and polymer analysis.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Spectroscopy
Background:
- Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry is a powerful technique for analyzing biomolecules and polymers.
- Post-source decay (PSD) and collision-induced dissociation (CID) are crucial for obtaining structural information from precursor ions.
- Optimizing instrument parameters is essential for achieving high resolution and mass accuracy in these experiments.
Purpose of the Study:
- To investigate the impact of instrument-operating parameters on product-ion resolution and mass accuracy in MALDI-TOF PSD and CID experiments.
- To identify and optimize critical parameters for enhanced performance.
- To demonstrate the improved capabilities for analyzing peptides and synthetic polymers.
Main Methods:
- Systematic variation of instrument voltages, precursor-ion selection, and segment mass range settings.
- Analysis of product-ion spectra from peptides (Substance P, bradykinin, angiotensin I, angiotensin II) and synthetic polymers (poly(methyl methacrylate), polystyrene).
- Evaluation of mass resolution (M/ΔM) and absolute mass error (Da).
Main Results:
- Optimization of reflectron voltages for PSD and CID improved spectral resolution.
- Mass resolution up to 2500 (M/ΔM FWHM) was achieved.
- Precursor-ion selection and mass range settings significantly influenced product-ion mass accuracy.
- Average absolute error below 0.1 Da was demonstrated for various test materials.
- Coincidence peaks in the precursor-ion selection window were identified as a common issue.
Conclusions:
- Instrument parameter optimization is critical for enhancing resolution and mass accuracy in MALDI-TOF PSD/CID.
- Improved parameters enable more reliable structural elucidation of peptides and polymers.
- Poly(ethylene glycol) (PEG) can be effectively used as a mass calibrant for PSD/CID spectra.
- The optimized method extends the applicability of MALDI-TOF PSD/CID for precise mass measurements.