Introduction to DART MS

Technology Transition Workshop

Introduction to DART MSRobert B. Cody JEOL USA, Inc.


Outline

Definition of terms DART operating principle TOF mass spectrometer overview The information we obtain


Definitions of MS terms and general concepts


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)


Resolving Power

R=M/ MR = Resolving Power M = m/z M = difference in mass that can be separated


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


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


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


Why the definition matters

R = 500 (10% valley)

R = 500 (FWHM)

R = 5000 (FWHM)


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


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)


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 +.


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/


DART Basic Principles

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


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.


Prototype DART sources

Original prototype DART source (mid-2002)

Second DART prototype (Early 2003)


The Whole Package:AccuTOF-DART


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


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.


DART Schematic


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


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


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


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


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*


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


Notes on the AccuTOF Design and Operation

See the JEOL News Article on the AccuTOF-LC product page on www.jeolusa.com


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


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.


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


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


What if ions that have the same mass have slightly different energies?

Reflectron: make the more energetic ions travel further


Reflectron Time of flight mass analyzer principle1. Fast riders miss the turn

Me

Lance


Reflectron Time of flight mass analyzer princip

2. Fast riders turn around; have to travel further


Reflectron TOF

3. Fast riders start to catch up


Reflectron TOF

Focal point

4. Fast riders catch up, will eventually pass


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


JMS-T100LC AccuTOFTMIon Source Ion Transportation Analyser

Detection system To the data collection system

TMP2 RP TMP1 RP


AccuTOFTM Ion SourceIon Source Ion Transportation Analyser


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


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


AccuTOFTM Ion TransportIon Source Ion Transportation Analyser


TMP2 RP TMP1 RP


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


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.


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


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

+ + + + + +

-

-

Ion Source


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

Ion Source


Flight cycle of oa-TOF MS New ions are introduced in the ion acceleration part.

4. Continuing flight

Ion Source


Flight cycle of oa-TOF MS The ion acceleration region is filled with the new ions.

5. Low mass ion reaches detector

Ion Source


Flight cycle of oa-TOF MS 6. High mass ion reaches detector

Ion Source


Flight cycle of oa-TOF MS

7. The detection of all ions is completed

Ion Source


AccuTOFTM Detection system DetectionIon Source Ion Transportation system Analyser To the data collection system

TMP2 RP TMP1 RP


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


MCP

Diameter 40mm Thickness 0.6mm I.D. of channel 10m Gap of each channel 12m


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


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


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.


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.


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


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


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


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


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


m V

Result of spectrum accumulation by continuous averager No. of Ions


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


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


1

2

3 RP TMP1 RP

TMP2

1: Orifice 1 2: Peaks voltage 3. Multiplier V


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.



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


We can treat this as an unknown


Elemental compositionsMeasured Exact MassConstraints

Candidate compositionsIsotope pattern matching

Ranked compositionsElemental Composition Program


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


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


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


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.


Components in a smokeless powder

SearchFromList Program


Whew! Confused? Itll make more sense when you see it in the lab.

Introduction to DART MS

Documents

dart http

dart prototype

dart msrobert

proteins dart

power r

valley r

accutofdart product

sample electron