Time shift for improved ion mobility spectrometry or separation digitisation

1. A method of analysing ions comprising:

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

(ii) transmitting ions which emerge from said separator through a transfer device with a first transit time t1, energising a pusher electrode or orthogonal acceleration electrode and obtaining first data;

(iii) transmitting ions which subsequently emerge from said separator through said transfer device with a second greater transit time t2, energising said pusher electrode or orthogonal acceleration electrode and obtaining second data; and

(iv) repeating steps (ii) and (iii) one or more times;

wherein said method further comprises:

energising said pusher electrode or orthogonal acceleration electrode with a period t3, wherein t2-t1 is arranged to equal t3/n and wherein n=2; and

combining said first and second data to form a composite data set.

2. A method as claimed in claim 1 , wherein said physico-chemical property comprises ion mobility or differential ion mobility.

3. A method as claimed in claim 1 , wherein said physico-chemical property comprises mass or mass to charge ratio.

4. A method of mass spectrometry comprising a method as claimed in claim 1 .

5. An analytical device comprising:

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

a transfer device;

a pusher electrode or orthogonal acceleration electrode;

an analyser; and

a control system arranged and adapted:

(i) to cause ions to separate according to a physico-chemical property in said separator;

(ii) to transmit ions which emerge from said separator through said transfer device with a first transit time t1, to energise said pusher electrode or orthogonal acceleration electrode and to analyse said ions with said analyser to obtain first data;

(iii) to transmit ions which subsequently emerge from said separator through said transfer device with a second greater transit time t2, to energise said pusher electrode or orthogonal acceleration electrode and to analyse said ions with said analyser to obtain second data; and

(iv) to repeat steps (ii) and (iii) one or more times;

wherein said control system is further arranged and adapted:

to energise said pusher electrode or orthogonal acceleration electrode with a period t3, wherein t2-t1 is arranged to equal t3/n and wherein n=2; and

to combine said first and second data to form a composite data set.

6. An analytical device as claimed in claim 5 , wherein said separator comprises an ion mobility spectrometer, a differential ion mobility spectrometer or other separation device.

7. An analytical device as claimed in claim 5 , wherein said separator comprises a device for separating ions according to their mass or mass to charge ratio.

8. An analytical device as claimed in claim 5 , further comprising a device arranged and adapted to pulse ions into said separator.

9. An analytical device as claimed in claim 5 , wherein said analyser comprises an orthogonal acceleration Time of Flight mass analyser having a pusher electrode or an orthogonal acceleration electrode.

10. An analytical device as claimed in claim 9 , wherein said pusher electrode or orthogonal acceleration electrode is energised asynchronously with respect to said separator.

11. A mass spectrometer comprising an analytical device as claimed in claim 5 .

12. A method of analysing ions comprising:

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

(ii) transmitting ions which emerge from said separator through a first ion path with a first transit time t1, energising a pusher electrode or orthogonal acceleration electrode and obtaining first data;

(iii) transmitting ions which subsequently emerge from said separator through a second different ion path with a second greater transit time t2, energising said pusher electrode or orthogonal acceleration electrode and obtaining second data; and

(iv) repeating steps (ii) and (iii) one or more times;

wherein said method further comprises:

energising said pusher electrode or orthogonal acceleration electrode with a period t3, wherein t2-t1 is arranged to equal t3/n and wherein n=2; and

combining said first and second data to form a composite data set.

13. A method of mass spectrometry comprising a method as claimed in claim 12 .

14. An analytical device comprising:

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

a transfer device;

a pusher electrode or orthogonal acceleration electrode;

an analyser; and

a control system arranged and adapted:

(i) to cause ions to separate according to a physico-chemical property in said separator;

(ii) to transmit ions which emerge from said separator through a first ion path through said transfer device with a first transit time t1, to energise said pusher electrode or orthogonal acceleration electrode and to analyse said ions with said analyser to obtain first data;

(iii) to transmit ions which subsequently emerge from said separator through a second different ion path through said transfer device with a second greater transit time t2, to energise said pusher electrode or orthogonal acceleration electrode and to analyse said ions with said analyser to obtain second data; and

(iv) to repeat steps (ii) and (iii) one or more times;

wherein said control system is further arranged and adapted:

to energise said pusher electrode or orthogonal acceleration electrode with a period t3, wherein t2-t1 is arranged to equal t3/n and wherein n=2; and

to combine said first and second data to form a composite data set.

15. A method of analysing ions comprising:

(i) separating ions according to a physico-chemical property in a separator during a first cycle of separation and transmitting ions which emerge from said separator through a transfer device with a first transit time t1, energising a pusher electrode or orthogonal acceleration electrode and obtaining first data;

(ii) separating ions according to said physico-chemical property in said separator during a second separate cycle of separation and transmitting ions which subsequently emerge from said separator through said transfer device with a second greater transit time t2, energising said pusher electrode or orthogonal acceleration electrode and obtaining second data; and

(iii) repeating steps (i) and (ii) one or more times;

wherein said method further comprises:

energising said pusher electrode or orthogonal acceleration electrode with a period t3, wherein t2-t1 is arranged to equal t3/n and wherein n=2; and

combining said first and second data to form a composite data set.

16. An analytical device comprising:

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

a transfer device;

a pusher electrode or orthogonal acceleration electrode;

an analyser; and

a control system arranged and adapted:

(i) to cause ions to separate according to a physico-chemical property in said separator during a first cycle of separation and to transmit ions which emerge from said separator through said transfer device with a first transit time t1, to energise said pusher electrode or orthogonal acceleration electrode and to analyse said ions with said analyser to obtain first data;

(ii) to cause ions to separate according to a physico-chemical property in said separator during a second separate cycle of separation and to transmit ions which subsequently emerge from said separator through said transfer device with a second greater transit time t2, to energise said pusher electrode or orthogonal acceleration electrode and to analyse said ions with said analyser to obtain second data; and

(iii) to repeat steps (i) and (ii) one or more times; and

wherein said control system is further arranged and adapted:

to energise said pusher electrode or orthogonal acceleration electrode with a period t3, wherein t2-t1 is arranged to equal t3/n and wherein n=2; and

to combine said first and second data to form a composite data set.