We demonstrate the improvement of fluorescence immunoassay (FIA) diagnostics in deploying a newly developed compact diode-pumped solid state (DPSS) laser with emission at 315 nm. The laser is based on the quasi-three-level transition in Nd:YAG at 946 nm. The pulsed operation is either realized by an active Q-switch using an electro-optical device or by introduction of a Cr<sup>4+</sup>:YAG saturable absorber as passive Q-switch element. By extra-cavity second harmonic generation in different nonlinear crystal media we obtained blue light at 473 nm. Subsequent mixing of the fundamental and the second harmonic in a β-barium-borate crystal provided pulsed emission at 315 nm with up to 20 μJ maximum pulse energy and 17 ns pulse duration. Substitution of a nitrogen laser in a FIA diagnostics system by the DPSS laser succeeded in considerable improvement of the detection limit. Despite significantly lower pulse energies (7 μJ DPSS laser versus 150 μJ nitrogen laser), in preliminary investigations the limit of detection was reduced by a factor of three for a typical FIA.
We introduce a fiber optical sensor system that can be applied to environmental analysis. The compact system is based on laser-induced, time-resolved fluorescence emission spectroscopy. It uses a miniaturised all solid state laser which is operated at 266 nm as the excitation source and a spectrograph/image intensifier/CCD-camera for time-resolved detection of the fluorescence. The versatility of the instrument is demonstrated by the analysis of various substances using multivariate calibration techniques. Xylene could be analysed in natural water samples in the presence of other mono-aromatics with a detection limit of 10 ?g/l. The fluorescence tracer sulforhodamine G was analysed in river water with a detection limit of 10 ng/l. Furthermore the system is able to detect oil contaminations in soil in the concentration range of 100 ppm and above.
We introduce a fiber optical sensor which is capable of analyzing polycyclic aromatic hydrocarbons (PAHs) and monoaromatics like benzene, toluene, xylene, and ethylbenzene (BTXE) in natural water samples. 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 at 266 nm and 355 nm. The 3-D data set of a time-resolved fluorescence spectrum is reduced to a 2-D data set by a factor based technique, i.e. by dividing the raw data by a decay matrix with exponential decay profiles. The resulting data have a 2-D spectral format but still contain the temporal information. With these data a partial least squares regression has been carried out and optimized for a quantitative evaluation of the data. After the calibration xylene could be selectively analyzed in the 0 - 200 ppb range with a prediction error of 15 ppb. The PAH calibration was able to predict the concentration of 9 out of 15 EPA PAHs with errors between 0.07 (mu) g/l (benzo[a]pyrene) and 1.6 (mu) g/l (anthracene, naphthalene).
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.