Solid-phase microextraction of PAHs from water samples using mesoporous carbon nitride coating

Solid-phase microextraction (SPME) has been widely applied in environmental, food, clinical and biological analysis since the pioneering work of Pawliszyn and Arthur in the early 1990s [1]. This technique is a solvent-free and green equilibrium-based sample pretreatment method that integrates sampling, isolation and enrichment into one step. The extraction ability of SPME is primarily determined by the nature of the sorbent coated on the fiber. Therefore, the development of novel coatings is a key focus for current research on SPME [2]. Carbon-based nano materials have been used to form a sorption layer on SPME fibers. Their affinity for relatively strong sorption of organic pollutants, combined with other properties (very large specific surface, durability, chemical and thermal stability), make them promising options that can be applied in SPME as adsorbents. Fullerenes, carbon nanotubes (CNTs), graphene, ordered mesoporous carbon (OMC) and their functionalized forms are good SPME coatings [3]. Carbon nitrides (CNs) are fascinating materials with unique properties including semi-conductivity, high hardness, chemical robustness and high chemical, thermal and mechanical stability. These properties make it popular in many fields, such as water splitting, sensor, and NO decomposition and hydrogenation reactions [4]. The in-built N-rich functional groups and electronic delocalization properties endow graphitic carbon nitride (g-CN) with complex sorption mechanism, containing complexion, hydrogen bond, redox reaction, π–π conjugation, hydrophobic effect, acid-base reaction and electrostatic interaction [5]. Herein, an MCN with a highly ordered mesoporous structure and a very large Brunauer-Emmett-Teller (BET) surface area (503 m2 g-1) has been coated on the surface of stainless steel wire to prepare highly sensitive SPME fiber. The SPME-GC-MS method showed low detection limit (0.2 ng L-1 to 2 ng L-1), wide linear range (2 ng L-1 to 2000 ng L-1) and good recoveries in extraction and determination of PAHs in real water samples. The relative standard deviations (RSDs) for the six replicated tests using a single fiber ranged from 3.2% to 7.1%. The fiber to fiber reproducibility for three parallel fibers ranged from 5.4% to 9.7%