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Artefacts in fast atom bombardment mass spectrometry
748
ABSTRACTS
nides and glutathione conjugates were obtained. Examples, including an underivatized pentapeptide, a glycine conjugate, an N-hydroxymethyl metabolite and the differentiation between a 7-hydroxy acid and the corresponding lactone, are presented.
N-Formyl-2-aminoethanol as a matrix for fast atom bombardment of non-polar biomolecules for mass spectrometry L. TIP, C. VERSLUIS, J. W. D A L L I N G A and W. H E E R M A * Laboratory q/'Analytical Chemistry, University of Utrecht, Croesestraat 77A, 3522 AD Utrecht (The Netherlands) ABSTRACT N-Formyl-2-aminoethanol (FAE) appears to be a very suitable matrix for the fast atom b o m b a r d m e n t (FAB) mass spectrometry of many (bio)organic molecules. Its positive- and negative-ion FAB spectra show the protonated and deprotonated molecule as the base peak (m/z 90 and m/z 88 respectively) together with a series of molecular cluster ions with decreasing abundances at successive odd and even mass numbers due to the nitrogen atom in the molecule. The most important fragment ions of the matrix correspond to the losses of H 2 0 and CO. The advantages of this matrix are: (1) the low evaporation rate due to its low vapour pressure; (2) the good dissolving properties for polar and non-polar compounds and co-solvents; (3) the excellent signal responses of compounds with a limited polarity; and (4) the good analyte-to-matrix ratio. The chemical stability of FAE appears to be good with respect to neutral and basic compounds. The presence of acids seems to catalyse the decomposition of FAE into aminoethanol, which easily forms an adduct ion with the protonated molecule of the analyte. Very good results using the matrix have been obtained by us with c o m p o u n d s having a decreased hydrophilic character. These include (per)methylated oligosaccharides and peptides containing relatively many amino acids with non-polar side-chains. The positive- and negative-ion FAB mass spectra of these compounds show abundant [M + H] +, [M - H] and sequence ions, while the ions resulting from the matrix do not dominate.
Artefacts in fast atom bombardment mass spectrometry II. Aggregate ions involving hydrochloric acid and diethanolamine J. R. J O C E L Y N PARI~
Environment Canada, R.R.E.T.C., Ottawa, Ontario KIA OH3 (Canada) PIERRE LAFONTAINE
Agriculture Canada, P.R.C., Ottawa, Ontario K1A 0C6 (Canada) and J A C Q U E L I N E M. R. BI~LANGER
Indust 0, Science and Technology Canada, Science Sector, Ottawa, Ontario KIA OH5 (Canada) ABSTRACT Hydrochloric acid was used as a doping agent on a diethanolamine (DEA) support matrix. The spectra exhibit several undesirable artefact peaks resulting from the protonation of D E A itself and from the aggregation products between D E A and HCI. A major series of ions are observed at m/z values corresponding to [nDEA + (n - 1)HCI + H] +. No stoichiometric adducts are recorded. They arise strictly from the stepwise addition o f D E A HC1 aggregates to a protonated D E A ion and to the so-formed adduct ions. Although these aggregates complicate the interpretation of the spectra, they are informative in the search for a general theory on the ionization processes in fast atom b o m b a r d m e n t mass spectrometry.
ABSTRACTS
nides and glutathione conjugates were obtained. Examples, including an underivatized pentapeptide, a glycine conjugate, an N-hydroxymethyl metabolite and the differentiation between a 7-hydroxy acid and the corresponding lactone, are presented.
N-Formyl-2-aminoethanol as a matrix for fast atom bombardment of non-polar biomolecules for mass spectrometry L. TIP, C. VERSLUIS, J. W. D A L L I N G A and W. H E E R M A * Laboratory q/'Analytical Chemistry, University of Utrecht, Croesestraat 77A, 3522 AD Utrecht (The Netherlands) ABSTRACT N-Formyl-2-aminoethanol (FAE) appears to be a very suitable matrix for the fast atom b o m b a r d m e n t (FAB) mass spectrometry of many (bio)organic molecules. Its positive- and negative-ion FAB spectra show the protonated and deprotonated molecule as the base peak (m/z 90 and m/z 88 respectively) together with a series of molecular cluster ions with decreasing abundances at successive odd and even mass numbers due to the nitrogen atom in the molecule. The most important fragment ions of the matrix correspond to the losses of H 2 0 and CO. The advantages of this matrix are: (1) the low evaporation rate due to its low vapour pressure; (2) the good dissolving properties for polar and non-polar compounds and co-solvents; (3) the excellent signal responses of compounds with a limited polarity; and (4) the good analyte-to-matrix ratio. The chemical stability of FAE appears to be good with respect to neutral and basic compounds. The presence of acids seems to catalyse the decomposition of FAE into aminoethanol, which easily forms an adduct ion with the protonated molecule of the analyte. Very good results using the matrix have been obtained by us with c o m p o u n d s having a decreased hydrophilic character. These include (per)methylated oligosaccharides and peptides containing relatively many amino acids with non-polar side-chains. The positive- and negative-ion FAB mass spectra of these compounds show abundant [M + H] +, [M - H] and sequence ions, while the ions resulting from the matrix do not dominate.
Artefacts in fast atom bombardment mass spectrometry II. Aggregate ions involving hydrochloric acid and diethanolamine J. R. J O C E L Y N PARI~
Environment Canada, R.R.E.T.C., Ottawa, Ontario KIA OH3 (Canada) PIERRE LAFONTAINE
Agriculture Canada, P.R.C., Ottawa, Ontario K1A 0C6 (Canada) and J A C Q U E L I N E M. R. BI~LANGER
Indust 0, Science and Technology Canada, Science Sector, Ottawa, Ontario KIA OH5 (Canada) ABSTRACT Hydrochloric acid was used as a doping agent on a diethanolamine (DEA) support matrix. The spectra exhibit several undesirable artefact peaks resulting from the protonation of D E A itself and from the aggregation products between D E A and HCI. A major series of ions are observed at m/z values corresponding to [nDEA + (n - 1)HCI + H] +. No stoichiometric adducts are recorded. They arise strictly from the stepwise addition o f D E A HC1 aggregates to a protonated D E A ion and to the so-formed adduct ions. Although these aggregates complicate the interpretation of the spectra, they are informative in the search for a general theory on the ionization processes in fast atom b o m b a r d m e n t mass spectrometry.