Tandem ion mobility spectrometer

1. A method for analyzing ions comprising:

providing ions from an ion source to a first ion mobility analyzer,

separating the ions according to mobility in the first ion mobility analyzer;

selecting precursor ions of at least one limited mobility range;

fragmenting the selected precursor ions into fragment ions;

trapping the fragment ions in a second ion mobility analyzer, wherein the second ion mobility analyzer is a trapped ion mobility spectrometry (TIMS) analyzer;

separating the fragment ions according to mobility in the second ion mobility analyzer; and

detecting the separated fragment ions.

2. The method according to claim 1 , wherein steps of separating in the first ion mobility analyzer, selecting and fragmenting are repeated while the second ion mobility analyzer is operated to accumulate the repeatedly fragmented ions prior to separating them according to mobility.

3. The method according to claim 1 , wherein the selected ions are fragmented between the first and the second ion mobility analyzer.

4. The method according to claim 3 , wherein the selected ions are fragmented by collision induced dissociation which results from accelerating the selected ions in or into a gas filled region by applying electric DC potentials to at least two annular electrodes which are located between the first and the second ion mobility analyzer.

5. The method according to claim 1 , wherein the selected ions are fragmented inside the second ion mobility analyzer.

6. The method according to claim 5 , wherein the selected ions are pushed by a gas flow against a rising edge of an electric DC field barrier of the second ion mobility analyzer and photons are introduced at the rising edge for inducing photo-dissociation of the selected ions in the second ion mobility analyzer.

7. The method according to claim 5 , wherein the selected ions are pushed by a gas flow against a rising edge of an electric DC field barrier of the second ion mobility analyzer and ETD reactant ions or highly excited or radical neutral particles are introduced upstream of the rising edge for inducing electron transfer dissociation of the selected ions in the second ion mobility analyzer or fragmentation of the selected ions by reactions with the highly excited or radical neutrals in the second ion mobility analyzer.

8. The method according to claim 1 , wherein the ions are separated according to mobility in time in the first ion mobility analyzer and the ions of the limited mobility range are selected by adjusting the transmission of an ion gate which is located between the first and the second ion mobility analyzer.

9. The method according to claim 1 , wherein the ions are trapped and separated according to mobility in space in the first ion mobility analyzer, said first ion mobility analyzer being a trapped ion mobility spectrometry (TIMS) analyzer, and the ions of the limited mobility range is selected by adjusting an instrumental parameter of the first ion mobility analyzer or by changing the mobility of ions of the limited mobility range such that the ions of the limited mobility range leave the first ion mobility analyzer while other trapped ions stay trapped in the first ion mobility analyzer.

10. The method according to claim 1 , wherein the trapping time of the selected ions prior to fragmentation is varied in subsequent measurements in order to determine the mobility of fragment ions as a function of time.

11. The method according to claim 1 , wherein the selected ions are activated prior to the fragmentation and/or the fragment ions are activated prior to the separation in the second mobility analyzer.

12. The method according to claim 11 , wherein activation energy introduced into the selected ions and/or fragment ions is varied in order to determine the mobility of the fragment ions as a function of the activation energy.

13. The method according to claim 1 , wherein the fragment ions are further analyzed by acquiring mass spectra or acquiring fragment mass spectra.

14. A method for analyzing ions comprising:

providing ions from an ion source to a first ion mobility analyzer,

separating the ions according to mobility in the first ion mobility analyzer;

selecting ions of a limited mobility range;

activating or reacting the selected ions;

trapping the activated or reacted ions in a second ion mobility analyzer wherein the second ion mobility analyzer is a trapped ion mobility spectrometry (TIMS) analyzer;

separating the trapped ions according to mobility in the second ion mobility analyzer; and

detecting the separated ions.

15. The method according to claim 14 , wherein selected ions can be activated or reacted between the first and the second ion mobility analyzer or inside the second ion mobility analyzer while they are trapped.

16. The method according to claim 15 , wherein the activation energy introduced into the selected ions is be varied in subsequent measurements in order to determine the mobility of the activated ions as a function of the activation energy.

17. The method according to claim 14 , wherein the trapping time of the activated or reacted ions prior to their separation according to mobility is varied in subsequent measurements in order to determine the mobility of activated or reactant as a function of time.

18. An ion mobility spectrometer comprising an ion source, a first ion mobility analyzer, a second ion mobility analyzer located downstream of the first ion mobility analyzer, a fragmentation cell or reaction cell, which is located between the first and the second ion mobility analyzer or is part of the second ion mobility analyzer, and an ion detector wherein the second ion mobility analyzer is a trapped ion mobility spectrometry (TIMS) analyzer.

19. The ion mobility spectrometer according to claim 18 , wherein the activation cell comprises means for radiative heating, like an infrared laser or an infrared laser diode, or means for generating dipolar or rotational acting electric AC fields.

20. The ion mobility spectrometer according to claim 18 , wherein the fragmentation cell or the activation cell comprises an infrared light source and at least one optical element for focusing the emitted light along the axis or at one or more specific positions inside the trapping region of the second ion mobility analyzer.

21. The ion mobility spectrometer according to claim 18 , further comprising an ion gate located between the first and the second ion mobility analyzer and a DC generator connected to the ion gate for supplying transient electric DC potentials to the ion gate.