Gradient extractive phase prepared by controlled rate infusion method: An applicable approach in solid phase microextraction for non–targeted analysis

Abstract

The aim of this study is to introduce an extractive phase based on gradient concept by continuous changing in chemical functional groups for non–targeted analysis. For this purpose, three different two–component coatings containing (3–aminopropyl)trimethoxysilane (APTES) as polar and either phenyltriethoxysilane (PTES), octyl–trimethoxysilane (OTMS) or methyltrimethoxysilane (MTMS) as nonpolar precursors were formed on the modified stainless steel wires using controlled rate infusion (CRI) method. The presence of polar and/or non–polar functional groups on the surface of substrate was evaluated by Fourier–transform infrared spectroscopy (FTIR) together with contact angles determined alongside the gradient surface. The morphology and thickness of the prepared fibers were also investigated by scanning electron microscopy (SEM). Furthermore, uniform single–component fibers from polar (APTES) and nonpolar (PTES) coatings were fabricated in order to be compared with the gradient sorbent. The gradient phase was implemented as a fiber coating in headspace– or immersed–solid phase microextraction of various compounds including chlorobenzenes, polycyclic aromatic hydrocarbons, chlorophenols and volatile organic compounds (Log Kow range: −0.77 to 4.64). Under the optimized condition, the limits of detection and quantification were obtained in the range of 0.01–0.5 μg L−1 and 0.05–1.5 μg L−1, respectively. The intra–day and inter–day relative standard deviations of 2–10% and 11–17% were achieved, respectively. The method was successfully applied to the extraction of VOCs from real water sample and relative recoveries were between 89 and 105%. The capability and efficiency of the gradient coating appears to be quite appropriate for non–targeted analysis.