1st detect presentation - apr 2012 - tedw

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In-Vacuo Thermal Desorption and Detection of Explosives Using a Miniature Mass Spectrometer

Warren Mino, David Rafferty, Abrar Riaz, Michael Spencer, William Stott, James Wylde

1st Detect Corp

April 2012 Trace Explosives Detection Workshop


MMS-1000

True Portable Mass Spectrometer Cylindrical Ion Trap Commercial release at Pittcon 2012

Portable Size & Lightweight 6”x 12”x 8” / 4 - 7 kg (9-16 lbs.)

Highly Sensitive ppm - direct leak ppb - membrane inlet ppt - pre-concentrator

Key Performance Specifications 30 - 450 amu (customizable to ~650 amu) < 0.5 amu resolution (< 0.3 amu typical) 1 sec cycle time (user programmable) MS2 capable (MS3 in manual mode) with > 90% efficiency ~ 45 W average power consumption (~65 W max) Auto-tune with internal standard

Deployments Pesticide detection (food products) Evolved gas analysis Explosives & CWA / threat detection

Cost Competitive with IMS


MOTIVATION

Why mass spectrometry for explosives detection? Increased specificity and resolution

Increased number of threats detected simultaneously

Confirmational / orthogonal analysis (e.g., GC-MS, MS/MS, etc.)

Easily adapted to new threats

Multiple ionization techniques

However, detection of explosives using MS is hampered by: Mass specs are inherently vapor analyzers – explosives tend to have low vapor pressures

Vacuum nature of MS – need to cross vacuum barrier

Thermal disassociation of explosives beyond recognition


PRE-CONCENTRATOR

SBIR Phase I & Phase II awarded by DTRA & DPG

Used to measure permeation rate through protective clothing (ASTM F079*)

Enables fast analysis of swatch testing

Challenge: Detect 13 TICs to 40 pg / l using miniature mass spec

1 l / min flow

30 second cycle time

Non-cryogenic

Universal

Accommodate hydrophobic and hydrophilic compounds

*Standard Test Method for Permeation of Liquids and Gases through Protective Clothing Materials under Conditions of Continuous Contact


PRE-CONCENTRATOR

Novel sorbent and design configuration

Increases concentration gain 103 to 105

Dramatically increases the sensitivity of the instrument

30 second cycle time

Gain effected by two means: Chemical gain of sorbent

Evacuation gain


Objective: Find lower limit of detection from membrane inlet and determine gain in concentration (improvement in sensitivity) with the pre-concentrator

Kin-Tek gas generator was used to create 4 different concentrations of tetrachloroethylene (TCE) and toluene

TCE Conc: 1.338 ppm, 671 ppb, 340 ppb, and 170 ppb

Toluene Conc: 1.218 ppm, 610 ppb, 305 ppb, 155 ppb

The lowest concentrations (170 ppb TCE) and (155 ppb Toluene) were used for measuring with the Pre-concentrator

Pre-concentrator was set to 5 seconds of sampling

Pre-concentrator temperature profile was ramped over 15 seconds

PRE-CONCENTRATOR


PRE-CONCENTRATOR

TCEm/z 166

Counts: 756

Toluenem/z 91

Counts: 698

Sample output (TCE 1.338 PPM Toluene 1.218 PPM)


PRE-CONCENTRATOR

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5000

10000

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Ion

Curr

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Pre-

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Inle

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Ion

Curr

ent (

coun

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Mem

bran

e In

let

Concentration (ppb)

Toluene

Toluene (MIMS)

Toluene (PC)

P/C Gain ~252x

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Curr

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Mem

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Concentration (ppb)

TCE

TCE (MIMS)

TCE (PC)

P/C Gain ~224x

Measured gains

TCE: 225x

Toluene: 252x

However:

Lower concentrations governed by lower limit of gas generator

Lowest gas generator concentration saturated detector with P/C activated

Gains expected 103 - 105


PRE-CONCENTRATOR

Measured gains on QQQ with diluted samples (< 1 ppb)

Gain 103 – 105 measured

Instrument ppb -> pptr

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

Direct Sorbent 1 Sorbent 2 Sorbent 3 Sorbent 4

Tota

l Ion

Cur

rent

Pre-concentrator GainNitrobenzene

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05


Tota

l Ion

Cur

rent

Pre-concentrator GainAcetone

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04


Tota

l Ion

Cur

rent

Pre-concentrator GainEthyl Acetate


EXPLOSIVES DETECTION

Objective: demonstrate that the MMS-1000 with EI is able to measure a representative list of explosives

Experimental: Explosive standards (1 mg/ml in MeOH) presented to pre-concentrator

Headspace sampled for 10 seconds

Pre-concentrator evacuated (~1 mTorr)

Analyte desorbed using 30 second ramp profile


EXPLOSIVES DETECTION

The requisite plot for vapor folks……


PERFLUORODECALIN

443

RDX

EXPLOSIVES


PERFLUORODECALIN

443

UREA NITRATE

EXPLOSIVES


PERFLUORODECALIN

443

AMMONIUM NITRATE

EXPLOSIVES


EXPLOSIVES

PERFLUORODECALIN

443

HMTD


EXPLOSIVES

PERFLUORODECALIN

443

PETN


EXPLOSIVES

PERFLUORODECALIN

443

EGDN


PERFLUORODECALIN

443

EGDN

SEPARATION

P/C can be operated with a temperature ramp rather than ‘flash’ desorbed Software also allows for single ion monitoring Will provide functionality similar to GC but without the time and power requirements


CONTACT SAMPLING


CONTACT SAMPLING - EXAMPLE

PERFLUORODECALIN

443 199

179

152

138

162 124

93

DIAZINON


PHOTOIONIZATION

Xylene


PHOTOIONIZATION

Methyl Salicylate


Headspace over traditional and nitrate based HMEs demonstrated with pre-concentrator

Characteristic spectra measured for candidate explosives

Thermal desorption demonstrated with vacuum based MS

Alternate ionization demonstrated for parent precursor molecule detection

Next steps:

Salts

Characterization (detection limits, interferents, de-convolution / identification, etc.)

Optimization

CONCLUSIONS


Acknowledgements Defense Threat Reduction Agency, JSTO-CBD

University of North Texas

1st Detect Houston R&D Team

Thank you for your time

1st detect presentation - apr 2012 - tedw

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