An array biosensor developed for performing simultaneous analysis of multiple samples for multiple analytes has been miniaturized and fully automated. The biochemical component of the multi-analyte biosensor consists of a patterned array of biological recognition elements ("capture" antibodies) immobilized on the surface of a planar waveguide. A fluorescence assay is performed on the patterned surface, yielding an array of fluorescent spots, the locations of which are used to identify what analyte is present. Signal transduction is accomplished by means of a diode laser for fluorescence excitation, optical filters and a CCD camera for image capture. A laptop computer controls the miniaturized fluidics system and image capture. Data analysis software has been developed to locate each spot and quantify the fluorescent signal in each spot. The array biosensor is capable of detecting a variety of analytes including toxins, bacteria and viruses and shows minimal interference from complex physiological sample matrices such whole blood and blood components, fecal matter, saliva, nasal secretions, and urine. Some results from recent field trials are presented.

In recent years Ion-Sensitive Field Effect Transistor (ISFET) based transducers create valuable applications in physiological data acquisition and environment monitoring. This paper presents a mixed-mode ASIC design for potentiometric ISFET-based bio-chemical sensor applications including H+ sensing and hand-held pH meter. For battery power consideration, the proposed system consists of low voltage (3V) analog front-end readout circuits and digital processor has been developed and fabricated in a 0.5mm double-poly double-metal CMOS technology. To assure that the correct pH value can be measured, the two-point calibration circuitry based on the response of standard pH4 and pH7 buffer solution has been implemented by using algorithmic state machine hardware algorithms. The measurement accuracy of the chip is 10 bits and the measured range between pH 2 to pH 12 compared to ideal values is within the accuracy of 0.1pH. For homeland environmental applications, the system provide rapid, easy to use, and cost-effective on-site testing on the quality of water, such as drinking water, ground water and river water. The processor has a potential usage in battery-operated and portable devices in environmental monitoring applications compared to commercial hand-held pH meter.

An integrated multi-functional biochip based on integrated circuit complementary metal oxide semiconductor (CMOS) sensor array for use in medical diagnostics and pathogen detection has been described. The usefulness and potential of the biochip as a rapid, inexpensive screening tool for detection of bioenvironmental pathogens will be demonstrated. Detection of aerosolized spores was achieved by coupling the miniature system to a portable bioaerosol sampler, and the performance of the antibody-based recognition and enzyme amplification method was evaluated. The bioassay performance was found to be compatible with the air sampling device, and the enzymatic amplification was found to be an attractive amplification method for detection of low spore concentrations. The combined portable bioaerosol sampler and miniature biochip system detected 100 B. globigii spores, corresponding to 17 aerosolized spores/L of air.

We describe a novel sensor of ammonia based on a planar optical waveguide made of a thin film of polymer polyimide doped with indicator dye bromocresol purple. The film of dye-doped polyimide demonstrated reversible increase of absorption with a peak near 600 nm in response to presence of ammonia in ambient air. Coupling of input and output optic fibers with the waveguide was done by means of coupling prisms or coupling grooves. The latter configuration has the advantage of low cost, less sensitivity to temperature variation, and the possibility of coupling from both sides of the waveguide. Special experimental setup was built to test the sensor. It included test gas chamber with sealed optic fiber feed-throughs, gas filling line, laser source, photodetector, and signal processing hardware and software. The sensor was capable of detecting 100 ppm of ammonia in air within 8 seconds. Further increase of sensitivity can be achieved by adding more dye dopant to the polymer, increase of the length of the waveguide, and suppression of noise. Overexposure of the sensor to more than 5000 ppm of ammonia led to the saturation of the polymer film and, as a result, significant decrease of sensitivity and increase of the response time. The sensor can be used as low cost component of a distributed optical network of chemical sensors for monitoring presence of hazardous industrial pollutants in air.

New technologies are needed for detection and identification of gaseous species in near-real time. Voltammetry, applied to cermet electrochemical cell microsensors, was shown in this study to be promising in its ability to discern and quantify gases. The miniature cermet cells were fabricated from ceramic, metallic, and metal oxide components, and reacted uniquely with gases and mixtures in the atmosphere. Neural net chemometrics algorithms were used to interpret the waveforms to extract information about the presence and concentration of constituent gases. Results to date have shown that these sensors can correctly identify more than thirty electroactive gases while showing a high tolerance for interferents. A single element sensor can determine gas concentrations from the part per million level to the percentage level while arrays provide even better detection and discrimination. This work focuses on four constituents of diesel exhaust: benzene, 1,3-butadiene, acrolein, and acetaldehyde. Voltammetric sensors demonstrated reproducible responses to four concentrations of each constituent spiked into diesel exhaust.

Sub-Doppler laser wave-mixing spectroscopy is presented as a sensitive and high-resolution optical method for measuring isotopes and hyperfine structures. By fingerprinting isotopes at sensitive levels, one can track biohazardous pollutants in various environmental samples since isotope and hyperfine profiles are unique and characteristic of specific locations and sources including those for heavy metal contaminants and chemical runoff. We present an unusually sensitive optical absorption method that offers isotope specificity and resolution at excellent detection sensitivity levels. Sub-Doppler laser wave-mixing spectroscopy is a resonant nonlinear optical technique which uses three intersecting laser beams to produce a signal beam that has all the coherent properties of the original input laser beams. This laser-like signal beam can be efficiently directed, collected, filtered and detected. The use of counter-propagating input beams minimizes Doppler broadening and the resulting sub-Doppler spectral resolution is suitable for isotope and hyperfine splitting measurements. This relatively simple absorption-based method offers better sensitivity and selectivity levels and it requires minimum sample preparation steps.

This paper describes a self-contained, portable Raman instrument that has been developed for environmental and homeland defense applications. The instrument consists of a 830-nm diode laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode for detection. The primary component of this system is the AOTF and it has been selected based on its spectral range along with its high resolution, ~7.5 cm^-1. Software has been developed in house using C programming language for controlling the instrument (i.e. the AOTF frequency, the signal acquisition, etc.). Evaluation of this instrument has been performed by analyzing several standard samples and comparing to a conventional Raman system. In addition to system evaluation, this paper will also discuss potential applications of this instrument to trace detection of hazardous chemicals using the Raman Integrated Tunable Sensor (RAMiTs) coupled with surface-enhance Raman scattering process.

A multi-gas analyzer based on intracavity Raman scattering has been evaluated and its performance compared with traditional industrial emission monitoring techniques. In this setup, the analyzer has the ability to monitor pollutants, such as SO₂, as well as CO, CO₂, N₂ and O₂. Since this is one of the first and most recent attempts to utilize this technology in the chemical industry, this work focuses on typical performance parameters and how well this analyzer fits a typical industrial application. The basic theory of operation, sampling system considerations and results of the calibration effort are presented. Limitations of the technology are also outlined in an effort to show where this analyzer competes with traditional process measurement systems. When applicable, this technique could replace multiple analyzer systems and their associated sampling systems, leading to improved analyzer reliability and maintainability.

Trace gas analysis by near-infrared Tunable Diode Laser Absorption Spectroscopy (TDLAS) has evolved over the past decade from a laboratory specialty to an accepted, robust, and reliable industrial process monitoring and control technology. Early industrial-quality TDLAS analyzers occupied full instrumentation racks and frequently cost several hundred thousands of dollars to purchase and install. The technology has now been refined to the point where complete TDLAS analyzers are available in lightweight battery-operated packages similar to a smoke detector that cost a few thousand dollars. This paper summarizes the current state-of-the-art in near-IR TDLAS sensors, focusing on miniature low-cost devices, and some of their applications.

Surface Plasmon Resonance (SPR) spectroscopy offers many potential industrial applications. SPR sensors are suitable to monitor liquid and gas phase mixtures. The use of fiber-optic SPR sensors enables the possibility of remote sensing in real-time. The sensors can be made as small as 45mm long using 200um optical fibers. Measurement of organic vapors and salinity are demonstrated using the SPR sensors. The mixing dynamics are easily accessible using SPR sensors. The mixing of hexanes and isopropanol in static solution was monitored in real time. Another important application is the analysis of the excess dielectric properties for various binary mixtures using a SPR sensor. Binary mixtures with similar refractive index were measured. Strong deviations from ideality are seen using SPR to monitor the dielectric properties. SPR sensors can be integrated to production lines to monitor the extend of products or compounds inline.

This report describes laboratory development and process plant applications of Raman spectroscopy for detection of hydrogen isotopes in the Tritium Facilities at the Savannah River Site (SRS), a U.S. Department of Energy complex. Raman spectroscopy provides a lower-cost, in situ alternative to mass spectrometry techniques currently employed at SRS. Using conventional Raman and fiber optics, we have measured, in the production facility glove boxes, process mixtures of protium and deuterium at various compositions and total pressures ranging from 1000 - 4000 torr, with detection limits ranging from 1-2% for as low as 3-second integration times. We are currently investigating fabrication techniques for SERS surfaces in order to measure trace (0.01-0.1%) amounts of one isotope in the presence of the other. These efforts have concentrated on surfaces containing palladium, which promotes hydrogen dissociation and forms metal hydride bonds, essentially providing a chemical enhancement mechanism.

Multidimensional fluorescence is employed as an analytical tool for analyzing natural waters. Excitation-Emission Matrices (EEMs) are shown to contain spectral profiles of natural fluorophores as well as polyaromatic pollutants. A database of date-ordered EEMs was established to investigate fluorescence properties of several rivers and estuarial sites in the Boston area. Multiway Partial Least Squares Discriminant Analysis (NPLS-DA) regression models were constructed with calibration data from each sample site for classification of future test data to geographic origin. Parallel factor (PARAFAC) analysis resolved the pure component spectra for longitudinal and seasonal characterization studies. Time Resolved Excitation Emission Matrix (TREEM) spectroscopy exhibits extraction of further spectral information with the addition of a fluorescence decay time dimension. Location characterization of port waters by fluorescence fingerprinting is demonstrated. This spectroscopic technique shows promise as a regulatory tool for fingerprinting ships' ballast water to determine its harbor of origin. A deployable instrument for in situ analysis is proposed.

The monitoring of metals in the environment is well advanced technically and analytically, though the sustainable development requirements induce the need of new methods of metal assessment in the terrestrial and aquatic environment. The current metal monitoring in soil is based on the total content that does not allow for assessment of their environmental mobility and bioavailability. The new techniques should enable metal partitioning with respect to susceptibility to migrate and exert the toxic effect on the target organisms. This statement is exemplified in the screening survey for metals of the area impacted by the catastrophic flood of 1997 in the Odra River valley in Poland. Metals enrichment of soils due to river sediments deposition, as well as their mobility in soils of the affected area were assessed in view of potential risk to the receptors. Sampling cells positioning by GPS and the assessment of the post-flood changes in metal spatial distribution with use of the Geographical Information System (GIS) were most helpful, while the sequential extraction analytical procedure for evaluation of binding strength and major chemical forms of metals was conducted manually and thus was very laborious. Automation of metal partitioning, and bioavailable forms assessment by DGT technique would have given the most valuable information and reduce the time needed for the manual analysis.

On the basis of data from long-term monitoring studies carried out in the impact area of the Smolnica coal mining waste disposal site in the Upper Silesia Coal Basin (Poland), the extent and propagation of originally good groundwater quality degradation that resulted from infiltration to the Quaternary aquifer of contaminants leached from the disposal site, as well as major trends of the natural water quality alteration were evaluated. For assessment of spatial and temporal groundwater quality trends in the vicinity of the disposal site, geostatistical methods were applied. Water quality alteration trends were monitored with use of two major constituents: chlorides and sulfates showing significant changes in time and space. The spatial variability was assessed with use of the GeoEas and Surfer models; for data aggregation and trend analysis, the SigmaPlot was used; preliminary data analysis was accomplished with use of the Statgraphics Plus for Windows software. The hydrogeochemical background of two analyzed compounds for each separate hydrogeochemical zone in the waste disposal area was simulated by a probabilistic method. Time- and space-dependent characteristics of chloride and sulfate distribution along with assessed data for the hydrogeochemical background provided a basis for the long-term evaluation of the groundwater chemical composition and deterioration rate variability in the area of the mining waste disposal site.

Planar waveguides have evanescent fields sensitive to index of refraction changes in the volume immediately above the waveguide surface. These fields extend up to 5000 Å above the surface. Placing a chemically sensitive polymer film within this region provides the basis for a chemical sensor. Polymer-analyte interactions change the index of refraction causing the propagating light velocity to change in a direction opposite to that of the index change. To measure this change, a reference propagating beam, adjacent to the sensing beam, is optically combined with the sensing beam creating an interference pattern of alternating dark and light fringes. When chemical or physical changes occur in the sensing arm, the interference pattern shifts. Real-time Fourier transform signal processing converts the time-dependent pattern to total phase shift which, is a measure of total analyte absorbed. Employing different polymer detection layers produces phase shifts whose pattern of response is used to identify and quantify the analytes present. Data taken from contaminated well sites measured using this interferometric sensor, and verified by independent laboratory measurements, is presented.

Carbonation-induced corrosion of steel is one of the principal causes of deterioration of reinforced concrete structures. When concrete carbonates, its pH decreases from a value in excess of 12.6 to less than 9 and, hence, a measure of the pH is an indicator of the degree of carbonation. This paper describes the development, testing and evaluation of two types of fibre optic sensors for the pH monitoring. One of these used a sol-gel based probe tip, into which an indicator dye has been introduced and the second used a disc containing an indicator operating over a narrower range of pH with shorter lifetime. Both were connected to a portable spectrometer system, which is used to monitor the spectral changes in optical absorption of the probe tip. A white light source to interrogate the active elements is used as the systems operate in the visible part of the spectrum. The two types of sensors have been found to be sensitive to the changes in pH due to carbonation, but the response time depended on the thickness of the coating material in the case of the sol-gel sensor. The durability of the sensors is still under investigation. The disc type sensor has a life span of approximately 1 month and, hence, it is not suitable for embedding in concrete for long-term monitoring of pH changes. However, it can be used for assessing the pH in vivo. The harder sol-gel is more durable and, hence, has a slower, but acceptable response time.

Microarrays are being widely used in genomic, proteomic, and diagnostic applications. The binding events to the microarrays are measured with fluorescent labels. Fluorescent microarray readers offer high sensitivity and normalization of the reference and test samples. The use of labels increases the number of steps involved in array testing, concerns about storage labels, and cost of additional labeling steps. This paper describes an alternative approach that does not require the use of fluorescent or other labels. The binding events on the microarray introduce changes in polarization of the illuminated light which is measured to determine the concentrations of biomolecules bound to the microarray. Oligonucleotide microarrays were synthesized and tested on the imaging microarray reader. The refractive index changes of 0.006 and changes in thickness of 1 nm are demonstrated at a spatial resolution of 20 μm over a field of view of 1 cm². This ellipsometric technique offers an attractive alternative to fluorescence-based measurement and could be very valuable in some of the genomic, proteomic, diagnostic, and sensing applications.