Method of separating ions

An ion mobility spectrometer or separation device comprising:

• an ion mobility separator comprising a first region arranged and adapted to accumulate consecutive populations of ions, and a second region downstream of said first region;
• and
• a control system arranged and adapted:
• (i) to accumulate a first population of ions in said first region of said ion mobility separator;
• (ii) to separate said first population of ions according to their ion mobility in said first region of said ion mobility separator;
• and
• (iii) to accumulate a second population of ions in said first region of said ion mobility separator whilst said first population of ions are being separated according to their ion mobility in said ion mobility separator,
• wherein, in step (ii), said control system is arranged and adapted to separate said first population of ions according to their ion mobility in said first and second regions of said ion mobility separator;
• wherein said first region of said ion mobility separator switches between a trapping mode, in which the first region is configured such that ions are substantially trapped within said first region and not caused to separate according to their ion mobility, and an ion mobility separation mode, in which the first region is configured such that ions are separated according to their ion mobility within said first region.

A method of separating ions in a device, wherein the device comprises a first region, an accumulation region upstream of the first region and a second region downstream of the first region, wherein said first region, said second region, and said accumulation region comprise RF-confined regions, and the method comprises the steps of:

• (i) driving a first population of ions through the first and second regions so as to separate a first population of ions according to their ion mobility, whilst accumulating a second population of ions in the accumulation region;
• (ii) after the first population of ions has exited the first region, but prior to the first population of ions exiting the second region, transferring the second population of ions into the first region and trapping the second population of ions within the first region without causing the second population of ions to separate according to their ion mobility;
• and then
• (iii) driving the second population of ions through the first and second regions so as to separate the second population of ions according to their ion mobility, whilst accumulating a third population of ions in the accumulation region;
• (iv) repeating steps (ii) and (iii) for the third and further populations of ions so as to successively separate the third and further populations of ions;
• and
• wherein said first region of said ion mobility separator switches between a trapping mode, in which the first region is configured such that ions are substantially trapped within said first region and not caused to separate according to their ion mobility, and an ion mobility separation mode, in which the first region is configured such that ions are separated according to their ion mobility within said first region.