New results on matrix-assisted laser desorption/ionization mass spectrometry of widely polydisperse hydrosoluble polymers

Polyvinylpyrrolidone (PVP) of molecular weight (Mw) 40 000 and 160 000 and polydispersity of 1.8-2.2 was shown to yield matrix-assisted laser desorption/ionization (MALDI) mass spectra with the correct molar mass distribution of the polymer. This is a unique behavior among widely polydisperse samples and was ascribed to the capacity of PVP to complex the MALDI matrix. This result prompted us to test a new sample preparation technique consisting of flash-freezing followed by freeze-drying of the solution of the polymer with the matrix. In this paper we describe our preliminary results on MALDI-MS of polydisperse polymers obtained by this technique. This sample preparation method allowed us to obtain, for the first time, spectra yielding the true molecular weight distribution of polydisperse samples such as dextran, lichenan, nigeran, and poly(ethylene oxide).