Mass-correlated pulsed extraction: theoretical analysis and implementation with a linear matrix-assisted laser desorption/ionization time of flight mass spectrometer.

The pulsed extraction (PE) of ions produced by matrix-assisted laser desorption/ionization in time-of-flight mass spectrometers greatly improves mass resolution but, unfortunately, this method is mass dependent. Here we report an approach to expand the capabilities of the PE method so as to provide uniform focusing conditions over a wide mass range. Along with an extraction pulse, an additional pulse is applied to correct the mass dependency of the standard PE method. We describe the algorithm for derivation of this correction pulse waveform, where the first-order focusing conditions are valid all along the mass region of interest. Experimental verification of this method for correction of ion velocities demonstrated better mass resolution than standard PE over a wide mass range.