A novel polyaniline coated titania composite nanotube (TiO2@PANI CNT) array was fabricated on a titanium wire by direct electrochemical oxidation. The effects of acid media, the concentration of aniline monomers and applied voltages on the electropolymerization of aniline were investigated. Surface morphological and compositional analyses revealed that a thin PANI coating was uniformly immobilized onto the TiO2 nanotube array. This TiO2@PANI CNT coating combined the merits of both PANI and TiO2, and thereby has several advantages over that of individual PANI and TiO2 coatings such as improved extraction efficiency for UV filters, enhanced mechanical stability and prolonged service life. Coupled with a high performance liquid chromatography-ultraviolet detector (HPLC-UV), the applicability of the developed fiber was evaluated through extraction of UV filters. The linear range is 0.25–500 μg L−1 with correlation coefficients of 0.9953 to 0.9998. The recoveries varied from 92.6% to 110% and the relative standard deviations for single fiber repeatability and fiber-to-fiber reproducibility were between 4.3% and 5.7% and between 6.9% and 9.3%, respectively. The limits of detection ranged from 0.04 to 0.06 μg L−1. The developed SPME-HPLC-UV method is suitable for sensitive determination of UV filters in environmental water samples.

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.The porous nanostructured coatings were firstly in situ fabricated on the surface of NiTi fibers by multiple peroxide oxidation. The developed SPME-HPLC method was successfully used for the enrichment and analysis of PAHs in environmental water samples. Moreover, the fabricated fibers present good preparation reproducibility, high mechanical strength and stability.Download high-res image (98KB)Download full-size image

Electrophoretic deposition (EPD) was hyphenated with electrochemical anodization for the fabrication of phenyl modified mesoporous silica (MPS-Ph) particles onto Nitinol (NiTi) wire as a solid-phase microextraction (SPME) fiber. The anodized NiTi wire offers an ideal conductive fiber substrate with a large available contact surface for subsequent EPD and surface modification of MPS particles. The resulting NiTi-based fiber showed better extraction selectivity and efficiency for polycyclic aromatic hydrocarbons (PAHs) compared with commercial polydimethylsiloxane and polyacrylate fibers. Under optimized conditions for SPME of PAHs, the proposed method presented wide linear ranges from 0.02 to 500 μg L−1 with correlation coefficients higher than 0.999. The limits of detection ranged from 3.6 ng L−1 to 5.2 ng L−1. Relative standard deviations (RSDs) for single fiber repeatability varied from 4.3% to 5.4% for intra-day and inter-day measurements (n = 5), and RSDs for fiber-to-fiber reproducibility from 6.0% to 6.9% (n = 5). Moreover, the resulting fiber was stable for at least 200 extraction and desorption cycles in SPME and was fabricated in a precisely controllable manner. The proposed method was successfully applied to the selective preconcentration and sensitive determination of target PAHs in river water, rain water and wastewater samples with recoveries from 89.4% to 102%.

•In situ growth of TiO2NTs array coated Ti fiber was fabricated by direct anodization of Ti wire.•The nitrogen-enriched carbonaceous coating was achieved by carbonization of PANI coated TiO2NTs.•The fabricated fiber showed high extraction capability and good selectivity for UV filters.•The proposed method was suitable for the sensitive determination of trace UV filters in real water.•The N-C/TiO2NTs/Ti fiber has high stability and long service lifetime.A novel solid-phase microextraction (SPME) fiber was fabricated by direct electrodeposition of polyaniline (PANI) coated the titania nanotube arrays in situ grown on the titanium wire followed by carbonization at 500 °C under nitrogen atmosphere. The resulting titanium-based fiber with nitrogen-enriched carbonaceous material coated titania nanotubes (N-C/TiO2NTs/Ti) showed better extraction performance for ultraviolet (UV) filters among model aromatic compounds compared with common PANI as well as commercial polydimethylsiloxane and polyacrylate coatings. The influence of various experimental parameters on the extraction efficiency of UV filters were investigated and optimized. The calibration curves were linear from 0.2 to 200 μg L−1 for each analyte with correlation coefficients above 0.9980. Limits of detection (LODs) and limits of quantitation (LOQs) ranged from 0.03 to 0.05 μg L−1 and from 0.11 to 0.18 μg L−1 for UV filters, respectively. Relative standard deviations (RSDs) for single fiber repeatability ranged from 3.3% to 4.1% (n=5) and RSDs for fiber-to-fiber reproducibility (n=3) varied from 5.7% to 7.7%. The proposed method was successfully applied to the preconcentration and determination of target UV filters in river water and wastewater samples with good recoveries from 86.2% to 113%. Moreover this novel Ti-based fiber is mechanically and chemically stable, and can be easily prepared in a highly reproducible manner.The titanium-based fiber with nitrogen-enriched carbonaceous material coated titania nanotubes (N-C/TiO2NTs/Ti) was fabricated by direct electrodeposition of polyaniline (PANI) coated the TiO2NTs array grown on the Ti wire followed by carbonization at 500 °C under nitrogen atmosphere.

•The TiO2/NiOCNSs was obtained by hydrothermal treatment of Nitinol wires.•Unique TiO2/NiOCNSs have double-faced open access sites with large surface area.•A novel TiO2/NiOCNSs-Ph fiber coating was achieved by SAM process.•The fiber has high extraction capability and better selectivity for UV filters.•The proposed method was applied to UV filters in environmental water samples.A novel titanium and nickel oxide composite nanosheets (TiO2/NiOCNSs) coating was in situ grown on a Nitinol (NiTi) wire by direct hydrothermal treatment and modified by self-assembly of trichlorophenylsilane for solid phase microextraction (SPME). TiO2/NiOCNSs were radially oriented and chemically bonded to the NiTi substrate with double-faced open access sites. Moreover the phenyl modified TiO2/NiOCNSs (TiO2/NiOCNSs-Ph) coating exhibited original surface supporting framework favorable for effective SPME. The extraction performance of TiO2/NiOCNSs-Ph coated NiTi (NiTi-TiO2/NiOCNSs-Ph) fiber was investigated for the concentration and detection of ultraviolet (UV) filters, polycyclic aromatic hydrocarbons (PAHs), phthalate acid esters and polychlorinated biphenyls coupled to HPLC with UV detection. The novel fiber exhibited better selectivity for UV filters and PAHs and presented greater extraction capability compared to commercial polydimethylsiloxane and polyacrylate fibers. Under the optimized conditions for SPME of UV filters, the proposed method presented linear ranges from 0.1 to 300 μg/L with correlation coefficients of higher than 0.999 and limits of detection from 0.030 μg/L to 0.064 μg/L. Relative standard deviations (RSDs) were below 7.16% and 8.42% for intra-day and inter-day measurements with the single fiber, respectively. Furthermore RSDs for fiber-to-fiber reproducibility from 6.57% to 8.93% were achieved. The NiTi-TiO2/NiOCNSs-Ph fiber can be used up to 200 times. The proposed method was successfully applied to the preconcentration and determination of trace target UV filters in different environmental water samples. The relative recoveries from 87.3% to 104% were obtained with RSDs less than 8.7%.

A novel, uniform nanosheet coating was hydrothermally grown in situ on pretreated NiTi alloy wire in an aqueous NaOH solution. The nanosheets were covalently linked to the NiTi substrate and crosslinked. They were radially oriented around the NiTi wire and composed of more titanium oxide than nickel oxide (TiO2/NiO). The TiO2/NiO composite nanosheet (TiO2/NiOCNSs) coating exhibited a porous structure, providing a desirable nanostructured support for subsequent uniform electrodeposition of AuNPs, which greatly improved the available surface area. The extraction performance of the AuNPs modified TiO2/NiOCNSs coated NiTi fiber was evaluated using aromatic compounds as model analytes and was coupled to HPLC with UV detection. The results obtained indicated that the novel fiber exhibited excellent extraction efficiency and good selectivity for polycyclic aromatic hydrocarbons (PAHs). The main experimental factors for PAHs extraction were optimized. Under the optimized conditions, good linearity was obtained in the range of 0.05–350 μg L−1 with correlation coefficients greater than 0.998. The limits of detection for the developed method ranged from 0.012 μg L−1 to 0.053 μg L−1. The single fiber repeatability and fiber-to-fiber reproducibility were less than 6.05% and 7.19%, respectively. The developed method was successfully applied to the selective concentration and sensitive determination of trace PAHs in different environmental water samples. Relative recoveries varied from 86.3% to 104% at spiking levels of 7 μg L−1 and 30 μg L−1 with relative standard deviations in the range of 4.4–7.5%. Furthermore, the novel fiber could be fabricated in a highly reproducible manner, and had a high stability and long life span.

•Fenton's oxidation method was first introduced to prepare nitinol-based fibers.•Flower-like nanocomposite was successfully in situ grown on the nitinol surface.•The novel fiber exhibits excellent extraction capability and selectivity for PAHs.•This novel fiber is considerable stable and has long life span.•The developed method is suitable for the determination of target PAHs in real water.A novel flower-like nanostructure was successfully in situ fabricated on the surface of nitinol wire through Fenton’s oxidation for the first time. It was found that the densely immobilized coating on the surface of the nitinol fiber was composed of nickel and titanium oxide nanocomposite (NiO/TiO2NC). The NiO/TiO2NC coated fiber was used to extract aromatic compounds coupled with high performance liquid chromatography (HPLC) with UV detection and exhibited excellent extraction efficiency for polycyclic aromatic hydrocarbons (PAHs) with larger delocalized π-system among the studied analytes. Important factors affecting extraction efficiency of PAHs were examined. Under the optimized conditions, the calibration curves were linear in the range from 0.05 to 500 μg L−1 with correlation coefficients of R2≥0.999, and the lowest limit of detection of 0.006 μg L−1 was achieved for benzo[a]pyrene. Furthermore, the intra-day and inter-day precisions for the single fiber varied from 4.69% to 5.97% and from 5.28% to 6.32% for five replicates of PAHs at the spiking level of 50 μg L−1, respectively. The fiber-to-fiber precision for five fibers prepared in different batches ranged from 6.19% to 8.35%. The developed method was successfully applied to concentration and determination of target PAHs from real environmental water samples. Moreover, this novel nitinol-based fiber exhibited long lifespan. Therefore, the proposed fiber can be used as a promising candidate for a conventional fused silica-based fiber in SPME.A novel flower-like nanostructure was successfully in situ grown on the surface of nitinol wire through Fenton’s oxidation (Fig. 1). The fabricated nitinol fiber was successfully used for selective concentration and sensitive determination of PAHs in environmental water samples. Moreover, the fiber has larger surface area and long lifespan. Fig. 1 Preparation process of NiO/TiO2NC fiber.

•The growth of cedar-like AuNPs coating was achieved on an etched stainless steel substrate.•The fiber exhibits high extraction capability and good selectivity for B[a]p, Phe, Dip and Nap.•The novel fiber with unique structure can be fabricated in a highly reproducible manner.•This fiber is stable enough to withstand at least 200 extraction and desorption replicates.•The proposed method was suitable to target aromatic hydrocarbons in environmental water.A novel cedar-like Au nanoparticles (AuNPs) coating was fabricated on an etched stainless steel (SS) wire by direct chemical deposition and used as an efficient and unbreakable solid phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent growth of AuNPs in chloroauric acid solution. As a result, the uniform cedar-like AuNPs coating with larger surface area was tightly attached to the etched SS wire substrate. The AuNPs coated etched SS fiber (AuNPs/SS) was examined for SPME of ultraviolet (UV) filters, phthalate esters and aromatic hydrocarbons coupled to high-performance liquid chromatography with UV detection. The fabricated fiber exclusively exhibited excellent extraction efficiency and selectivity for some aromatic hydrocarbons. Influential parameters of extraction and desorption time, temperature, stirring rate and ionic strength were investigated and optimized. The limits of detection ranged from 0.008 μg L−1 to 0.037 μg L−1. The single fiber repeatability varied from 3.90% to 4.50% and the fiber-to-fiber reproducibility ranged from 5.15% to 6.87%. The recovery of aromatic hydrocarbons in real water samples spiked at 2.0 μg L−1 and 20 μg L−1 ranged from 94.38% to 106.2% with the relative standard deviations below 6.44%. Furthermore the growth of the cedar-like AuNPs coating can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and withstands at least 200 extraction and desorption replicates.

•Zn–ZnO coating was directly fabricated on an etched stainless steel wire substrates.•The Zn–ZnO nanosheets coating has flower-like nanostructure with high surface area.•The fiber has high extraction capability and good selectivity for some ultraviolet filters.•The fabrication of Zn–ZnO nanosheets coating is simple, convenient and reproducible.•The proposed method was suitable for the concentration and determination of target UV filters in environmental water samples.A novel zinc–zinc oxide (Zn–ZnO) nanosheets coating was directly fabricated on an etched stainless steel wire substrate as solid-phase microextraction (SPME) fiber via previous electrodeposition of robust Zn coating. The scanning electron micrograph of the Zn–ZnO nanosheets coated fiber exhibits a flower-like nanostructure with high surface area. The SPME performance of as-fabricated fiber was investigated for the concentration and determination of polycyclic aromatic hydrocarbons, phthalates and ultraviolet (UV) filters coupled to high performance liquid chromatography with UV detection (HPLC-UV). It was found that the Zn–ZnO nanosheets coating exhibited high extraction capability, good selectivity and rapid mass transfer for some UV filters. The main parameters affecting extraction performance were investigated and optimized. Under the optimized conditions, the calibration graphs were linear over the range of 0.1–200 μg L−1. The limits of detection of the proposed method were 0.052–0.084 μg L−1 (S/N = 3). The single fiber repeatability varied from 5.18% to 7.56% and the fiber-to-fiber reproducibility ranged from 6.74% to 8.83% for the extraction of spiked water with 50 μg L−1 UV filters (n = 5). The established SPME-HPLC-UV method was successfully applied to the selective concentration and sensitive determination of target UV filters from real environmental water samples with recoveries from 85.8% to 105% at the spiking level of 10 μg L−1 and 30 μg L−1. The relative standard deviations were below 9.7%.

A facile and efficient electrodeposition approach for the controllable preparation of dendritic silver nanostructure was developed on an etched stainless steel (ESS) wire. Subsequently, self-assembled of alkyldithiols (HS–Cx–SH, x = 2, 3, 6, 8) was performed on the dendritic Ag coating via Ag–S bonding. The octanedithiol modified Ag nanodendrites (AgNDs) coated ESS fiber (HS–C8–S–AgNDs/ESS) was then assessed for SPME of polycyclic aromatic hydrocarbons (PAHs), ultraviolet (UV) filters, polychlorinated biphenyls (PCBs), chlorophenols (CPs), phthalate esters (PAEs) and substituted anilines coupled to high-performance liquid chromatography with UV detection (HPLC-UV). This fiber exhibits higher extraction capability and good selectivity for PAHs, UV filters, PCBs and triclosan compared to CPs, PAEs and substituted anilines. In particular, the microextraction conditions were investigated and optimized for SPME performance of UV filters. Under the optimized conditions, the developed method showed good linearity between 0.30 and 400 μg L−1 with corresponding correlation coefficients in the range of 0.9973–0.9986. The limits of detection ranged from 0.05 to 0.12 μg L−1. The relative standard deviation for fiber-to-fiber reproducibility of five fabricated fibers in the same batch was less than 8.2%. The expanded uncertainties were below 6.9% (coverage factor k = 2). The developed method was practically applied to the preconcentration and determination of trace UV filters from real environmental water samples.

A novel organic–inorganic composite coated fiber was developed by direct chemical deposition of Au nanoparticles (AuNPs) followed by self-assembly of mercaptoundecanol using an etched stainless steel (ESS) wire as a supporting substrate for selective solid-phase microextraction (SPME). The ESS wire offered a very large contact surface for the subsequent growth of AuNPs in chloroauric acid solution. As a result, a uniform AuNP coating with a cedar-like structure was formed on the ESS wire and used as an alternative substrate for self-assembly of mercaptoundecanol (HS-C11-OH) via Au–S bonding. The mercaptoundecanol modified AuNP coated ESS (ESS/AuNPs-S-C11-OH) fiber was then assessed for SPME of ultraviolet filters, phthalic acid esters and polycyclic aromatic hydrocarbons (PAHs) coupled to high-performance liquid chromatography with UV detection. This fiber exhibits high extraction capability and better selectivity for PAHs. Moreover, main parameters affecting extraction were investigated and optimized. Under the optimized conditions, the developed method showed good linearity between 0.05 and 300 μg L−1 with corresponding coefficients in the range of 0.9973–0.9992. The limits of detection ranged from 0.010 to 0.044 μg L−1. The relative standard deviation for the fiber-to-fiber reproducibility of five fabricated fibers was less than 6.52%. The developed method was successfully applied to the preconcentration and determination of PAHs from environmental water samples. Furthermore, the preparation of the ESS/AuNP-S-C11-OH fiber can be performed in a highly reproducible manner. This fabricated fiber exhibits high stability and withstands at least 200 extraction and desorption replicates.

A novel porous sponge-like zinc–zinc oxide (Zn–ZnO) coating was directly prepared on an etched stainless steel wire substrate as a solid-phase microextraction (SPME) fiber via previous electrodeposition of a robust ZnO coating. The scanning electron micrograph of the Zn–ZnO coated fiber exhibits a porous spongy nanostructure with a large surface area. The SPME performance of the prepared fiber was investigated for the concentration and determination of polycyclic aromatic hydrocarbons, phthalates and ultraviolet (UV) filters by high performance liquid chromatography coupled with UV detection (HPLC-UV). It was found that the porous sponge-like Zn–ZnO coating exhibited high extraction capability, good selectivity and rapid mass transfer for some UV filters. The main parameters affecting extraction performance were investigated and optimized. Under optimized conditions, the calibration graphs were linear over the range of 0.1–200 μg L−1. The limits of detection of the proposed method were 0.032–0.064 μg L−1 (S/N = 3). The single fiber repeatability varied from 5.5% to 7.2% and the fiber-to-fiber reproducibility ranged from 7.1% to 8.3% for the extraction of spiked water with 50 μg L−1 UV filters (n = 5). The established SPME-HPLC-UV method was successfully applied to the selective concentration and sensitive determination of target UV filters from real environmental water samples with recoveries from 80.3% to 99.2% at the spiking level of 5 μg L−1 and 50 μg L−1. The relative standard deviations were below 9.3%.

A new nitrogen-containing carbon nanoparticle (N-CNP) coated fiber was developed for solid phase microextraction (SPME) with direct electrodeposition of a polyaniline coating on etched stainless steel wire using a potentiostatic technique followed by carbonization at 500 °C under a nitrogen atmosphere. The extraction performance of the N-CNP coating was investigated towards polycyclic aromatic hydrocarbons (PAHs), ultraviolet (UV) filters and phthalate acid esters (PAEs) in water samples coupled to high performance liquid chromatography with UV detection (HPLC-UV). This N-CNP coating shows excellent selectivity for UV filters compared to that for PAHs and PAEs. Under optimized conditions, the linearity of UV filters was in the range of 0.02–200 μg L−1 with a corresponding correlation coefficient of 0.9921–0.9993. The recoveries ranged from 89.2% to 119%. The relative standard deviations of a single fiber were between 4.83% and 7.82% (n = 5) and fiber-to-fiber were between 7.94% and 10.14% (S/N = 3). Their limits of detection and the limits of quantitation ranged from 0.006–0.203 μg L−1 and 0.02–0.67 μg L−1, respectively. The proposed SPME-HPLC-UV procedure was successfully used for the selective concentration and sensitive determination of UV filters in environmental water samples. Furthermore, this new robust fiber was easily prepared in a reproducible manner.

Self-assembled gold nanoparticles (AuNPs) coating was performed using an etched stainless steel wire as a support for solid-phase microextraction (SPME) of ultraviolet (UV) filters in environmental water coupled to HPLC. The highest extraction efficiencies were achieved within 30 min at 55 °C and pH 7 with stirring rate of 800 rpm. Under the optimized conditions, the calibration graphs of the UV filters (BP-3, OD-PABA, EHMC and EHS) were linear in the range of 0.004–200 μg L−1. The limits of detection of the method were 0.43–570 ng L−1 (S/N = 3). The relative standard deviation (RSD) of AuNPs-SPME-HPLC was 1.91%–4.20% (n = 5) for spiked water of 20 μg L−1 each UV filter. In the case of real water samples, the obtained recoveries were between 77.9% and 108% with RSD of 3.12%–8.04%.A robust self-assembled gold nanoparticles (AuNPs) coating was developed by chemical position on the etched SS wire via Au-S bonding of octanedithiol. This new fiber exhibits high stability and excellent extraction capability. Moreover, it was successfully applied to the concentration and determination of target UV filters from environmental water samples.

•A novel C8–S–AuNPs coating was achieved through electrodeposition and SAM process.•A unique floccular structure with extremely larger surface area was obtained.•The fiber has high extraction capability and better selectivity for UV filters.•The fiber has high stability and long lifetime.•The SPME–HPLC method was applied to target UV filters in environmental water samples.In the present study, a novel approach for rapid electrodeposition on an etched stainless steel (SS) wire followed by self-assembled monolayer (SAM) was proposed for the fabrication of solid-phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent electrochemical deposition of gold nanoparticles (AuNPs). As a result, uniform AuNPs coating was tightly attached to the etched SS wire substrate. After SAM of 1,8-octanedithiol onto AuNPs coating via Au-S bonding, a unique floccular structure with extremely large surface area was obtained for the fabricated fiber. The mercaptooctyl groups modified AuNPs coated etched SS fiber (C8–S–AuNPs/SS) was then assessed for SPME of phthalate esters (PAEs), polychlorinated biphenyls (PCBs), chlorophenols (CPs), ultraviolet (UV) filters, polycyclic aromatic hydrocarbons (PAHs) and substituted anilines coupled to high-performance liquid chromatography with UV detection. This fiber exhibits higher extraction capability and better selectivity for some PCBs, CPs, UV filters and PAHs. Extraction conditions were investigated and optimized for SPME performance of UV filters. Under the optimized conditions, the developed method showed good linearity between 0.10 and 400 μg L−1 with corresponding coefficients in the range of 0.9989–0.9998. The limits of detection ranged from 0.025 to 0.056 μg L−1. The relative standard deviation for fiber-to-fiber reproducibility of five fabricated fibers was less than 9.4%. The developed method was successfully applied to the preconcentration and determination of trace UV filters from environmental water samples. Furthermore the fabrication of the C8–S–AuNPs/SS fiber can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and long lifetime, and could be a potential alternative for the conventional fused silica fiber.

•In situ fabrication of TiO2-nanosheets coating was successfully achieved by one step anodization.•The TiO2-nanosheets coating exhibits high extraction capability and good selectivity for some UV filters.•The TiO2-nanosheets coating embedded into the Ti wire substrate and has long service time.•The TiO2-nanosheets can be easily fabricated in a highly reproducible manner.•The proposed method was successfully applied to selective concentration and determination of target UV filters in real environmental water samples.A novel TiO2-nanosheets coated fiber for solid-phase microextraction (SPME) was fabricated by anodization of Ti wire substrates in ethylene glycol with concentrated NH4F. The in situ fabricated TiO2-nanosheets were densely embedded into Ti substrates with about 1 μm long, 300 nm wide and 80 nm thick. The as-fabricated TiO2-nanosheets coating was employed to extract polycyclic aromatic hydrocarbons, phthalates and ultraviolet (UV) filters in combination with high performance liquid chromatography-UV detection (HPLC-UV). It was found that the TiO2-nanosheets coating exhibited high extraction capability and good selectivity for some UV filters frequently used in cosmetic sunscreen formulations. The main parameters affecting extraction performance were investigated and optimized. Under the optimized conditions, the calibration graphs were linear in the range of 0.1–400 μg L−1. The limits of detection of the proposed method were between 0.026 μg L−1 and 0.089 μg L−1 (S/N = 3). The single fiber repeatability varied from 4.50% to 8.76% and the fiber-to-fiber reproducibility ranged from 7.75% to 9.64% for the extraction of spiked water with 50 μg L−1 UV filters (n = 5). The SPME-HPLC-UV method was successfully established for the selective preconcentration and sensitive detection of target UV filters from real environmental water samples. Recovery of UV filters spiked at 10 μg L−1 and 25 μg L−1 ranged from 88.8% to 107% and the relative standard deviations were less than 9.8%. Furthermore the in situ growth of the TiO2-nanosheets coating was performed in a highly reproducible manner and the TiO2-nanosheets coated fiber has high mechanical strength, good stability and long service life.

A novel rod-like TiO2 based solid-phase microextraction (SPME) coating was directly fabricated by in situ anodization of Ti wire substrates in ethylene glycol and aqueous solution with 5 wt% NH4F (v/v = 1:1). The compact rod-like TiO2 has much larger surface area with a diameter of about 150 nm and a length of about 1.2 µm. The SPME performance of the as-fabricated fiber was investigated for the concentration and determination of polycyclic aromatic hydrocarbons, phthalates and ultraviolet (UV) filters coupled to high performance liquid chromatography with UV detection (HPLC-UV). It was found that the rod-like TiO2 coating exhibited high extraction capability, good selectivity and rapid mass transfer for some UV filters. The main parameters affecting extraction performance were investigated and optimized. Under the optimized conditions, the calibration graphs were linear in the range of 0.05–200 µg L−1. The limits of detection of the method were 0.024–0.032 µg L−1 (S/N = 3). The single fiber repeatability varied from 5.44% to 7.81% and the fiber-to-fiber reproducibility ranged from 7.41% to 8.63% for the extraction of spiked water with 50 µg L−1 UV filters (n = 5). The SPME-HPLC-UV method was successfully applied to the selective concentration and determination of target UV filters from real environmental water samples with recoveries from 84.68% to 104.8% at the spiking level of 5 µg L−1, 25 µg L−1 and 50 µg L−1. The relative standard deviations were below 9.82%. Furthermore, the in situ growth of the rod-like TiO2 coating on a Ti wire by one-step anodization is simple, rapid and reproducible. The rod-like TiO2 coating was cross-linked and embedded into the Ti wire substrate. As a result, the as-fabricated fiber is robust and has long service time.

A new approach for rapid preparation of porous polyaniline (PANI) coating on a stainless steel (SS) wire was developed in nitric acid containing aniline. The SS wire was first etched in hydrofluoric acid and then used as a working electrode for electrodeposition of PANI coating. The etching procedure on a SS wire provides porosity necessary for higher extraction capability of PANI coating and for the extraction phase to hold firmly onto the SS fiber. The porous structure of the PANI coating prepared in nitric acid (PANI–NO3) was more uniform than that prepared in sulfuric acid (PANI–SO4). These PANI coatings were applied to solid-phase microextraction (SPME) of bisphenol A (BPA) coupled with high performance liquid chromatography with ultraviolet detection (HPLC-UV). Their SPME performance was compared and SPME conditions based on the PANI–NO3 coating were further optimized. The linear range was 0.01–100 ng mL−1 with a correlation coefficient of 0.9996. The relative standard deviation was 2.36% for a spiked sample with BPA of 10 ng mL−1 (n = 5) and the limit of detection was 0.005 ng mL−1. The fiber-to-fiber reproducibility of 6.41% was achieved for three PANI–NO3 coated fibers prepared under the same conditions. Finally, the porous PANI–NO3 coating was used for the selective and efficient preconcentration of dissolved BPA in drinking water and beverages. The recoveries of spiked BPA in the real samples ranged from 90.56% to 108.2%. The prepared PANI–NO3 coated fibers have high mechanical strength and chemical stability, long lifetime, high extraction efficiency and good selectivity for the extraction of BPA in complex matrices.

Absorption and excited state intramolecular proton transfer (ESIPT) fluorescence of 2′-ethylhexyl salicylate (EHS) were examined in the presence of cationic, non-ionic, and anionic surfactants. It was found that linear EHS molecule was solubilized in micelles with its flexible and hydrophobic 2′-ethylhexyl chain toward the micellar core and with its rigid salicyl moiety toward the micelle-water interface. The UV absorption of EHS was improved and the intramolecular hydrogen bonding formation of EHS was favored, resulting in greatly enhanced ESIPT fluorescence. The excited EHS molecules decay via visible luminescence and non-radiative deactivation. The binding sites of EHS in micelles were explained at a molecular level in terms of molecular structures and sizes of EHS and surfactants. Dynamic fluorescence quenching and spectral measurements of ester hydrolysis of EHS provide further evidences for the binding sites of EHS in different micelles.

A novel organic–inorganic composite coated fiber was developed by direct chemical deposition of Au nanoparticles (AuNPs) followed by self-assembly of mercaptoundecanol using an etched stainless steel (ESS) wire as a supporting substrate for selective solid-phase microextraction (SPME). The ESS wire offered a very large contact surface for the subsequent growth of AuNPs in chloroauric acid solution. As a result, a uniform AuNP coating with a cedar-like structure was formed on the ESS wire and used as an alternative substrate for self-assembly of mercaptoundecanol (HS-C11-OH) via Au–S bonding. The mercaptoundecanol modified AuNP coated ESS (ESS/AuNPs-S-C11-OH) fiber was then assessed for SPME of ultraviolet filters, phthalic acid esters and polycyclic aromatic hydrocarbons (PAHs) coupled to high-performance liquid chromatography with UV detection. This fiber exhibits high extraction capability and better selectivity for PAHs. Moreover, main parameters affecting extraction were investigated and optimized. Under the optimized conditions, the developed method showed good linearity between 0.05 and 300 μg L−1 with corresponding coefficients in the range of 0.9973–0.9992. The limits of detection ranged from 0.010 to 0.044 μg L−1. The relative standard deviation for the fiber-to-fiber reproducibility of five fabricated fibers was less than 6.52%. The developed method was successfully applied to the preconcentration and determination of PAHs from environmental water samples. Furthermore, the preparation of the ESS/AuNP-S-C11-OH fiber can be performed in a highly reproducible manner. This fabricated fiber exhibits high stability and withstands at least 200 extraction and desorption replicates.

A new approach for rapid preparation of porous polyaniline (PANI) coating on a stainless steel (SS) wire was developed in nitric acid containing aniline. The SS wire was first etched in hydrofluoric acid and then used as a working electrode for electrodeposition of PANI coating. The etching procedure on a SS wire provides porosity necessary for higher extraction capability of PANI coating and for the extraction phase to hold firmly onto the SS fiber. The porous structure of the PANI coating prepared in nitric acid (PANI–NO3) was more uniform than that prepared in sulfuric acid (PANI–SO4). These PANI coatings were applied to solid-phase microextraction (SPME) of bisphenol A (BPA) coupled with high performance liquid chromatography with ultraviolet detection (HPLC-UV). Their SPME performance was compared and SPME conditions based on the PANI–NO3 coating were further optimized. The linear range was 0.01–100 ng mL−1 with a correlation coefficient of 0.9996. The relative standard deviation was 2.36% for a spiked sample with BPA of 10 ng mL−1 (n = 5) and the limit of detection was 0.005 ng mL−1. The fiber-to-fiber reproducibility of 6.41% was achieved for three PANI–NO3 coated fibers prepared under the same conditions. Finally, the porous PANI–NO3 coating was used for the selective and efficient preconcentration of dissolved BPA in drinking water and beverages. The recoveries of spiked BPA in the real samples ranged from 90.56% to 108.2%. The prepared PANI–NO3 coated fibers have high mechanical strength and chemical stability, long lifetime, high extraction efficiency and good selectivity for the extraction of BPA in complex matrices.