MALDI mass spectrometry of biomolecules and synthetic polymers using alkali hexacyanoferrate (II) complexes and glycerol as matrix

Abstract

K 4[Fe(CN) 6]/glycerol and Na 4[Fe(CN) 6]/glycerol have been investigated as liquid matrix systems for UV-MALDI MS applying a N 2 laser. Analyte molecules were detected as sodium or potassium adduct ions and, in the case of proteins, as well as protonated molecular ions. Mass accuracies were comparable to those found with standard solid matrix systems with −0.06 to +0.05% deviation in the reflectron mode and with −0.24 to +0.13% in the linear mode. Useful results could be obtained within a mass range of 15 000 Da for single-charged proteins and 8000 Da for potassium cationized polyethylene glycols. Detection limits were found for hydrophilic compounds in the low picomol range and for lipophilic compounds as triacylglycerols or peracetylated and partially benzylated carbohydrates in the low femtomol range. As shown by scanning electron microscopic investigations, the generation of a thin homogenous matrix layer was essential for a successful mass spectrometric experiment. A very careful cleaning of the target surface with glacial acid prior to matrix deposition improved the formation of such a matrix film that maximum sensitivity as well as good reproducibility of the experiments could be achieved.