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 2mg of BEA zeolite. The precipitate is subsequently treated with equal volumes (100μL) 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 4.2K 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 1mL of water, the limits of detection varied from 1.1ngL-1 (benzo[a]pyrene) to 194ngL-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. © 2013 Elsevier B.V.