Controlled growth of oriented porous hexagonal ZnO nanosheets on nitinol fibre as superior coatings in solid-phase microextraction coupled to HPLC-UV for preconcentration and determination of polycyclic aromatic hydrocarbons in water†

The controlled growth of oriented hexagonal ZnO nanosheets (ZnONSs) on a nitinol (NiTi) fibre substrate without a seeding layer was presented by using ZnCl₂ as a precursor and KCl as a supporting electrolyte and a capping agent. The effect of the electrolytic composition and electrodeposition parameters on the morphology of ZnONSs was investigated. After annealing, novel porous ZnONSs (P-ZnONSs) were obtained and the overall morphology of oriented hexagonal ZnONSs was well maintained. The P-ZnONS coated NiTi (NiTi@P-ZnONS) fibre was used for solid-phase microextraction (SPME) coupled to HPLC-UV and showed good adsorption selectivity for polycyclic aromatic hydrocarbons (PAHs). As compared with that of the ZnONS coated NiTi (NiTi@ZnONS) fibre, the adsorption efficiency of the NiTi@P-ZnONS fiber was further improved. Moreover, the NiTi@P-ZnONS fibre showed superior adsorption capability for PAHs compared to typical commercially available 7-μm polydimethylsiloxane and 85-μm polyacrylate fibres. After the optimisation of SPME conditions with the NiTi@P-ZnONS fibre, good linearity was obtained in the range of 0.03–200 μg L⁻¹ (R² ≥ 0.9980) with low limits of detection (0.011–0.115 μg L⁻¹) and limits of quantification (0.037–0.383 μg L⁻¹). The intra-day and inter-day relative standard deviations (RSDs) of the proposed method with a single fibre ranged from 3.02% to 4.75% and 3.20% to 5.83%, respectively. Meanwhile, the proposed method was used for the selective preconcentration and determination of trace target PAHs in real water samples. Relative recoveries varied from 82.8% to 105% with RSDs from 3.34% to 8.58%. Additionally, this fibre presented good solvent resistance to perform a whole analytical process.