<title>Speciation of aromatic compounds with excitation-emission matrix measurements</title>

Abstract

Research in our group has shown that a multiple channel laser-induced fluorescence (LIF) system is an effective tool for in situ monitoring of polyaromatic hydrocarbons (PAHs). The system delivers ten laser beams to a samples and simultaneously detects the fluorescence signals from the individual channels, generating an excitation-emission matrix (EEM) of the sample. Speciation of chemical present in a mixture EEM is conducted by target factor analysis. To determine the capability of the technique for speciation, various aromatic compounds were measured with the LIF system. The pure-component EEMs were analyzed against each other as targets to separate the compounds into classes with the target factor analysis method. Then EEMs of mixtures containing 2-5 components were analyzed using the pure- component EEMs as standards. In this preliminary study of eleven target aromatic compounds, nine were successfully identified individually, while two spectroscopically very similar compounds, naphthalene and 2-methylnaphthalene, could be differentiated from the other nine but not from each other. In such cases, the technique can correctly identify the presence of the class, e.g., naphthalenes, instead of an individual components, and the quantitative results for the class must be interpreted accordingly.