Method and apparatus for control of mobility-based ion species identification
System for control of ion species behavior in a time-varying filter field of an ion mobility-based spectrometer to improve species identification, based on control of electrical and environmental aspects of sample analysis.
1. A Differential Mobility Spectrometer method for identifying chemical species in a sample, including the steps of:
a) providing a DMS filter field, said filter field being adjustable to a plurality of DMS filter operating conditions, said DMS filter operating conditions being characterized as influencing mobility behavior of ion species in said field,
b) processing an ionized sample in said filter field at a first set of said operating conditions, said ionized sample including at least one ion species, said processing being based upon aspects of mobility behavior of said at least one ion species in said first set of operating conditions,
c) detecting a spectral peak associated with said at least one ion species and said first set of operating conditions,
d) provisionally identifying said at least one ion species based upon said detection and said association and by reference to a store of detection data,
e) changing said operating conditions of said filter into a second set of operating conditions based upon said provisional identification and predicting the effect of such change upon said provisionally identified at least one ion species measured in terms of change in at least one characteristic of said spectral peak,
f) detecting again said spectral peak associated with said at least one ion species at said second set of operating conditions and confirming said predicted effect,
g) based upon said first detection and said confirmation, verifying said provisional identification of said detected at least one ion species for identifying said at least one ion species.
2. The method of claim 1 wherein said operating conditions include the parameters of RF field strength and field compensation level.
3. The method of claim 1 wherein changing said operating conditions of said filter based upon said provisional identification includes changing said operating conditions in terms of waveform characteristics, RF frequency, duty cycle, gas composition, pressure, presence of H 2 O or polar molecules, or flow rate, and predicting the effect of such change upon said provisionally identified at least one ion species measured in terms of change in at least one characteristic of said spectral peak.
4. The method of claim 1 further including a third parameter set of variables used to make a third detection at a third set of field conditions to confirm said provisional identification.
5. The method of claim 1 wherein said analyzing an ionized sample in said filter field at a first set of said operating conditions includes scanning at least one parameter of said operating conditions and generating a mobility scan for said sample, said scan including said at least one spectral peak.
6. The method of claim 5 wherein said method includes scanning a plurality of parameters of said operating conditions.
7. The method of claim 1 wherein said compensation is expressed as a DC voltage.
8. The method of claim 1 further including the use of methylenechloride as a dopant to cause peak shift of detected chemicals.
9. A Differential Mobility Spectrometer filter system for identifying chemical species in a sample, comprising
a) an DMS filter, including at least a pair of electrodes between which is established a DMS filter field, said filter field being adjustable to a plurality of DMS filter operating conditions, said DMS filter operating conditions being characterized as influencing mobility behavior of ion species in said filter field,
b) an sample supply, including an inlet for receipt of a sample, said supply providing said sample in an ionized condition to said DMS filter field at a first set of said operating conditions, said ionized sample including at least one ion species,
c) a processor for analysis of said ionized sample based upon aspects of mobility behavior of said at least one ion species in said first set of operating conditions,
d) a detector downstream from said DMS filter for detecting a spectral peak associated both with said at least one ion species and said first set of operating conditions,
e) an intelligent controller for provisionally identifying said at least one ion species based upon said detection and said association and by reference to a store of detection data,
f) said controller adjusting said operating conditions into a second set of operating conditions based upon knowledge of said provisional identification and predicting the effect of such change upon said provisionally identified at least one ion species measured in terms of change in at least one characteristic of said spectral peak,
g) said controller instructing detector to redetect said spectral peak associated with said at least one ion species at said second set of operating conditions to make a confirmation of said predicted effect, and
h) said controller verifying said provisional identification of said detected at least one ion species based upon said first detection and said confirmation, and said controller enabling identifying said at least one ion species based on said verification.
10. The system claim 9 wherein said operating conditions include the parameters of RF field strength and field compensation level.
11. The system of claim 10 wherein said compensation is expressed as a DC voltage.
12. The system of claim 9 further including said controller instructing said detector to make a third detection at a third set of field conditions to confirm said provisional identification.
13. The system of claim 9 wherein analyzing an ionized sample in said filter field at a first set of said operating conditions includes scanning at least one parameter of said operating conditions and generating a mobility scan for said sample, said scan including said at least one spectral peak.
14. The system of claim 13 wherein said controller scans a plurality of parameters of said operating conditions.
15. The system of claim 9 wherein said operating conditions include waveform characteristics.
16. The system of claim 9 further including the step of using methylenechloride as a dopant to cause peak shift of detected chemicals.
17. The system of claim 9 wherein said changing said operating conditions is in terms of waveform characteristics, RF frequency, duty cycle, gas composition, pressure, presence of H 2 O or polar molecules, or flow rate, and predicting the effect of such change upon said provisionally identified at least one ion species measured in terms of change in at least one characteristic of said spectral peak.
18. A Differential Mobility Spectrometer method for identifying chemical species in a sample, including the steps of:
a) providing a DMS filter field, said filter field being adjustable to a plurality of DMS filter operating conditions, said DMS filter operating conditions being characterized as influencing mobility behavior of ion species in said field,
b) processing an ionized sample in said filter field at a first set of said operating conditions, said ionized sample including at least one ion species, said processing being based upon aspects of mobility behavior of said at least one ion species in said first set of operating conditions,
c) detecting a spectral peak associated with said at least one ion species and said first set of operating conditions,
d) provisionally identifying said at least one ion species based upon said detection and said association and by reference to a store of detection data,
e) based upon said provisional identification, changing said operating conditions into a second set of operating conditions at least in terms of RF frequency, duty cycle, gas composition, pressure, presence of H 2 O or polar molecules, or flow rate, and predicting the effect of such change upon said provisionally identified at least one ion species measured in terms of change in at least one characteristic of said spectral peak,
f) again detecting said spectral peak associated with said at least one ion species at said second set of operating conditions and confirming said predicted effect,
g) based upon said first detection and said confirmation, verifying said provisional identification of said detected at least one ion species for identifying said at least one ion species.