Surface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique that enables trace detection of analytes of relevance using fieldable equipment. SERS uses the enhanced Raman signals observed when an analyte adsorbs to a roughened metal substrate, generally gold, silver, or copper. Coupled to a microscope, single molecule detection has been demonstrated. With a fieldable instrument, enhancements of 108 compared to unenhanced Raman spectroscopy are expected, allowing trace detection in the field. Proper development of the metal substrate will optimize the sensitivity and selectivity towards the analytes of interest. In this presentation, we will discuss applications under development at EIC Laboratories that are of importance to Homeland Defense. We will review the capabilities of SERS to detect buried explosives, explosives associated with nuclear weaponry and chemicals involved in the nuclear enrichment process. We will discuss the detection of chemical and biological warfare agents in the water supply in research performed under the Joint Service Agent Water Monitor. We will demonstrate the current detection limits, the reproducibility of the signal, and results collected using actual chemical warfare agents, and show how the results can be extended to vapor detection. We will also discuss the current state-of-the art for fieldable instrumentation. The emphasis on portability and speed will be stressed; SERS acquisitions are restricted to 30 s or less.

The bioterrorism of October 2001 caused by the distribution of anthrax through the U.S. postal system was compounded by the significant delay associated with positive identification of the Bacillus anthracis spores and the unknown extent of their distribution along the eastern seaboard. In the ensuing two years, literally thousands of hoaxes, letters containing harmless powders, have been mailed creating additional anxiety. Thus, there is a need for instruments and/or methods that can not only identify anthrax-causing spores to save lives, but also identify hoax materials to eliminate costly shutdowns. Here we present Raman spectra of Bacillus cereus spores, an anthrax surrogate, as well as of 30 common substances that might be used as hoax materials. We also examine the choice of laser excitation, 785 nm or 1064 nm, and its impact on the ability to measure visible particles in 5 minutes or less, and to provide a complete answer to the question of suspicious material identity.

In the past decade, the Unites States and its allies have been challenged by a different kind of warfare, exemplified by the terrorist attacks of September 11, 2001. Although suicide bombings are the most often used form of terror, military personnel must consider a wide range of attack scenarios. Among these is the intentional poisoning of water supplies to obstruct military operations in Afghanistan and Iraq. To counter such attacks, the military is developing portable analyzers that can identify and quantify potential chemical agents in water supplies at microgram per liter concentrations within 10 minutes. To aid this effort we have been investigating the value of a surface-enhanced Raman spectroscopy based portable analyzer. In particular we have been developing silver-doped sol-gels to generate SER spectra of chemical agents and their hydrolysis products. Here we present SER spectra of several chemical agents measured in a generic tap water. Repeat measurements were performed to establish statistical error associated with SERS obtained using the sol-gel coated vials.

Brookhaven National Laboratory (BNL), Edgewood Chemical and Biological Center (ECBC) and ITT Industries Advanced Engineering and Sciences Division (AES) have been collaborating on the transitioning and subsequent development of a short-range, non-contact Raman lidar system specifically designed to detect and identify chemical agents on the battlefield. [The instrument, referred to as LISA (Laser Interrogation of Surface Agents), will the subject of an accompanying paper.] As part of this collaboration, BNL has the responsibility for developing a spectral database (library) of surrogates and precursors for use with LISA’s pattern recognition algorithms. In this paper, the authors discuss the phenomenon of UV Raman and resonance-enhanced Raman spectroscopy, the development of an instrument-independent Raman spectral library, and highlight the exploitable characteristics present in the acquired spectral signatures that suggest potential utility in our country’s efforts on Homeland Security.

Resonance Raman spectroscopy is an enhanced Raman technique that can be used to selectively identify a particular analyte in complex matrices. Resonance Raman requires the excitation laser to overlap with an absorption band of the analyte of interest. Since analytes have diverse absorption spectra, dilute concentrations may be detected when resonantly enhanced. A significant portion of interesting molecules absorb only in the UV; unfortunately current UV Raman instrumentation for scientifically desirable spectral resolution is large and costly. In the area of Homeland Defense, explosives, nerve agents, amino acid residues (for toxin analysis) and nucleic acids (for DNA detection and identification of bacteria) are all enhanced using UV laser sources. EIC Laboratories has developed a more user-friendly UVRRS spectrograph that is based upon the use of an echelle grating. The spectrograph has a footprint of 7" x 11" and is capable of providing 4 cm^-1 resolution over a fairly wide spectral range. The spectrograph design and spectra from analytes of particular relevance will be presented.

Advanced autonomous detection of chemical warfare agents and toxic industrial chemicals has long been a major military concern. At present, our capability to rapidly assess the immediate environment is severely limited and our domestic infrastructure is burdened by the meticulous procedures required to rule out false threats. While significant advances have recently been accomplished in remote spectral sensing using rugged FTIRs and point detectors, efforts towards low cost chemical discrimination have been lacking. Foster-Miller has developed a unique waveguide spectrometer which is a paradigm shift from the conventional FTIR approach. The spectrometer provides spectral discrimination over the 3-14 μm range and will be the spectrometer platform for both active and passive detection. Foster-Miller has leveraged its innovations in infrared fiber-optic probes and the recent development of a waveguide spectrometer to build a novel infrared sensor platform for both point and stand-off chemical sensing. A monolithic wedge-grating optic provides the spectral dispersion with low cost thermopile point or array detectors picking off the diffracted wavelengths from the optic. The integrated optic provides spectral discrimination between 3-12 μm with resolution at 16 cm^-1 or better and overall optical throughput approaching 35%. The device has a fixed cylindrical grating bonded to the edge of a ZnSe conditioning “wedge”. The conditioning optic overcomes limitations of concave gratings as it accepts high angle (large FOV) light at the narrow end of the wedge and progressively conditions it to be near normal to the grating. On return, the diffracted wavelengths are concentrated on the discrete or array detector (pixel) elements by the wedge, providing throughput comparable to that of an FTIR. The waveguide spectrometer coupled to ATR probes, flow through liquid cells or multipass gas cells provides significant cost advantage over conventional sampling methodologies. We will present the enabling innovations along with present performance, sensitivity expectations and discrimination algorithm strategy.

Critical to our ability to respond effectively to a biothreat attack is the development of sensitive and specific sensor systems that can easily be used for rapid screening of potential victims for infection due to biothreat agents and detection of pathogens in the environment. To help address these needs, we have developed a Reagentless Optical Biosensor (ROB) based on protein specific assays and waveguide-based evanescent fluorescence excitation. Modeled on host pathogen interactions, the sensor's membrane based assay provides rapid, sensitive detection without the addition of reagents. We report here the development of two waveguide based detection systems: a laboratory sensor test-bed system and a handheld, battery operated, prototype. Evanescent fluorescence excitation using planar optical waveguides provides spatial filtering of background auto-fluorescence found in many natural samples, thereby permitting direct analysis of complex environmental and medical samples. The waveguide based assay is fully self-contained in a small, exchangeable cartridge that is optically coupled to the sensor detection system making ROB simple to use and offering the possibility of inexpensive, disposable sensor elements. Using assays for cholera toxin we compare results using flourimetry of vesicle solutions against results for our waveguide based test-bed and prototype sensor systems.

Integrated optics micoresonators (μ-resonators) are microstructures with dimensions typically in the order of tens of microns down to a few microns, whose response depends critically on optical wavelength and material properties. Recent experimental studies have shown that they are suitable as refractive index sensors, absorption sensors, and microresonator-assisted single and two-photon fluorescence. The absorption and fluorescence spectra are material-specific properties, that the devices can readily detect by using different excitation wavelengths. Therefore, the devices are suitable for non-specific agent detection. Due to their inherent small size and the ease of cascading several microresonators, they are suitable building blocks for a sensing array allowing sensing/detection of multiple quantities/agents on a single chip, by e.g., using different chemo-optical transduction layers on top of the microresonators. Such devices have a chip-area of only a few 100 μm², making them suitable for sensing ultra-small analyte volumes (which is advantageous for bio-chemical sensing). In this contribution, sensing arrays based on integrated optics microresonators and their prospects for Homeland Security applications are discussed. Several device-concepts based on integrated optics microresonators will be treated. Their performance is analyzed using realistic parameters and experimental results of microresonator devices realized in silicon oxynitride (SiON) technology. The potential integration of theses devices with microelectronics, micro-mechanics and micro total analysis systems is discussed.

Over the past decade, a massive effort has been made in the development of planar lightwave circuits (PLCs) for application in optical telecommunications. Major advances have been made, on both the technological and functional performance front. Highly sophisticated software tools that are used to tailor designs to required functional performance support these developments. In addition extensive know-how in the field of packaging, testing, and failure mode and effects analysis (FMEA) has been built up in the struggle for meeting the stringent Telcordia requirements that apply to telecom products. As an example, silica-on-silicon is now a mature technology available at several industrial foundries around the world, where, on the performance front, the arrayed-waveguide grating (AWG) has evolved into an off-the-shelf product. The field of optical chemical-biological (CB) sensors for homeland security application can greatly benefit from the advances as described above. In this paper we discuss the currently available technologies, device concepts, and modeling tools that have emerged from the telecommunications arena and that can effectively be applied to the field of homeland security. Using this profound telecom knowledge base, standard telecom components can readily be tailored for detecting CB agents. Designs for telecom components aim at complete isolation from the environment to exclude impact of environmental parameters on optical performance. For sensing applications, the optical path must be exposed to the measurand, in this area additional development is required beyond what has already been achieved in telecom development. We have tackled this problem, and are now in a position to apply standard telecom components for CB sensing. As an example, the application of an AWG as a refractometer is demonstrated, and its performance evaluated.

We are exploring the ability of cross reactive sensor arrays to monitor the presence of chemical warfare agents. The sensing platform developed in our lab uses a variety of fluorescent microbead sensors, either 3 or 5 microns in diameter. The sensors have a wide range of surface functionalities and are coated with fluorescent dyes that change their emission properties upon interaction with analyte vapors. Every time the sensors are interrogated with light they photobleach which leads to signal loss and a decreased array lifetime. In order to monitor for long periods of time, a strategy has been developed that extends the array lifetime. Here, we implement a method to increase the lifetime of an array by up to 10-fold, as we incrementally expose small sections of the array at a time. We divide the array into sections by moving an optical slit across the face of the fiber.

The concept of modified cladding based sensors represents the largest class of intrinsic fiber optic chemical sensors. In this design, the passive cladding of the optical fiber is replaced by an active coating, called modified cladding. The analyte in this case diffuses into the coating and induces changes in the absorbance, fluorescence, or some other spectroscopic property of the modified cladding, the coating acts as a chemo-chromic transducer and sensing takes place by intensity modulation. This design i.e. of the coating based sensors, has found enormous applicability in the realm of chemical and biochemical sensing which also includes environmental monitoring and detection of chemical warfare agents. In this paper, the development of an intrinsic fiber optic sensor for detection of organophosphate dimethyl-methyl phoshopnate (DMMP) is presented. DMMP is a chemical precursor to the nerve agent sarin. The chemo-chromic transducer material used as a modified coating on the fiber core is NDSA (Naphthalene disulphonic acid) doped polypyrrole. This coating material shows conductivity and absorbance change when exposed to DMMP. The fabrication of the sensor device is a three step process which involves (a) etching a small section of the optical fiber to expose the core, (b) coating the etched section of the optical fiber with the polymer, (c) integration of sensor components and testing. Thin film characterization is done using the UV-Vis spectrophotometer on in-situ coated films of polypyrrole on a glass substrate to check for absorbance change upon exposure to DMMP. The development procedure is presented next and encouraging results are discussed.

Analytical instruments capable of detecting nerve agents in battlefield conditions where speed, accuracy and ease of operation are a must in today's military. Fast detection and decontamination of nerve agents in very low concentrations is the primary focus of our research. The method presented here focuses on optimizing polymer stabilized sensing elements on the surface of SPR fiber-optic probes. A number of polymers & polymer supported metal complexes capable of reversibly binding to the species of interest & which have robust operation in hostile environments are incorporated with the fiber optic sensing elements. An optical technique, such as Surface Plasmon Resonance (SPR), better suited to rapid data collection without sample pretreatment is employed. The approach using polymer-based optical fibers with off-the-shelf SPR system components has been tested for the detection of Pinacolyl methylphosphonate (PMP), a simulant for nerve agent Soman. Surface initiated polymeric sensors have higher sensitivity toward detecting PMP than bulk-polymerized sensors.

This paper describes the design and development of a small, portable alarm device that can be used by first responders to an emergency event to warn of the presence of low levels of a toxic nerve gas. The device consists of a rigid reusable portion and a consumable packet that is sensitive to the presence of acetylcholinesterase inhibitors such as the nerve gases Sarin or Soman. The sensitivity level of the alarm is set to be at initial physiological response at the meiosis level, orders of magnitude below lethal concentrations. The AChE enzyme used is specific for nerve-type toxins. A color development reaction is used to demonstrate continued activity of the enzyme over its twelve-hour operational cycle.

U.S. and Coalition forces fighting terrorism in Afghanistan and Iraq must consider a wide range of attack scenarios in addition to car bombings. Among these is the intentional poisoning of water supplies to obstruct military operations. To counter such attacks, the military is developing portable analyzers that can identify and quantify potential chemical agents in water supplies at microgram per liter concentrations within 10 minutes. To aid this effort we have been investigating the value of a surface-enhanced Raman spectroscopy based portable analyzer. In particular we have been developing silver-doped sol-gels to generate SER spectra of chemical agents and their hydrolysis products. Here we present SER spectra of methyl phosphonic acid and cyanide as a function of pH, an important factor affecting quantitation measurements, which to our knowledge has not been examined. In addition, dipicolinic acid, a chemical signature associated with anthrax-causing spores, is also presented.

Pyrolysis-Gas Chromatography-Ion Mobility Spectrometry (Py-GC-IMS) has been used to detect chemical resident in water by obtaining the characteristic information on the structure and molecular weight. It is a great challenge to analyze this 2-dimensional signal because the noise is not stationary. In this paper, one approach has been designed to remove noise baseline and suppress noise power. The provided data is used for analyze the improvement under controlled experiment. Receiver Operating Characteristic (ROC) curve is also used to analyze the performance and it shows the proposed method improves the detection results.

Both Fourier Transform Infrared (FTIR) spectrometers and sampling techniques have seen a paradigm shift over the past 20 years. Infrared (IR) spectroscopy using the mid IR “fingerprint” region shows excellent specificity for determining the presence and quantity of well over 50000 organic chemical species. Tiny amounts of sample suffice for identification using a chemically inert scratch resistant diamond micro internal reflection crystal. For air quality, FTIR can be used as a point monitor, sniffing air samples in an IR cell or using a long open-air path with a remote reflector or direct passive remote sensing. This makes IR ideal for first responders and haz/mat professionals provided the FTIR is compact, rugged and easy to use in the field. Already FTIR is widely used in industrial plants often directly at the process. In parallel FTIR is increasingly used in mobile field environments including airborne platforms as well as for satellite-based sounders. This paper presents a resume of the evolution of FTIR and sampling technology and the boundaries of applicability of field deployed FTIR chemical sensors for the assessment of suspect substances as well as air pollution at the site of an emergency situation.

A new point sensor for identifying chemical weapons of mass destruction and other hazardous materials based on Fourier transform infrared (FT-IR) spectroscopy is presented. The sensor is a portable, fully functional FT-IR system that features a miniaturized Michelson interferometer, an integrated diamond attenuated total reflection (ATR) sample interface, and an embedded on-board computer. Samples are identified by an automated search algorithm that compares their infrared spectra to digitized databases that include reference spectra of nerve and blister agents, toxic industrial chemicals, and other hazardous materials. The hardware and software are designed for use by technicians with no background in infrared spectroscopy. The unit, which is fully self-contained, can be hand-carried and used in a hot zone by personnel in Level A protective gear, and subsequently decontaminated by spraying or immersion. Wireless control by a remote computer is also possible. Details of the system design and performance, including results of field validation tests, are discussed.

We report recent progress toward the development of infrared point sensors for the detection of chemical warfare agents and explosive related chemicals, which pose a significant threat to both health and environment. Technical objectives have focused on the development of polymer sorbents to enhance the infrared response of these hazardous organic compounds. For example, infrared point sensors which part-per-billion detection limits have been developed that rapidlypartition chemical warfare agents and explosive related chemicals into polymer thin films with desirable chemical and physical properties. These chemical sensors demonstrate novel routes to reversible sensing of hazardous organic compounds. The development of small, low-power, sensitive, and selective instruments employing these chemical sensors would enhance the capabilities of federal, state, and local emergency response to incidents involving chemical terrorism. Specific applications include chemical defense systems for military personnel and homeland defense, environmental monitors for remediation and demilitarization, and point source detectors for emergency and maintenance response teams.

Pacific Northwest National Laboratory (PNNL) continues to expand its library of quantitative infrared reference spectra for remote sensing. The gas-phase data are recorded at 0.1 cm^-1 resolution, with nitrogen pressure broadening to one atmosphere to emulate spectra recorded in the field. It is planned that the PNNL library will consist of approximately 500 vapor-phase spectra associated with the U.S. Department of Energy’s environmental, energy, and public safety missions. At present, the database is comprised of approximately 300 infrared spectra, many of which represent highly reactive or toxic species. For the 298 K data, each reported spectrum is in fact a composite spectrum generated by a Beer’s law plot (at each wavelength) to typically 12 measured spectra. Recent additions to the database include the vapors of several semi-volatile and non-volatile liquids using an improved dissemination technique for vaporizing the liquid into the nitrogen carrier gas. Experimental and analytical methods are used to remove several known and new artifacts associated with FTIR gas-phase spectroscopy. Details concerning sample preparation and composite spectrum generation are discussed.

Real-time and in-situ detection and discrimination of aerosol particles, especially bio-aerosols, continues to be an important challenge. The technique labeled TAOS (Two-dimensional Angular Optical Scattering) characterizes particles based upon the angular distribution of elastically scattered light. The detected angular distribution of light, labeled the TAOS pattern, depends upon the particle’s shape, size, surface features, and its complex refractive index. Thus, the absorptive properties of a particle affect the TAOS pattern. Furthermore, we expect to use this change in the TAOS pattern, which occurs when the particle absorption band includes the input wavelength, to characterize the strength of the absorption. Thus, by illuminating a particle in the mid-infrared wavelength range, high frequency vibrational modes that are unique to the aerosol can be reached and quantified. Spherical aerosol particles (in the diameter range of 50-60 micrometers) were generated via a droplet generator and illuminated by an Interband Cascade (IC) laser designed to emit in the 3-5 micrometers wavelength range. The TAOS pattern of the elastically scattered light was detected with an InSb-focal-plane-array infrared camera.

We have previously reported a combined mid-infrared spectroscopic/statistical modeling approach for the discrimination and identification, at the strain level, of both sporulated and vegetative bacteria. This paper reports on the expansion of the reference spectral library: transmissive Fourier-transform mid-infrared (trans-FTIR) spectra were obtained for three Escherichia bacterial strains (E. coli RZ1032, E. coli W3110, and E. coli HB101 ATCC 33694), and two Pseudomonas putida bacterial strains (P. putida 0301 and P. putida ATCC 39169). These were combined with the previous spectral data of five Bacillus bacterial strains (B. atrophaeus ATCC 49337, B. globigii Dugway, B. thuringiensis spp. kurstaki ATCC 35866, B. subtilis ATCC 49760, and B. subtilis 6051) to form an extended library. The previously developed four step statistical model for the identification of bacteria (using the expanded library) was subsequently used on blind samples including other bacteria as well as non-biological materials. The results from the trans-FTIR spectroscopy experiments are discussed and compared to results obtained using photoacoustic Fourier-transform infrared spectroscopy (PA-FTIR). The advantages, disadvantages, and preliminary detection limits for each technique are discussed. Both methods yield promising identification of unknown bacteria, including bacterial spores, in a matter of minutes.

A microsphere-based DNA biosensor array with high packing density and low detection limits has been previously developed. Polymeric 3.1-μm-diameter microspheres are employed as the detection elements, where each microsphere is functionalized with single-stranded oligonucleotide probe sequences. The biosensor array is fabricated by randomly distributing a stock microsphere suspension, containing various oligonucleotide-functionalized microspheres, on the distal end of a chemically etched imaging fiber bundle. By placing the microspheres into wells at the end of each individual fiber, each optical channel is connected to a single microsphere. The microspheres are encoded with a unique combination of dyes in order to determine a particular microsphere’s location in the randomized array. Specific fluorescence responses are observed after hybridization with fluorescently labeled complementary targets. Enhancement of the signal to noise ratio is possible because of intrinsic redundancy of sensing elements built into the array. This microsphere-based DNA biosensor has several major advantages over existing platforms including higher sensitivity, micron-sized features, and rapid throughput. Microsphere-based DNA arrays have been successfully applied to genomic discrimination of bacteria, gene expression analysis, and the detection of bioagents.

Raman spectroscopy has proven to be a plausible solution to the difficult challenge of on-site detection of biological threats. Adding to the challenge is the fact that many biological species, spores specifically, have relatively low scattering cross sections. The intrinsic need to detect these threats at low concentrations and in the presence of strong background signals necessitates the need for surface enhancement schemes. With an available technique to quickly identify bacterial spores, we hope to find spectral differences between target species in order to incorporate library technologies with the on-site sensor. We are investigating many of the reported substrate classes such as: Nano-sphere lithography (NSL), Film over nano-sphere (FONS), nano-shells, electrochemically roughened metals, and dispersed and immobilized colloids. The key aspects of this work include discerning what architectural features provide the largest enhancement and reproducibility. We will present preliminary results of bacterial spore identification as well as a comparison of the substrates studied.

Nanoscale polymeric coatings are used in a variety of sensor systems. The influence of polymer coating morphology on sensor response was investigated and it was determined that coating morphology plays a particularly important role in transducers based on optical or acoustic resonance such as surface acoustic wave (SAW) or surface plasmon resonance (SPR) devices. Nanoscale polymeric coatings were deposited onto a number of miniature devices using a "solvent-free" deposition technique known as Rapid Expansion of Supercritical Solutions (RESS). In RESS, the supercritical solvent goes into the vapor phase upon fast depressurization and separates from the polymer. Therefore, dry polymer particles are deposited from the gas phase. The average diameter of RESS precipitates is about two orders of magnitude smaller than the minimum droplet size achievable by the air-brush method. For rubbery polymers, such as PIB and PDMS, the nanoscale solute droplets produced by RESS agglomerate on the surface forming a highly-uniform continuous nanoscale film. For glassy and crstalline polymers, the RESS droplets produce uniform particulate coatings exhibiting high surface-to-volume ratio. The coating morphology can be changed by controlling the RESS processing conditions.

Steady state and lifetime fluorescence measurements were acquired to measure the binding activity associated with molecularly imprinted polymer (MIP) microparticles imprinted to dipicolinic acid. Dipicolinic acid is a unique compound associated with the sporulation phase of spore-forming bacteria (e.g., genus Bacillus and Clostridium). Vinylic monomers were polymerized in a dimethylformamide solution containing the dipicolinic acid as a template. The resulting MIP was then pulverized and size selected into small microscale particles. Samplers were adapted incorporating the MIP particles within a dialyzer (500 MW). Tests were run on replicate samples of biologically active cultures representing both stationary phase and sporulation post fermentation products in standard media. The permeability of the membrane permitted diffusion of lighter molecular weight constituents from media effluents to enter the dialyzer chamber and contact the MIP. Extractions of the media were measured using steady state and lifetime fluorescence. Results showed dramatic steady state fluorescence changes as a function of excitation, emission and intensity and an estimated lifetime of 5.8 ns.

The time-resolved and steady-state changes in fluorescence were investigated from one spore-forming (Bacillus subtilis) and four non-spore forming (Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, and Pseudomonas aeruginosa) bacteria subjected to different bactericidal agents. The bactericidal agents were sodium hypochlorite (bleach) hydrogen peroxide, formaldehyde, and UV light exposure. Application of sodium hypochlorite resulted in an almost total lose of fluorescence signal and large decrease in the optical density of the bacterial suspension. Addition of hydrogen peroxide resulted in a 35% decrease in emission intensity fom the Sa and an 85-95% decrease for the other bacteria. Ultraviolet light exposure resulted in a 5-35% decrease in the emission intensity of the tryptophan band. The addition of formaldehyde to the bacteria did not result in significant changes in the steady-state emission intensity, but did shift the tryptophan emission peak position to shorter wavelengths by 3 to 5 nm. Time-resolved fluorescence measurements showed that the fluorescence lifetime of tryptophan in the bacteria could not be described by a single exponential decay, and was similar to that of tryptophan in neutral aqueous solution. Upon addition of formaldehyde to the Gram positive bacteria (Bs and Sa) the strength of the short lifetime component increased dramatically, while for the Gram negative bacteria, a smaller increase was observed. These fluorescence changes reflect the different mechanisms of the bactericidal agents and may provide a useful tool to monitor the effectiveness of disinfectants.

The use of the equilibrium vapor cell method quantitatively supplies one or more analytes in the presence of water vapor by using the vapor liquid equilibrium properties of aqueous solutions to delivery target vapors. This study demonstrates vapor generation of ammonia, ethanol, and ammonia/ethanol mixtures from aqueous solutions. Gravimetrically prepared aqueous solutions of ethanol and/or ammonia along with vapor liquid equilibrium data permits assessment of the mixed vapor target amounts delivered into an optical cell. Acquisition of the infrared vapor phase spectra is completed with a laboratory spectrometer for the target vapors in the Beer's law concentration region using a fixed pathlength optical cell. Even though ideal solution behavior is assumed for the ethanol/ammonia interactions in the ternary solutions, the infrared spectral results between the binary and ternary solutions are shown to compare favorably.

Passive infrared (IR) remote sensors are gaining wide acceptance as an analytical tool for the remote detection of chemical vapor plumes. A common problem in plume detection for remotely sensed data is the ability to obtain a quality background signature. Many detection methods employ techniques to extract the signatures of the unknown components in order to determine the overall classification of a desired signature. However, this is often the most difficult step since no prior background knowledge is available. In this document, a novel implementation of partial least squares (PLS) regression is proposed for the automatic detection of dimethylmethylphosphonate (DMMP) vapors from remotely sensed hyperspectral image data. In this implementation, prior knowledge of the target signature is used to extract the analyte information directly from the scene. The various unknown and interfering signatures are implicitly modeled by the PLS algorithm as components that maximize a covariance criterion. This implicit modeling is beneficial since it allows for the detection of a single target chemical without the need for a separate background subtraction procedure.

The rapid detection of weaponized bacteria and toxins is a major problem during a biological attack. Although sensitive detection formats exist for many biowarfare agents, they often require advanced training and complex procedures. Luna has developed simple, rapid means for determining the presence of pathogens and bacterial toxins in water supplies using fluorescence-based assays that can be adapted for field use. The batteries of rapid assays are designed for i) determining cell viability and bacterial loads by exploiting metabolic markers (e.g., acid-production, redox potentials, etc) and ii) detecting bacterial toxins using fluorescent, polymerized affinity liposomes (fluorosomes). The viability assays were characterized using E. coli, S. aureus and the anthrax simulant, B. globigii. The viability assays detected bacterial loads of ~ 10⁴ CFU/ml and with simple filtration ~ 100CFU/ml could be detected. The affinity fluorosomes were characterized using cholera toxin (CT). Affinity liposomes displaying GM1 and anti-CT antibodies could detect CT at <μg/ml levels. Stability studies showed that affinity vesicles could be stored for weeks at 4°C or freeze-dried with no significant loss of binding capacity. Using an in-house fiber optic fluorescence system, Luna characterized the binding of affinity fluorosomes to respective targets and determined the responses of bacterial loads in the fluorescent viability assays. Using this two-tiered approach, Luna demonstrated that water susceptible to sabotage could be easily monitored and confirmed for specific agents using simple, general and specific fluorescence-based detection schemes based on metabolism and ligand-target interactions.