Complexity of polymer structures has increased in order to tailor desirable properties and functions for ever more demanding applications. However, this increased complexity also results in more challenging structural analysis. The introduction of mobility separation prior to mass spectrometric analysis facilitates the analysis of more complex polymer systems. DMA/MS solutions from SEADM (including the Mobility Front End) have the ability to extend the dynamic range and separate isomeric compositions and therefore has an advantage over many high-resolution mass spectrometers. Ion sources such as ESI can be combined with DMA/MS to detect more even complex chemistries such as copolymers.
With SEADM Mobility Front End, it is possible to obtain detailed endgroup information, and discrimination of molecules with same nominal masses without the time-consuming LC technique. A further benefit associated with the DMA is the possible combination with a solvent-free sample preparation, since DMA is a solvent-free gas-phase separation.
Two-dimensional plot of ion abundance (color scale) as a function of mass/charge (y axis) and DMA voltage (x axis).
Furthermore, fast 2D discovery mode is possible with TOF and Trap spectrometers. In this mode, a complete mass-mobility 2D plot (see figure on the right) can be obtained in a few minutes.
As an example, the University of Yale has applied the DMA/MS approach using Mobility Front End for the characterization of Polyethilene Glycol (PEG) reaching masses of 100 kDa and charge states up to z = 10. The results were supported by molecular dynamics simulations and approximate calculations of electrical mobilities for computed structures (see Figure below).
Left: Ion abundance (color scale) versus inverse mobility (x axis) and m/z for PEG electrosprayed in 10 mM Me2AF water/methanol (50/50 v). Right: MD simulations comparable to the schemes of Figure on the left are included for several lengths of z = 4