This Small Business Innovation Research (SBIR) Phase I project is to develop and demonstrate a low cost, hand-held, reagentless instrument to provide real-time, in-situ, detection of trace chemical contaminants in water for environmental, municipal waste treatment, industrial waste, and other fixed and mobile water measurement settings. A specific example of the Trace Chemical (TraC) sensor is aimed at an on-line or off-line monitoring system that will improve the reliability and performance of wastewater treatment systems that are designed to remove nitrogen through Simultaneous Nitrification and DeNitrification (SNdN). This is an example of a major source of potential environmental contamination. The technology of the proposed innovative sensor is deep ultraviolet excited resonance Raman (DUV-RR) and native fluorescence spectroscopy which will enable real time, in situ, measurement of nitrate and nitrite in Biological Nutrient Removal (BNR) system reactors without the need for reagents, sample handling, or complex calibration procedures. The TraC sensor integrates two new technologies to provide dramatic reductions in size, weight, power consumption, and cost: a new technology narrow and stable linewidth deep UV laser and a new technology high data rate linear resistive gate CCD array detector.
The broader impact/commercial potential of this project is to replace many analytical instruments that are currently employed to measure bulk or trace contaminants in water, air, soils, or surfaces. Most existing instruments require a significant amount of sample preparation and handling as well as the use of reagents and other consumables. Optical methods of analyzing contaminants continue to gain importance because of the basic non-contact, non-invasive nature, and speed of the measurement. Raman and native fluorescence spectroscopy has been increasingly employed to provide high levels of specificity in chemical identification without the need for dye tags or labels. This has been done to date in instruments mostly operating in the visible and infrared. Operating at these wavelengths has provided significant limitations in the types and concentrations of chemicals that can be detected because of low cross-sections and/or fluorescence obscuration of weak Raman emissions at these wavelengths. Moving to the deep UV below 250 nm offers a solution which has been demonstrated in large laboratory instruments but not yet possible in hand-held instruments. This will open up many markets for trace contaminant detection in a broad range of water, and soil environmental, force protection, and municipal, industrial, agricultural, and medical applications.
During the Phase I effort, we developed and demonstrated a new miniature, real-time, reagentless, optical sensor system design and methods for detection of a wide range of trace chemical contaminants in water and on surfaces. The technology of the sensor is a fusion of deep ultraviolet excited resonance Raman (RR) and native fluorescence (NF) spectroscopy. Raman spectra, which provide information about chemical bonds within target chemicals, are dependent on the excitation wavelength and are measured in molecular vibration energy terms above (Stokes) or below (anti-Stokes) the excitation wavelength. Fluorescence spectra, which provide information about the overall electronic configuration of the target chemicals, are independent of excitation wavelength. Therefore, as the excitation wavelength is reduced below the lower limit of fluorescence, about 260 nm to 270 nm, a fluorescence-background-free region above the excitation wavelength expands in which the normally weak Raman emissions can be observed. Raman and native fluorescence spectroscopy excited in the deep UV below 250 nm offer dramatic advantages over other methods for detection of trace chemicals in water or on surfaces including: 1) the lack of need for reagents or sample handling; 2) much higher sensitivity and specificity than absorption, or Raman and fluorescence methods with excitation in the near UV, visible or IR; 3) separation of the RR and NF spectral regions and elimination of cross-interference of RR and NF emissions which enable these two forms of orthogonal measurements to provide more specific information about trace chemicals; and 4) no interference with water absorption bands. These deep UV based sensors have been demonstrated to show great promise to dramatically change the way two diverse commercial businesses conduct essential present processes with large savings in both direct costs, speed, and down time of equipment. These applications are: sub ppm independent detection of nitrate and nitrite for automated control of nitrogen reduction in wastewater treatment plants; and cleaning validation for pharmaceutical manufacturing equipment. These two commercial applications employ the advantages in sensitivity and specificity of using of deep UV Raman and fluorescence spectroscopic methods enabled by new patented deep UV lasers, which provide higher sensitivity and specificity chemical detection at dramatically lower size, weight, power consumption, and cost. This new Trace Chemical (TraC) sensor technology additionally offers similar advantages to a wider range of applications compared to current portable sensors at equal or lower cost. Among the specific findings of the Phase I effort were that we could achieve very low limits of detection of nitrates and nitrites at exceptionally high specificity in wastewater using the TraC sensor design employing a Photon Systems’ deep UV 248 nm laser with an overall benefit of over 100 times small size and weight, over 1000 time lower power consumption, and 20 to 30 times lower cost than demonstrated previously using deep UV Raman and fluorescence methods. Part of this demonstration was a new flow cell to improve Raman and fluorescence signal strength and reduce interferences, which enabled limits of detection of below 100 ppb of nitrates and nitrites in water, independent of the presence of other chemical contaminants. The price of the TraC sensor was shown to be similar or less expensive than absorption based sensors, while still providing much higher sensitivity and specificity. We also demonstrated that competitive absorption sensor methods had high false positive detection for nitrates and nitrates and were not suitable for independent monitoring of nitrates and nitrites for automated nitrogen reduction processes. During the Phase I effort, we also demonstrated the benefits of our deep UV sensor methods with a large pharmaceutical company, proving that we could detect, with high specificity, two different active pharmaceutical ingredients residues on stainless steel surfaces equivalent to the surfaces in pharmaceutical manufacturing equipment at concentrations more than 10 to 200 times lower than manufacturers internal regulations, and substantially lower than FDA regulation levels. Our deep UV sensor would enable cleaning validation of pharmaceutical manufacturing equipment within a few hours compared to present cleaning validation protocols (sample collection with swabs and subsequent HPLC analysis), which take 4 days and very large costs in labor, equipment down time, and related costs.
