Fluorimetric detection of water pollutants with a fiber coupled solid-state UV-laser

Aromatic hydrocarbons are important and dangerous pollutants of the aquatic environment. With the method of Laser-Induced Fluorescence (LIF) it is possible to detect Benzene, Toluene, Xylene (BTX) as well as Polycyclic Aromatic Hydrocarbons (PAH) sensitively. The detection of these molecules by a continously working in-situ method is achieved by combining LIF with fiberoptic guidance of light. We present results on the detection of BTX and PAH by excitation with 266 nm and 355 nm radiation from a diode-pumped solid-state laser especially developed for sensor applications. The system is operated with thermoelectric cooling and battery supply independent of any installations is projected. The laser delivers pulses of 7 ns/140 mu J in the UV at a repetition rate of 100 Hz. Using time-resolved and spectrally-resolved detection of the fluorescence signal, the system delivers information that can be used to discriminate between BTX and PAH-molecules. We have also performed extensive investigations of the influence of scattering particles on the sensor signal. This led to specific optimizations of the sensor-head for different applications.