Dye laser excited fluorescence spectroscopy of matrix isolated polycyclic aromatic hydrocarbons

The importance of inhomogeneous broadening in matrix isolation spectra of PAHs has been confirmed by the achievement of site selection. Emission bandwidths as low as 1.3 cm^{-1 (for perylene in heptane matrices) were obtained. Site selection fluorometry of matrix isolated PAHs has also been shown to exhibit analytical calibration curves which are linear over at least two orders of magnitude. An internal standard was not needed. Expressed in terms of relative standard deviation, the precision of matrix isolation site selection fluorometric analysis was on the order of 8%. Detection limits for benzo(a)pyrene (BaP) and 1,5-dihydroxynaphthalene (1,5-DHN) were approximately 1 ng and 50 ng, respectively. In both cases, the detection limits were limited by peak-to-peak laser intensity variations.}

Quantitative calibration curves for BaP and 1,5-DHN using perylene and BaP, respectively, as internal standards were nonlinear. Linearity was restored when the internal standards were not used. The nonlinearity was shown not to be a function of laser excitation or of site selection, and was attributed to energy transfer, an effect which was previously thought to play an insignificant role in matrix isolation fluorescence spectroscopy.