Researchers in the Netherlands have shown how the detection efficiency of large molecules can be increased by incorporating an active pixel detector into a MALDI-TOF (matrix-assisted laser desorption/ionization-time of flight) mass spectrometer. Ron Heeren and his team, Foundation for Fundamental Research on Matter (FOM) Institute for Atomic and Molecular Physics (AMOLF), realized that when a standard microchannel plate (MCP) is used, the ion-to-electron conversion efficiency decreases with decreasing ion momentum, that is, when the ions have a higher mass. Thus, high-mass ions may not even be detected.
The team solved the problem by replacing the standard spectra obtained by using an MCP with an analog-to-digital converter with a Timepix detector that consists of a 512 × 512 detector array and is operated in time-of-flight mode. This modification gives spectra that have a 30-fold improvement in signal-to-noise ratios, and enhanced detection of low-abundance ions, as demonstrated from the spectra of selected proteins. Key to this approach is that the charge required to record an event is above the intrinsic electronic noise of the system, so every ion that arrives produces a real signal, and also that the multiple ions can be simultaneously recorded if they arrive at different areas of the detector. One significant advantage of this technique is that it can also record the spatial distribution of ions, and may thus give insights into dynamic chemical phenomena.
- Enhanced Detection of High-Mass Proteins by Using an Active Pixel Detector,
Shane R. Ellis, Julia H. Jungmann, Donald F. Smith, Jens Soltwisch, Ron M. A. Heeren,
Angew. Chem. Int. Ed. 2013.