High-resolution mass spectrometry with a multiple pass quadrupole mass analyzer.

The peak shape narrows and the resolution improves if the ions are simply reflected back and forth through a conventional quadrupole mass analyzer. CO(+) and N(2)(+) at m/z = 28 are separated to 50% valley with half of the original signal remaining. These two ions can be resolved to baseline (m/Δm) = 5000 with 1% of the original signal remaining.