MALDI post-source decay and LIFT-TOF/TOF investigation of alpha-cyano-4-hydroxycinnamic acid cluster interferences.
Large signals from alpha-cyano-4-hydroxycinnamic acid (CHCA) matrix complexes with sodium and potassium ions were found to interfere with sensitive matrix-assisted laser desorption/ionization (MALDI) analysis of a hydrochloric acid digest of gelatine preparations. The nature of some selected matrix clusters was investigated by conventional post-source decay and LIFT-TOF/TOF experiments. The matrix clusters fragmented readily by neutral evaporation to give smaller sized matrix cluster species without matrix disintegration. Their characterization distinguished them from peptide signals, in particular from those that had the same nominal mass and differed only in the fractional part of the mass as encountered for gelatine-derived peptides. Knowledge of the molecular composition of these cluster species allowed using them for internal calibration of the MALDI mass spectra. The hydrolytic peptides could be analyzed with increased sensitivity when using 2,5-dihydroxy benzoic acid (DHB) as the MALDI matrix.
Neubert
Hendrik
H
Drug Control Centre, King's College London, London, United Kingdom. hendrik.neubert@kcl.ac.uk
Halket
John M
JM
Fernandez Ocaña
Mireia
M
Patel
Raj K P
RK
D000818:Animals; D003373:Coumaric Acids / Q000032:analysis* / Q000737:chemistry*; D005780:Gelatin; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013552:Swine
D003373:Coumaric Acids; C007175:alpha-cyano-4-hydroxycinnamate; D005780:Gelatin