The use of a cut-off filter has been compared with a monochromator for emission energy selection in the fluorescence detector used in the analysis of environmental samples for polycyclic aromatic hydrocarbons by liquid chromatography. The use of a cut-off filter can provide greater sensitivity for compounds that are well separated by the chromatography. However, samples that contain a large number of compounds often result in overlapping peaks, and for such samples, it has been found that the spectral selectivity of monochromatic emission selection reduces the interference due to compounds eluting near the compounds of analytical interest. This spectral selectivity results in greater sensitivity and a smaller quantitation error in the analysis of these complex samples.