Method of selecting ions by ion mobility separation and isolation of ions

An analytical instrument comprising:

• a closed-loop ion mobility separator comprising a closed loop ion guide;
• one or more ion traps arranged upstream of the closed-loop ion mobility separator;
• an ion entry/exit device and;
• a control system, configured to cause ions corresponding to a target ion of interest to be selected by:
• causing the ion entry/exit device to inject analyte ions into the closed-loop ion mobility separator and causing the closed-loop ion mobility separator to separate the analyte ions according to their ion mobility;
• causing first ions, of the analyte ions, within a first ion mobility drift time range that corresponds to the target ion of interest to be isolated and causing the ion entry/exit device to eject the first ions to be stored in the one or more ion traps;
• causing the ion entry/exit device to inject the first ions into the closed-loop ion mobility separator and causing the closed-loop ion mobility separator to separate the first ions according to their ion mobility;
• and
• causing second ions, of the first ions, within a second ion mobility drift time range that corresponds to the target ion of interest to be isolated and causing the ion entry/exit device to eject the second ions to be stored in the one or more ion traps.