Data from a new field screening technique using a fiber optic laser induced fluorescence (LIF) petroleum, oil, and lubricant (POL) chemical sensor deployed from a truck mounted cone penetrometer is presented. The system provides real-time, in situ measurement of petroleum hydrocarbon contamination and soil type to a maximum depth of 150 feet with a vertical spacing of two inches. Each depth measurement records the fluorescent spectrum from 350 to 720 nm. Spectral signatures can be used to track a single or multiple contaminants across a site. Real-time measurement permits on site interpretation and `plume chasing.' Field data from SCAPS (Navy) field operations is presented to show how the system can be used for rapid three-dimensional delineation of a POL contaminant plume.

The acquisition of fiber optic reflectance spectra of diesel fuel marine (DFM) dispersed on sea sand is described. Reflectance spectra are acquired by collection of the diffusely scattered light from a black body source imaged onto a specially designed sample cell. Samples of DFM were prepared by diluting a stock standard containing 10 wt% DFM on sea sand. Interactive band analysis is used to remove the background absorption due to residual water on the sand. Results indicate a linear relationship between the band depth at 3.68 microns and the concentration of DFM. Statistical analysis of ten replicate measurements of a 0.02 wt% DFM on sea sand gives the average band depth and 95% confidence interval of 0.02875 +/- 0.000654. An instrumental detection limit of 0.0033 percent reflectance is calculated from the standard deviation of the replicate measurements.

This manuscript summarizes the effort to demonstrate the feasibility of developing a field- portable Fourier transform infrared (FTIR) instrument that can perform a quick and accurate chemical analysis of unknown waste materials at Air Force bases without removing a sample for analysis. We report that devices containing a tapered infrared fiber optic sensor can remotely detect and quantify the range of liquid hazardous waste typically found at air force bases. Partial least squares (PLS) calibration equations were formulated and shown to accurately predict the concentration of components in a mixture with an error of +/- 0.05% volume.

Explosives are one of many hazardous waste problems of concern to the Department of Defense. Defective storage facilities or byproducts of weapons manufacture have led to contamination of soil and water with explosives. Most explosives are toxic, thus posing an ecological and human health hazard. The ability to do on-site or down-stream detection of explosives will be invaluable for site characterization and remediation by saving both time and money. The evanescent wave fiber optic biosensor that was developed at NRL has been modified for the detection of trinitrotoluene (TNT), by developing a competitive immunoassay on the surface of an optical probe. A fluorescently labelled analog of TNT, trinitrobenzenesulfonic acid (TNB), was used as the competitor. Enzyme-linked immunosorbent assays were performed to determine the best fluorescently labeled competitor available to be able to achieve high sensitivity in the fiber optic assay. For the competition assay, 7.5 ng/ml Cyanine 5-ethylenediamine-labelled TNB (Cy5-EDA-TNB) was exposed to an antibody-coated optical fiber generating specific signal above background that corresponds to the 100% or reference signal. Inhibition of this signal was observed in the presence of TNT with the percent inhibition proportional to the TNT concentration in the sample. Detection sensitivities in aqueous solutions containing 10 ng/ml TNT (8 ppb) have been achieved using this system.

X-ray fluorescence (XRF) is a well-established, non-destructive method of determining elemental concentrations at ppm levels in complex samples. It can operate in atmosphere with no sample preparation, and provides accuracies of 1% or better under optimum conditions. This report addresses two sets of issues concerning the use of x-ray fluorescence as a sensor technology for the cone penetrometer, for shipboard waste disposal, or for other in-situ, real- time environmental applications. The first issue concerns the applicability of XRF to these applications, and includes investigation of detection limits and matrix effects. We have evaluated the detection limits and quantitative accuracy of a sensor mock-up for metals in soils under conditions expected in the field. In addition, several novel ways of improving the lower limits of detection to reach the drinking water regulatory limits have been explored. The second issue is the engineering involved with constructing a spectrometer within the 1.75 inch diameter of the penetrometer pipe, which is the most rigorous physical constraint. Only small improvements over current state-of-the-art are required. Additional advantages of XRF are that no radioactive sources or hazardous materials are used in the sensor design, and no reagents or any possible sources of ignition are involved.

An optical biosensor has been developed for detection of pesticides, based on surface plasmon resonance (SPR) technique. Concentration of the pesticides was measured in liquid or gas. We specially originated organic film on a disposable element. A setup on the base of Kretschmann arrangement was improved by using a computer-controlled angular scanning system. The detection concentration limit of dinitrophenole (DNP) was 10^-9 M. Some samples exhibited effect down to 10^-11 M of DNP. The results obtained provide reason for further development of SPR sensor as applied to pesticides monitoring.

We have fabricated stable sulphide and telluride based chalcogenide glasses and characterized their properties. The glasses do not exhibit crystallization upon reheating up to and beyond the fiber draw temperature. We have drawn unclad telluride fibers with a minimum attenuation of 0.11 dB/m at 6.6 micrometers which represents the lowest loss reported for a chalcogenide glass containing high levels of Te. Preliminary core/clad telluride and sulphide glass fibers have been drawn using the rod-in-tube process with a minimum loss of 0.7 dB/m at 6.6 micrometers and 0.6 dB/m at 4.89 micrometers , respectively. Improvements in glass quality and processing utilizing the rod-in-tube and double crucible techniques will lead to lower losses. We also demonstrate the capability of the telluride fibers for evanescent sensing of numerous organic and inorganic liquids and their mixtures in the 3 - 12 micrometers region.

Automation of dissolution studies has traditionally followed the manual process. Further enhancements of this type of assay will involve the elimination of some of the manual steps but cannot increase the complexity of the system. We have moved the analytical measurement away from the conventional spectrometer, where the sample is brought to the instrument, and into the dissolution vessel itself. This step should lead to an increased data throughput at a reduced cost through savings in labor, instrumentation, and waste.

A novel fiber optic Raman probe for determination of organic vapors is described. The probe utilizes an absorbent resin, C-18, to concentrate the organic vapors in the optical path of the Raman probe. The probe exhibits a fully reversible response to organic vapors such as carbon tetrachloride or benzene.

New manufacturing technologies are reported which produce stabilized optical dichroic filters with spectral immunity to environmental exposures. Optical filters manufactured by this means provide durability and longevity needed for critical fluorometry applications. The trend for environmental monitoring of hazardous petroleum fuels is turning towards optical technologies. State-of-the-art fiber optic chemical sensors based upon fluorescence employ a number of optical components, one of critical importance being a dichroic filter to accurately separate excitation from emission signals. Optical interference filter production consists of the physical vapor deposition of multilayer thin films upon suitable substrates. Conventional electron-beam thin-film evaporation techniques yield films having porous structures; the resultant filters are spectrally unstable when exposed to varying environmental conditions. The use of this type of filter in fluorescence instrumentation can result in unacceptable drift and therefore significant inaccuracies in vapor detection. The new Corion Reactive Low Voltage Ion Plating Process (RLVIP) produces durable stabilized filters having fixed, permanent characteristics immune to harsh environmental exposures. This novel manufacturing process is described, and the durability, stability and longevity of these filters are evaluated. Spectral measurements, as well as environmental exposure test results are presented. Important applications of these new products are reviewed. Comparisons with traditionally manufactured filters are made.

An optical monitoring technique that will produce an accurate qualitative measurement of simple multi-component optical spectra with a single direct measurement of interferogram phase is described. The analysis of absorption, emission or transmission spectra has proven to be a powerful tool for detecting chemical constituents in gaseous or liquid process streams. The pre-eminent instrument for this is the Fourier transform spectrometer (FTS); however, the high cost and relative fragility of these systems has prevented their widespread incorporation into chemical systems characterization. Using interferometric techniques similar to those used in FTS, but in a dramatically simplified embodiment, this system may provide the wavelength specificity and sensitivity of an FTS, with the low cost and ruggedness of a simple filter radiometer.

The use of FT-IR spectroscopy, either in the mid-IR region or near-IR region, offers fundamental advantages over other technologies. Spectral region selection criteria are reviewed, to help define when to use the mid-IR region or the near-IR region (or even when to use parts of both New fiber optic sampling probes for transmission, attenuated total reflection, diffuse reflection and web sensing have solved nagging problems. What many process analyzer specialists are discovering is that new probes are becoming available each month, offering newer process tolerance (can tolerate higher temp or pressure) or even new sampling approaches altogether. This paper describes on-line applications in pharmaceuticals, specialty chemicals, polymer production and refinery production which demonstrate the range of techniques used to appropriately optimize the on- line analyzer. In addition, calibration transfer issues are discussed, demonstrating the importance of the software tools to help sort out the causes for cal errors (spectral contamination, etc.).

A diffuse reflectance spectroscopy system is described which can operate in a contact and non- contact mode on powders, slurries and other diffusely scattering materials. Diffuse reflectance spectra are presented for a number of samples including common household materials. A comparison is made of the probe with a Bio-Rad diffuse reflectance accessory. Second derivative spectra are shown of a calibration mixture of polymer additives. The use of the diffuse reflectance system for non-destructive tablet hardness measurements is discussed. Sensor multiplexing for diffuse reflectance spectroscopy is reviewed.

A computer algorithm, which matches theoretical to measured infrared reflectance spectra, was successfully employed to determine multiple thin film properties of integrated circuits. Properties, such as film thickness, dielectric constant, and free carrier concentration were determined for a variety of important electronic films both in the laboratory and in process reactors. The latter measurements were accomplished by optically interfacing a Fourier transform infrared (FT-IR) spectrometer to several reactors. Real-time process monitoring allowed determination of deposition rate, free carrier activation temperature, and the influence of reactor conditions on film properties. Finally, these measurements were nondestructive, performed in-situ and within seconds, demonstrating the utility of this method for real-time process monitoring and control.

We have developed in-situ infrared sensors for on-line measurements of particle size distributions and temperatures during the manufacture of metal powders produced by the supersonic inert gas molten atomization technique. The sensors are based on novel applications of Fourier transform infrared spectroscopy and advanced numerical analysis techniques based on sound physical models. We have demonstrated the ability to measure the infrared transmission and emission of a hot molten particle stream. We have also identified a promising mathematical approach which deconvolves particle size distributions from extinction spectra.

An on-line carbon-in-ash monitor based on in-situ infrared emission spectrometry is described. Laboratory measurements of the infrared spectral emissivity of flyash are presented in order to demonstrate that emissivity can be correlated to the residual carbon content in the range of interest for pulverized coal-fired power plants. Data collected during a field test at a pilot-scale combustor are presented in order to demonstrate that the emissivity measurements could be made in situ on a realistic facility, and that the spectral emissivity could be correlated to the residual carbon content. Since this measurement can be made in-situ in a few seconds using an FT-IR spectrometer, an infrared emissivity based carbon-in-ash monitor will be capable of providing data on a time scale appropriate for implementation in combustion control strategies while avoiding the disadvantages associated with extractive ash sampling.

The tightening of environmental regulations presents new challenges to chemical manufacturing and utility plant managers, and also to analyzer manufacturers. The recent rules promulgated as a result of the 1990 Clean Air Act have substantially lengthened the list of chemicals requiring reporting for stack and fugitive emissions monitoring. Releases of 189 toxic compounds must now be controlled, up from only 7 previously. These HAP requirements will grow in number and spread by application to other industries. Other new legislation is forcing industry to police itself, by mandating `voluntary' reports of releases within hours of the incident. Similar constraints are coming for wastewater releases. This trend is expected to accelerate for the next few years and spread to other countries. Though current regulations mandate only periodic documentation, intermittent monitoring (quarterly or monthly) clearly will not suffice. The regulators are forcing continuous release monitoring for hazardous air and water pollutants. Environmental activism (by GreenPeace and others) and increased political awareness are indications that European regulators will soon follow the U.S. EPA's lead. These waste streams are nearly always complex multicomponent mixtures requiring sophisticated analyzers to identify and quantify the species present. This paper identifies several complex waste streams (incinerator stacks, ambient air, and industrial wastewater) and describes the successful application of on-line FT-IR analyzers.

This paper describes an inexpensive point sensor for chemical detection. The sensor is based on a novel integrated optic interferometer that provides a highly stable platform for measuring low concentrations of specific chemicals in gaseous or aqueous environments. Sensing is accomplished by monitoring refractive index changes in a thin-film surface coating, with specificity for a particular chemical achieved by using a surface coating that selectively interacts with that chemical. Multiple surface coatings can be used for simultaneous detection of several chemicals. This approach has a number of key advantages: (1) it is capable of quantifying concentrations down to at least the parts-per-billion level, yet has a broad dynamic range, (2) it is rapid response (<EQ 1 second), allowing real-time detection, (3) it is fully reversible, permitting continuous measurement, (4) it neither generates nor is susceptible to environmental interference (e.g.; electromagnetic fields, radiation, corrosive chemicals), (5) it is compact (centimeter dimensions), (6) it requires minimal power (<EQ 100 milliWatts), and (7) it is low cost. Chemicals investigated to date include ammonia, benzene, toluene, chlorine, chlorine dioxide and hydrogen. Applications range from worksite and workforce monitoring to agricultural and industrial process control.

We have demonstrated the utility of a fiber-optic Raman spectrometer with a charge coupled device (CCD) detector for measurements on a variety of chemical systems. Applications have included remote characterization of nuclear wastes, monitoring the heterogeneously catalyzed conversion of quadricyclane to norbornadiene, and monitoring emulsion and suspension polymerization reactions. Instrument control and calibration are essential elements for successful on-line monitoring. We wish to be able to compare measurements made with on- line systems with reference measurements made on laboratory instruments. Raman spectra are fundamental properties of molecular species. With suitable control and calibration of the measurement systems, spectra taken on different systems can be directly compared. We have built into our measurement system both hardware and software to provide automated wavenumber and intensity calibration and correction. The wavenumber axis calibration is based on measurement of the spectrum of atomic lines due to neon. The neon spectrum is provided by an inexpensive and compact lamp connected to the spectrometer by a dedicated optical fiber. In using atomic lines for calibration we must be able to determine peak positions reliably with an uncertainty much less than the sampling interval in the digitized spectrum. We describe a way of doing this as part of our calibration procedure. Intensity axis calibration involves correction for pixel-to-pixel and wavelength-dependent sensitivity variation of the detector and wavelength- and time-dependent throughput variations of the spectrograph and optical fiber probe. The data needed for these corrections are obtained by measurements with a calibrated white light source and with a standard sample. The white light source is a compact tungsten halogen bulb with its own dedicated optical fiber. The standard sample, a stable, readily available material, is incorporated into the measurement system at the sample end of the fiber optic probe. A computer-controlled, stepper motor driven positioner places the neon, white light and sample fibers at the focus of the spectrometer entrance optics as required.

We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures, even when the mixture is noisy and contaminated with unknowns.

The introduction of fiber optic accessories for the Hewlett-Packard 8452A diode array spectrophotometer has greatly expanded its utility and, in particular, has enhanced its use as a process application development tool. There is a clear trend toward fiber optic based process photometric analyzers. With the advent of spectroscopy using fiber optics, the stage is set for a logical transition of laboratory developed applications to process implementation. This is particularly true when both the laboratory spectrophotometric and the process photometric analyzers are capable of using the same sensors. This paper presents an example of an application development and its transition to process implementation.

Purus, Inc. is field testing a portable fiber optic chemical sensor for the semi-specific determination of ppb levels of trichloroethylene (TCE), carbon tetrachloride and chloroform in water, soil and gaseous samples. The sensor consists of a flow optrode, proprietary reagent delivery and recovery system, fiber optic transmitter-receiver, embedded micro controller, display, and communication port. The reagents react with gaseous halogenated compounds that diffuse in through a gas permeable membrane to form a colored product, and the product is detected by its absorbance of light from a 560 nm light emitting diode. The analysis time is about 3 minutes at the detection limit of a few (mu) g/L in water and may be shortened at higher concentrations and further refinements to the hardware. Field trial results are presented for a site undergoing ground water remediation for trichloroethylene. Influent water streams containing > 100 ppm TCE, effluent water streams containing < 20 ppb TCE may be routinely monitored with high precision and accuracy. These results demonstrate the viability of using this fiber optic chemical sensor as an effective low cost screening tool for assessment, monitoring, and process control applications.

The pyrolysis of TNT and other explosive compounds generates signature compounds that can be efficiently detected by electrochemical sensors. This concept was implemented in the development and testing of a sensor probe for the Site Characterization and Analysis Penetrometer System (SCAPS) for the in situ detection of TNT, RDX, HMX, and other nitrogen-containing soil contaminants. This paper describes the results of laboratory studies and field tests conducted to determine the feasibility of employing electrochemical sensors for detecting subsurface explosives contaminants. A method for the in situ pyrolysis of explosives contaminants in soils was developed, and laboratory tests determined that electrochemical sensing of the pyrolysis products was sensitive, selective, reversible, and capable of broad dynamic range. A penetrometer probe that accommodates the electrochemical sensors (including power supply and signal conditioning electronics), the pyrolyzer unit, the pneumatic components, and geophysical sensors for soil classification was designed and fabricated. Results of tests conducted at the Louisiana Army Ammunition Plant during September 1994, which demonstrated the performance of the SCAPS sensor under actual field conditions, are presented.

A laser-induced fluorescence (LIF) excitation-emission matrix (EEM) probe has been developed in the laboratory, and installed and tested in a cone penetrometer. The laser excitation system uses the fourth harmonic of a flashlamp-pumped Nd:YAG laser (at 266 nm) to pump a Raman shifter. Up to ten laser beams (in the wavelength region of 257 to 400 nm) from the Raman shifter are launched into optical fibers that are connected to the optical fibers of the cone penetrometer probe through standard connectors. In the probe head, the laser radiation is focused onto the outer surface of sapphire windows that are in contact with the soils. The fluorescence emission is collected by ten collection fibers that take the fluorescence to a detection system consisting of a spectrograph and a CCD detector. This probe allows real- time collection of LIF-EEMs of pollutants adsorbed on solids or dissolved in groundwater. LIF-EEMs provide a substantial amount of spectral information that can be used to determine the composition and quantity of pollutants in soils. This probe can be used to measure POL (petroleum, oil, lubricants), PAH (polycyclic aromatic hydrocarbons), and other fluorescent pollutants. The LIF-EEM instrument has been developed in the laboratory, and installed in a cone penetrometer truck for a field test at Hill Air Force Base, Utah. The experience of the test is discussed.

The HPMT, which may be an alternative for photomultiplier tubes (PMTs) in many applications, is a vacuum tube in which the latest technologies of photocathodes and photodiodes are combined. Photo-electrons are accelerated and bombarding a reversely biased PIN diode, where they create many electron-hole-pairs. The resulting charge pulse can be amplified and further processed. The HPMT shows many superior characteristics compared to regular PMTs, because it does not suffer the statistical fluctuations common for electron multiplication processes. An energy resolution of up to 14 photo-electrons is presented, together with striking figures for dynamic range and timing behavior.

A fiber optic chemical dosimeter has been developed for use in the remote detection of vapors of toxic amine rocket fuels (hydrazine and its substituted derivatives) that are used at U.S. Air Force and civilian launch sites. The dosimeter employs a colorimetric indicating reagent immobilized in a porous sol-gel cladding on multimode fiber. This reagent reacts selectively with the fuel vapor to produce a strongly absorbing cladding that introduces light propagation losses in the fiber; these losses indicate the presence of hydrazine (N₂H₄) vapor. The absorption occurs over a broad spectral range ideally suited for interrogation by semiconductor diode lasers. We have shown that the dosimeter yields an average hydrazine detectivity of 2.3 ppb-hr with a standard deviation of 1 ppb-hr, a value that meets U.S. Air Force current detection requirements. Prolonged exposures of the dosimeter to laboratory air have not adversely affected the dosimeter. Additionally, its response to ammonia vapor has been determined to be 9200 times smaller than its response to hydrazine vapor.