Mass Analyzers. mass measurement accuracy/reproducibility. % of ions allowed through the analyzer. Highest m/z that can be analyzed

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1 Mass Analyzers Double Focusing Magnetic Sector Quadrupole Mass Filter Quadrupole Ion Trap Linear Time-of-Flight (TOF) Reflectron TOF Fourier Transform Ion Cyclotron Resonance (FT-ICR-MS)

2 Mass Analyzers Resolution R = m / Δm Accuracy/Precision mass measurement accuracy/reproducibility Transmission % of ions allowed through the analyzer Mass Range Highest m/z that can be analyzed Scan Speed How many spectra per unit of time

3 Double-Focusing Magnetic Sector

4 Double-Focusing Magnetic Sector Magnetic Sector m q = r 2 B 2 2V B = magnetic field strength r = radius of curvature in magnetic field V = accelerating voltage m = ion mass q = ion charge All ions of the same m/z will have the same radius Only if the Ion kinetic energy is constant

5 Double-Focusing Magnetic Sector Electric Sector r = 2Ek qe Ek = ion kinetic energy r = radius of curvature in electric field E = magnitude of electric field q = ion charge All ions exiting the electric sector have the same kinetic energy

6 Double-Focusing Magnetic Sector

7 Magnetic Sector Typically a voltage of 5-10kV is used to accelerate ions To obtain a full spectrum, magnetic field is scanned To obtain a HR scan, voltage is scanned at constant magnetic field To gain maximum sensitivity at one mass SIM scan is done B and E are constant for one or more masses

8 Double-Focusing Magnetic Sector Advantages Very High Resolution (60,000) High Accuracy (<5 ppm) 10,000 Mass Range Disadvantages Very Expensive Requires Skilled Operator Difficult to Interface to ESI Low resolution MS/MS without multiple analyzers

9 Quadrupole Mass Filter

10 Quadrupole E = U - Vcos(2πνt) E = potential applied to the rods U = DC potential V = RF amplitude ν = RF frequency t = time Quadrupole is scanned at a constant U/V

11 Quadrupole Mass Filter

12 Quadrupole Typically U varies from V V varies from V (-3000 to +3000) Scanning U/V at a fixed ratio gives a full scan Higher values of U/V give higher resolution RF only (U=0) transmits all ions Higher sensitivity through SIM scan Jumping to specific points on the U/V line

13 Quadrupole Mass Filter Advantages Inexpensive Easily Interfaced to Many Ionization Methods Disadvantages Low Resolution (<4000) Low Accuracy (>100ppm) MS/MS requires multiple analyzers Low Mass Range (<4000) Slow Scanning

14 Quadrupole Ion Trap HPLC Inlet Octopoles Nebulizer Gas lnlet Nebulizer Needle Capillary Skimmer Lenses Main RF Auxillary RF (1/3 Frequency of Main RF) Conversion Dynode Endcap Electron Multiplier Drying Gas Optimized Asymptote Angle Vacuum Partition Ring Electrode

15 Quadrupole Ion Trap

16 Quadrupole Ion Trap Ions are injected into the trap and all ions are trapped RF and DC are scanned to sequentially eject ions for detection Specific ions can be trapped while others are ejected Ion velocity can be increased to induced fragmentation

17 Quadrupole Ion Trap Advantages Inexpensive Easily Interfaced to Many Ionization Methods MS/MS in one analyzer Disadvantages Low Resolution (<4000) Low Accuracy (>100ppm) Space Charging Causes Mass Shifts Low Mass Range (<4000) Slow Scanning

18 Time-of-Flight (TOF) mv 2 2 = zvs = Ek d t = v t 2 = m z d 2 2Vs B = magnetic field strength v = ion velocity Vs = accelerating voltage m = ion mass q = ion charge All ions of the same m/z will have the same flight time Only if the Ion kinetic energy is constant

19 Linear Time-of-Flight (TOF) Advantages Extremely High Mass Range (>1 MDa) Fast Scanning Disadvantages Low Resolution (4000) Low Accuracy (>200ppm) MS/MS not possible

20 TOF Ions are accelerated with 5-35 kv Space focusing of source ions is accomplished by delayed extraction An electrostatic analyzer (reflectron) is used correct for kinetic energy spread

21 Reflectron Time-of-Flight (MALDI-TOF) IS 1 IS 1 / IS 2 G round potential PCIS / Deflection Drift region P 2 + P 1 + P 1 + P 1 + Linear detector T arget Pare nts and Ref lec tor Ref lec tor plate fragments detector

22 Reflectron Time-of-Flight (ESI-TOF) Reflectron Drift Region Orthogonal Interface: Accelerator Detector Flight Tube RF Ion Guide ESI Source Spray Chamber Courtesy Bruker Datonics BioTOF user s Manual

23 Reflectron Time-of-Flight (TOF)

24 Reflectron Time-of-Flight (TOF) Advantages High Resolution (>20,000 in some models) High Accuracy (<3ppm) 10,000 Mass Range Fast Scanning >100 Hz Disadvantages Low Resolution for MS/ MS (PSD)

25 FT-ICR-MS

26 qvb = mv2 r Centripital Force FT-ICR-MS qb 2πm = v 2πr B = magnetic field strength v = ion velocity f = orbital frequency m = ion mass q = ion charge r= orbital radius = r and v drop out f v = 2πf r Circular Path At constant B, orbital frequency is inversely related to m/z Frequency is independent of kinetic energy

27 FT-ICR-MS Ions are all trapped radially by a magnetic field (typically 3-15 T) Axial trapping by DC potential Ion radius is increased by RF pulse also brings orbits into phase Orbiting ions induce RF current in receiver plates Image current is a composite of all frequences in time domain FFT gives frequency (mass) spectrum

28 FT-ICR-MS Actively shielded magnet ESI source source chamber transfer stage analyzer stage capillary ion guide cell ESI needle (atmosphere) 5 L/sec rotary vane 10-1 mbar 250 L/sec turbo-drag pump 10-4 mbar 500 L/sec turbo pump 10-6 mbar 70 L/sec turbo pump 10-8 mbar 500 L/sec turbo pump mbar

29 FT-ICR-MS

30 FT-ICR-MS

31 FT-ICR-MS

32 FT-ICR-MS

33 FT-ICR-MS

34 FT-ICR-MS

35 FT-ICR-MS Electrospray: Broadband Spectrum of Bovine Serum Albumin (66kDa) 7.0T Actively Shielded Magnet 52+ Δm = a.u. 1/Δm = a.u. mass = a.u m/z m/z

36 FT-ICR-MS Electrospray: Deconvoluted Spectrum of Bovine Serum Albumin (66kDa) 7.0T Actively Shielded Magnet Δm = a.u m/z

37 FT-ICR-MS Advantages Extremely High Resolution (>500,000) Very Good Accuracy (<1 ppm) MS/MS in one analyzer Disadvantages Expensive Requires Superconducting Magnet Slow MS/MS