Determination of polycyclic aromatic hydrocarbons with molecular weight 302 in water samples by solid-phase nano-extraction and laser excited time-resolved shpol'skii spectroscopy

Abstract

Monitoring of high-molecular weight polycyclic aromatic hydrocarbons (HMW-PAH) via simple and cost effective methods still remains a challenge. In this article, we combine solid-phase nano-extraction (SPNE) and 4.2 K laser-excited time resolved Shpol'skii spectroscopy (LETRSS) into a valuable alternative for the water analysis of dibenzo[a,l]pyrene, dibenzo[a,h]pyrene, dibenzo[a,i]pyrene and naphtho[2,3-a]pyrene. In comparison to the original SPNE procedure, the present method improves PAH recoveries and reduces extraction time from 30 to 20 min per sample. Quantitative release of HMW-PAH into the Shpol'skii matrix (n-octane) is best accomplished with a mixture of 48 μL of methanol and 2 μL of 1-pentanethiol. Their migration into the 50 μL layer of n-octane provides highly resolved spectra with distinct fluorescence lifetimes for unambiguous isomer determination. Complete analysis takes less than 30 min per sample and consumes only 100 micro-liters of organic solvents. 500 μL of water are sufficient to obtain limits of detection ranging from 16 ng L⁻¹ (dibenzo[a,l]pyrene) to 55 ng L⁻¹ (dibenzo[a,i]pyrene), relative standard deviations better than 3% and analytical recoveries above 90%. Although a straightforward comparison to chromatographic methods is not possible because of the lack of analytical figures of merit on HMW-PAH, the excellent precision of measurements, limits of detection and overall recoveries makes SPNE-LETRSS an attractive approach to water analysis of HMW-PAH.