A new setup for collection and detection of fluorescence spectrum using a double-frequency Nd-YAG laser as incident light source and coupled with multichannel CCD (charge coupled device) detector and flow injection system was described in this paper. The parameters ofthe setup were optimized. Fluorescence spectra are measured in the range of35Onm'7OOnm with the wavelength resolution of 0.3 nm and spectral response sensitivity ofdetector is O.1LX. High S/N ratio fluorescence spectrum of Rhodamine B (RhB) solution was measured and the detection limit is iO mol L. The setup has been applied to the simultaneous determination of Cu and Fe in food samples. The determination is based on the fluorescence quenching reaction owing to catalytic effects of the metallic ions on the oxidation reaction of RhB and H202.The fluorescence spectra of RhB are collected by CCD diode array detector and the overlapping spectra are processed using artificial neural networks (ANN) algorithm. The experimental variables were optimized and the proposed method is validated on determination of Cu and Fe in a wheat reference material and the food samples. The determination results of samples are in good agreement between the proposed method and Atomic Absorption Spectrophotometry (AAS). The average spiked recoveries are 93.3% 95.8% for Cu and 93.4%'lOO.2% for Fe with relative standard deviation ofO.6%' 7.5%. Fluorometric analysis is extremely sensitive and is used widely in biochemistry, analytical and clinical chemistry. Its sensitivity is usually 23 orders of magnitude higher than absorption spectrophotometry1 . For low concentrations of analytes the fluorescence intensity is directly proportional to the concentration and also proportional to the intensity of the incident radiation. Lasers are known to have extremely very strong radiation with nanow intrinsic line-widths and coherent and highly directional properties. They are thus ideal tools for high-sensitive fluorescence analysis. Current hyphenated approaches using multidimensional instrumentation such as CCD-diode array detector allows to scan a fluorescence spectrum in about 0. 1s. Flow injection analysis has become an important technique in food analysis as a result of its high speed and precision and the ease with which it is automated' . The main purpose of this work was to develop an auto-continuous analytical system applying a double-frequency Nd-YAG laser (532nm) as the exciting light source and a CCD-diode array detector with rapidly scanning fluorescence spectrum in flow injection analysis for determining multiple components in food samples. Compared with the conventional fluorescence spectrophotometer, the setup can offer the better reproducibility of analytical wavelength and improve precision and signal-to-noise ratio. A block diagram of the setup is shown in Fig.1.Fig. 1 Schematic diagram of CCD-detector-laser induced fluorescence setup Laser: YAG laser with a double frequency crystal of KDP; P1, P2 and P3: beam splitters; Fl and F2: lens; 5: sample in flow cell; M: mirror;...
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