A comparative study of a liquid and a solid matrix in matrix-assisted laser desorption/ionization time-of-flight mass...

We present experimental matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) results comparing a liquid (glycerol/K(4)[Fe(CN)(6)]) and a solid matrix (2,5-dihydroxybenzoic acid, DHB) with respect to analyte signal stability and initial ion velocity. For applications requiring stable production of analyte ions over a long period of time, the liquid matrix is superior to the solid matrix. The stable analyte ion signal obtained from a liquid matrix allowed the measurement of collision cross sections of small poly(ethylene glycol) (PEG(n)) adduct ions in the flight tube with good resolution. The initial velocity of these adduct ions was measured. It was found that analyte molecules from the liquid matrix have initial ion velocities significantly smaller than those from the solid matrix. MALDI-TOF measurements for large molecules using a liquid matrix are therefore likely to result in smaller systematic errors in mass calibrations due to initial ion velocity.