Optimised ion mobility separation timescales for targeted ions

1. An analytical device for analysing ions comprising:

a separator for separating ions according to a physico-chemical property;

an interface, transfer device or region comprising one or more ion guides, each ion guide comprising a plurality of electrodes;

and

a control system arranged and adapted:

(i) to maintain a first DC voltage or potential gradient along said one or more ion guides so as to cause a first group of ions which emerges from said separator to be transmitted through said interface, transfer device or region with a first transit time t1; and

(ii) to subsequently maintain a second DC voltage or potential gradient along said one or more ion guides so as to cause a second group of ions which subsequently emerges from said separator to be transmitted through said interface, transfer device or region with a second different transit time t2, wherein t2>t1.

2. An analytical device as claimed in claim 1 , wherein said physico-chemical property comprises ion mobility.

3. An analytical device as claimed in claim 1 , wherein said separator comprises an ion mobility separator or a differential ion mobility separator.

4. An analytical device as claimed in claim 1 , wherein said physico-chemical property comprises mass or mass to charge ratio.

5. An analytical device as claimed in claim 1 , comprising a quadrupole rod set mass to charge ratio filter arranged downstream of said interface, transfer device or region.

6. An analytical device as claimed in claim 5 , wherein said control system is further arranged and adjusted:

(i) to cause said mass to charge ratio filter to transmit ions having mass to charge ratios within a first mass or mass to charge ratio range; and then

(ii) to cause said mass to charge ratio filter to transmit ions having mass to charge ratios within a second different mass or mass to charge ratio range.

7. An analytical device as claimed in claim 6 , wherein the mass to charge ratio filter is configured to switch between transmitting ions in the first group of ions and subsequently transmitting ions in the second group of ions, wherein the second transit time t2 is increased relative to the first transit time t1 so that the second group of ions arrive at the mass to charge ratio filter after the mass to charge ratio filter has switched such that the ions in the second group are transmitted by the mass to charge ratio filter.

8. An analytical device as claimed in claim 1 , wherein said second DC voltage or potential gradient is less than said first DC voltage or potential gradient.

9. An analytical device as claimed in claim 1 , wherein said control system is arranged and adapted to transmit said first group of ions which emerges from said separator through said interface, transfer device or region with a first transit time t1 and to transmit said second group of ions which subsequently emerges from said separator through said interface, transfer device or region with a second different transit time t2 within or during a single cycle of separation of ions within said separator.

10. A mass spectrometer comprising an analytical device as claimed in claim 1 .

11. An analytical device as claimed in claim 1 , comprising a collision, fragmentation or reaction cell.

12. An analytical device as claimed in claim 1 , comprising a Time of Flight mass analyser.

13. A method of analysing ions comprising:

separating ions according to a physico-chemical property in a separator;

providing an interface, transfer device or region comprising one or more ion guides, each ion guide comprising a plurality of electrodes;

maintaining a first DC voltage or potential gradient along said one or more ion guides so as to cause a first group of ions which emerges from said separator to be transmitted through said interface, transfer device or region with a first transit time t1; and

subsequently maintaining a second DC voltage or potential gradient along said one or more ion guides so as to cause a second group of ions which subsequently emerges from said separator to be transmitted through said interface, transfer device or region with a second different transit time t2, wherein t2>t1.

14. A method as claimed in claim 13 , wherein the steps of transmitting said first group of ions which emerges from said separator through said interface with a first transit time t1 and transmitting said second group of ions which subsequently emerges from said separator through said interface with a second different transit time t2 are performed within or during a single cycle of separation of ions within said separator.

15. A method of mass spectrometry comprising a method as claimed in claim 13 .

16. An analytical device for analysing ions comprising:

a separator for separating ions according to a physico-chemical property;

an interface, transfer device or region comprising one or more ion guides, each ion guide comprising a plurality of electrodes;

a control system arranged and adapted:

(i) to transmit a first group of ions which emerges from said separator through said interface, transfer device or region with a first transit time t1; and

(ii) to transmit a second group of ions which subsequently emerges from said separator through said interface, transfer device or region with a second different transit time t2;

wherein said control system is arranged and adapted to apply one or more transient DC voltages or potentials to said plurality of electrodes so that said first group of ions are translated along said one or more ion guides with a first velocity, and to apply one or more transient DC voltages or potentials to said plurality of electrodes so that said second group of ions are translated along said one or more ion guides with a second different velocity.

17. An analytical device as claimed in claim 16 , wherein said second velocity is slower than said first velocity.

18. An analytical device as claimed in claim 16 , comprising a quadrupole rod set mass or mass to charge ratio filter arranged downstream of said interface.

19. A method of analysing ions comprising:

providing an analytical device as claimed in claim 16 ;

separating ions according to a physico-chemical property in the separator;

transmitting a first group of ions which emerges from said separator through said interface, transfer device or region with a first transit time t1; and

transmitting a second group of ions which subsequently emerges from said separator through said interface, transfer device or region with a second different transit time t2 .