Simultaneous analysis of PAHs and BTEX in soil by a needle trap device coupled with GC-FID and using response surface methodology involving Box-Behnken design

Polyaniline silica (Silica/PANI) organic-inorganic nanocomposite was synthesized by combining electrospinning and in-situ polymerization processes. This strategy prevented the aggregation of PANI during the polymerization and led to higher synthesis's yield and more uniformity of the produced composite. The structure and morphology of the nanocomposite was characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The prepared nanocomposite was then packed inside a stain-steel needle and evaluated as a needle trap device (NTD), for simultaneous headspace extraction of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in polluted soil samples, before GC-FID analysis, as a low-cost and robust detector. Response surface methodology (RSM) involving Box-Behnken design (BBD) was implemented to evaluate the effective experimental variables and subsequent introduction of a multiple function to describe the experimental conditions for the extraction of the analytes. Wide calibration plots (1-2000 ng g⁻¹ for BTEX and 0.2–2000 ng g⁻¹ for PAHs) with acceptable linearity (R² > 0.99) were obtained under the optimal conditions. The limits of detection were found to be 0.02–0.1 ng g⁻¹for BTEX and 0.001–0.01 ng g⁻¹ for PAHs. The calculated standard deviations were 7.3–13.2% (n = 6). The developed NTD-GC-FID method was successfully applied for the extraction and determination of PAHs and BTEX in contaminated soil samples.