Miniaturized laser-induced fluorescence system with a fiber optic probe for the analysis of aromatic compounds

We introduce a fiber optical sensors which is capable of analyzing polycyclic aromatic hydrocarbons (PAHs) and monoaromatics like benzene, tolouene, xylene, and ethylbenzene. The compact system is based on laser-induced, time-resolved fluorescence emission spectroscopy. It uses a miniaturized all solid state laser which can be operated alternately at 266 nm and 355 nm. The excitation light is guided through an optical fiber to the sensor head. The fluorescence light is collected by 4 optical fibers, which are placed around the excitation fiber, and guided to a detector, which consists of a spectrograph, a gateable image intensifier and a CCD camera. Time resolved spectra are recorded by moving the gate relative to the laser pulse. The focus of our work is the analysis of water but preliminary results of soil analysis are also presented. Limits of detection have been demonstrated for 15 PAHs from the EPA- list in water and some important mono-aromatics. Additionally some typical applications are presented, i.e. detection of fuel in water and diesel in soil.