ANALYSIS OF POLYNUCLEAR AROMATIC-COMPOUNDS USING LASER-EXCITED SYNCHRONOUS FLUORESCENCE

Monitoring the presence and distribution of polynuclear aromatic compounds (PACs) in the environment is an important task due to the presence of these species in many types of environmental samples. Molecular fluorescence is often used for this task, usually after extensive sample cleanup and separation, due to the speed and the inherent sensitivity of the technique for PACs. When synchronous fluorescence is used for PAC analysis, the amount of sample pretreatment can often be reduced due to the greater selectivity of the technique relative to conventional fluorescence emission. Another method of increasing sensitivity and selectivity is to use lasers as the excitation source in molecular fluorescence. An added advantage of lasers is the high source coupling and fluorescence collection efficiencies when fiber optics are used for remote sensing applications. In this work, the applicability of laser-excited synchronous fluorescence for the analysis of PAC mixtures is evaluated. A prototype laser-excited synchronous luminescence (LSL) instrument has been previously determined to offer significant advantages over conventional laser-excited fluorescence [C.L. Stevenson and T. Vo-Dinh, Appl. Spectrosc., 47 (1993) 430]. An improved version of the LSL instrument is presented here with superior scanning precision and extended wavelength scanning range. In addition to demonstrating the capabilities of the improved LSL instrument for mixture analysis, the sensitivity of this improved instrument is compared to that of a commercial fluorimeter. Finally, the capability of the LSL instrument to further improve selectivity using time-resolved synchronous fluorescence is illustrated.