Coupling Atmospheric Pressure Photoionization (APPI) with Differential Mobility Analysis (DMA) – Mass

Spectrometry for the detection of non-polar environmental analytes within gaseous samples

Ross McCullochArturo Álvaro Carballido

Sociedad Europea de Análisis Diferencial de Movilidad SL (SEADM)(European Society of Differential Mobility Analyzers)

Marie Curie Industry-Academia Partnerships and Pathways (IAPP)

Motivation and objectives

• Motivation

Develop an ion source for the analysis of vapour samples

containing non-polar analytes using DMA-MS technologies

• Objectives• Objectives

1. Prototype APPI-DMA-MS source design

2. Characterize and identify key applications

3. Refine source design: produce a commercially viable

device

Key SEADM Technologies

• Differential Mobility Analyzer (DMA)

– Integrates with MS to add an ion mobility dimension

– Intended to reduce need for LC equipment

– Minimizes sample throughput time

– Provide high sensitivity, selectivity & reduce background levels– Provide high sensitivity, selectivity & reduce background levels

• Secondary Electrospray Ionization (SESI)

– Based on a simple nanospray source configuration

– Intended for the analysis of vapours

– Demonstrated high sensitivity

Differential Mobility Analyzer (DMA)

• The principle

• Continuous ion sampling / high duty cycle

• Ion transmission up to 50%

• Resolving power as high as 80

• Complete mobility scans in less than 1 minute

Secondary Electrospray Ionization, SESI

Two modes:

1) Nanospray for

liquid samples

2) SESI for vapour

analysis

- Gas-phase analyte

ionization process

- Electrospray charger ions

� Sub ppt LODs

� Reduced matrix impact

� Low flow configurations for

increased sensitivity

Vapour Sampling Method

VapourSampler

The Lab The Field

• Vapour analysis (explosive screening, breath, etc.)

• Mixture of explosives

separated according to

mobility.

SESI-DMA applications

4.0e4

4.5e4

5.0e4

5.5e4

1366.05

PETN

• Detection limits in ppq

range for vapour analysis.

• Cargo container screening

/ security applications.

900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1550 1600IS, Volts

0.0

5000.0

1.0e4

1.5e4

2.0e4

2.5e4

3.0e4

3.5e4

Inte

nsity

, cps

1451.97 1489.84 1528.71 1568.32TNT

EDGN

RDX

NG

Mobility / V

Inte

nsi

ty /

cp

s

Why APPI ?

• ESI/SESI suitable for polars, not ideal for non-polars

• Applied typically to LC-MS methods; good for non-polar analysis

• Gas-phase chemical ionization method; adapts well to vapour analysis

• Dopant (D) generally used to enhance analyte (M) ionization efficiency

Atmospheric Pressure Photoionization, APPI

1) Robb, D. B., Covey, T., & Bruins, A. (2000). Atmospheric pressure photoionization: an ionization method for

liquid chromatography-mass spectrometry. Analytical chemistry, 72(15), 3653-3659.

• Analytes are efficiently ionized within the gas-phase through

various pathways:

Charge exchange, proton transfer, electron capture, charged adduction, etc.

• Works effectively in positive and negative ionization modes.

• Applicable to both polar and non-polar compounds.

Atmospheric Pressure Photoionization, APPI

“Most universal source for LC-MS”

• Broad linear dynamic range.

• Minimal susceptibility to matrix effects.

• Comprehensive review of APPI-LC-MS fundamentals:

2) Robb, D. B., & Blades, M. W. (2008). State-of-the-art in atmospheric pressure photoionization for LC/MS.

Analytica chimica acta, 627(1), 34-49.

APPI-DMA Prototype Version 1.0

• Based upon 1st generation field-free APPI source configuration3

• Shown to provide advanced sensitivity for LC-MS applications

• 2 configurations:APPI-MS APPI-DMA-MS

3) McCulloch, R. D., Robb, D. B., Blades, M. Design modifications enabling a performance comparison between early and current generation

commercially available atmospheric pressure photoionization (APPI) sources, Proceedings of 57th ASMS conference, Philadelphia, PA (2009)

DIOXDETECTOR (Fast Atmospheric Dioxin Detection)

• Project objective: Method for quantification of dioxins and furans.

• Track PCDDs/PCDFs in air, soil and vegetable matter at surroundings

of incineration facility.

• Samples collected and extracted

– No direct vapour analysis

• APCI/ESI/SESI evaluated.

– Insufficient sensitivity/ineffective

• APPI developed to tackle problem.

Support of this work was provided by the LIFE+ Program

• Method Development: fullscan

Negative mode:

• Analytes infused, toluene solvent

• Dioxins and furans - [M-Cl+O]-

HxF HxD

Hexachlorodibenzodioxin and furan @ 2 ng/mL, in toluene @ 2 µL/min,

Suitability for Dioxin/Furan Screening

• SEADM: APPI-MS (no DMA);

AB Sciex 3200 series QTrap

• Analysis of liquid standards

• LODs ranging from 0.15-1.40 pg;

- most detected near 1 pg level

Log scale

- most detected near 1 pg level

• Method suitable for trace analysis

� NDAMN4 - (HR-GC-MS)

• Complying with regulations (US EPA

Method 1613B1 and Regulation (EC) No.

1883/20062).

4) The National Dioxin Air Monitoring Network (NDAMN) – Report of the Results of Atmospheric Measurements of Polychlorinated

Dibenzo-p-Dioxins (PCDDs), Polychlorinated Dibenzofurans (PCDFs) and Dioxin-Like-Polychlorinated Biphenyls (PCBs) in Rural and Remote

areas of the United States from June 1998 through November 2004.

The practical application: Dioxins & Furans – Site X

• Samples obtained

from various locations

• Air (~700 m3), soil (~5 g)

and biota/plant (~ 20 g)

matter collected &

extractedextracted

• Samples delivered to

SEADM for analysis

• Toxic equivalency (TEQ)

estimated

• Project in early stages

Blue – January, Red – February, Green - March

• Method development: fullscan

Positive mode:

• Analytes infused, toluene solvent

• Polycyclicaromatic Hydrocarbons (PAHs) – M+

Ex. BghiP

m/z → 276

Ex. Benzo(ghi)perylene - 100 ng/mL in toluene @ 2 µL/min

Thermal desorption – APPI-MS

9.00e4

9.50e4

1.00e5

1.05e5

1.10e513.80

2.310.94 15.308.79

3.89

Benzo(a)pyrene, BaP – Desorbed at 250oC

MRM method; 12 consecutive samples

2 µL of 100 ng/mL – 200 pg

4.E+05

5.E+05

BaP - 252/250

σarea ~ 30%

2 4 6 8 10 12 14 16 18 20 22 24Time, min

0.00

5000.00

1.00e4

1.50e4

2.00e4

2.50e4

3.00e4

3.50e4

4.00e4

4.50e4

5.00e4

5.50e4

6.00e4

6.50e4

7.00e4

7.50e4

8.00e4

8.50e4

9.00e4

Inte

nsity

, cps

10.53 16.8412.22

7.03

5.40

18.37

R² = 0.999

R² = 0.999

0.E+00

1.E+05

2.E+05

3.E+05

4.E+05

0 200 400 600C

ou

nts

/s

mass / pg

BaP - 252/248

• Toluene added to auxiliary gas

Adding the DMA Mobility Element

Impacting Mobility

and Resolution

• DMA gas velocity or

pump speed

8000 RPM

Scan time < 1 min

pump speed

• Gas selection

(N2, CO2, Ar, etc.)

• Additives

(Benzene, IPA, toluene,

water, etc.)

14000 RPM

- Infusion of a standard PAH panel - 100 ppb in toluene @ 2 µL/min

Benzo(a)pyrene Benzo(k)fluoranthene

• Separating isomers/congeners remains a technical challenge for the DMA

• Ex. BaP and BkF indistinguishable to MS; even in MRM mode

Blue – BaP + BkF Green – BaP Red – BkF

1800

2000

2200

2400

2600

2800

2927

Benzo(k)fluoranthene

m/z - 252 m/z - 252

1600 1620 1640 1660 1680 1700 1720 1740 1760 1780 1800 1820 1840 1860 1880 19000

200

400

600

800

1000

1200

1400

1600

1800

1737.66

Mobility / V

Inte

nsi

ty /

cp

s

• Continued goal to improve DMA resolution

Deconvolution possible:

Blue – BaP + BkF Red – BaP Green – BkF

PAH panel – Desorption APPI-DMA-MS• Analytes deposited on a filter cartridge by micro pipette; desorbed at 250 oC

• Ion Mobility (Z) voltage optimized and fixed for each analyte

• Method suitable low level PAH detection (Isomers often not separable)

• Next step: collect real samples – demo full TD-APPI-DMA-MS workflow

1 µL standard panel - 100 ppb, 6 analytes (100 pg each)

Continued Focus

• Apply complete APPI-DMA-MS workflows:

– Develop complete PAH vapour sampling method

• Expand range of applications:

– PCBs, pesticides, explosives, biologicals– PCBs, pesticides, explosives, biologicals

• Optimize APPI: evaluate alternative geometries & refine the design

• General goal to improve DMA resolving power and performance

Acknowledgements

• SEADM

• Marie Curie (IAPP)

• Dr. Juan Fernandez de la Mora, Yale University

• LIFE+ Program

- Thank you -