Optical spectroscopy is one of the most powerful methods for quantitatively analyzing the composition of gas mixtures, including at trace levels. This is due to the fact that the vast majority of polyatomic molecules exhibit distinct optical absorption features in the mid-wave and longvawe infrared (MWIR and LWIR, respectively) spectral regions. Probing these features with tunable lasers allows simultaneous, quantitative measurement of the composition of multiple gases, even if their absorption features overlap.
Pranalytica stands in a unique position among gas sensing companies as a pioneer in both novel methods and algorithms for gas sensing, and in game-changing spectroscopic light sources.
Pranalytica's unique, patented algorithms for quantitative measurement of constituent gases in a mixture with overlapping absorption features have originally been developed with funding from DRAPA. Subsequently Pranalytica's unique method for quantifying gas sensor performance in the presence of interfering species has become a de-facto method of chemical sensor evaluation.
In parallel, Pranalytica successfully leveraged its position as the world leader in commercial high performance MWIR and LWIR quantum cascade lasers (QCLs) to create high performance spectroscopic laser sources.
Combining its unique laser and sensing technologies has allowed Pranalytica to field gas sensing instruments of unparalleled performance. Our instruments are characterized for their very high sensitivity (typically parts per billion – ppb – or better), combined with excellent immunity to interference from other gases that plague many competing sensors.
Our sensors, based on our unique suite of Optical-Nose (O-Nose™) Technology, have found acceptance in a wide range of applications. In the industrial arena, our sensors continuously and autonomously monitor technological processes in semiconductor fab lines or trace gas contamination with sub-ppb precision, facilitating yield improvements and cost-effective process control. In the environmental sciences, our sensors monitor gaseous precursors to smog, enabling better understanding of pollution control and mitigation. In medicine, Pranalytica's sensors analyze human breath to monitor kidney dialysis, to detect early onset of a dangerous pregnancy complication, pre-eclampsia, and other applications. In the security landscape, our sensors provide monitoring safeguards against chemical warfare agents, explosives, and toxic industrial chemicals. Pranalytica has recently expanded its sensing technology to remote detection of explosives via optical spectroscopy, allowing their reliable identification at safe distances.
Combining unmatched gas sensing expertise with world-leading spectroscopic laser sources, Pranalytica has the track record to successfully tackle the most difficult gas sensing problems, allowing its customers to solve problems that may be intractable by any other means.
Figure 1. Schematic of the "optical nose" technology platform (O-Nose™)
Since the O-Nose technology is based on a platform concept, the carbon dioxide laser can be replaced with a carbon monoxide laser [4], a spin-flip Raman laser [5], or a tunable semiconductor laser [6]with or without obtaining power boost from an optical amplifier such as a fiber amplifier [7]. This flexibility will permit, in the future, virtually limitless options for measurement of any trace gas species [8]. Specifically, a combination of the CO2 and a CO laser based instrumentation was shown to detect ppb levels of ammonia, benzene, 1,3-butadiene, 1-butene, ethylene, methanol, nitric oxide, nitrogen dioxide, propylene, trichloroethylene, and HCN [9,10]. The O-Nose technology is the engine of the Nephrolux™ that measures ppb level ammonia in expired human breath in presence of large number of other interfering species including >4% carbon dioxide, >10% water vapor, and more that 200 volatile organic compounds. This instrument is user friendly and has been deployed in UCLA's kidney dialysis center and in the OB/GYN center in the Olive View Medical Clinic in Sylmar, CA where they are used exclusively by physicians and nurse practitioners to collect clinical data on kidney dialysis patients and potential pre-eclampsia patients. The O-Nose technology is also the engine in the Nitrolux™ that is designed to measure sub-ppb levels of ammonia in semiconductor industry clean rooms and ambient air monitoring. Because at ppb and sub-ppb levels, the absorption caused by the gaseous species being detected is very small, a number of optoacoustic cells can be inserted in the path of the optical beam. Such "optical multiplexing" allows monitoring of multiple streams of gases simultaneously in the industrial environment. [11]
REFERENCES
1. C. K. N. Patel, "Interpretation of CO2 Optical Maser Experiments", Phys. Rev. Lett. 12, 518 (1964).
2. Brian Wiemeyer U.S. Patent 6,658,032 ( December 2, 2003).
3. L. B. Kreuzer, and C. K. N. Patel, "Nitric Oxide Air Pollution Detection by Optoacoustic Spectroscopy", Science 173, 45-47 (1971).
4. C. K. N. Patel, "CW Laser on Vibrational-Rotational Transitions of CO", Appl. Phys. Lett. 7, 246-247 (1965).
5. C. K. N. Patel and E. D. Shaw, "Tunable Stimulated Raman Scattering from Conduction Electrons in InSb", Phys. Rev. Lett. 24, 451-455 (1970).
6. Michael E. Webber, Douglas S. Baer and Ronald K. Hanson, "Ammonia Monitoring near 1.5 µm with diode-laser absorption sensors," Applied Optics 40, 2031-2042 (2001); Michael E. Webber, Ricardo Claps, Florian V. Englich, Frank K. Tittel, Jay B. Jeffries and Ronald K. Hanson, "Measurements of NH3 and CO2 with distributed-feedback diode lasers near 2.0 µm in bioreactor vent gases," Applied Optics 40, 4395-4403 (2001).
7. M.E. Webber, M.B. Pushkarsky, and C.K. N. Patel, "Fiber-amplified enhanced photoacoustic spectroscopy using near-infrared tunable diode lasers," Applied Optics 42 (12), April 2003
8. C. K. N. Patel, "Opto-Acoustic Spectroscopy Applied to the Detection of Gaseous Pollutants", in Monitoring Toxic Substances, ed. Dennis Schuetzle, (ACS Symposium Series No. 94), pp. 177-194 (1978)
9. N. D. Kenyon, L. B. Kreuzer, & C. K. N. Patel, "Air Pollution Detection: Ten Pollutants Detected Using CO and CO2 Lasers with Sensitivity of 1 PPB", Science 177, 347-349 (1972).
10. R. J. H. Voorhoeve, C. K. N. Patel, L. E. Trimble, and R. J. Kerl, "Hydrogen Cyanide Production During Reduction of Nitric Oxide Over Platinum Catalysts", Science 190, 149-151 (1975).
11. M.B. Pushkarsky, M.E. Webber, O. Baghdassarian, L.R. Narasimhan, and C.K. N. Patel, "Laser-Based photoacoustic ammonia sensors for industrial applications," invited paper for Applied Physics B Special Issue: Trends in Laser Sources, Spectroscopy Techniques and Their Applications to Trace Gas Detection, 75 (2-3), September 2002.