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Materials & Engineering Sciences Center

Materials & Engineering Sciences Center. Atoms to Continuum. External Second Gate, Fourier Transform Ion Mobility Spectrometry: “FT-IMS” Next Generation Ion Mobility Spectrometer. Edward E. Tarver, Ph.D. Analytical Material Sciences Department

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Materials & Engineering Sciences Center

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  1. Materials & Engineering Sciences Center Atoms to Continuum External Second Gate, Fourier Transform Ion Mobility Spectrometry: “FT-IMS” Next Generation Ion Mobility Spectrometer Edward E. Tarver, Ph.D. Analytical Material Sciences Department Sandia National Laboratories-Livermore, California

  2. Materials & Engineering Sciences Center Atoms to Continuum Ion Mobility Spectrometry • Real-time response: few seconds analysis time. • Sensitivity: low part-per-billion detection without pre-concentration. • Versatility: simultaneous/universal response. • Simplicity of electronics: no vacuum pumps/chromatographs. • Field portability: low power, size and weight. Battery powered military and commercial units available. • Unattended monitoring: perimeter and network defense.

  3. Materials & Engineering Sciences Center Atoms to Continuum Drift Gas Exhaust AirDrift Gas Inlet Faraday Collector Signal Out - Ion Drift Region Sample Inlet - 63Ni Ionization Region Drift Gas Flow - - High Voltage Repeller Entrance Gate Focusing Rings Aperture Grid Commercial/Military IMS Drift Tube

  4. Materials & Engineering Sciences Center Atoms to Continuum

  5. Materials & Engineering Sciences Center Atoms to Continuum The observed peak tailing is due to ion-molecule reactions occurring during time-of-flight and further compounded by the signal averaging process.

  6. Materials & Engineering Sciences Center Atoms to Continuum Fourier Transform Ion Mobility Spectrometry • Increased Sensitivity, Lower Detection Limits: Sensitivity depends on the duty cycle. FT-IMS operates with 50% ion gating efficiency compared to 1% with conventional IMS. Fifty times moreions transmitted and detected than conventional IMS. • Improved Resolution, Fewer False Alarms: FT-IMS dual-gate design eliminates broadening due to ion-molecule reactions and averaging process. Conventional IMS sums all variations in ion velocity, broadening peaks and reducing resolution. No need to average with FT-IMS. • Suited for Miniaturization: FT-IMS performance allows miniaturization of detectors. • Adaptable to Current IMS Systems: No hardware modifications to drift tube.

  7. Materials & Engineering Sciences Center Atoms to Continuum Ion Gating in FT-IMS LOW FREQUENCY HIGH FREQUENCY CYCLE REPEATED (IF DESIRED) open Entrance gate pulse closed open Exit gate pulse closed 1. Gates are open and closed for equal amounts of time no matter how frequently they are pulsed. 2. Ion collection during half of the analytical cycle time, i.e., 50% duty cycle. 3. Low frequency greater Signal/Noise, High frequency better Resolution.

  8. Materials & Engineering Sciences Center Atoms to Continuum Fourier Transform of the Ion Mobility Interferogram Fourier Transform Ion Mobility Interferogram Ion Mobility Spectrum 8

  9. Materials & Engineering Sciences Center Atoms to Continuum Conventional IMS vs. FT-IMS

  10. Materials & Engineering Sciences Center Atoms to Continuum FT-IMS Allows Tunable Resolution

  11. Materials & Engineering Sciences Center Atoms to Continuum

  12. Materials & Engineering Sciences Center Atoms to Continuum TNT Response as a Function of Scanning Time

  13. Materials & Engineering Sciences Center Atoms to Continuum PETN Response as a Function of Scanning Frequency

  14. Materials & Engineering Sciences Center Atoms to Continuum HNS Response at 10kHz and 20kHz Scanning Frequency

  15. Materials & Engineering Sciences Center Atoms to Continuum HMX Response: Frequency Range and Scan Time 20

  16. RDX Response as a Function of Frequency Range Scanned Materials & Engineering Sciences Center Atoms to Continuum

  17. Materials & Engineering Sciences Center Atoms to Continuum Resolution vs. Aspect Ratio as Indicator of Peak Quality • RESOLUTION (R): R = Drift Time (ms) / Peak Width at Half Height (ms) • Resolution calculation ignores peak broadening below Half Height • where peak tailing and overlap limits ability to separate adjacent peaks. • Drift time dependent: broad, low intensitypeaks with long drift times can • give higher Resolution (R) than strong, sharp peaks with short drift times. • Misleading indicator of instrumental resolving power. • ASPECT RATIO: AR = Peak Height (h) / Peak Width at Base (w) • Unbiased indicator of peak quality, includes peak width below Half Height. • Aspect Ratio is Independent of drift time and describes actual peak shape.

  18. Materials & Engineering Sciences Center Atoms to Continuum Resolution Number vs. Aspect Ratio(Drift Time/w1/2) (Peak Height/wb) R = 5/2 = 2.5 R = 20/2 = 10 R = 32/2 = 16 R = 40/2.5 = 16 AR = 3.25/.375 = 8.6 AR = 8.6 AR = 8.6 AR = 0.235 0 5 10 15 20 25 30 35 40 45 Drift Time (ms)

  19. Materials & Engineering Sciences Center Atoms to Continuum Resolution in IMS • Selected Bench-top IMS Instruments • IMS 5000 UVIMS-MCC Itemiser AirSentry IonScan 400B • Draeger G.A.S. G.E./Ion Track SAES/Molecular Smiths Detection • Safety Co. Technol. Analytics • Germany Germany U.S.A. Italy U.K. • Tritium 63Ni or UV 63Ni 63Ni 63Ni • 30-60 NA 25 44 • Selected Handheld IMS Instruments • RAID-M IMS Mobile µIMS VaporTracer Quantum Sniffer LCD3.2 • Bruker Draeger G.A.S. G.E./Ion Track Implant Sciences Smiths Detection • Daltonics Safety Co. Technol. Corporation • Germany Germany Germany U.S.A. U.S.A. U.K. • 63Ni Tritium 63Ni 63Ni Laser Corona • 30+ 50 30-60 NA 50 NA • Reference: Analytical Chemistry, Product Review. October 1, 2003. Pages 435-438A

  20. Materials & Engineering Sciences Center Atoms to Continuum Peak Quality Determines False Alarm Rate Peak Resolution: R = td/w1/2Aspect Ratio: AR = h/wb PEAKIMSX2G-FT-IMSIMSX2G-FT-IMS Ko =1.84 SA 10K 20K 40K SA 10K 20K 40K TNT 40.97 30.27 36.59 10.74 156.8 101.6 PETN 41.23 28.74 39.56 13.68 209.8 18.88 HNS 41.94 28.74 34.31 5.98 188.4 130.2 HMX 41.35 28.57 40.98 3.02 185.6 36.56 RDX ------ 28.84 50.92 ------ 113.4 31.89 Averages: 41.3729.0337.728.35170.8 63.82 Ko =1.54 TNT 45.59 30.41 30.75 42.47 9.12 156.8 134.0 56.87 PETN 38.20 37.42 41.40 ------ 5.68 47.14 75.90 ------ HNS 45.70 26.86 40.67 ------ 12.8 51.70 77.13 ------ HMX 42.04 31.76 41.49 65.99 7.52 147.4 56.84 29.81 RDX 46.33 ------ 34.11 75.27 9.32 ------ 17.86 ------ Averages: 43.5731.61 37.6861.248.88100.872.34 ------

  21. Materials & Engineering Sciences Center Atoms to Continuum acetone RDX reactant ion peak 8.5 ms

  22. Materials & Engineering Sciences Center Atoms to Continuum 8.5 ms RDX Note the comparative resolution of the peak a 8.5 ms. FT-IMS is able to resolve both species Present whereas signal averaging cannot. The peak at 12 ms is residual acetone.

  23. Materials & Engineering Sciences Center Atoms to Continuum Handheld FT-IMS

  24. Materials & Engineering Sciences Center Atoms to Continuum FT-IMS: Rear View

  25. Materials & Engineering Sciences Center Atoms to Continuum FT-IMS: 9-Volt Batteries in Parallel

  26. Materials & Engineering Sciences Center Atoms to Continuum FT-IMS: Interior View

  27. Materials & Engineering Sciences Center Atoms to Continuum FT-IMS: Vertical Battery Arrangement

  28. Materials & Engineering Sciences Center Atoms to Continuum Acknowledgements Sandia National Laboratories, Research Foundations & Laboratory Directed Research and Development Grants Sandia National Laboratories, Livermore CA Analytical Material Sciences Department Dr. Jim Wang, Mr. Anh Phan, Dr. Kent Pfeiffer, Mr. John Warmouth Professor Herbert Hill, Washington State University, Pullman WA Professor David Harris, Harvey Mudd College, Claremont CA United States Department of the Navy: Contract N4175603GO14803

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