Use of 2-Hydroxy-1-naphthoic Acid as a Matrix for Matrix-assisted Laser Desorption/Ionization Mass Spectrometry of Low Molecular Weight Porphyrins and Peptides

Abstract

Use of the matrix-assisted laser desorption/ionization matrix 2-hydroxy-1-naphthoic acid provides a 2–4-fold enhancement of ion signal for low molecular mass porphyrins over other matrices including α-cyano-4-hydroxycinnamic acid, 2-(4-hydroxyphenylazo)benzoic acid, sinapinic acid and 2,5-dihydroxybenzoic acid. Tetraphenyl-, octaethyl-and tetramethoxyphenylporphyrins give strong signals corresponding to [M+H]+ ions and limits of detection between 100 and 500 fmol. Significant fragmentation is observed for the octaethylporphyrins at high laser power and moderate fragmentation is observed for the other classes of porphyrins. The 2-hydroxy-1-naphthoic acid matrix also gives strong signals corresponding to [M+H]+ and/or [M+Na]+ ions for peptides, including methionine enkephalin, bacitracin, bradykinin, renin substrate and insulin.