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A New Type of Electronic Nose for Analyzing Malodor
• Introduction - Electronic Nose and Sensor Arrays
• Fast Chromatography as a Sensor Arrays
•Quantifiable Results - US EPA Validation
• VaporPrintsTM Images and Pattern Recognition
• Breath and Common Mouthwash odors
•Other Useful VaporPrintTM Applications
• Summary and Conclusions
Edward J. Staples, Ph.D.
Electronic Sensor Technology1077 Business Center CircleNewbury Park, California
Ph: 805-480-1994 FAX: 805-480-1984WebSite: www.estcal.comemail: [email protected]
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A New Type of Electronic Nose for Analyzing Malador
A new type of Electronic Nose which simulates the human olfactory response with a 500 element array of nearly orthogonal sensors in 10 seconds is described in this paper. This electronic nose is the first to be validated by the US EPA with both volatiles as well as semi-volatile organic compounds. Application of this new technology to identify and quantify breath odors can identify specific analytes and their concentrations in breath. This new eNose contains a large number of orthogonal sensors, very detailed VaporPrintTM images which are used to identify complex odors and fragrances. With orthogonal 500 sensors, the olfactory response can be mapped into a visual image and this allows accurate pattern recognition by humans as well as computers.
Unlike conventional sensor arrays this eNose speciates and quantifies the individual analytes present in breath. This paper will present results obtained from bacteria and other malodors associated with human diseases. In addition, VaporPrintTM images associated with common mouthwashes will be presented.
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Electronic Noses(Sensor Arrays)
•Technical Approach– Sensor Arrays to mimic
the human olfactory response
– Visual Image– Pattern Recognition
•Specificity– Orthogonality– Sensor Separation– Meaningful Sensor
Sequence or Order
•Ability to Calibrate– Sensitivity– Accuracy– Precision– Speed
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Fast Gas Chromatography
•GC/SAW Electronic Nose with programmable sampling preconcentrator
• 10 Second Analysis Speed
• Volatile Compounds - ppb MDL
• Semi-Volatile Compounds - ppt MDL
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Cal 1 in Air
Cal 1 Air0oC SAW30 secondSample
Cal 2 Air0oC SAW30 secondSample
chloroform
benze
ne
toluene
ethylben
zene
1,1,2,2 trich
loroethan
e
1,2 DCE
Carbon te
trach
loride
TCE PCE Xylene
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Calibration Filesfor Air
* 30 Second Sample 0oC Detector
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Water Calibration
Cal 1Water0o SAW30 sec Sample
Cal 2Water0o SAW30 sec Sample
chloroform
benze
ne
toluene
ethylben
zene
1,1,2,2 trich
loroethan
e
1,2 DCE
Carbon te
trach
loride
TCE
PCEXylen
e
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Calibration Filesfor Water
* 30 Second Sample 0oC Detector
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Minimum Detection Levels for Common VOC
30 second Sample of Vapor0oC SAW Detector
MINIMUM DETECTION LEVEL
Analyte AIR (ppb) WATER (ppb)
Chloroform45 0.65
Cis 1,2 Dichloroethene47 1.7
Benzene42 0.96
Carbon Tetrachloride130 16.49
Trichloroethylene6.3 0.40
Toluene11 0.15
Tetrachloroethylene5.7 0.57
Ethylbenzene2.7 0.07
O - Xylene2.5 0.11
1,1,2,2 Tetrachloroethane3.6 0.56
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Chromatogram viewed as a serial polling of a sensor array
•Step 1 - Preconcentrate
•Step 2 - Desorb & Inject
•Step 3 - Observe elution of analytes from GC column
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Display Formatsand Vapor Signatures
FrequencyPattern
Ethlybenzene
Benzene
Tolueneo-Xylene
124 Trimethylbenzene
DerivativePattern
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VaporPrintTM Pattern Recognition
•Evaluation performed using Humans and Artificial Intelligence/Neural Net Software
•Result - Human perception is practically optimal at recognizing VaporPrintTM images.
Example
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Useful Attributes of an Electronic Nose
• Dental and Oral Characteristics – visual, sound, tactile– X-ray images– olfactory evaluation
(quantitative)
• Electronic Nose– improves olfactory capabilities– transfers olfactory stimulus to
visual pattern recognition
Oldsmobile Alero
Oldsmobile Aurora
Example: Learning to recognize
the olfactory image ‘that new car smell’
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•Volatile Organics
•Bacteria Odor Signatures
•Breath Odor
•Detection/Diagnostics
•Gastrointestinal
•Salivary Treatment
•Animal studies
•Other– Medical Diagnosis– Early
identification of Infectious disease
– Biological agents– Body Odors
Near Real Time (10 Seconds)Chromatography
with an Electronic Nose
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Now the Speed of a Sensor Array and the Performance of a Fast Gas
Chromatograph
SAW SensorVapor
Signature
ProcessedVapor
Signature
US EPA ValidatedChromatography
Software DefinableSensor Arrays
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VaporPrintTM Images of Mouthwash Odors
Tom’s Spearmint Tom’s Peppermint Scope Peppermint
Long’s Mint Scope mint Long’s Blue Mint
Listerine Mint
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Comparison of Mints
Long’s Mint
Listerine Cool Mint
Long’s Blue Mint
Quantitative Comparisons (Analyte by Analyte)
Vol-1 Mint-M3 Mint-M2 Mint-M1 Mint-h1 Mint-h2 Amount
(ppm) Amount
(ppm) Amount
(ppm) Amount
(ppm) Amount
(ppm) Amount
(ppm)
19 76.9 184 144 scope mint1 16.6 976 85.4 140 Listerine Cool Mint
13 119 115 Longs Blue Mint 10.4 38.2 152 419 Longs Mint
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Long’s and ScopeMint
Scope Peppermint
Scope Mint
Tom’s Peppermint
Tom’s Spearmint
Listerine Cool Mint
Long’s Blue Mint
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Salmonella typhimurium
Strep pneumonia
Shigella flexneri Salmonella
enteritidis
Hemophilus influenza Enterococcus
faecalis E. Coli O157E. Coli
Staph aureus
Pseudomonas aeruginosa
Klebsiella pneumonia
Candida albicans
Cultures Prepared by: Department of Pathology and Laboratory Medicine, State Public Health Laboratory of Nevada
VaporPrintTM of Infectious Bacteria Cultures
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DioxinsOnions Garlic
CoffeeMushroomsAuto Exhaust
Peanut Butter Cup
PCBAroclor 1260
US Currency
DieselGasoline Kitt-Kat
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Summary
• Flash Chromatography using Surface Acoustic Wave GC Detectors– Small, Solid State, low cost– no polymer coatings to degrade >> high
stability
• 10 Second analysis time provides a fast and portable malodor analyzer
• Functional Electronic Nose– Serial Polling simulates 500 orthogonal
Sensors in 10 Seconds– Minimal overlapping responses (co-
elution)– EPA Methods Insure Accuracy &
Precision
• Sensitivity– ppb for VOCs– ppt for Semi-VOC
• Save Money and Time with real time Quantitative Results in-situ
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