Analysis of trace-level nitrated polycyclic aromatic hydrocarbons in water samples by solid-phase microextraction with gas chromatography and mass spectrometry.

A solid-phase microextraction coupled with gas chromatography and mass spectrometry method has been developed for the determination of ten nitrated polycyclic aromatic hydrocarbons in water samples. Five different kinds of commerical fibers were used to compare the extraction efficiency, including 65 μm polydimethylsiloxane/divinylbenzene, 100 μm polydimethylsiloxane, 30 μm polydimethylsiloxane, 7 μm polydimethylsiloxane, and 85 μm polyacrylate fibers. Five factors were also selected to optimize conditions, including extraction temperature, time, stirring speed, salt concentration, and headspace volume. Taguchi design was applied to design the experiments and obtain the best parameters. The results show that 65 μm polydimethylsiloxane/divinylbenzene fiber directly immersed into aqueous solution for 35 min at 55°C with a constant stirring rate of 1150 rpm were the optimal conditions. Under these conditions, the limits of quantification were 0.007-0.063 μg/L, and the relative standard deviation based on six replicates ranged from 2.8 to 9.5%. The spiked recoveries ranged from 69.1 to 110.1%. Intra- and inter day relative standard deviations at three concentration levels were less than 12%, and the recoveries were 66.4-111.5%. The proposed method is reliable for analyzing nitrated polycyclic aromatic hydrocarbons in different water samples.