Pre-concentration of water samples with BEA zeolite for the direct determination of polycyclic aromatic hydrocarbons with laser-excited time-resolved Shpol'skii spectroscopy

Abstract

A unique method for screening fifteen US Environmental Protection Agency polycyclic aromatic hydrocarbons (EPA-PAHs) in drinking and lake water samples is reported. One milliliter volume of water sample is mixed and centrifuged with 2 mg of BEA zeolite. The precipitate is subsequently treated with equal volumes (100 μL) of a 70/30 methanol–water mixture and n-octane. Fifteen EPA-PAHs are directly determined (no chromatographic separation) in the layer of n-octane via 4.2 K laser-excited time-resolved Shpol'skii spectroscopy. A mathematical equation is derived to correlate the PAH concentration in the water sample to its concentration in the layer of Shpol'skii solvent (n-octane). Qualitative and quantitative analyses are based on the collection of wavelength–time matrices, i.e. data formats that carry with them spectral and lifetime information. With 1 mL of water, the limits of detection varied from 1.1 ng L − 1 (benzo[ a ]pyrene) to 194 ng L − 1 (naphthalene). The analytical recoveries of the new method are in good agreement with those obtained via high-performance liquid chromatography. The simplicity of the experimental procedure and the use of microliters of organic solvent make the new method a valuable and environmentally friendly alternative for the routine monitoring of EPA-PAHs in water samples. • Green methodology is presented for monitoring of polycyclic aromatic hydrocarbons. • Complete analysis is possible with 1 mL of water. • Sample analysis consumes 2 mg of zeolite and 170 μL of solvent. • Limits of detection are at the ng L − 1 to pg L − 1 concentration level.