Securing Our Nations Water Supplies:Detecting Poisons by SERS

Providing Chemical Information When & Where You Need It

Support:EPA: EP-D-05-034, EP-D-06-084

www.rta.biz

Frank Inscore, Chetan Shende, Atanu Sengupta, and Stuart Farquharson

Challenge: specific, fast, sensitive

• Specificity – identify chemical agents & hydrolysis products• No False Positives!

• Speed – monitor poisoned water (batch & continuous)• 10 min or less

• Sensitivity – Requirements to protect • CN – 6 mg/L (6 ppm) • HD - 100 microg/L (100 ppb) TDG• Nerve - 5 microg/L (5 ppb) MPA

Part-per-billion is challenging!

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Analysis: CWA Hydrolysis Products

SP

O

O

NSH

NOH

PO

OOH

PO

O

SP

O

OHN

VXH2O + EMPADIASH ethanol

H2O

MPA+

EtOH MPA+ EA2192H2O

+DIASH

PO

O

PO

O

PO

O N

PO

O N

PO

O

PO

O

PO

O

PO

O

PO

O N

C N

F

F

F

GA

GB

GD

GF

OH

OH

OH

HCN

HF

HF

HF

2-propanol

2-pinacolyl

cyclohexanol

MPA

MPA

MPA

IMPA

PMPA

CMPA

H2O

H2O

H2O

+

+

+

+

+

+

+

OH

H2O

H2O

H2O

H2O

H2O ethanol +

OHEDMAPA DMAPA

HCNH2O

H3O+ + CN-

SCl Cl

SOH OH

HDTDGH2O 2 HCl +

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Approach: Surface-enhanced Raman Spectroscopy

h

Plasmon Field

ν

H

NH

H

H

H

N

NN

N

Ag

Surface-EnhancedRaman Photon

When a molecule is within a plasmon field,

the efficiency of Raman scattering can increase by 1 million times!

Sub part-per million detection becomes possible.

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SPO

ON

VX

Chemical contribution can provide additional 103 enhancement

Single Molecule Detection: requires 1012 -1014

SERS-Active Substrates

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10-3M

10-5M

10-8M(~10 ppb)

benzenethiol

Approach: RTA SERS Sampling Systems

Metal Particle

Sol-Gel Matrix

AdsorbedMolecules

Moleculesin Solution

Laser

RamanScattering

2001: Simple SERS Sample Vials

2001

1 10

2004: SERS-Active Capillary

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More suited to extract and pre-concentrate

2007: Functionalized Sol-Gel SERS Capillary

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2nd generation

Std SERS vials

PC

OTC unreduced reduced

RTA’s Portable Raman Analyzer

Advantages: • No sample preparation• Simple integration via fiber optics• Remote analysis, multi-component• Complete spectral coverage• Wavelength stability• Confident spectral subtraction• and library search/match• Real-time, On-demand analysis• Long term stability • Temperature and vibration immune• Shock resistant

25 poundswater tight

SERS-Active Capillary

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1064 nm

785 nm

Potassium Cyanide: IR, NR, SERS

Wavenumbers (∆cm-1)

Infrared (solid)

Raman (saturated solution, 1W, 10 min)

SERS (1 mg/ml water100 mW, 1-min)

CO2

2080 cm-1

2140 cm-1

Enhancement Factor ~ 3x106

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SERS: cyanide

100 mW 785 nm, 1-minSERS is Non-linear (Langmuir function)

PPM

100101

PPB

100101

2003 (Vial) 2005 (Capillary) 2007 (F-Cap)

PPT

100001001

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Thiodiglycol (TDG): SERS & NR

SERS: 1 mg/mL, 1.5-min100 mW 785 nm

Raman: neat solution, 5-min

300 mW 785 nm

Enhancement Factor = 2x105

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SERS: Thiodiglycol

PPM1

10

100

1000

100 mW 785 nm, 1-min

2005 (Capillary) 2007 (F-Cap)

PPB10

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SERS: MPA

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756PC

C

P

SERS: 0.1 mg/mL, 1-min,

100 mw 785 nm

Raman:1000 mg/mL, 5-min,

300 mw 785 nm

Enhancement Factor = 8x105

SERS: Methyl Phosphonic Acid

2003 (Vial) 2007 (F-Cap)

P-C760

100010010

1000 10010

PPM PPB

100 mW 785 nm, 1-minProviding Chemical Information When & Where You Need It

SERS: Methyl Phosphonic Acid

25 ppb

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SERS MPA

ppb

1000

500

250

125

0

0.025

0.05

0.075

0 100 200 300 400 500 600 700 800 900 1000Concentration (ppb)

Peak

hei

ght

SERS: 10 parts-per-billion

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MPA

TDG

CN

SERS: Alkyl Phosphonic Acids

1 ppm

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SERS: 10 parts-per-billion

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IpMPA

PMPA

CMPA

EMPA

DIASH

80 mW, 785 nm, 1-min

SERS: 10 parts-per-billion

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CEMS

CEES

HEES

40 mW, 785 nm, 30-sec

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SERS: 10 parts-per-billion

Fonofos

Chlorobenzoic Acid

Sunset Yellow

80 mW, 785 nm, 1-min

Summary: specific, fast, sensitive

• Specificity – identify chemical agents & hydrolysis products• No False Positives!

• Speed – monitor poisoned water (batch)• 10 min or less – 1 minute

• Sensitivity – Requirements• CN – 6 mg/L (6 ppm)• HD - 100 microg/L (100 ppb)• Nerve - 5 microg/L (5 ppb)

Lowest Measured Concentration!CN – 1 ng/L (1 ppt!)TDG - 10 microg/L (10 ppb)MPA - 10 microg/L (10 ppb)

“pH dependence MPA, DPA, CN by SERS”, SPIE, 5269, 117-125 (2004)“SERS Analyzer for Monitoring Chemical Agents and Their Hydrolysis Products”, IJHSE, 102-111 (2007)

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Continuous Monitoring

5”

3”

1.5”

1.5”threaded for

device attachment

SERS-CapillaryInterface Block

hole to passmounting

screw

1/8” Tygontubing

SERS-activecapillary

opening to pass light

Fiber Optic cable

to instrument

FO Probe& Mount

1) Preliminary lab Measurements

10 ppb CN!

3) Interface design to sample

extraction line

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2) 10 ppb food dyefor water

supply tests

Future Work: NeSSI &Real-World Sampling

Parker-Hannifin Swagelok

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Regulated Water

Sample Bottle

Waste Bottle

MeOH Pump

3-Way 3-Way Surface Ex- Surface 3-Way Surface SERS SurfaceValve Valve Connection tractor Connection Valve Connection Sensor Connection

Load Sample Into Extractor (5 min)

NeSSI &Real-World Sampling

Providing Chemical Information When & Where You Need It

Regulated Water

Sample Bottle

Waste Bottle

MeOH Pump

3-Way 3-Way Surface Ex- Surface 3-Way Surface SERS SurfaceValve Valve Connection tractor Connection Valve Connection Sensor Connection

Load Sample Into SERS Capillary (10 sec)

NeSSI &Real-World Sampling

Providing Chemical Information When & Where You Need It

Regulated Water

Sample Bottle

Waste Bottle

MeOH Pump

3-Way 3-Way Surface Ex- Surface 3-Way Surface SERS SurfaceValve Valve Connection tractor Connection Valve Connection Sensor Connection

Measure SERSLoad Next Sample Into Extractor (5 min)

NeSSI &Real-World Sampling

Providing Chemical Information When & Where You Need It

In Progress