UV-Laser and LED Fluorescence Detection of Trace Organic Compounds in Drinking Water and Distilled Spirits

Current methods for the analysis of drinking water and many other liquids often call for the use of reagents and may require extensive sample preparation (American Public Health Association, 1989). For the case of water supplies and water treatment plants, this analysis is usually carried out once every few days or weeks (Killinger & Sivaprakasam, 2006). Most of the analysis is usually conducted using classical analytical chemical techniques, such as mass spectrometry, liquid chromatography, or fluorescence based or tagged reagents (Crompton, 2000). These analytical techniques are sensitive and provide accurate assessment of the chemistry related to the quality of the liquids. However, they often take considerable time and are usually not performed in real-time, especially for the case of a flowing process line. On the other hand, previous fluorescence spectroscopic measurements of ocean water by Coble showed that deep-UV excitation of naturally occurring organic compounds in water can yield significant and unique fluorescence signals in the near UV to visible wavelength range without the need to use additional reagents or sample preparation (Coble, 1996; Coble, 2007). As a result, we have been studying deep-UV laser-induced-fluorescence techniques for the detection of trace species in water and other liquids with the goal of using the natural fluorescence of trace species in the water or liquid samples and being able to provide readings within the time span of a few seconds. Toward this goal, we have developed a reagentless deep-UV laser and UV-LED induced fluorescence (LIF) system to detect and continuously observe in real time trace levels of colored dissolved organic matter (CDOM) or Dissolved Organic Compounds (DOCs) in water and distilled spirits, such as drinking water, and related water/alcohol based liquids with a sensitivity exceeding that of commercial spectrofluorometers. Our system has been used to detect ppb trace levels of plasicizer Bisphenol-A (BPA) that have leached into drinking water, and has detected and monitored trace levels of DOCs within ocean currents (Killinger & Sivaprakasam, 2006; Sivaprakasam et al. 2003; Sivaprakasam & Killinger, 2003). Recently, our LIF system has been used to measure fluorescence of reverse osmosis processed water and different types of drinking water (Sharikova & Killinger, 2007; Sharikova & Killinger, 2010). These LED/LIF applications have now been extended to additional water related samples, including humic acid samples, tannic acid and chlorinated water samples, juices, coffee, and several wines and distilled spirits; these recent results are presented in this paper.