Silicon carbide nanomaterial as a coating for solid-phase microextraction

Use of hydroxypropyl β-cyclodextrin hybrid monolithic material as adsorbent for dispersive solid-phase extraction of fluoroquinolones from environmental water samples

In this study, the hydroxypropyl β-cyclodextrin hybrid monolithic material was fabricated and firstly applied as adsorbent for dispersive solid-phase extraction coupled with high-performance liquid chromatography to detect trace-level seven fluoroquinolones in water samples. The prepared hydroxypropyl β-cyclodextrin hybrid monolithic material was characterized by fourier transform infrared spectroscopy, scanning electron microscopy and adsorption experiments, which showed excellent specific adsorption to the target fluoroquinolones. Under the optimized conditions, the extraction methodology showed satisfactory precision with relative standard deviations between 2.6 and 5.6%, good linearity (R² ≥0.9990) and satisfactory recoveries (82.5∼91.8%). The limits of detection and limits of quantification of the method were in the range of 0.4∼1.2 ng mL^-1 and 1.4∼4.0 ng mL^-1 respectively, which confirmed the possibility of quantifying trace levels. Furthermore, the material could be reused at least five times. These results demonstrated that the hydroxypropyl β-cyclodextrin hybrid monolithic material was a promising adsorbent for fluoroquinolones, and the established method combined dispersive solid-phase extraction with high-performance liquid chromatography was suitable for the determination of fluoroquinolones in aqueous samples. This article is protected by copyright. All rights reserved.

Temperature and time-controlled hydrothermal growth and sorption selectivity of titania nanowires on titanium fiber for highly efficient solid-phase microextraction

Two kinds of TiO₂ nanowires (TiO₂NWs) with different orientation were in-situ grown on Ti substrates by controlling temperature and time during the hydrothermal process. The adsorption performance was evaluated by using typical aromatic compounds as model analytes coupled to HPLC with UV detection. The results demonstrated that the TiO₂NWs coating grown at higher temperature within longer time had better affinity towards PAHs. For this purpose, the key experimental factors affecting the adsorption performance of the TiO₂NWs coating fabricated at 200 °C for 10 h were further investigated and optimized for the extraction of PAHs. Under the optimized conditions, the proposed method presented linear responses in the concentration ranges of 0.05 to 200 μg·L^-1 PAHs with correlation coefficients more than 0.998. LODs (S/N=3) were 0.008 to 0.034 μg·L^-1. Moreover, RSDs for the single fiber repeatability of the intra-day and the inter-day analyses were less than 5.6% (n=5) and 5.8%, respectively. RSDs for the fiber-to-fiber reproducibility were between 5.1% and 6.5%. Finally, the proposed method was successfully applied to the selective preconcentration and determination of trace PAHs in environmental water samples. In addition, The fabricated Ti fiber can be used at least 200 times due to its high mechanical and chemical stability.

Highly efficient solid-phase microextraction of polycyclic aromatic hydrocarbons in water based on worm-like nickel-titanium oxide nanocomposites coating grown on a nickel-titanium alloy wire by low-voltage anodization

A novel worm-like nickel-titanium oxide nanocomposite coating was directly grown on a nickel-titanium alloy wire by low-voltage electrochemical anodization in alkaline ethylene glycol and water solution. The in situ growth of nickel-titanium oxide nanocomposites greatly depended on the volume ratio of ethylene glycol to water and temperature. Coupled to high-performance liquid chromatography with UV detection by static desorption in the mobile phase, the adsorption performance of the as-prepared fiber was evaluated for solid-phase microextraction of representative environmental analytes in water. The results indicate that the as-prepared fiber exhibits higher extraction capability for polycyclic aromatic hydrocarbons than commercial polydimethylsiloxane and polyacrylate fibers. After optimizing the extraction parameters, the calibration graphs of the developed method was linear in the range of 0.05-200 μg/L with correlation coefficients above 0.998. Limit of detection ranged from 0.013 to 0.145 μg/L for seven target analytes. Relative standard deviations of intraday and interday analyses varied from 4.0 to 5.3% and from 4.7 to 6.3% with the single fiber, respectively. The relative recoveries of 84.4-109% were achieved for highly efficient enrichment and determination of target analytes in spiked river and snow water. Moreover, the as-prepared fiber can be used more than 200 times.

Modulating the selectivity of solid-phase microextraction fibers based on morphological, compositional, and size-depended control of bimetallic oxide nanostructures grown on nickel-titanium alloy substrates

Nickel-titanium oxide nanotubes (NiTiONTs), nanoparticles, and nanopores were in situ grown on NiTi fiber substrates by controlling anodization parameters. The adsorption performance of different bimetallic oxide nanostructures was evaluated using typical aromatic compounds including chlorophenols, phthalic acid esters, ultraviolet filters (UVFs), and polycyclic aromatic hydrocarbons (PAHs) coupled to HPLC-UV. The results clearly indicate that these NiTiO nanostructures show good extraction capability for UVFs and PAHs. The extraction performance of UVFs and PAHs greatly depends on the surface morphologies and sizes of the grown NiTiO nanostructures along with their elemental compositions. Compared with NiTiO nanoparticle and nanopore coatings, the longer well-aligned NiTiONT coating exhibits better extraction capability and selectivity for PAHs than for UVFs. Therefore, the extraction parameters of the NiTi@NiTiONT fiber for PAHs were investigated and optimized. Under optimized conditions, the proposed method was linear in the range 0.05-200 μg L^-1 with correlation coefficients above 0.999. Limits of detection were between 0.008 and 0.124 μg L^-1. Relative standard deviations (RSDs) of the intra-day and the inter-day analyses with the single fiber varied from 4.09 to 6.33%. RSDs for fiber-to-fiber reproducibility of the proposed method with five fibers prepared in different batches were between 5.75 and 7.43%. The applicability of the proposed method was investigated by the enrichment and determination of target PAHs in environmental water samples and relative recoveries of 84.5 ± 6.5 - 116 ± 7.8% were achieved. Notably, the prepared fiber was stable up to 250 times. Graphical abstract.

Durable molybdenum oxide coated solid-phase microextraction fiber for highly selective and efficient extraction of polycyclic aromatic hydrocarbons in water

A bonding method was developed for coating molybdenum oxides onto a steel wire substrate, which was used as a solid-phase microextraction fiber, was coupled with gas chromatography. Based on the characterization, it is found that the as-prepared molybdenum oxides material contained a nanobelt structure with a uniform size and good dispersibility. In addition, there were a large number of small protrusions on the surface of the nanobelts. These characteristics provided a large specific surface area for extraction. Molybdenum oxides exhibited a high extraction selectivity for polycyclic aromatic hydrocarbons owing to its moderate coordination. After the optimization of the factors, method detection limits of < 1.25 μg/L were achieved, and the calibration curves were linear within the range of 2-600 μg/L. In addition, repeatability was demonstrated, and the relative standard deviation < 6.4%. The molybdenum oxides coating had a high scratch resistance, which could effectively prevent coating wear and failure. Combined with the high thermal and chemical stability, the service life of the coating was improved and could be used 150 times without a significant reduction in the extraction performance. Finally, the as-prepared fiber had a comparable extraction capacity and higher partition coefficients that those of commercial polyacrylate fibers.