27-05-2013, 12:44 PM
The Electronic Nose--A New Law Enforcement Tool
[attachment=54323]
abstract
A commercially available Electronic Nose may provide law enforcement
officers with a new investigative tool. An Electronic Nose
provides a recognizable visual image of specific vapor mixtures (fragrances)
containing possibly hundreds of different chemical species.
Conventional drug and bomb detectors use specific detectors designed
to filter out interfering substances and achieve YES or NO detection of
specific chemicals under very diverse conditions. However an electronic
nose is different because it is designed to quantify and characterize
all types of smells universally, including those from bombs and
drugs of abuse. It is this universality which leads to a wide diversity
of applications.
The new electronic nose is fast (10 seconds), operates over a
wide range of vapor concentrations, has picogram sensitivity, and is
simple to use and calibrate. The Electronic Nose has the ability to recognize
as well as quantify many different and sometimes complex fragrances.
This is achieved using pattern recognition and a visual fragrance
pattern, called a VaporPrint™ derived from an integrating
solid-state detector. Each smell or fragrance contains multiple analytes
with a distinct relationship to each other. A VaporPrint™ image
allows a complex ambient environment to be viewed and recognized
as part of a previously learned image set. Using the ability of the law
enforcement officer to recognize visual patterns allows quick assessment
of unknown smell or vapor.
Electronic Noses and Sensor Arrays
A type of vapor analyzer using an array of dissimilar sensors
simulating the human olfactory response has become known as an
Electronic Nose [Ref. 1]. An Electronic Nose provides a recognizable
visual image of specific vapor mixtures (fragrances) containing possibly
hundreds of different chemical species. An electronic nose is designed
to quantify and characterize all types of smells universally.
Sensors are selected for their chemical affinities and chemisorbing
polymer films are commonly used for this purpose. Many sensors can
be used and a serial polling of each sensor reading produces a histogram
of sensor outputs as indicated in Figure 1. The responses are uncorrelated
and sometimes multiple sensors
respond to the same vapor e.g.
overlap. Because of this, it is almost
impossible to calibrate this type of
Electronic Nose with test vapors containing
more than one compound. A
further issue is sensitivity because the
vapor sample being tested by the array
must be shared among each sensor in
the array.
Fast Gas Chromatography as an Electronic Nose
A new fast gas chromatography system using a Surface Acoustic
Wave (SAW) detector [Ref. 2] is depicted in Figure 2. The system
includes a heated inlet, vapor preconcentrator, temperature ramped and
direct heated GC column, and a SAW detector. Sensitivity is excellent
because the SAW detector has picogram sensitivity and there is no dilution
of vapor sample. The system inlet can sample ambient air,
desorbed vapor samples, or headspace vapors from liquid samples.
VaporPrint™ Images and Pattern Recognition
A polar plot of chromatogram time with the radial direction
being the sensor signal or the derivative of sensor signal provides an
important graphical feature well suited Electronic Nose pattern recognition
algorithms [Reg. 4,5]. The SAW sensor detects the amount of
analyte condensing (and evaporating) on a quartz surface and the SAW
frequency corresponds to the total (integral) amount of analyte condensed.
The SAW crystal is the only integrating GC detector, all others
detect the flux of column flow. The derivative of the detector output
is only used to determine retention time. The amount of analyte
detected is determined by sensor frequency.
Law Enforcement Applications and Requirements
Conventional drug and bomb detectors use specific detectors designed
to filter out interfering substances and achieve YES or NO detection
of specific chemicals under very diverse conditions. However
an electronic nose is different because it is designed to quantify and
characterize all types of smells universally, including those from
bombs and drugs of abuse. It is this universality which leads to the
wide diversity of applications among law enforcement users. As an
example of general drug enforcement, the following table downloaded
from the Los Angeles police narcotics department web site [Ref. 6],
illustrates the wide variety of compounds to be detected.
Commercial Availability of Electronic Nose
In 1997 Electronic Sensor Technology, Newbury Park, CA, began
the first commercial production of a GC/SAW electronic nose or
chemical vapor analyzer that performed flash chromatography, Vapor-
Print™ imaging, and sensor arrays with user defined alarm levels.
With single-handed ease, this instrument delivered 10 second chromatograms
using a patented Surface Acoustic Wave (SAW) sensor.
The electronic nose is designed to operate in the field as well as in the
laboratory. The instrument is stable over time, robust in construction,
and operates over a temperature range of 0oC-40oC.
Summary and Conclusions
A commercially available Electronic Nose can provide law enforcement
officers with a new investigative tool. The Electronic Nose
provides a recognizable visual image of specific vapor mixtures (fragrances)
containing possibly hundreds of different chemical species.
The new electronic nose is fast (10 seconds), operates over a wide
range of vapor concentrations, has picogram sensitivity, and is simple
to use and calibrate. The Electronic Nose has the ability to recognize
as well as quantify many different and sometimes complex fragrances.
This is achieved using pattern recognition and a visual fragrance pattern,
called a VaporPrint™ derived from an integrating solid-state detector.
A VaporPrint™ image allows a complex ambient environment
to be viewed and recognized as part of a previously learned image set.
Using the ability of the law enforcement officer to recognize visual
patterns allows quick assessment of unknown smell or vapor.
[attachment=54323]
abstract
A commercially available Electronic Nose may provide law enforcement
officers with a new investigative tool. An Electronic Nose
provides a recognizable visual image of specific vapor mixtures (fragrances)
containing possibly hundreds of different chemical species.
Conventional drug and bomb detectors use specific detectors designed
to filter out interfering substances and achieve YES or NO detection of
specific chemicals under very diverse conditions. However an electronic
nose is different because it is designed to quantify and characterize
all types of smells universally, including those from bombs and
drugs of abuse. It is this universality which leads to a wide diversity
of applications.
The new electronic nose is fast (10 seconds), operates over a
wide range of vapor concentrations, has picogram sensitivity, and is
simple to use and calibrate. The Electronic Nose has the ability to recognize
as well as quantify many different and sometimes complex fragrances.
This is achieved using pattern recognition and a visual fragrance
pattern, called a VaporPrint™ derived from an integrating
solid-state detector. Each smell or fragrance contains multiple analytes
with a distinct relationship to each other. A VaporPrint™ image
allows a complex ambient environment to be viewed and recognized
as part of a previously learned image set. Using the ability of the law
enforcement officer to recognize visual patterns allows quick assessment
of unknown smell or vapor.
Electronic Noses and Sensor Arrays
A type of vapor analyzer using an array of dissimilar sensors
simulating the human olfactory response has become known as an
Electronic Nose [Ref. 1]. An Electronic Nose provides a recognizable
visual image of specific vapor mixtures (fragrances) containing possibly
hundreds of different chemical species. An electronic nose is designed
to quantify and characterize all types of smells universally.
Sensors are selected for their chemical affinities and chemisorbing
polymer films are commonly used for this purpose. Many sensors can
be used and a serial polling of each sensor reading produces a histogram
of sensor outputs as indicated in Figure 1. The responses are uncorrelated
and sometimes multiple sensors
respond to the same vapor e.g.
overlap. Because of this, it is almost
impossible to calibrate this type of
Electronic Nose with test vapors containing
more than one compound. A
further issue is sensitivity because the
vapor sample being tested by the array
must be shared among each sensor in
the array.
Fast Gas Chromatography as an Electronic Nose
A new fast gas chromatography system using a Surface Acoustic
Wave (SAW) detector [Ref. 2] is depicted in Figure 2. The system
includes a heated inlet, vapor preconcentrator, temperature ramped and
direct heated GC column, and a SAW detector. Sensitivity is excellent
because the SAW detector has picogram sensitivity and there is no dilution
of vapor sample. The system inlet can sample ambient air,
desorbed vapor samples, or headspace vapors from liquid samples.
VaporPrint™ Images and Pattern Recognition
A polar plot of chromatogram time with the radial direction
being the sensor signal or the derivative of sensor signal provides an
important graphical feature well suited Electronic Nose pattern recognition
algorithms [Reg. 4,5]. The SAW sensor detects the amount of
analyte condensing (and evaporating) on a quartz surface and the SAW
frequency corresponds to the total (integral) amount of analyte condensed.
The SAW crystal is the only integrating GC detector, all others
detect the flux of column flow. The derivative of the detector output
is only used to determine retention time. The amount of analyte
detected is determined by sensor frequency.
Law Enforcement Applications and Requirements
Conventional drug and bomb detectors use specific detectors designed
to filter out interfering substances and achieve YES or NO detection
of specific chemicals under very diverse conditions. However
an electronic nose is different because it is designed to quantify and
characterize all types of smells universally, including those from
bombs and drugs of abuse. It is this universality which leads to the
wide diversity of applications among law enforcement users. As an
example of general drug enforcement, the following table downloaded
from the Los Angeles police narcotics department web site [Ref. 6],
illustrates the wide variety of compounds to be detected.
Commercial Availability of Electronic Nose
In 1997 Electronic Sensor Technology, Newbury Park, CA, began
the first commercial production of a GC/SAW electronic nose or
chemical vapor analyzer that performed flash chromatography, Vapor-
Print™ imaging, and sensor arrays with user defined alarm levels.
With single-handed ease, this instrument delivered 10 second chromatograms
using a patented Surface Acoustic Wave (SAW) sensor.
The electronic nose is designed to operate in the field as well as in the
laboratory. The instrument is stable over time, robust in construction,
and operates over a temperature range of 0oC-40oC.
Summary and Conclusions
A commercially available Electronic Nose can provide law enforcement
officers with a new investigative tool. The Electronic Nose
provides a recognizable visual image of specific vapor mixtures (fragrances)
containing possibly hundreds of different chemical species.
The new electronic nose is fast (10 seconds), operates over a wide
range of vapor concentrations, has picogram sensitivity, and is simple
to use and calibrate. The Electronic Nose has the ability to recognize
as well as quantify many different and sometimes complex fragrances.
This is achieved using pattern recognition and a visual fragrance pattern,
called a VaporPrint™ derived from an integrating solid-state detector.
A VaporPrint™ image allows a complex ambient environment
to be viewed and recognized as part of a previously learned image set.
Using the ability of the law enforcement officer to recognize visual
patterns allows quick assessment of unknown smell or vapor.