Aerosol Matrix-Assisted Laser Desorption Ionization: Effects of Analyte Concentration and Matrix-to-Analyte Ratio

We have recently developed an aerosol-liquid introduction interface for matrix-assisted laser desorption ionization (MALDI) mass spectrometry. In this study, we examine the effect of matrix-to-analyte ratio and analyte concentration on analyte ion yield. These studies were performed using bradykinin, gramicidin S, bovine insulin, and myoglobin as analytes and α-cyano-4-hydroxycinnamic acid and 4-nitroaniline as matrices. The optimum matrix-to-analyte molar ratio for aerosol MALDI was determined to be 10-100:1, which is lower than that typically used for conventional surface MALDI (10010 000:1). The ion yield was found to be a nonlinear function of analyte concentration. Possible explanations for these observations are discussed.