A MALDI sample preparation method suitable for insoluble polymers

Polyamides are insoluble or poorly soluble in common organic solvents, which makes normal sample preparation for matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry very difficult. An new analytical protocol for MALDI analysis of polyamides or other insoluble samples is described. It consists of pressing a pellet from a solid mixture of the polymer and a matrix, both in the form of finely ground powder. This sample preparation is compared with the common dried droplet sample preparation method and found to perform much better, both in terms of robustness against variation of experimental parameters and high-mass capability.