A mass spectrometer is disclosed comprising a first device, a second device and a switch arranged and adapted: (i) to direct ions at a first time T1 to the first device and to substantially prevent ions from entering the second device; and (ii) to direct ions at a second later time T2 to the second device and to substantially prevent ions from entering the first device. At the first time T1 the second device may not be in an operational state to potentially optimally fragment, react, mass filter or otherwise process ions since the second device may be in a process of equilibration, changing state, re-filling, recharging, transition, replenishing, switching voltage or altering an operational parameter. Likewise, at the second time T2 the first device may not be in an operational state to potentially optimally fragment, react, mass filter or otherwise process ions since the first device may be in a process of equilibration, changing state, re-filling, recharging, transition, replenishing, switching voltage or altering an operational parameter.