DIRECT EXAMINATION OF SEPARATION PROCESSES BY LASER INDUCED FLUORESCENCE

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Polycyclic aromatic compounds (PACs) are an important group of pollutants which are found at trace levels throughout the environment. They consist of two or more fused aromatic rings, with a large number of isomeric forms. In addition, subtle changes in structure can result in dramatic changes in their observed chemical and toxicological properties. Together they form the largest known class of chemical carcinogens and mutagens, with sixteen PACs consisting of only cabon and hydrogen (polycyclic aromatic hydrocarbons or PAHs) identified by the EPA. One method which can discriminate between various structural classes of PACs is the use of selective quenching agents in fluorescence spectroscopy. In a quenching approach, an excited-state fluorophore is deliberately deactivated by a collision with a quencher that selectively promotes nonradiative relaxation. This method can provide valuable photophysical and photochemical information about the individual fluorophore that can be used for classification or identification. In addition, when combined with separation methods it can be used to simplify the qualitative and quantitative analysis of complex samples by selective discrimination against interfering components. This project is concerned with evaluating the effectiveness and selectivity of novel quenchers of PACs. Given the nature of the experiments, the purity of both fluorophores and quenchers is important. Mass spectrometry can be used to determine the presence and identity of impurities, which in turn helps determine the best method for their removal. MS analysis of the purified reagents is carried out to confirm the absence of impurities before experimental work can be begun.