p-nitroaniline/glycerol:: a binary liquid matrix for matrix-assisted laser desorption/ionization analysis

Liquid matrices for matrix-assisted laser desorption/ionization (MALDI) analysis offer advantages over solid matrices including increased shot-to-shot reproducibility and the ability to provide conditions more suitable for the retention of non-covalent complexes, Unfortunately, most of the liquid matrices available do not absorb at UV wavelengths. A second component to increase chromophoric absorption and to permit control over the chemical properties of the matrix can aid in overcoming some of the limitations currently faced by the MALDI technique. In the work reported here, a binary matrix that combines the advantages of the fluidity and low vapor pressure of glycerol with the weak basicity and chromophoric properties of p-nitroaniline is evaluated. Both positive-ion and negative-ion spectra are obtained for proteins, carbohydrates and oligonucleotides, The potential for analysis of chelates and noncovalent interactions using this liquid binary matrix is also explored.