Pre-concentration of water samples with BEA zeolite for the direct determination of polycyclic aromatic hydrocarbons with laser-excited time-resolved Shpol'skii spectroscopy Walter B. Wilson a , Andréia A. Costa b , Huiyong Wang a , Andres D. Campiglia a, ⁎, José A. Dias c , Sílvia C.L. Dias c a University of Central Florida, 4000 Central Florida Blvd., Physical Science Building, Orlando, FL 32816-2366, USA b Universidade de Brasília, Faculdade UnB, Gama, Engenharia de Energia, Brasília-DF 72405-610, Brazil c Universidade de Brasilia, Campus Darcy Ribeiro, Instituto de Quimica, Caixa Postal 4478, Brasilia-DF 70904-970, Brazil abstract article info Article history: Received 19 December 2012 Received in revised form 1 April 2013 Accepted 2 April 2013 Available online 16 April 2013 Keywords: Zeolites BEA Polycyclic aromatic hydrocarbons Solid-phase extraction Laser-excited time-resolved Shpol'skii spectroscopy Shpol'skii spectroscopy Water analysis A unique method for screening fifteen US Environmental Protection Agency polycyclic aromatic hydrocar- bons (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 spec- troscopy. 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 alter- native for the routine monitoring of EPA-PAHs in water samples. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are important environ- mental pollutants originating from a wide variety of natural and anthropogenic sources. PAHs are generally formed during incom- plete combustion of organic matter containing carbon and hydrogen. Since combustion of organic materials is involved in countless natural processes or human activities, PAHs are omnipresent and abundant pol- lutants in air, soil, and water [1–3]. Many PAHs are highly suspect as eti- ological agents in human cancer [4–7]. Well-known examples are the sixteen PAHs included in the US Environmental Protection Agency (EPA) list, namely benz[a]anthracene, benzo[b]fluoranthene, benzo[k] fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, indeno[1,2,3-cd] pyrene, naphthalene, acenaphthylene, acenaphthene, fluorene, phen- anthrene, anthracene, fluoranthene, pyrene, chrysene, and benzo[g,h,i] perylene [8]. On drinking waters, the EPA recommends the routine monitoring of benzo[a]pyrene. This is the most toxic PAH in the EPA list, and its concentration alone is often used as a measure of risk. According to the EPA, its maximum contaminant level (MCL) in drinking waters should not exceed 200 ng L -1 [9]. In addition to benzo[a]pyrene, the European Union and the World Health Organization (WHO) have reg- ulated fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo [g,h,i]perylene, and indeno[1,2,3-cd]pyrene [10,11]. MCL values were set at 10 ng L -1 for the highly toxic benzo[a]pyrene and 200 ng L -1 for the remaining PAHs. These rather low MCL values make the analysis of EPA-PAHs par- ticularly challenging. The classic approach for water analysis follows the sequence of sample collection, PAH extraction, and chromato- graphic analysis. Sample extraction pre-concentrates PAH, simplifies matrix composition, and facilitates analytical resolution in the chro- matographic column. Among the numerous approaches to extract and pre-concentrate PAH, the preferred methods are either based on liquid–liquid extraction [12–14] or solid-phase extraction [15–26]. Both remove PAHs from water samples into an organic solvent suitable for chromatographic analysis. High performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC–MS) are the basis of current EPA methodology [15–20,27–31]. UV absorption and room temperature fluorescence detection are both widely used in HPLC, but the specificity of these detectors is modest. When HPLC is ap- plied to “unfamiliar” samples, EPA recommends the use of a supporting Microchemical Journal 110 (2013) 246–255 ⁎ Corresponding author. Tel.: +1 4078234162. E-mail address: andres.campiglia@ucf.edu (A.D. Campiglia). 0026-265X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.microc.2013.04.001 Contents lists available at SciVerse ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc