Determination of molecular mass 302 polycyclic aromatic hydrocarbons in Standard Reference Material 1597a by reversed-phase liquid chromatography and constant energy synchronous fluorescence spectroscopy

High-performance liquid chromatography with fluorescence detection is often used for the analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental extracts. Since fluorescence chromatograms are usually recorded at a single set of excitation and emission wavelengths, qualitative parameters for PAH identification are restricted to characteristic retention times. The research presented here explores the use of constant energy synchronous fluorescence spectroscopy (CESFS) for the analysis of co-eluting PAHs with similar chromatographic behaviors under normal and reversed-phase conditions. Twenty-one PAH isomers with molecular mass (MM, g/mol) 302 were studied. Synchronous fluorescence spectra were recorded under stop-flow conditions with the aid of a commercial HPLC system. PAHs were extracted from a coal tar sample (Standard Reference Material 1597a) and fractionated by normal-phase liquid chromatography (NPLC). Qualitative and quantitative analysis of NPLC fractions was carried out via reversed-phase liquid chromatography-CESFS (RPLC-CESFS). Of the 21 isomers investigated in the coal tar sample, 16 were spectrally identified in the absence of matrix interference. Three of the remaining isomers were tentatively identified in the presence of moderate spectral interference. Thirteen isomers were used to investigate the accuracy of the RPLC-CESFS approach. Mass fractions statistically equivalent to the NIST reported values (P = 95%; N-1 = N-2 = 3) were obtained for ten isomers ranging from 2.04 (dibenzo[a,h]pyrene) to 10.41 mg/kg (naphtho[2,1-a]pyrene). The non-destructive nature of CESFS provides an additional layer of selective and accurate information to the analysis of PAH isomers with MM 302.