MS imaging for visualizing synthetic polymers using average MW and p as indices - MSTips 305
Matrix assisted laser desorption/ionization (MALDI) mass spectrometry is a powerful tool for the analysis of synthetic polymers. This technique, when combined with a high-resolution time-of-flight mass spectrometer, can be used to identify differences in monomer, polymer end groups, and their molecular weight distributions. The molecular weight distribution is often expressed as number average molecular weight (Mn), weight average molecular weight (Mw), and dispersity (D). More recently, MALDI mass spectrometry imaging (MALDI-MSI) has been used to visualize the locations of compounds on sample surfaces. The MALDI-MSI raw data includes the position information (X and Y) as well as the mass spectral information (m/z and intensity) for each position. A target compound peak can then be specified to calculate the ion intensity for each pixel in order to draw a mass image. MALDI-MSI has been widely used to show the localization of proteins, peptides, lipids, and drugs on frozen tissue sections. However, this technique has not been widely used for polymer analysis. One reason for this is that polymers have molecular weight distributions which means that mass images based on specific degrees of polymerization (specific m/z value typically used by conventional methods) do not necessarily express a clear picture for the full polymer localization. In this report, we investigate a MSI visualization method for synthetic polymers that uses Mn, Mw and D as indices for visualization.