Introduction to DART MS

1. Introduction to DART MS Robert B. Cody JEOL USA, Inc.

2. Outline • Definition of terms • DART operating principle • TOF mass spectrometer overview • The information we obtain

3. Definitions of MS terms and general concepts

4. High Resolution Mass Spectrometry • We will be using exact-mass measurements to to confirm knowns and to determine elemental compositions for unknowns • Resolving power defines how well the mass spectrometer can separate close peaks (interferences) • The elemental composition software gives us other information for each candidate composition (e.g. unsaturation)

5. Resolving Power R = M / DM R = Resolving Power M = m/z DM = difference in mass that can be separated

6. 0.1 Resolving Power Defined as: FWHM (Full width at half maximum) R = M / DM R = 5000 m/z 500 DM = Peak width at half-height = 0.1

7. 500 501 Resolving Power Defined as: 10% Valley Definition R = M / DM R = 500 m/z 500 and 501 can be separated at a 10% Valley DM = 1

8. Examples for C36H74 (m/z 506.579) R = 500 (10% valley) R = 5000 (10% valley) Separate m/z 500 from 501 Separate m/z 500 from 500.1

9. Why the definition matters R = 500 (FWHM) R = 500 (10% valley) R = 5000 (FWHM)

10. Mass accuracy millimass units (0.001) or “mmu” ppm = 106 * (DM / M) parts-per-million (ppm) “Resolution” (reciprocal of resolving power) Note: ppm is a m/z – dependent value

11. Unsaturation (aka “rings and double bonds” aka “double bond equivalents”) Value is calculated from elemental composition Indicates total rings, double bonds, triple bonds Exact integer (e.g. “4.0”) or half-integer (“3.5”) H+ CH3COO- D = 1.5, subtract 0.5 H3O+ D = -0.5, add 0.5 C3H7O+. D = 0.5, add 0.5 C6H6+. D = 4.0

12. Examples of Even-electron ionsand Odd-electron ions Even-electron ions (half integer unsaturation) : Protonated molecule [M+H]+ Deprotonated molecule [M-H]- Chloride adduct [M+Cl]- Ammoniated molecule [M+NH4]+ Fragment F+ Odd-electron ions (exact integer unsaturation) : Molecular radical cation M+. Molecular radical anion M-. Fragment F +.

13. On-line Resources DART Users’ Google Newsgroup http://groups.google.com/group/dart-mass-spectrometer-users?hl=en JEOL USA, Inc. Web Pages http://www.jeolusa.com IonSense Web Page http://www.ionsense.com Wikipedia article on DART http://en.wikipedia.org/wiki/DART_ion_source Proton affinities, ionization energies (NIST) http://webbook.nist.gov/chemistry/

14. DART Basic Principles See the JEOL News Article on the AccuTOF-DART product page on www.jeolusa.com

15. DART:“Direct Analysis in Real Time” • Operational in Jan. 2003 • Patent filed in April 2003 • Public disclosure, Jan. 2005 • Commercial product introduced March 2005 • First open-air, ambient ion source for MS 1. Cody, R. B.; Laramee, J. A. “Method for atmospheric pressure ionization” US Patent Number 6,949,741 issued September 27, 2005. 2. Laramee, J. A.; Cody, R. B. “Method for Atmospheric Pressure Analyte Ionization” US Patent Number 7,112,785 issued September 26, 2006.

16. Prototype DART sources Original prototype DART source (mid-2002) Second DART prototype(Early 2003)

17. The Whole Package:AccuTOF-DART™

18. Why DART? • Fast and easy way to introduce samples • Minimal sample preparation for most samples • Can tolerate “dirty” or high-concentration samples and without contamination • Fast fingerprinting of materials

19. Nothing comes without a price • Chromatography/MS still has advantages over DART in detection limits, selectivity and sensitivity for certain samples • Not useful for large biomolecules (no good for DNA analysis, proteins) • DART does not ionize metals, minerals, etc.

20. DART Schematic

21. DART Ionization Penning ionization Sample ionized directly by energy transfer from metastables (M*) Proton transfer (positive ions) 1. He* ionizes atmospheric water 2. Ionized water clusters transfer proton to sample Electron capture (negative ions) 1. Penning electrons rapidly thermalized 2. Oxygen captures electrons 3. O2- ionizes sample M* DART Source MS API Interface

22. Penning Ionization Metastable atoms or molecules react with analytes that posses ionization potentials less than the metastable energy, M*+ S  S+. + M + electron The helium 23S state has 19.8 eV of internal energy and lasts up to 8 minutes in vacuum. Most molecules have ionization energies much lower than 19.8 eV

23. Proton Transfer Metastable atoms react with atmospheric water to produce ionized water clusters Dominant reaction mechanism when helium carrier used: He(23S) energy = 19.8 eV Huge reaction cross section: 100 A2 He(23S) + H2O H2O+• + He(11S) + electron H2O+• + H2O  H3O++ OH• H3O+ + nH2O  [(H2O)n+1H]+ [(H2O)nH]++ M  MH++ nH2O

24. Typical DART Low-Mass Background 100 80 60 40 Rel. Abund. 20 0 Normal DART Parameters 15 20 25 30 35 40 45 50 55 [(H2O)2+H]+ m/z NH4+ H3O+ [(H2O)3+H]+ NO+

25. Negative Ion Formation Electrons produced by direct or surface Penning ionization are rapidly thermalized Thermal electrons react with atmospheric oxygen and water to produce ionized clusters Oxygen/water cluster ions react with analyte molecules to produce analyte ions e-* + G  e- + G* e- + O2 O2-. O2-. + S  [S-H]- + OOH. O2-. + S  S-. + O2 O2-. + S  [S+O2]-.*+ G  [S+O2]-. + G*

26. Typical DART Negative-IonLow-Mass Background Note the absence of nitrogen oxide ions that would be produced by electrical discharge in air. NO2- and NO3- are problematic for detection of nitro explosives and reduce anion detection sensitivity

27. [M+H]+ Positive ions [M+H-2H2O]+ [M+H-H2O]+ [M-H]- Negative ions Example Ascorbic acid, C6H8O6 Sampled directly from a melting point tube

28. Notes on the AccuTOF Design and Operation See the JEOL News Article on the AccuTOF-LC product page on www.jeolusa.com

29. Types of mass spectrometers • Scanning: • magnetic sector, quadrupole and triple quadrupole • Trapped-ion: • Fourier transform, 3D ion trap, Orbitrap • linear trap (used in triple quadupole MS) • Time-of-flight • Hybrids

30. DART can be fit on most mass spectrometer types DART signals can be transient, so, • scanning mass specs work best with selected ion monitoring or fast scanning • Selected reaction monitoring on triple quadrupole MS is good for target compound quantitation. • Ion traps work, but are not a good choice for quantitative analysis • Time-of-flight is fastest MS for transient signals, and gives high-resolution data for the entire mass spectrum with no sensitivity loss.

31. Time of flight principle L’Alpe D’Huez de Spectrometrie de Masse Detector Light ions moving quickly If everyone starts at the same time and has the same kinetic energy, lighter riders will move faster Heavy ions moving slowly

32. A more realistic TOF mass spectrometer Ion source: Short burst of ions Ion detector Flight tube High voltage to accelerate ions Kinetic Energy = qE = mv2/2

33. What if ions that have the same mass have slightly different energies? Reflectron: make the more energetic ions travel further

34. Reflectron Time of flight mass analyzer principle 1. Fast riders miss the turn Lance Me

35. Reflectron Time of flight mass analyzer principle 2. Fast riders turn around; have to travel further

36. Reflectron TOF 3. Fast riders start to catch up

37. Reflectron TOF Focal point 4. Fast riders catch up, will eventually pass

38. Time-of-flight math All ions fly with the same kinetic energy. Flight time is inversely proportional to the square root of the mass/charge ratio. M: mass of ion [u] mu: Atom mass unit (1.6605 x 10-27 [kg/u]) v: flight speed of ion [m/s] q: charge number of ion e: unit electric charge (1.602 x 10-19 [C]) V: Accelerating voltage [V]

39. JMS-T100LC AccuTOFTM Detection system Ion Transportation Ion Source Analyser To the data collection system TMP2 RP TMP1 RP

40. AccuTOFTMIon Source Detection system Ion Transportation Ion Source Analyser To the data collection system TMP2 RP TMP1 RP

41. Orthogonal ESI ion source and API interface Desolvating Chamber LC Eluent Nebulizer Gas Orifice2 Desolvating Gas Ion Guide Ring Lens Orifice1 RP TMP

42. Ion Source and Atmospheric Pressure Ionization (API) Interface Orthogonal ESI Minimize contamination into API interface Simple API interface Robust, few parameters, minimal maintenance Off-axis skimmers and ring lens, bent ion guide Keep contamination out of high-vacuum region

43. Detection system Ion Transportation Ion Source Analyser To the data collection system TMP2 RP TMP1 RP AccuTOFTMIon Transport

44. Ion transport region Strong acceleration of ions only occurs in high-vacuum region Minimize CID and scattering Quadrupole RF ion guide focuses ions to a small spot size Spatial focus for good resolution “High-pass” filter (ions greater than given m/z) Multi-function focusing and steering lenses Beam should be perpendicular

45. AccuTOFTMAnalyzer Detection system Ion Transportation Ion Source Analyser To the data collection system TMP2 RP TMP1 z y RP x

46. AccuTOFTM Analyzer Two-step acceleration Spatial focusing of ion beam Single reflectron Energy focusing of ion beam in the x-direction Minimize ion loss oa(Orthogonal-Acceleration)-TOF MS Kinetic energy spread in y-direction has no effect on resolution The ions produced by the ESI ion source are used efficiently. z (injection) y (reflectron) x

47. Flight cycle of oa-TOF MS 1. Introduction of ion Two kinds of ions are introduced at the same time. Low mass ion High mass ion Mixture of both ions

48. Flight cycle of oa-TOF MS 2. Turn on the pulser voltage Mixture of ions at the start of flight

49. Flight cycle of oa-TOF MS • 3. Turn off the pulser voltage • continuing flight － mass separation

50. Flight cycle of oa-TOF MS • 4. Continuing flight • New ions are introduced in the ion acceleration part.