Technology Transition Workshop
Introduction to DART MSRobert B. Cody JEOL USA, Inc.
Technology Transition Workshop
Outline
Definition of terms DART operating principle TOF mass spectrometer overview The information we obtain
Technology Transition Workshop
Definitions of MS terms and general concepts
Technology Transition Workshop
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)
Technology Transition Workshop
Resolving Power
R=M/ MR = Resolving Power M = m/z M = difference in mass that can be separated
Technology Transition Workshop
Resolving Power Defined as: FWHM (Full width at half maximum)R=M/ M R = 5000 m/z 500 M = Peak width at half-height = 0.1
0.1
Technology Transition Workshop
Resolving Power Defined as: 10% Valley DefinitionR=M/ M R = 500 m/z 500 and 501 can be separated at a 10% Valley M=1500
501
Technology Transition Workshop
Examples for C36 H74 (m/z 506.579)
R = 500 (10% valley) Separate m/z 500 from 501
R = 5000 (10% valley) Separate m/z 500 from 500.1
Technology Transition Workshop
Why the definition matters
R = 500 (10% valley)
R = 500 (FWHM)
R = 5000 (FWHM)
Technology Transition Workshop
Mass accuracy
millimass units (0.001) or mmu
ppm = 106 * ( M / M) parts-per-million (ppm) Resolution (reciprocal of resolving power) Note: ppm is a m/z dependent value
Technology Transition Workshop
Unsaturation(aka rings and double bonds aka double bond equivalents)O
H+
CH3COOD = 1.5, subtract 0.5CH3
H3C
C6H6+. D = 4.0
C3H7O+. D = 0.5, add 0.5
H3O+ D = -0.5, add 0.5
Value is calculated from elemental composition Indicates total rings, double bonds, triple bonds Exact integer (e.g. 4.0) or half-integer (3.5)
Technology Transition Workshop
Examples of Even-electron ions and Odd-electron ionsProtonated molecule [M+H]+ Deprotonated molecule [M-H]Chloride adduct [M+Cl]Ammoniated molecule [M+NH4]+ Fragment F+
Even-electron ions (half integer unsaturation) :
Odd-electron ions (exact integer unsaturation) :Molecular radical cation M+. Molecular radical anion M-. Fragment F +.
Technology Transition Workshop
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/
Technology Transition Workshop
DART Basic Principles
See the JEOL News Article on the AccuTOF-DART product page on www.jeolusa.com
Technology Transition Workshop
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.
Technology Transition Workshop
Prototype DART sources
Original prototype DART source (mid-2002)
Second DART prototype (Early 2003)
Technology Transition Workshop
The Whole Package:AccuTOF-DART
Technology Transition Workshop
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
Technology Transition Workshop
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.
Technology Transition Workshop
DART Schematic
Technology Transition Workshop
DART IonizationPenning ionization Sample ionized directly by energy transfer from metastables (M*) Proton transfer (positive ions)
M*DART Source
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
MS API Interface
Technology Transition Workshop
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
Proton Transfer
Technology Transition Workshop
He(23S) + H2O H2O+ + He(11S) + electron H2O+ + H2O H3O+ + OH H3O+ + nH2O [(H2O)n+1 H]+ [(H2O)nH]+ + M MH+ + nH2O 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
Technology Transition Workshop
Typical DART Low-Mass Background
Normal DART Parameters10080
[(H2O)2+H]+
Rel. Abund.
60 40 20 0
NH4+
H3O+ NO+
[(H2O)3+H]+
15
20
25
30
35
40
45
50
55
m/z
Technology Transition Workshop
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*
Technology Transition Workshop
Typical DART Negative-Ion Low-Mass BackgroundO2[H2O3][H2O4][H C O]320 40 m /z 60
Rel . abundance
[H C O]480 10 0
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
Technology Transition Workshop9 5
ExampleAscorbic acid, C6H8O65 2 HO
O H HO
O
[M+H]+O
Rel. Abund.
10050 0
HO
177.0410
Positive ions
9 (m a
1 2 7 1 3 0 1 3 3 1 3 6 1 3 9 1 4 2 1 4+ 1 4 8 1 5 1 1 5 4 1 5 7 1 6 0 1 6 3 1 6 6 1 6 9 1 7 2 5 2 i )n A l i s c o r b i c b A c id
[M+H-2H O]
[M+H-H2O]+
100
150
m/zRel. Abund.
[M-H]175.0232
10050 0
Negative ions
100
150
m/zSampled directly from a melting point tube
Technology Transition Workshop
Notes on the AccuTOF Design and Operation
See the JEOL News Article on the AccuTOF-LC product page on www.jeolusa.com
Technology Transition Workshop
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
Technology Transition Workshop
DART can be fit on most mass spectrometer typesDART 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.
Technology Transition Workshop
Time of flight principleIf everyone starts at the same time and has the same kinetic energy, lighter riders will move fasterLight ions moving quickly Detector
Heavy ions moving slowly
LAlpe DHuez de Spectrometrie de Masse
Technology Transition Workshop
A more realistic TOF mass spectrometer
Ion source: Short burst of ions
Flight tubeHigh voltage to accelerate ions
Ion detector
Kinetic Energy = qE = mv2/2
Technology Transition Workshop
What if ions that have the same mass have slightly different energies?
Reflectron: make the more energetic ions travel further
Technology Transition Workshop
Reflectron Time of flight mass analyzer principle1. Fast riders miss the turn
Me
Lance
Technology Transition Workshop
Reflectron Time of flight mass analyzer princip
2. Fast riders turn around; have to travel further
Technology Transition Workshop
Reflectron TOF
3. Fast riders start to catch up
Technology Transition Workshop
Reflectron TOF
Focal point
4. Fast riders catch up, will eventually pass
Technology Transition Workshop
Time-of-flight math
All ions fly with the same kinetic energy.
1 ( M mu ) v 2 = q e V 2M: mass of ion [u] mu: Atom mass unit (1.6605 x 10-27 [kg/u]) q: charge number of ion V: Accelerating voltage [V] v: flight speed of ion [m/s]
e: unit electric charge (1.602 x 10-19 [C])
Flight time is inversely proportional to the square root of the mass/charge ratio.
L q tof M V
Technology Transition Workshop
JMS-T100LC AccuTOFTMIon Source Ion Transportation Analyser
Detection system To the data collection system
TMP2 RP TMP1 RP
Technology Transition Workshop
AccuTOFTM Ion SourceIon Source Ion Transportation Analyser
Detection system To the data collection system
TMP2 RP TMP1 RP
Technology Transition Workshop Orthogonal ESI ion source and API interface LC Eluent Nebulizer Gas Desolvating Chamber
Desolvating Gas
Orifice2 Ion Guide
Ring Lens Orifice1 RP TMP
Technology Transition Workshop
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
Technology Transition Workshop
AccuTOFTM Ion TransportIon Source Ion Transportation Analyser
Detection system To the data collection system
TMP2 RP TMP1 RP
Technology Transition Workshop
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
AccuTOFTM AnalyzerIon Source Ion Transportation Analyser
Technology Transition WorkshopDetection system To the data collection system
TMP2 RP TMP1 RPz y x
Technology Transition Workshop
AccuTOFTM Analyzerz y (injection) x (reflectron)
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.
Technology Transition Workshop
Flight cycle of oa-TOF MS 1. Introduction of ion Two kinds of ions are introduced at the same time.
Ion Source
Low mass ion High mass ion Mixture of both ions
Technology Transition Workshop
Flight cycle of oa-TOF MS 2. Turn on the pulser voltage Mixture of ions at the start of flight
+ + + + + +
-
-
Ion Source
Technology Transition Workshop
Flight cycle of oa-TOF MS 3. Turn off the pulser voltage continuing flight mass separation
Ion Source
Technology Transition Workshop
Flight cycle of oa-TOF MS New ions are introduced in the ion acceleration part.
4. Continuing flight
Ion Source
Technology Transition Workshop
Flight cycle of oa-TOF MS The ion acceleration region is filled with the new ions.
5. Low mass ion reaches detector
Ion Source
Technology Transition Workshop
Flight cycle of oa-TOF MS 6. High mass ion reaches detector
Ion Source
Technology Transition Workshop
Flight cycle of oa-TOF MS
7. The detection of all ions is completed
Ion Source
Technology Transition Workshop
AccuTOFTM Detection system DetectionIon Source Ion Transportation system Analyser To the data collection system
TMP2 RP TMP1 RP
Technology Transition Workshop
Detectorin the atmosphere in the vacuum To impedance converter
Anode Dual MCPa.
e-
a.
Micro-channel plate (MCP) 40mm Dual MCP Anode Combined with high voltage capacitor Patent pending
Technology Transition Workshop
MCP
Diameter 40mm Thickness 0.6mm I.D. of channel 10m Gap of each channel 12m
Technology Transition Workshop
Data collection system for oa-TOF MS
- Requirements High time resolution m/z 609, R=6,000 Peak width: 3.5ns
Continuous data collection High duty cycle
Real-time accumulation of mass spectrum
Technology Transition Workshop
Data collection system for oa-TOF MS TDC Super-high speed digital stop watch Measures the arrival time of ions A premise is that there are a few ions Each ion arrives separately. Ion counting detection: signal is 0 or 1.
Continuous Averager A signal from the detector is converted digital value by a highspeed ADC (Analog-toDigital Converter). Spectrum can be accumulated continuously in real time.
TDC (Time-to-Digital Converter)59us Start Input High Voltage Pulser Amp Discriminator
Technology Transition Workshop
Time-to-Digital ConverterStop Input
No. TOF [us] 1 29.4235 2 46.2890 ....
No. of Ions Detected in a Cycle
Histogram MemoryTo Data System
Technology Transition Workshop Simulation of spectrum accumulation by TDCOutput fromAm plifier Cycle 1 20 15 m V 10 5 0 1 5 9 13 17 21 25 29 33 37 41 45
Histgramm ory em Cycle 1 3 2 1 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46
No. of Ions
Technology Transition Workshop Simulation of spectrum accumulation by TDCOutput fromAm plifier Cycle 2 20 15 m V 10 5 0 1 5 9 13 17 21 25 29 33 37 41 45
Histg ramm ory em Cycle 2 3 2 1 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46
No. of Ions
Technology Transition Workshop Simulation of spectrum accumulation by TDCOutput from Am plifier Cycle 3 20 15 10 5 0 1 5 9 13 17 21 25 29 33 37 41 45 Histgram m ory em Cycle 3 No. of Ions 3 2 1 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46
m V
Technology Transition Workshop Simulation of spectrum accumulation by TDCOutput fromAm plifier Cycle 4 20 15 10 5 0 1 5
The ion which had about two times higher intensity was detected. It is counted only once (not twice) with TDC.
m V
9 13 17 21 25 29 33 37 41 45
Histgram m ory em Cycle 4 No. of Ions 3 2 1 0 1 5 9 13 17 21 25 29 33 37 41 45
Technology Transition Workshop Simulation of spectrum accumulation by TDCOutput from Am plifier Cycle 5 20 15 10 5 0 m V
Two ions detected in succession!
17
25
45
1
5
9
13
21
29
33
37
41
Histgram m ory Cycle 5 em No. of Ions 3 2 1 29 45 1 5 9 13 17 21 25 33 37 41 0
The second ion can't be counted during dead time.
Technology Transition Workshop
Result of spectrum accumulation by TDCm el sp od ectrum: No. of Ions 25 20 15 10 5 0
21
29
41
13
17
25
33
37
Histgram m ory Cycle 5 em No. of Ions 3 2 1 29 45 1 5 9 13 17 21 25 33 37 41 0
45
1
5
9
The ratio of the peak intensity isn't correct. A high intense peak shifts to low mass side.
Technology Transition Workshop
Continuous Averager
Continuous Averager59us Timing Control Circuit High Voltage Pulser Amp ADC (8bit) Adder
Summing Memory
To Data System Intensity 15 28 .... No. of Data Points on a Spectrum (up to 256K points)
Simulation of spectrum accumulation by continuous averagerOutput fromAm plifier Cycle 1 20 15 m V 10 5 0 150 40 30 20 10 0
Technology Transition Workshop
5
9 13 17 21 25 29 33 37 41 45Cycle 1
mV
13
17
21
25
29
33
37
41
45
1
5
9
Simulation of spectrum accumulation by continuous averagerOutput fromAm plifier Cycle 2 20 15 m V 10 5 0 150 40 30 20 10 0
Technology Transition Workshop
5
9 13 17 21 25 29 33 37 41 45Cycle 2
m V
21
29
41
1
5
9
13
17
25
33
37
45
Simulation of spectrum accumulation by continuous averagerOutput from Am plifier Cycle 3 20 15 10 5 0 150 40 30 20 10 0
Technology Transition Workshop
m V
5
9 13 17 21 25 29 33 37 41 45Cycle 3
m V
17
25
45
1
5
9
13
21
29
33
37
41
Simulation of spectrum accumulation by continuous averagerOutput from Am plifier Cycle 4 20 15 10 5 0 150 40 30 20 10 0
Technology Transition Workshop
m V
5
9 13 17 21 25 29 33 37 41 45Cycle 4
m V
17
25
45
1
5
9
13
21
29
33
37
41
Simulation of spectrum accumulation by continuous averagerOutput from Amplifier Cycle 5 20 15 10 5 0 1 5 9 13 17 21 25 29 33 37 41 45Cycle 5 50 40 30 20 10 0 m V 17 25 45 1 5 9 13 21 29 33 37 41
Technology Transition Workshop
m V
Result of spectrum accumulation by continuous averager No. of Ions
Technology Transition Workshop
The ratio of the peak intensity is correct. There is no shift of the ion peak.
m el sp od ectrum: 25 20 15 10 5 0
21
29
41
13
17
25
33
37
Cycle 5 50 40 30 20 10 0
m V
17
25
45
13
21
29
33
37
41
1
5
9
45
1
5
9
Technology Transition Workshop
Specifications Mass resolution 6,000 FWHM, Reserpine m/z 609
Sensitivity Reserpine 10pg S/N>10 LC-ESI Flow rate: 0.2mL/min Mass chromatogram of m/z 609, RMS
Mass accuracy 5ppm RMS With internal reference (Typically better than that!)
Only 3 analyzer parameters are critical Detection for routine DART analysis systemIon Source Ion Transportation Analyser To the data collection system
Technology Transition Workshop
1
2
3 RP TMP1 RP
TMP2
1: Orifice 1 2: Peaks voltage 3. Multiplier V
Technology Transition Workshop
The 3 important parameters 1: Orifice 1: Typically 20V Increase O1 to increase fragmentation
2: Peaks voltage (RF ion guide voltage) Divide by 10 to estimate lowest detected m/z
3. Multiplier V: Typically 2200V to 2600V Increase multiplier to increase signal (and noise)
Information from the TOF mass spectrum Exact mass + isotope peaks: elemental composition Fragmentation: distinguish isomers Fingerprint pattern: material ID Ion abundance: quantitative analysis Other experiments: H/D exchange, derivatization, etc.
Technology Transition Workshop
Technology Transition Workshop
Example: DART mass spectrum of a leaf
What is this?
10080
304.154 290.174
Rel. Abund.
60 40 20 0
100
150
200
250
300
350
m/z
Technology Transition Workshop
We can treat this as an unknown
Technology Transition Workshop
Elemental compositionsMeasured Exact MassConstraints
Candidate compositionsIsotope pattern matching
Ranked compositionsElemental Composition Program
Technology Transition Workshop
We have a composition. Now what? m/z 304.1548 is C17H22NO4
ScopolamineFragments at m/z 138, 156 9 9N
CocaineFragments at m/z 182, 82N O
138 C8H12 NO+5 6 O O O H
H
O O
O
H
O
156 C8H14 NO2+1 3
182 C10 H16 NO2+2 4 2 8 o2 x y4 , l3 i - c (b a e 2 5 2 n zi do ) y- - m o c 8 l 2 6 2 xe y t- , hm y e l
2 0 4 e
2 1 4
2 2 4
2 0 2 2 1 2 2 2 2 2 3 2 ( m 2 3a 4 i )n 8 -l2i b 4 z 4a b 2 i [53 . 2y. 1 c o 2l c 6 t 4 a- 2 - n 2 ea7 4 b A c 4 ] o c r
2 7 2 t h y , l [ 1 eR
Technology Transition Workshop
API interface change potentials to LC Eluent fragmentation induceNebulizer Gas Desolvating Chamber
Desolvating Gas
Orifice2 Ion Guide Ring Lens Orifice1
Control fragmentation with Orifice 1 and Ring Lens potentials
RP
TMP
Technology Transition Workshop
Fragment spectrum increase cone voltage from 20 V to 60 V
Atropine 10080
Scopolamine C8H12 NO+138.089
290.174
C8H14 NO2+156.099
Rel. Abund.
Scopolamine304.154
60 40 20 0
C8H14 N+ 100 150 200 250 300
m/z
For comparison, m/z 305.1548 fragments from a dollar bill
Technology Transition Workshop
CocaineC10 H16 NO2+10080 Rel. Abund. 60 40 20 0182.118
C17 H22 NO4+ C5H8N+82.065
100
150
200
250
300
350
m/z
orwe can search for candidates from a list of target compounds.
Technology Transition Workshop
Components in a smokeless powder
SearchFromList Program
Technology Transition Workshop
Whew! Confused? Itll make more sense when you see it in the lab.