[Show abstract][Hide abstract] ABSTRACT: 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%.
Chinese Journal of Analytical Chemistry 02/2015; 43(2). DOI:10.1016/S1872-2040(15)60803-9 · 0.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel Ti-TiO2-ZrO2 fiber for solid-phase microextraction (SPME) was fabricated by chemical oxidization of a Ti wire substrate and subsequent electrodeposition of ZrO2 nanoparticles coating. The chemically oxidized procedure afforded in situ fabrication of porous TiO2 nanostructures on a Ti wire and provided a desirable substrate for further deposition of ZrO2 nanoparticles coating. The best extraction capability was obtained by ZrO2 nanoparticles with a size distribution of 20-30 nm and a coating thickness of about 4.5 µm after 10 cyclic voltammetry scans. The main parameters affecting the Ti-TiO2-ZrO2 fiber for SPME of ultraviolet (UV) filters were investigated coupled to high-performance liquid chromatography with UV detection. Good linearity was achieved in the range of 0.5-500 µg•L-1 with correlation coefficients higher than 0.996. Limits of detection were 0.032-0.082 µg•L-1 (S/N=3). The single fiber repeatability ranged from 4.3% to 12% and the fiber-to-fiber reproducibility from 4.3% to 11% for SPME of spiked water with 50 µg•L-1 UV filters (n=5). Furthermore this fiber has high stability, long service life and high extraction capability for UV filters compared to the commercially available polymeric fibers.
[Show abstract][Hide abstract] ABSTRACT: Porous polyaniline coatings doped with different counter ions were electrodeposited on the surface of stainless steel wires using controlled potentiostatic coulometry. Prior to electropolymerization, the stainless steel wires were chemically etched to improve subsequent immobilization of the polyaniline coatings on the substrate and to increase the effective surface area. Porous polyaniline coatings doped with sulfate, nitrate, and perchlorate counter ions were employed for solid-phase microextraction (SPME) of 2-chlorophenol, 2,4-dichlorophenol, triclosan, and 2,4-dichlorophenoxyacetic acid coupled to high-performance liquid chromatography. The results demonstrated that the perchlorate doped polyaniline coating exhibited the highest extraction efficiency for 2-chlorophenol, 2,4-dichlorophenol, and triclosan at pH 5.0, indicating that the extraction capability was modified by introducing different counter ions into the coatings. As a result, the perchlorate doped polyaniline coated fiber was further used for the optimization of extraction condition s . The method provided linear dynamic ranges over 2 to 4 orders of magnitude. The limits of detection were 0.006 µg · L−1, 0.005 µg · L−1, and 0.040 µg · L−1 for 2-chlorophenol, 2,4-dichlorophenol, and triclosan, respectively. The precision expressed as the relative standard deviation ranged from 2.20% to 5.04% for spiked water at 10 µg · L−1 (n = 5) and the fiber to fiber reproducibility was between 3.27% and 5.91% (n = 5). The method was successfully applied to the determination of chlorophenolics in real water samples. The recoveries of chlorophenolics in spiked water at 5.0 µg · L−1 were between 99.60% and 108.7% with relative standard deviations between 3.24% and 5.47%.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: A new method was developed for the simultaneous determination of six phthalic acid esters (PAEs) in different environmental water samples using salt-assisted dispersive liquid-liquid microextraction with carbon tetrachloride as an extraction solvent and acetonitrile as a dispersive solvent coupled with high performance liquid chromatography with UV detection. The influence of the added NaCl on the enrichment factor (EF) in DLLME was investigated. The salting-out effect causes the hydrophobicity of organic analytes to be increased and high EFs to be more pronounced than those in salt-free water. Greater EF, wider linearity, better recovery, smaller relative standard deviation (RSD) and lower limit of detection were obtained at higher concentration of NaCl. Under optimized extraction conditions, good linearity was observed for all analytes in a range of 1.00-100 μg L−1 with the correlation coefficient (r2) ≥0.9992. The limits of detection based on the signal to noise ratio of 3 were 0.01-0.03 μg L−1. The recoveries of PAEs were 97.5-105.5% for spiked water with 20 μg L−1 of PAEs. The repeatability of the proposed method expressed as RSDs ranged from 3.13 to 5.32% (n = 3). EFs are in the range of 78 to 262 fold. The method was applied to the determination of PAEs in water samples from local river, rain and urban wastewater treatment plants with the standard addition, the recoveries of PAEs were 86.2-105.0%, 93.8-107.0% and 92.4-106.3%, and the RSDs were below 6.79%. The current procedure afforded a convenient, inexpensive and reliable sample preparation with high extraction efficiency for trace PAEs in environmental water samples.
[Show abstract][Hide abstract] ABSTRACT: A novel mesoporous-coated stainless steel wire microextraction coupled with the HPLC procedure for quantification of four polycyclic aromatic hydrocarbons in water has been developed, based on the sorption of target analytes on a selectively adsorptive fiber and subsequent desorption of analytes directly into HPLC. Phenyl-functionalized mesoporous materials (Ph-SBA-15) were synthesized and coated on the surfaces of a stainless steel wire. Due to the high porosity and large surface area of the Ph-SBA-15, high extraction efficiency is expected. The influence of various parameters on polycyclic aromatic hydrocarbons extraction efficiency were thoroughly studied and optimized (such as the extraction temperature, the extraction time, the desorption time, the stirring rate and the ionic strength of samples). The results showed that each compound for the analysis of real water samples was tested under optimal conditions with the linearity ranging from 1.02×10(-3) to 200 μg/ L and the detection limits were found from 0.32 to 2.44 ng/ L, respectively. The RSD of the new method was smaller than 4.10%.
[Show abstract][Hide abstract] ABSTRACT: Organic–inorganic hybrid mesoporous silicas of SBA-15 with different sizes of organic functionalities of methyl, propyl, or octyl were prepared by the single-step co-condensation of inexpensive tetraethyl orthosilicate and organotrialkoxysilane using Pluronic P123 as a templating agent under acidic conditions. Samples were characterized by FT-IR, XRD, TEM and SEM. The results show that different alkyl groups are attached covalently to the pore wall of SBA-15 after modification, respectively. The functionalized materials still preserve a desirable ordered two-dimensional P6mm hexagonal structure although the organotrialkoxysilane molar ratio is as high as 20%.
[Show abstract][Hide abstract] ABSTRACT: Phenyl-functionalized SBA-15 materials (Ph-SBA-15) were directly synthesized by using tri-block copolymer Pluronic P123 as templating agent under acidic conditions. The samples were characterized by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetry analysis (TGA) and N2 adsorption–desorption. The results show that the phenyl groups are covalently attached to the pore wall of SBA-15 after modification. The functionalized materials still preserve a desirable two-dimensional P6mm hexagonal structure and have large specific surface area and pore volume although the molar ratio of phenyltrimethoxysilane in total silica precursors is as high as 23.0%.