9‐Aminoacridine as a matrix for negative mode matrix‐assisted laser desorption/ionization

Abstract 9‐Aminoacridine (9AA) is introduced as a matrix for negative mode matrix‐assisted laser desorption/ionization (MALDI). While most traditional MALDI matrices have been acidic in character, 9AA is a moderately strong base. The mechanism by which 9AA brings about ionization in the negative mode appears to involve abstraction of a labile proton in an acid/base reaction. Most MALDI matrices readily donate protons; 9AA readily accepts them leading to the formation of [M − H] − species. 9AA was first examined as a matrix for low molecular weight compounds having acidic protons, such as phenols, carboxylic acids, sulfonates, amines and alcohols. Also studied were larger molecules frequently analyzed by MALDI including oligonucleotides, oligoamides and proteins. Spectra obtained from 9AA were compared with those recorded using more traditional matrices such as 2,5‐dihydroxybenzoic acid (DHB) and α‐cyano‐4‐hydroxycinnamic acid (α‐CHCA).