Trace Gas (and Isotope) Analysis: A Portable, Turnkey Instrument
Picarro, Inc.
480 Oakmead Parkway
Sunnyvale, CA 94085
Telephone: 408-962-3900
http://www.picarro.com
Environmental Problem
Acrolein or acrylaldehyde is a volatile, flammable
material that is relatively chemically unstable and
has a chemical formula of Ch^CHCHO. It is com-
monly produced as a byproduct in the combustion
of most organic materials and can be found in auto-
mobile exhaust, wood smoke, smoke from grass
fires, and even in cigarette smoke. Acrolein also is
used in the chemical industry in the production of
polyesters, acrylics, and glycerol. It is extremely
toxic to humans via inhalation and dermal expo-
sure. Short-term inhalation exposure may result in
upper respiratory tract irritation and congestion.
Consequently, parties as diverse as forest firefighters
and chemical plant operators could benefit from
monitoring the level of acrolein vapor in high-risk
areas. This need could be met by a trace-gas ana-
lyzer that combines both sensitivity and selectivi-
ty—the ability to quantitatively measure trace
acrolein in the presence of numerous other gas
species.
SBIR Technology Solution
With support from the EPA's SBIR Program, Picarro,
Inc., worked to develop an analyzer based on
wavelength-scanned cavity ring down spectroscopy
(WS-CRDS) technology. The principles of the
approach are simple: to use high resolution
infrared absorption to uniquely identify and quanti-
fy acrolein vapor, and to utilize WS-CRDS in partic-
ular to avoid all of the major inherent limitations of
conventional infrared spectrometers and non-dis-
persive infrared (NDIR) gas analyzers. These limita-
tions include a lack of sensitivity due to the small
amount of vapor and low signal/noise, and a lack of
spectral resolution necessary to uniquely identify
acrolein in the presence of other trace gases (i.e.,
The heart of the WS-CRDS analyzer is a thermally
controlled optical measurement cavity with an
effective path length of ca. 20 kilometers, which
thereby eliminates the "small sample size" sensitivi-
ty issue. In addition, an onboard wavelength moni-
tor controls the narrow line tunable laser diode
source, ensuring that absorption lines unique to
acrolein can be scanned repeatedly, precisely, and
rapidly, providing both fast (seconds) detection and
a high degree of species selectivity. Signal/noise is
further enhanced by the fact that this analyzer
measures the decay within the optical cavity each
time the laser is repeatedly and rapidly switched
off. Thus, random variations in laser intensity do not
affect the time-based data, unlike conventional
intensity-based absorption measurements. Using
this approach, a WS-CRDS-based acrolein analyzer
that provides parts per billion sensitivity and preci-
sion as well as a high degree of selectivity (no
crosstalk from other gases) was developed success-
fully. In addition, the analyzer supports sampling
rates as fast as 1 Hz in a portable, rugged instru-
ment that does not require frequent calibration or
any other type of maintenance, thus allowing
remote unattended operation.
Commercialization Information
Picarro engineers recognized that this revolutionary
instrument was more than ideal to meet the fast-
growing needs of many gas sensing applications
across the environmental science field, particularly
for carbon/water cycle studies and greenhouse gas
measurements. This includes at sources (e.g., power
plants), sinks (e.g., sequestration sites), and direct-
ly/remotely in the ambient atmosphere. Specifically,
the combination of high sensitivity and massive
dynamic range of this WS-CRDS analyzer means
that it can measure high ambient concentrations of
CC>2 and water vapor in a plant canopy or trace
In 2008, Picarro's carbon dioxide isotopic analyzer
was recognized with the prestigious R&D 100 Award.
SBIR Success Stories
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amounts of Ch^ from a landfill. Moreover, the
dynamic range also means that the concentration
of trace isotopes can be measured directly, for
example, by comparing spectral features unique to
H2O and HDO as well as 12CO2 and 13CO2. This
provides the ability to directly measure isotope
ratios in real-time, with no sample preparation, in
a portable instrument. This is a tremendous advan-
tage, because the isotope ratio in detected green-
house gases allows their source to be identified
and classified (e.g., anthropogenic [fossil fuel] or
biogenic). Even CO2 from grass and forest fires has
different and characteristic isotope signatures.
In addition, the company recognized the potential
for WS-CRDS to monitor several other gases such
as hydrogen sulfide, ammonia, and hydrofluoric
acid for which monitoring at trace levels is
required, either for safety (toxicity) reasons or for
process control (e.g., in semiconductor fabrication).
A family of WS-CRDS-based portable trace-gas and
isotope analyzers was launched in 2007 to meet
the needs of several of these applications.
Company History and Awards
Headquartered in Sunnyvale, California, Picarro,
Inc., was founded in 1998 to develop trace-gas
sensing applications based on WS-CRDS technology
licensed from Stanford University, and then further
strengthened by nine additional Picarro patents.
The company continues to experience strong com-
pound growth for its family of analyzers targeting
the environmental and semiconductor markets.
In 2008, Picarro's carbon dioxide isotopic analyzer
was recognized with the prestigious R&D 100
Award. Dubbed the "Oscars of Invention" by the
Chicago Tribune, the R&D Awards are presented
annually by the editors of R&D, a unique broad-
spectrum publication targeted at technical innova-
tions in industry, universities, and government/
national laboratories for applications as diverse as
environmental, life sciences, pharma, metrology,
semiconductor, and nanotechnology.
SBIR Impact
Acrolein is a noxious byproduct of combustion and chemical man-
ufacturing for which a simple yet precise trace sensor is needed.
Picarro developed an ultra-sensitive and portable trace gas analyzer based
on wavelength-scanned cavity ring down spectroscopy technology.
This instrument meets the needs for established and emerging sensing
applications in the environmental and semiconductor markets, including
providing the first remote isotope sensing capability.
• This instrument has the ability to monitor several other gases including
CO2 and other important greenhouse gases.
Picarro continues to experience strong commercial sales for its
analyzers, which also have been recognized with a prestigious R&D
100 Award.
SBIR Success Stories
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