Re-visit the Organic Relative Ionization Efficiency in...

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Re-visit the Organic Relative Ionization Efficiency in AMS Wen Xu Oct 22, 2016 Portland, OR AMS User’s Meeting

Transcript of Re-visit the Organic Relative Ionization Efficiency in...

Page 1: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Re-visit the Organic Relative Ionization Efficiency in AMS

Wen Xu

Oct 22, 2016

Portland, OR

AMS User’s Meeting

Page 2: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

How a particle is detected in AMS

Pre-Amp

QMG M(s,l) -> M(g) -> M+, X+

M(s,l) -> N(g) -> N+, Y+

Chopper

Controller

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Efficiencies of detection at different stages

Pre-Amp

QMG

ELES

EB

CE

IE IE = σ × Je × tm

TE

Chopper

Controller

𝐼𝐸 = 𝜎 × 𝑙𝑚 ×𝑣𝑚

2 + 𝑣𝑒2

𝑣𝑚2 ) × 𝑛𝑒 = 𝜎 × 𝑣𝑒 × 𝑛𝑒) ×

𝑙𝑚𝑣𝑚

= 𝜎 × 𝐽𝑒 × 𝑡𝑚

Page 4: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Ionization efficiencies of molecules and relative ionization efficiencies to Nitrate

Pre-Amp

QMG

EL = 1 ES = 1 EB = 1

CE = 1

IE IE = σ × Je × tm

TE : m/z

dependence has

been corrected

out.

300 nm particles Capture Vaporizer

Chopper

Controller

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Experimental setup

Atomizer Drier DMA CPMA AMS

CPC

𝑅𝐼𝐸 𝑋 =𝑚𝐼𝐸 𝑋

𝑚𝐼𝐸 𝑁𝑂3=

𝐼𝐸 𝑋

𝑀𝑊 𝑋/

𝐼𝐸 𝑁𝑂3

𝑀𝑊 𝑁𝑂3

= 𝐼𝑐𝑜𝑟𝑟 𝑋)

𝐶𝐸 𝑋)×𝐶𝑃𝐶 𝑋)×𝑀𝑎𝑠𝑠𝑠𝑝 𝑋)/

𝐼𝑐𝑜𝑟𝑟 𝑁𝑂3)

𝐶𝑃𝐶 𝑁𝑂3)×𝑀𝑎𝑠𝑠𝑠𝑝 𝑁𝑂3)

Page 6: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

RIE measured on standard vaporizer

AMS OM/Input OM= RIE × CE

Many organic standards are chosen to represent

SOA components. For this group of standards with

CE ranging from 0.18 – 1.0, the average apparent

RIE is about 20% higher than the value 1.4

obtained from previous laboratory calibrations.

There is an apparent slightly positive correlation

between RIE and CE.

Page 7: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

RIE of organics measured by a QAMS on standard and capture vaporizer

Why RIE of squalane

(SQL) decreases as been

oxidized?

Page 8: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Organic RIE using AN as an internal standard

RIE of alcohol could be reliably measured

RIE of organic acid could not, likely because of displacement reaction:

NH4NO3 + HA NH4A + HNO3(g)

Page 9: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Calculated ionization cross section as a function of electron energy

Calculated BEB EI ionization cross section as a function of the

kinetic energy of impacting electrons for selected multifunctional

organics. (a) adipic acid, (b) azelaic acid, (c) citric acid, (d) glutaric

acid, (e) 1,2,6-hexanetriol, (f) levoglucosan, (g) malonic acid, (h)

succinic acid, (i) sucrose, (j) tartaric acid, (k) xylitol, (l) malic acid,

(m) maleic acid, (n) phthalic acid, (o) squalane, (p) tetra-ethylene-

glycol, (q) d-threitol.

𝜎𝐵𝐸𝐵 =𝑆

𝑡 + 𝑢 + 1[𝑙𝑛𝑡

21 −

1

𝑡2 + 1 −1

𝑡−

𝑙𝑛𝑡

𝑡 + 1

where t=T/B, u = U/B, S = 4πa02NR2/B2, a0 is Bohr radius and equal

to 0.5292 Å, R is Rydberg constant and equal to 13.61 eV, T is the

kinetic energy of impacting electron, B is the binding energy of

electron in that molecular orbital, U is the kinetic energy of electron

in that molecular orbital, N is the occupancy number and can be

either 2 or 1 for occupied or partially occupied molecular orbital,

respectively.

Page 10: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Is the slope in Jimenez et al. (2003) really the RIE?

RIE = IE(Org) / IE(NO2) × MW(NO2) / MW (Org)

IE = σ × Je × tm

RIE = σ(Org) / σ(NO2) × MW(NO2) / MW (Org)

× tm(Org) / tm(NO2)

Not discussed in Jimenez et al. (2003)

Page 11: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Then why for most organics we are not far off? And why we are off for squalane?

• 𝑡𝑚 =𝑙𝑚

𝑣𝑚= 𝑙𝑚/

8𝑅𝑇

𝜋𝑀𝑊

On AMS vaporizer, most of the organics will decompose to smaller molecules

first because of the high vibrational excitation induced by the high vaporizer

temperature (600 C).

However, some organics, such as Squalane (a saturated hydrocarbon), does not

thermally decompose even at 600 C. As a result, tm for squalane will be much

longer than NO2 because of its high molecular weight.

Page 12: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Calculated RIE considering tm (2)and ignoring tm (1)

2.35 vs 7.10

RIE: 3.38

RIE: 2.96

Name Abbr. Class O/C H/C OSc MW (g mol-1) Cross section

(Å2)

RIE1 RIE2 RIEexp

Adipic acid ADI 0.67 1.67 -0.33 146.14 16.95 1.51 2.69 1.05(0.22)

Azelaic acid AZE 0.44 1.78 -0.89 188.22 24.27 1.68 3.40 1.87(0.23)

Citric acid CIT 1.17 1.33 1.00 192.12 18.85 1.28 2.61 2.87(0.61)

Glutaric acid GLA 0.80 1.60 0.00 132.12 14.45 1.43 2.41 0.99

Malonic acid MLOA 1.33 1.33 1.33 104.06 9.76 1.22 1.84 3.39(0.38)

Succinic acid SUA Acid 1.00 1.50 0.50 118.09 12.13 1.34 2.14 1.17(0.13)

Tartaric acid TAR 1.50 1.50 1.50 150.09 14.27 1.24 2.24 2.31(0.26)

Malic acid MLA 1.25 1.50 1.00 134.09 13.11 1.28 2.17

Maleic acid MLEA 1.00 1.00 1.00 116.07 11.31 1.27 2.02

Phthalic acid PHL 0.50 0.75 0.25 166.14 18.37 1.44 2.74

Oleic acid OLE 0.11 1.89 -1.67 282.46 45.14 2.08 5.16 2.96(0.44)3

1,2,6-hexanetriol HEX 0.50 2.33 -1.33 134.17 18.10 1.76 3.00 2.02(0.17)

Levoglucosan LEV 0.83 1.67 0.00 162.14 18.53 1.49 2.79 1.54(0.23)

Sucrose SUR 0.92 1.83 0.00 342.30 39.68 1.51 4.12 1.55(0.15)

Xylitol XYL Alcohol 1.00 2.40 -0.40 152.15 18.31 1.57 2.85 1.57(0.21)

Tetra-ethylene-glycol TGLY 0.63 2.25 -1.00 194.23 25.72 1.73 3.54

D-threitol THL 1.00 2.50 -0.50 122.12 14.95 1.60 2.60

Hexadecanol HDL 0.06 2.13 -2.00 242.44 41.35 2.22 5.10 3.38(0.41)3

Squalane SQL Hydrocarbon 0.00 2.07 -2.07 422.83 76.00 2.35 7.10 6.19(1.64)

DOS DOS Ester 0.15 1.92 -1.62 426.67 65.58 2.00 6.10

Ammonia NH3 17.03 3.04 2.33 1.42 5.2(0.6)4

Sulfur dioxide SO2 Inorganic 64.07 4.99 1.02 1.20 1.5(0.3)4

Water H2O 18.02 2.28 1.65 1.03 2~63

Page 13: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Calculated vs Experimental RIE

1. Molecular weight effect

2. Thermal decomposition

effect

3. Using CO2 to estimate H2O

and CO

Three sources of Biases

Page 14: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

The mysterious RIE of NH3

Name Abbr

.

Class O/C H/C OSc MW (g

mol-1)

Cross

section (Å2)

RIE1 RIE2

Ammonia NH3 17.03 3.04 2.33 1.42

Sulfur dioxide SO2 Inorganic 64.07 4.99 1.02 1.20

Water H2O 18.02 2.28 1.65 1.03

RIE Measured : (NH4) 4 to 6

: (SO4) ~1.2𝑡𝑚 =

𝑙𝑚𝑣𝑚

= 𝑙𝑚/8𝑅𝑇

𝜋𝑀𝑊

T effect? Not possible

Page 15: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

No matrix effect of NH4 RIE

Same RIE of NH4 in NH4NO3 and (NH4)2SO4

Molecular salt evaporation? Not possible.

Page 16: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

The higher RIE of POA might be offset by the lower lens transmission efficiency

Page 17: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Conclusion

• It’s a really complicated problem. Even in terms of relative ionization efficiency.

• We can’t explain NH3 RIE in theory.

• We could explain the high RIE observed for squalane.

• For most of the SOA and organics we are interested in, Jimenez et al. (2003) paper should still be applicable (ignoring the tm effect).

• For POA, because of the lens transmission cut off around 100 nm, we are still probably close.

Page 18: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

Questions?

Comments?

Insults?

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Page 20: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

120

100

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0

2.8x10-32.62.42.22.0

Particle time-of-flight time (sec)

20

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tof_mz71_7664 tof_mz71_two_7664 tof_mz71_three_7664 tof_mz85_7664 tof_mz85_two_7664 tof_mz55_7664 tof_mz41_7664 tof_mz41_two_7664

Squalane Single Particle signal

Page 21: Re-visit the Organic Relative Ionization Efficiency in AMScires1.colorado.edu/jimenez-group/UsrMtgs/UsersMtg17/AMS_Users... · Ionization efficiencies of molecules and relative ionization

200

150

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0

3.23.02.82.62.42.22.0

x10-3

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0

25

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tof_mz29_6418 tof_mz29_two_6418 tof_mz43_6418 tof_mz43_two_6418 tof_mz43_three_6418 tof_mz57_6418 tof_mz57_two_6418 tof_mz61_6418 tof_mz61_two_6418 tof_mz73_6418 tof_mz85_6418

Sucrose Single Particle Signal