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What is Trace? Ultra-Trace? PowerPoint Presentation
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What is Trace? Ultra-Trace?

What is Trace? Ultra-Trace?

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What is Trace? Ultra-Trace?

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  1. What is Trace? Ultra-Trace? Trace: ppt (thousand) -ppm Ultra Trace: <ppb

  2. Front Ends: • GC • LC • SPME • Electrophoresis • Ion Mobility • Mass (Ion) Analyzers: • Linear Quadrupole • Quadrupole Ion Trap (QIT) • Time-of-Flight (TOF) • Ion Cyclotron Resonance (FT-MS) • Sectors • OrbiTrap • Ion Mobility • Any Combination Hybrids (Triple Quads, Q-TOF, TOF-TOF, IM-TOF, IM-Q) • Detection: • Faraday Cup • Electron Multiplier • Microchannel Plate • Ionization Sources: • Electron Impact (EI) • Atmospheric Pressure Chemical Ionization (APCI) • MALDI • Electrospray/ Nanospray Ionization (ESI) • Corona Discharge • Inductively Coupled Plasma (ICP) • FAB, SIMS

  3. Sensitivity vs Selectivity: Resolution vs Resolving Power (MS): Resolution Chromatography:

  4. Denaturing CGE of SDS Proteins in 6%T Linear Polyacrylamide Bovine Serum Albumin Aldolase Phosphorylase B Volts b-Galactosidase Time (min)

  5. 1 Torr He NO O2 CO H2O CO2 N2 Relative Abundance Arrival Time (us)

  6. 10 Torr He NO O2 H2O CO2 CO N2 Relative Abundance Arrival Time (us)

  7. 100 Torr He NO H2O O2 CO N2 CO2 Relative Abundance Arrival Time (us)

  8. Why is resolution so important?

  9. Intro Math Divergance(“del” operator) The Leplacian (“del squared”)

  10. The equipotential field plot

  11. The Quadrupole Field (ideal, no space charge effects): The potential at any point (x,y,z) is defined as: Where, fo= the applied field l, s, g are weighing constants for their coordinate ro= constant for the device The applied field is the combination of a RF and DC (U) field: V= 0 to Peak W (rad/s) = 2pf(Hz)

  12. Conditions must be defined within the confines of the Laplace eq.: Functions that satisfy the Laplace Equation are harmonic! What functions can be used? Electrostatic Potential in a Charge-Free Region, Steady-State Temperature, or Gravitational Potential without Matter. Evaluating each of the partial derivatives:

  13. Plugging back into the Laplace eq.: All quadrupole devices must conform to the below constraints: Or the trivial solution:

  14. The Force (F) can be solved in any direction:

  15. Equations for motion can be determined from the Force eq.: How do we solve this second order DE?

  16. Mathieu’s Function “Mathieu equations occur in two main categories of physical problems. First, in applications involving elliptic geometries, for example in the analysis of the vibrating modes in elliptic membranes, the propagating modes in elliptic pipes, and the oscillations of water in a lake of elliptic shape. Mathieu equations arise after separating the wave equation using elliptic coordinates. Second, Mathieu equations arise in problems involving periodic motion, such as the trajectory of an electron in a periodic array of atoms, the mechanics of the quantum pendulum, and the oscillations of floating vessels.” Am. J. Phys. 71 (3) March 2003, p. 233

  17. Mathieu’s Equation (canonical form), solutions to the second order differential equations of the form: Our equation of motion can fit the Mathieu form, where: Similarly with y.

  18. Linear Quads Quadrupole Field: We remember the constraints from the Laplace eq.: If we are only interested in quadrupole MS (x,y) then: If we set l=1, then: The equipotential field plot

  19. Linear Quads r ro

  20. Linear Quads r ro

  21. qz=0.908 az=0

  22. 1MHz, radius=1cm U(Volts) V(Volts 0-peak)

  23. Quad Ion Traps Again we choose the simplest values to satisfy the Laplace constraints. Since the x and y positions = ro zo ro Transform into cylindrical coordinates: Geometrical constraints:

  24. Quad Ion Traps

  25. Equations of motion are: Quad Ion Traps To fit the Mathieu Equation:

  26. Quad Ion Traps

  27. Cylindrical Ion Traps

  28. z1 For a cylindrical ion trap, where r1

  29. For au=0, 0<qu<0.908

  30. @100 Volt0-p qz MHz m/z

  31. @4.2MHz qz Volt0-p m/z

  32. AFOSR DURIP BAA-2008-5

  33. Building Blocks of An ICP - MS • Atmospheric pressure • Sample introduction • Desolvation • Atomization • Ionization > 90% • -------------- --------------- • Vacuum • Ion focusing • Mass separation • Isotope detection 7Li+ 114Cd+ 208Pb+

  34. Ion Optics Quadrupole PlasmaTorch Turbo Pump Turbo Pump Interface Detector Rotary Pump Rotary Pump Generic ICP-MS System Hardware

  35. Applications: Forensic Analysis • Sample Preparation: Laser Ablation • Direct Solid Sampling • Very Little Sample Prep • Spatially Resolved In Situ Analysis • Integrated software control

  36. LSX-213 schematic

  37. 90 degree ion mirrorfor the highest sensitivity and low background Peltier cooled spraychamber and low sample uptake for low oxides and reduced sample usage Varian 810/820-MS OverviewInnovative Hardware technology Curved fringe rodsbefore quadrupole for high speed, low noise, low background Optimized interface for high transmission, good matrix tolerance and low oxides Collision Reactive Interface in 820 9 orders,all digital detectorfor easy setup and operation Robust, high efficiency, solid state 27 MHz RF generator andTurner Interlaced coilsfor stable, balanced plasma system (no torch shield required)

  38. 820 ICP-MS Ion Optics DesignPractical aspects • Ions are reflected and focused at 90° by the parabolic electrostatic field produced by an ion mirror • Ion mirror has a hollow structure • Photons, neutrals, & solid particles pass through • No contamination of the ion optics • Vacuum pump mounted behind ion mirror • Removes unwanted particles • Highly efficient vacuum conditions 15

  39. Ion Optics - Photon Stop Design • Ion beam aberrations present • Optical analogy – note different focal points • (still used by one competitor) • About 10-15% efficient

  40. Reference: Yoko Kishi, A Benchtop Inductively Coupled Plasma Mass-spectrometer, Hewlett-Packard Journal, August 1997 Offset Ion Optics Design Bessel box about 20% Ion transport efficiency 7

  41. + + + + N + + 4 D Focusing of the Ion Mirror skimmer Ion Mirror KE = PE

  42. Varians Ion Optics Design – the 90 Degree Ion Mirror