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Materials & Engineering Sciences Center Atoms to Continuum External Second Gate, Fourier Transform Ion Mobility Spectrometry: FT-IMS Next Generation Ion.

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Presentation on theme: "Materials & Engineering Sciences Center Atoms to Continuum External Second Gate, Fourier Transform Ion Mobility Spectrometry: FT-IMS Next Generation Ion."— Presentation transcript:

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 Sample Inlet Ion Drift Region Drift Gas ExhaustAir Drift Gas Inlet High Voltage Repeller 63 Ni Ionization Region Entrance Gate Focusing Rings Aperture Grid Faraday Collector Signal Out Commercial/Military IMS Drift Tube Drift Gas Flow - - - -

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 more ions 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 Entrance gate pulse Exit gate pulse open closed CYCLE REPEATED (IF DESIRED) LOW FREQUENCY HIGH FREQUENCY 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. Ion Gating in FT-IMS

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

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

17 Resolution vs. Aspect Ratio as Indicator of Peak Quality Materials & Engineering Sciences Center Atoms to Continuum 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 intensity peaks 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 Resolution Number vs. Aspect Ratio (Drift Time/w 1/2 ) (Peak Height/w b ) Materials & Engineering Sciences Center Atoms to Continuum 051015202530354045 Drift Time (ms) 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

19 Resolution in IMS Materials & Engineering Sciences Center Atoms to Continuum 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 63 Ni or UV 63 Ni 63 Ni 63 Ni 50 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. 63 Ni Tritium 63 Ni 63 Ni Laser Corona 30+ 50 30-60 NA 50 NA Reference: Analytical Chemistry, Product Review. October 1, 2003. Pages 435-438A

20 Peak Resolution: R = t d /w 1/2 Aspect Ratio: AR = h/w b PEAKIMS X2G-FT-IMS IMS X2G-FT-IMS K o =1.84SA10K 20K 40K SA10K 20K 40K TNT40.9730.27 36.59 10.74156.8 101.6 PETN41.2328.74 39.56 13.68209.8 18.88 HNS41.9428.74 34.31 5.98188.4 130.2 HMX41.3528.57 40.98 3.02185.6 36.56 RDX------28.84 50.92 ------113.4 31.89 Averages:41.3729.03 37.72 8.35170.8 63.82 K o =1.54 TNT45.5930.41 30.75 42.47 9.12156.8 134.0 56.87 PETN38.2037.42 41.40 ------ 5.6847.14 75.90 ------ HNS45.7026.86 40.67 ------ 12.851.70 77.13 ------ HMX42.0431.76 41.49 65.99 7.52 147.4 56.84 29.81 RDX46.33------ 34.11 75.27 9.32------ 17.86 ------ Averages:43.5731.61 37.68 61.24 8.88 100.8 72.34 ------ Peak Quality Determines False Alarm Rate Materials & Engineering Sciences Center Atoms to Continuum

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

22 Materials & Engineering Sciences Center Atoms to Continuum 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. 8.5 ms

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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