Application of poly 3,4-ethylenedioxythiophene and gold nanoparticles composite on a gold wire as a coating for determination of nitroaromatics in soil using cold fiber solid phase microextraction combined with gas chromatography

Abstract

Although several sensing techniques have been employed for nitroaromatics, developing novel detection approaches for environment analysis is still necessary. In this study, for the first time, the cooling assisted solid phase microextraction (CA-SPME) method was performed using poly 3,4-ethylenedioxythiophene and gold nanoparticles composite coating on a gold wire to extract nitroaromatic compounds. The surface morphology of the homemade SPME fiber was investigated through a field emission scanning electron microscope. The fiber was used to extract 4-nitrotoluene (4-NT), 1,3-dinitrobenzene (1,3-DNB), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) from the soil. To increase extraction efficiency and reduce interferences, extraction was performed from the sample headspace, and the fiber was cooled by a cooling apparatus. Then, the extracts of nitroaromatics were injected into the gas chromatography- flame ionization detector instrument to identify and quantify the analytes. A set of effective experimental parameters in fiber coating characteristics and extraction and separation procedures, including extraction temperature, extraction time, vial volume, and separation conditions in gas chromatography, were optimized. Under optimal conditions, recoveries of nitroaromatics ranged from 96.80% to 102.10%, and the detection limit values were in the range of 0.15 to 0.30 ng.g−1. The linear ranges were obtained to be 0.5–250.0 ng.g−1 and 1.0–250.0 ng.g−1 for 4-NT, 2,4-DNT, 2,6-DNT, and 1,3-DNB, respectively. Finally, the proposed method was successfully tested on real soil samples.