The disclosure features mass spectrometry systems and methods that include an ion source, an ion trap, a detector subsystem featuring first and second detector elements, and a controller electrically connected to the ion source, the ion trap, and the detector subsystem and configured so that during operation of the system, the controller: applies an electrical signal to the ion source to generate positively and negatively charged particles from sample particles in the system; applies an electrical signal to the ion trap to eject a plurality of particles from the ion trap through a common aperture of the ion trap, and determines information about the sample particles based on first and second electrical signals generated by the ejected particles.