Parameterising matrix-assisted laser desorption / ionization (MALDI): Effect of solvents and co-additives on analyte peak intensities

Eur. J. Mass Spectrom. 10, 487–493 (2004)
DOI: 10.1255/ejms.645

Parameterising matrix-assisted laser desorption / ionization (MALDI): Effect of solvents and co-additives on analyte peak intensities

S. Bashir,^a,c* R. Mutter^b,d and P.J. Derrick^a
^aInstitute of Mass Spectrometry and Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
^bDepartment of Chemistry, University of Warwick, Coventry CV4 7AL, UK

ABSTRACT:

The peak intensities obtained when 2,5- dihydroxybenzoic acid (DHB) was used as a ‘classic’ matrix were measured using substance P (SP) and betacyclodextrin (BCD) as analytes. Enhancements in peak intensities were observed going from 1:1 MeOH/H₂O to dimethylforamide (DMF) as matrix solvents. Also non-covalent interactions between SP and solvent and DHB were observed suggesting close interactions between matrix, solvent and analyte in the gas-phase. Peak enhancements were previously reported with ‘superDHB’ (DHB and 2- hydroxy-5-methoxybenzoic acid at 10% v/v). Co-addition of structural analogues and their respective absorption coefficients were determined. It was found that other analogues used as co-matrices could give analyte peak enhancement similar to reported for sDHB with the additional benefit that some analogues could act as matrices with DHB addition. No direct correlation was observed between absorption coefficient and the ability of the molecule to act as a ‘good’ UV MALDI matrix.

Keywords: MALDI, MALDI-TOF, matrix, co-additives, matrix intermediate, solvents, radicals, excited state, gas-phase, absorbance

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