Controllable Growth of Nanoporous Metal Oxide Composites on Nickel-Titanium Alloy Fibers for Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons

Abstract

Abstract Hydrothermal oxidation was used to prepare a nickel-titanium alloy (NiTi) wire as the solid-phase microextraction fiber. The experimental results demonstrated that a nanoporous nickel-titanium oxide composite coating was in situ grown on the surface of NiTi substrate by direct oxidation in aqueous H2O2 solution at 80 °C. The resulting oxide composite coating included more nickel and less titanium. The prepared NiTi fiber with Ni-rich oxide coating was used to extract typical aromatic compounds coupled with HPLC-UV and exhibited good extraction selectivity for polycyclic aromatic hydrocarbons (PAHs). The key factors affecting extraction efficiency of PAHs were examined. Under the optimized conditions, the calibration curves were linear in the range of 0.05–400 ng mL−1 with correlation coefficients over 0.999, and the limit detection of PAHs ranged from 0.026 ng mL−1 to 0.056 ng mL−1. Furthermore, the relative standard deviations (RSDs) for intra-day and inter-day repeatability of the single fiber ranged from 4.8% to 6.2% and 5.4% to 6.5% for five replicate analyses of PAHs at the spiking level of 50 ng mL−1, respectively. The RSDs for the fiber-to-fiber reproducibility of five fibers prepared in different batches ranged from 6.4% to 8.4%. The developed method was suitable for selective enrichment and detection of target PAHs in environmental water samples with relative recoveries from 89.9% to 108.5% and RSDs = 8.1%. Moreover, this novel NiTi fiber was mechanically strong and chemically stable, and its preparation was precisely controllable.