Tunable diode laser absorption spectroscopy

Gieseler et al. utilized tunable diode laser absorption spectroscopy to detect water vapor concentrations, gas velocities and mass flow during freeze-drying of pure water at different pressure and shelf temperature settings and of a 5%w/w mannitol solution. The analyzer was interfaced to the spool that connected the dryer chamber to the condenser. The reported method was advantageous in that primary and secondary drying end-point control based upon mass flow rate was independent of freeze-dryer size and configuration. ... 

H. Gieseler, W.J. Kessler, M. Finson, et al.. Evaluation of tunable diode laser absorption spectroscopy for in-process water vapor mass flux measurements during freeze drying, J. Pharm. Sci., 96(7), 1776-1793 (2007). 

Brassington, D. J., Tunable Diode Laser Absorption Spectroscopy for the Measurement of Atmospheric Species, in Spectroscopy in Environmental Science (R. J. H. Clark and R. E. Hester, Eds.), pp. 85-148, Wiley, New York, 1995. 

Fox, D. L L. Stockburger, W. Weathers, C. W. Spicer, G. I. Mackay, H. I. Schiff, D. J. Eatough, F. Mortensen, L. D. Hansen, P. B. Shepson, T. E. Kleindienst, and E. O. Edney, Intercomparison of Nitric Acid Diffusion Denuder Methods with Tunable Diode Laser Absorption Spectroscopy, Atmos. Environ., 22, 575-585 (1988). 

Mackay, G. I., H. I. Schiff, A. Wiebe, and K. Anlauf, Measurements of N02, H2CO, and HNO, by Tunable Diode Laser Absorption Spectroscopy during the 1985 Claremont Intercomparison Study, Atmos. Enriron., 22, 1555-1564 (1988). 

Schiff, H. I G. I. Mackay, and J. Bechara, The Use of Tunable Diode Laser Absorption Spectroscopy for Atmospheric Measurements, Res. Chem. Intermed., 20, 525-556 (1994a). 

Tunable diode laser absorption spectroscopy (TDLAS) has been used to measure oxides of nitrogen during flight (71). By tuning the laser to specific infrared absorption bands, the technique can selectively measure each compound. Detection limits are higher (25-100 pptrv for a 3-min response time) than the best chemiluminescent methods, and the instrumentation is less amenable to aircraft operations than the chemiluminescence techniques because of weight and size. 

Magnetic Resonance Imaging and Tunable Diode Laser Absorption Spectroscopy for In-Situ Water Diagnostics in Polymer Electrolyte Membrane Fuel Cells... 

In-situ measurement technique of water vapor concentration in gas flow channels in PEMFCs using tunable diode laser absorption spectroscopy (TDLAS)31-36 is also shown with fundamental descriptions on its measuring principle and validity of a practical system. Localized current density and through-plane water-back transport index are obtained with variation of vapor concentration along the gas channel taken into account. Demonstrative results showing that effect of the micro porous layer (MPL) on variation of through-plane water-back transport index is shown in an operating PEMFC. 

TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY (TDLAS) AS A DIAGNOSTIC TOOL FOR IN-SITU DETECTION OF WATER VAPOR CONCENTRATION IN PEMFCs... 

Localized remote sensing for chemical compositions in operating PEMFC can be performed by tunable diode laser absorption spectroscopy (TDLAS). Measurement of water vapor and carbon dioxide has been reported by using TDLAS.31-36 In TDLAS measurement, the absorption of the laser beam passing through the gas sample is expressed with the partial pressure of the absorbing species, Pa (atm), by Beer s law,... 

Chapters 4-6 address specific diagnostic methods in PEFCs. Martin et al. provide a detailed review of methods for distributed diagnostics of species, temperature, and current in PEFCs in Chapter 4. In Chapter 5, Hussey and Jacobson describe the operational principles of neutron radiography for in-situ visualization of liquid water distribution, and also outline issues related to temporal and spatial resolution. Tsushima and Hirai describe both magnetic resonance imaging (MRI) technique for visualization of water in PEFCs and tunable diode laser absorption spectroscopy (TDLAS) for measurement of water vapor concentration in Chapter 6. 

Figure 1. Optical arrangement for tunable diode laser absorption spectroscopy...

These experiments demonstrate that tunable diode laser absorption spectroscopy is well suited for in situ measurements of species concentrations in combustion flows, when a line-of-sight technique is appropriate, and for accurate measurements of spectroscopic parameters needed to characterize high-temperature absorption lines. The technique is sensitive, species specific and applicable to a large number of important combustion species including reactive intermediates, and hence it should prove to be a useful tool in future studies of combustion chemistry. The potential of tunable laser absorption spectroscopy in particleladen flows should also be noted (12), in that modulation of the laser wavelength on and off an absorption line allows simple discrimination against continuum extinction by particles. 

Principles of Tunable Diode Laser Absorption Spectroscopy.312... 

Tunable diode laser absorption spectroscopy involves measuring the attenuation of a beam from a diode laser... 

Jenkins, T. P, Bergmans, J. L., DeBarber, P A., Coffey, M. R., and Starnes, G. M. C. "In Situ Measurements of Temperature in a Coal-Fired Power Plant Using Tunable Diode Laser Absorption Spectroscopy." Paper presented at AFRC/JFRC 2004 Joint International Symposium, Maui, HI, 2004. 

In this paper, a fiber optic remote sensing multiplexed oxygen monitoring system is designed based on tunable diode laser absorption spectroscopy technique. It is an intrinsic sensing method to provide long term stability without the need of frequent calibrations. 

Key CL, chemiluminescence UV, ultraviolet IR, infrared FTIR, Fourier-transform infrared spectroscopy TOLAS, tunable diode laser absorption spectroscopy IDS, indigo-5,5 -disulfon-ate ASTM, American Society for Testing and Materials ERA, US Environmental Protection Agency approved methods JIS, Japanese Industrial Standard WHO, World Health Organization selected methods n.a., not available. 

Recently, very sensitive and selective measurements became possible by tunable diode laser absorption spectroscopy (TDLAS). Diode lasers that lase in the mid-infrared region give extremely high resolution (3 x 10 " cm ) and can tune the emission line to one of many vibration-rotation bands by changing the laser temperature and current (10-100K, 0.1-2.0 A). The TDLAS measurement is usually carried out at reduced pressure to avoid band broadening due to molecular collision. Practically interference-free measurements are possible with a typical detection limit of sub-ppbv levels (100 m path, at 25 Torr), although the TDLAS system is still expensive and under development. 

Various methods have been developed for remote gas sensing. These include differential optical-absorption spectroscopy (DOAS), differential absorption lidar (DIAL), and a number of methods that use spectroscopic methods with an atmospheric path in place of a laboratory long-path cell, for example tunable diode laser absorption spectroscopy (TDLAS) and Fourier transform infrared (FTIR) spectroscopy. 

Four different methods used for integrated-path remote gas sensing are discussed here. One of these (tunable diode laser absorption spectroscopy, TOLAS) uses a narrow linewidth source of radiation (usually a laser diode) and the other three methods use broadband sources of radiation. These three analyze the spectrum of the radiation after it has traversed the atmospheric path in different ways both differential optical absorption spectroscopy (DOAS) and Fourier transform infrared (FTIR) spectroscopy analyze the entire spectrum over the spectral region of interest, whilst absorption correlation methods record the spectrum after it has been filtered optically with either an optical filter or a sample of the target gas itself. These four methods use an active source of radiation. It is also possible to carry out integrated-path remote gas sensing using a passive source. 

Horii CV, Zahniser MS, Nelson DD, McManus JB, Wofsy SC. 1999. Nitric acid and nitrogen dioxide flux measurements a new appfication of tunable diode laser absorption spectroscopy . In Application of Tunable Diode and other Infrared Sources for Atmospheric Studies and Industrial Processing Monitoring, II, Fried A (ed.). SPIE vol. 3758. SPIE-The International Society for Optical Engineering Bellingham, WA 152-161. 

Roller C, Namjou K, Jeffers JD, Camp M, Mock A, McCann PJ, Grego J. 2002. Nitric oxide breath testing by tunable-diode laser absorption spectroscopy application in monitoring respiratory inflammation . Appl. Opt. 41(28) 6018-6028. 

The tunable diode laser absorption spectroscopy (TDLAS) sensor is a real-time, non-invasive device that is used to measure water vapor concentration and gas flow velocity in the duct connecting the freeze-drying chamber and the condenser using... 

Debo, D. (., Pikal, M. (., 2007a. Evaluation of Tunable Diode Laser Absorption Spectroscopy for in-process water vapor mass flux measurement during freeze drying./. Pharm. Sci. 96 1776-1793. 

Kuu, W. Y, Nad, S. L Sacha, G 2009. Rapid determination of vial heat transfer parameters using tunable diode laser absorption spectroscopy (TDLAS) in response to step-changes in pressure set-point during freeze-drying./. Pharm. Sci. 98 1136-1154. 

Schneid, S., Gieseler, H., Kessler, W., Pikal, M. J., 2007. Tunable Diode Laser Absorption Spectroscopy (TDLAS) as a residual moisture monitor for the secondary drying stage of freeze-drying. Proceedings of AAPS Annual Meeting and Exposition, San Diego (CA), USA. 

H.I. Sciiiff, G.I. Macay, J. Bechara The use of tunable diode laser absorption spectroscopy for atmospheric measurements. In Air Monitorimg by Spectroscopic Techniques, ed. by M.W. Sigrist, Chemical Physics Series Vol. 127 (John Wiley, New York 1994) p. 239... 

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