Researchers have devised a way to better measure levels of nitric oxide, an airborne pollutant and essential signaling molecule in the body.
The development could help scientists monitor pollution levels and diagnose disorders in patients.
Just a few molecules of nitric oxide per billion or trillion molecules of air can promote smog, acid rain and ozone layer depletion. In the body, it plays a role in heart rate, blood flow, nerve signals and immune function.
But nitric oxide has been a challenge for scientists to measure accurately outside the laboratory.
Now, Princeton and Rice University researchers have demonstrated a new method of identifying the gas using lasers and sensors that are highly sensitive, compact and inexpensive.
According to the researchers, their portable device could be used in myriad ways, including monitoring and controlling vehicle emissions and monitoring human exposure to pollutants in urban or industrial environments.
The device is particularly attractive to doctors because its results are not corrupted by water vapor present in a person's breath. Now, a test could reveal chronic obstructive pulmonary disease and inflammation.
The device is about the size of a shoe box.
A team that included laser molecular detection pioneers Frank Tittel and 1996 Nobel laureate Robert Curl developed the system and conducted preliminary tests during the 2008 Olympic Games in Beijing.
(It published its results in the Aug. 4 issue of the Proceedings of the National Academy of Sciences.)
Existing systems to detect nitric oxide have various drawbacks. Home carbon monoxide sensors are compact and inexpensive, but not very sensitive. On the other hand, mass spectrometers and gas chromatographs are far more sensitive but slow, complicated, expensive and impractical for use outside of a lab.
Optical systems and sensors round out current offerings, and also have prohibitive drawbacks.
The new system actually does use optical sensing, but produces a much stronger signal than current offerings.
Nitric oxide detectors have used similar methods before, but until now have been hampered by their reliance on large laser sources designed for laboratory use, he said. The new system, in contrast, uses a quantum cascade laser, a state-of-the-art device ideally suited for this sensing technique. This makes it possible to reliably detect the gas at a concentration of a few parts-per-billion. The device is so precise it can distinguish between different isotopes of nitrogen and oxygen in the nitric oxide molecules.
Better still, the new system can run much longer without intervention -- several hours compared to just a few minutes for the best current methods -- allowing for long-term unattended operation.