HaloSnif Fiber-Optic Spectrochemical Sensor

Description

HaloSnif is a fiber-optic spectrochemical sensor capable of detecting any volatile chlorinated compound in air or gas. During operation, HaloSnif operating at subambient pressure (40 torr) continuously draws an air sample through a critical orifice into the plasma excitation chamber where it is mixed with helium and excited with a radio-frequency signal inductively coupled to the plasma chamber. The plasma chamber is coupled via a fused silica optical fiber to the signal processor unit. The optical emission of the plasma is filtered with a narrow band pass filter designed to monitor the 837.6 nm emission line from the excited chlorine atom. The intensity of the chlorine emission is directly proportional to the concentration of chlorine containing species in the sample gas. The detection sensitivity for carbon tetrachloride is 5 ppmv. The response of the system is linear from the detection limit to 10,000 ppmv. The detection limit for other chlorine-containing compounds can be estimated by calculating the ratio of the percent of chlorine in the compound of interest to that of carbon tetrachloride.

Data acquisition is achieved using a LabView data acquisition software package mounted on a Macintosh computer system. The data acquisition system is interfaced to the electro-optical signal processing module via a 1 to 10 V analog output. Real-time concentrations of total chlorinated compounds are displayed on the monitor for observation by on-site personnel. All data are stored in computer memory for post-run processing and analysis.

Technical Performance Data

HaloSnif's response to chlorinated species is linear from its lower detection limit of 1 to 5 ppmv (for most compounds) in air to approximately 10,000 ppmv. In addition, HaloSnif is not sensitive to moisture or other nonchlorinated compounds present in the sample gas. HaloSnif operates at 40 torr. Equilibration times are normally less than 2 min to reach 90% of full scale. The total weight of the HaloSnif system is 50 lb. HaloSnif also features real-time multipoint environmental field monitoring, small probe size, and the ability to use multiple probes with one central detection and data acquisition system. HaloSnif requires 5 A of 110 VAC power to operate.

HaloSnif can be reconfigured as an element-specific detector for gas chromatography effluents containing chlorine- and fluorine-containing compounds. By simply replacing the critical orifice inlet with an open-face membrane material, HaloSnif is capable of measuring the concentration of total organic chlorine in water samples.

Cost. It is estimated that the final unit will be approximately $10K for the base system and approximately $250 per sensor assembly. Operations and maintenance costs are expected to be minimal.

Projected Performance

HaloSnif has the potential to detect gas phase compounds containing bromine, mercury, fluorine, and possibly phosphorus by simply modifying the analytical emission wavelength monitored by the detector.

Waste Applicability

HaloSnif is applicable to the detection of any volatile chlorine containing compound including carbon tetrachloride, trichloroethylene, tetrachloroethylene and chlorofluorocarbons in air or gases.

Status

All components of HaloSnif are commercially available. Field testing of the new compact unit will be conducted to determine its short-term and long-term maintenance requirements.

Regulatory Considerations

HaloSnif is considered intrinsically safe, and no environmental impacts are anticipated.

Potential Commercial Applications

Potential commercial applications of HaloSnif include monitoring at waste sites, chemical storage areas, and process-based manufacturing plants using CFCs.

Baseline Technology

The baseline technology is the photo ionization detector (PID), or conventional gas chromatography equipped with an electron capture or electrolytic conductivity detector.

Intellectual Property Rights

HaloSnif was developed at Pacific Northwest Laboratory (PNL). The patent has been assigned to PNL and the Department of Energy (DOE).

Patent No. 5,085,499, ``Fiber Optics Spectrochemical Emission Sensors.''

For more information, please contact:

DOE/OTD Environmental Technology

Information Service

(800) 845-2096

DOE Program Manager

David Biancosino

EM-551, Trevion II

U.S. Department of Energy

Washington, DC 20585

(301) 903-7961

Principal Investigator

Khris Olsen

Pacific Northwest Laboratory

Battelle Boulevard

P.O. Box 999

Richland, WA 99352

(509) 376-4114

Industrial Partnership

Quanta Physik

References

1. Griffin, J.W., K.B. Olsen, D.A. Nelson, B.S. Matson, and P.A. Eschbach, 1988. ``Fiber Optic Spectrochemical Emission Sensors,''. In the Proceedings of the SPIE 1988 Symposium. Boston, MA. September 6-9, 1988.

2. Griffin, J.W., B.S. Matson, K.B. Olsen, T.C. Kiefer, and C.J. Flynn. 1989. Fiber Optic Spectrochemical Emission Sensors: A Detector for Chlorinated and Fluorinated Compounds. Boston MA. SPIE, September 5-8, 1989.

3. Olsen, K.B., J.W. Griffin, T.C. Kiefer, R.S. Matson, and C.J. Flynn. 1992. ``A Fiber-Optic Spectrochemical Emission Sensor as a Detector for Volatile Chlorinated Compounds,''. ACS Symposium Series 479: Element Specific Chromatographic Detectors by Atomic Emission Spectroscopy; Ed. Peter C. Uden;

4. Anheier, N.C., K.B. Olsen, and J.W. Griffin, ``Fiber-Optic Spectrochemical Emission Sensor: A Detector for Volatile Chlorinated Compounds,'' Sensors and Actuators, in press.

5. DOE-RL, ``Technology Information Profile (Rev. 3), Technology Name: HaloSnif - Fiber Optic Spectrochemical Sensor,'' TTP Reference Number: RL-8503-PT, March 29, 1993.

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