has proper continuant part at some time orthogonal-acceleration ion source orthogonal-acceleration time-of-flight mass spectrometer oaTOF mass spectrometer A mass spectrometer which uses a time-of-flight mass-to-charge analyser to separate ions. Ions introduced into the mass analyzer are accelerated along the axis perpendicular to their initial direction of motion. CHMO:0000962 oa-TOF-MS oaTOF-MS oa-TOF MS oaTOF MS mass spectrometer