Reduced graphene-decorated covalent organic framework as a novel coating for solid-phase microextraction of phthalate esters coupled to gas chromatography-mass spectrometry.

Schiff base network-1 (SNW-1), as a new generation of covalent organic frameworks (COFs), was synthesized and modified by fabrication of a composite with graphene oxide (GO). The fabricated nanocomposite was characterized with FT-IR spectroscopy, XRD, FE-SEM, EDX, TGA, and the nitrogen adsorption-desorption technique. Characterization results showed that SNW-1 can reduce GO during the fabrication procedure and produce an effective and stable nanocomposite. This nanocomposite was deposited on the surface of a stainless steel wire via a single phase inversion method with the help of polyethersulfone, as a porous adhesive material. This robust and stable coating was used for head space solid-phase microextraction of phthalate esters (PhEs) from water samples. Determination of the PhEs was performed with gas chromatography coupled to mass spectrometry. SNW-1 is N-rich, and reduced-GO is full of hexagonal conjugated rings. Therefore, due to hydrogen binding and π-interaction, the coating has a high tendency to PhEs. Effective adsorption and desorption parameters were optimized. The performance of the method was evaluated in terms of linear ranges (LRs from 0.05 to 100 μg L with R ≥ 0.9942) and limits of detection (LODs in the range of 0.01-0.50 μg L). The average repeatability and fiber-to-fiber reproducibility were 6.8% and 9.2%, respectively. The method was employed to trace determination of PhEs in drinking water and pickled cucumber solution with good recovery (80.5-111.0%) and reliable reproducibility (5.5-9.5%). Graphical abstract Schematic representation of headspace-solid phase microextraction (HS-SPME) of phthalate esters (PhEs) from pickled cucumber solution and determination with gas chromatography-mass spectrometry (GC-MS).