Fast and sensitive analysis of nitro-phenanthrenes in water and soil samples using copper loaded polyaniline@magnetic halloysite nanotube composite coupled with gas chromatography–mass spectrometry

In this study, we developed ultrasonication assisted magnetic dispersive solid-phase microextraction (MDSPME) setup for extraction of two types of nitro-PAHs compound include 9-nitrophenanthrene (9-NPhe) and 3 nitrophenanthrene (3-NPhe) in environmental samples prior to GC–MS determination. Nitro-PAHs are derivatives of PAHs and mainly generated by incomplete combustion and pyrolysis of fossil fuels such as diesel and gasoline. These compounds can be 200% higher than the mutagenicity caused by their parent PAHs [1]. However, until the pre-concentration of ultra-trace is not carried out, favorable detection sensitivity might not be achieved. For this reason, new type of modified nanocomposite has made based halloysite nanotubes (HNT). HNT is a type of natural material, have attracted great interest because of their large surface area and high chemical and thermal stability [2]. The hybrid nanocomposite was obtained by fabricating magnetic HNT by polyaniline (PANI) and afterwards with copper. Its morphology and surface properties were characterized using of Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive spectroscopy and vibrating sample magnetometry. The performance of new sorbent was compared with magnetic HNT and magnetic HNT@PANI. Hydrophilic containing functional groups in HNT leading up to a suitable dispersion in aqueous matrixes, whiles PANI moiety contributes to the hydrophobic and π interactions with nitrophenanthrenes. The presence of copper on the polymeric structure is responsible for π electron-metal intractions and higher sorption capacity. Parameters affecting the extraction efficiencies such as desorption solvent type and volume, extraction and desorption time, sorbent amount, organic modifier content, salt concentration and matrix effect were investigated in detail. Under the optimal conditions, the limit of detection (S/N = 3) was 0.25 ng L-1 and the linearity was in the range of 0.01 to 100 μg L-1. The method precision expressed as relative standard deviations (RSD) was 4.6-6.1 % (intra-day), and of 7.2-9.6% (inter-day) respectively. Finally, the presented method was successfully applied to the fast determination of analytes in water and soil samples.