Due to a lack of reference materials, and in order to confirm each peak in the chromatograms for the extracts from airborne particulates eluted at the same time of the corresponding standard OH–PAHs, method validation was carried out using the emission and excitation spectra (Kishikawa et al., 2004). As shown in Figure 3, the excitation and emission spectra of the OH–PAHs in airborne particulates were in good agreement with those obtained from the standard solutions.