Fiber optic laser-induced fluorescence excitation emission detector applied to flow injection analysis

A multi-channel fiber optic laser induced fluorescence (LIF) detection system has been developed for flow injection analysis (FIA). It has been applied to the detection of standard PAH mixtures and real world samples. The instrument uses a fiber optic array to deliver Raman shifter generated excitation beams (260 nm - 340 nm) to samples flowing in a fused silica capillary. An identical fluorescence collection fiber optic array was positioned perpendicular to the excitation array to collect fluorescence generated by the sample at each excitation wavelength. A spectrograph and charge coupled device (CCD) were used to spectrally discriminate and detect the fluorescence delivered by each collection fiber. Several samples were investigated including standard PAH mixtures and a fuel oil sample. Identification and quantitation were accomplished using rank annihilation factor analysis (RAFA) using pure single component standards and the EEMs of mixtures measured during FIA of the unknown samples. For all components in the standard PAH mixtures, quantitative estimates of concentration were within a factor of 2.5 from the known values with some of the components being determined to within a factor of 1.3. For the complex fuel oil sample, 6 out of 8 components were correctly identified.