Analysis of Drinking Water Using LIBS

December 2012

Analysis of Drinking Water Using LIBS

Applied Research Associates, Inc. Proprietary Information

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2Applied Research Associates, Inc. Proprietary Information

To Be Covered

LIBS Overview Advantages Methods of Analysis Direct Analysis Pre-concentration Prior to LIBS Analysis PMACS 1000 (for pre-concentration) Summary

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How does LIBS work?

LIBS is a form of atomic emission spectroscopy

• Laser pulse creates a spark on the sample material

• Light emissions are collected and input into a spectrometer

• Processor is used to compare the emissions with our database

• Analysis results listed in seconds to minutes depending on sample complexity

Laser spark on soil

3-5 mm

laser

receiver

plasma on sample The Laser Plasma

Hotter than the sun’s surface

Plasma lasts ~20 µs

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LIBS Instrument Configurations are Application Specific

SPECTROGRAPH

LASERMIRROR

LENS

SAMPLE

DETECTOR

FIBEROPTIC

COMPUTER

0

5000

10000

15000

20000

25000

200 300 400 500 600 700 800 900 1000wavelength (nm)

inte

nsity

(cou

nts)

General LIBS Set-up

Table top ARA built food prototype: distinguishes E. Coli from Salmonella

LIBS Instruments • Customized for the application• Lab and production line deployment• Size, cost, complexity determined by the application

LIBS spectrum analyzed to ID pathogens

LVSB. anthracis

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Advantages of LIBS for Water Analysis

Rapid analysis for targeted species (<5 min for comprehensive analysis).

Simultaneous detection of all targeted species (eliminates separate tests for individual targets)

No chemical agents or consumables required in contrast to current reagent based methods.

Field deployable LIBS instrument through the use of compact and rugged components available commercially-off-the-shelf.

Automated analysis of all targets through instrument control and analysis software.

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Methods of Analysis Without Pre-concentration of sample using LIBS

• Useful when contaminant concentrations are high enough (103 – 109 cells/mL)• Samples could be dried on slides or a direct sampling method could be developed.

Pre-concentration of samples prior to LIBS testing• Useful when contaminant concentration are very low

Without Pre-concentration

With Pre-concentration

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Direct Analysis Pathogens and other contaminants can be detected in a variety of water matrices

by creating chemometric differentiation models for analysis of LIBS spectra and deploying models in an analysis algorithm specifically designed for the detection application.

Recent study of LIBS detection capability in tap water indicates detection is possible in many types of water for concentrations ranging ≥ 103 cells/mL

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Example of Analysis Algorithm for E. coli, Salmonella, and E. faecalis in Tap water

Blank slide or Other? Blank Slide

Tap Water Flow

Tap water or Other? Tap water

E. coli or Other? E. coli

Salmonella or E.

faecalis?Salmonella

E. faecalis

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Differentiation of uncontaminated Tap Water

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Differentiation of E. coli in Tap Water

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Differentiation of Salmonella from E. faecalis in Tap Water

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Pre-concentration prior to LIBS Analysis of Sample Collect and pre-concentrate particles and organisms in 200 mL

volume of aqueous suspension using the PMACS 1000 IntelliSense DesignTM flow system

Collect particles and organisms in the aqueous suspension on a filter substrate

Collect metal ions from the aqueous suspension on ion exchange membrane filters (e.g. 3M Empore® Extraction Disks; 3M Corp. St. Paul, MN).

Interrogate particles, organisms, and metals ions collected on filters using laser spark.

Spark scanned along surface

R.C. Chinni, D.A. Cremers, and R.A. Multari, “Analysis of material collected on swipes using Laser-Induced Breakdown Spectroscopy (LIBS),” Applied Optics, Vol. 49, Issue 13, pp. C143-C152 (2010).

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The unit as currently configured has dimensions 36x12x12 inches and a flow rate of 4 L/min. A typical concentration factor is x1000.

PMACS 1000

The device is shown in use at the Dunedin, FL water utility for groundwater collection of indicator organisms.

• Kearns, E.A., S. Magana, and D.V. Lim. 2008. “Automated concentration and recovery of microorganisms from drinking water using dead-end ultrafiltration,” J. Appl. Microbiol. 105:432-442.

• Leskinen, S.D. and D.V. Lim. 2008. “Rapid ultrafiltration concentration and biosensor detection of enterococci from large volumes of Florida recreational water,” Appl. Environ. Microbiol. 74:4792-4798.

Could be used for pre-concentration if necessary.

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Collection using the PMACS 1000

Closed

Backflushrecovery: pushing buffer in direction opposite to test fluid

(1) Filtration of several liters of drinking water supply (4 L/min. flow rate)

(2) Backflush to collect targeted materials on filters

Hollow fibers

Filter membrane

Closed

Filtered water either discarded or routed back to

supply at a location distant from intake to

filter

Supply

Diagram showing flow from a water supply through the PMACS unit to concentrate particles and organisms (metal ions collected on filter ).

Diagram showing flow during the Backflush to collect particles and organisms on a filter ( ).

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Differentiation of E. coli post pre-concentration

-6

-4

-2

0

2

4

6

8

10

12

Clas

sifica

tion

Valu

e

E.coli Contamination

Tampa Water Tap Concentrate

Albuquerque Tap Water (unconcentrated)

Each Point is the Average of 5 Measurements(5 seconds data collection per point)

-6

-4

-2

0

2

4

6

8

10

12

Clas

sifica

tion

Valu

e Tampa Water Tap Concentrate

Albuquerque Tap Water (unconcentrated)

E.coli in Tap Concentrate (CFU/mL)

Each Point is the Average of 40 Measurements(40 seconds data collection per point)

E.coli Contamination

10

10 2

10 3

10 4

10 5

10 6

10 7

10 8

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Summary ARA has demonstrated the ability to differentiate contaminates in water

matrices using LIBS• Multiple studies using samples provided by the University of South Florida

Basic Detection Blind Study (100%) Detection Limit Study (direct detection limit ~103 cells/mL) Study of LIBS post pre-concentration of sample (10 cells/mL demonstrated)

LIBS for water analysis could be used in real time to• Differentiate “good” from bad water• Monitor for specific contaminations in water• Flag changes in water composition

Advantages of using LIBS:• Fast• Simultaneous analysis of multiple parameters is easily possible• Results can be obtained on-site, in real time

Analysis of Drinking Water Using LIBS

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