Magnetic porous organic polymers (MOPs) with abundant thiol groups were synthesized successfully in high yield through a template-free and catalyst-free diazo-coupling reaction. The reaction was conducted under mild conditions in aqueous solution, in which the introduction of magnetism and thiol-functionalization was realized simultaneously, avoiding the use of environment-unfriendly organic solvents. The magnetic nanoparticles (MNPs) were embedded into hierarchical porous network structures of porous organic polymers (POPs) physically and the magnetism of thiol-functionalized MOPs (MOP-SH) was easily controlled by varying the amount of spiked MNPs. The obtained MOP-SH exhibited high thermal stability and chemical stability within a wide pH range (2–13), and good adsorption performance for Hg(II) over a wide pH range due to the abundant thiols in its hierarchical structure. After the adsorption process by using MOP-SH, the concentration of Hg in the spiked domestic sewage reached 1.1 μg L–1, which is even lower than the acceptable limit of national standard for drinking water (2 μg L–1). Besides, the prepared MOP-SH exhibited high adsorption capacity, fast adsorption kinetics, and easy-recycling behavior, providing a new avenue for the preparation of green functionalized adsorbents with good performance for water decontamination.

Protein phosphorylation analysis is important for understanding cell regulations. Mass spectrometry (MS) is a powerful technique for peptide phosphorylation analysis. However, quantification of low abundance phosphoproteins in a complex mixture of proteins is still a challenge. Here we report the development of hollow fiber (HF) supported TiO2 monolithic microextraction combined with capillary high performance liquid chromatography (capHPLC)-inductively coupled plasma-collision reaction cell (ICP-CRC)-MS for the absolute quantification of phosphopeptides. The membrane pores (∼200 nm) of the HF effectively carry more TiO2 on its surface to enhance the adherence of the TiO2 monolith with the HF. By using β-casein as a model phosphorylated protein, we optimized the HF-supported TiO2 monolithic microextraction towards phosphopeptides. Under the optimal conditions, a 100-fold enrichment factor was obtained and the monoliths can be reused 40 times. By monitoring 31P16O with O2 as a reaction gas in the CRC, polyatomic mass interference at m/z 31 is avoided and a low detection limit (2.9 nM) of phosphorus is achieved. The method of HF-supported TiO2 monolithic microextraction-capHPLC-ICP-MS provided the detection limit for phosphopeptides at the nM level. The proposed method was applied to the quantification of phosphopeptides in milk and milk powder samples.

In this work, iminodiacetic acid (IDA) functionalized magnetic nanoparticles (Fe3O4@SiO2@IDA) were prepared and the adsorption behavior of Cr(III)/(VI) on them was investigated. It was found that both Cr(III) and Cr(VI) could be quantitatively retained on Fe3O4@SiO2@IDA in the pH range of 2.5–3.5, while only Cr(III) could be adsorbed in the pH range of 4.0–9.0. Based on this, a new approach of magnetic solid phase extraction (MSPE) combined with graphite furnace atomic absorption spectrometry (GFAAS) was proposed for the speciation of trace Cr(III) and Cr(VI). Total Cr and Cr(III) were adsorbed on Fe3O4@SiO2@IDA under pH 3 and 5, respectively, followed by elution with 1.5 mol L−1 HNO3. And the concentration of Cr(VI) was calculated by subtracting Cr(III) from the total Cr. Factors affecting MSPE (pH of sample solution, concentration and volume of desorption reagent, desorption time, extraction time, sample volume) were investigated and the optimized conditions were achieved. With an enrichment factor of 100-fold, the detection limits of the proposed method were 9.1 and 12.8 ng L−1 for Cr(III) and total Cr with the relative standard deviations (RSDs) of 4.8 and 5.2% (c = 50 ng L−1, n = 7), respectively. In order to validate the accuracy of the proposed method, a certified reference material of GSBZ50009-88 environmental water was analyzed, and the determined value was in good agreement with the certified value. The proposed MSPE-GFAAS method is simple, fast, selective and sensitive for the speciation of trace Cr without any oxidation or reduction process. It has been applied in the speciation of trace Cr in natural water samples with satisfactory results.

•PDMS/MIL-100(Fe) coated stir bar was prepared for extraction of six triazines from environmental water.•It shows higher extraction efficiency for target triazines than commercial PDMS and PEG coated stir bar.•It exhibits relatively fast extraction/desorption kinetics and long lifespan.Polydimethylsiloxane (PDMS)/MIL-100(Fe) coated stir bar was prepared by sol gel technique, and good preparation reproducibility was achieved with relative standard deviations (RSDs) ranging from 2.6% to 7.5% (n=7) and 3.6% to 10.8% (n=7) for bar-to-bar and batch-to-batch, respectively. Compared with commercial PDMS coated stir bar (Gerstel) and PEG coated stir bar (Gerstel), the prepared PDMS/MIL-100(Fe) stir bar showed better extraction efficiency for target triazines compounds. It also exhibited relatively fast extraction/desorption kinetics and long lifespan. Based on it, a method of PDMS/MIL-100(Fe) coated stir bar sorptive extraction (SBSE)-high performance liquid chromatography-ultraviolet detector (HPLC-UV) was developed for the determination of six triazines (simazine, atrazine, prometon, ametryn, prometryne and prebane) in environmental water samples. Several parameters affecting SBSE of six target triazines including extraction time, stirring rate, sample pH, ionic strength, desorption solvent and desorption time were investigated. Under the optimal experimental conditions, the limits of detection (LODs, S/N=3) were found to be in the range of 0.021–0.079 μg L−1. The repeatability RSDs were in the range of 2.3–6.3% (n=7, c=0.5 μg L−1) and the enrichment factors (EFs) ranged from 51.1 to 102-fold (theoretical EF was 200-fold). The proposed method was applied to the analysis of target triazines in environmental water samples, with recoveries of 98.0–118% and 94.0–107% for spiked East Lake water and local pond water samples, respectively.Download high-res image (189KB)Download full-size image

•The adsorption behavior of inorganic Se on GO–TiO2 composite was investigated.•The adsorption difference of Se (IV/VI) on the composite was discussed.•A method of SPE-GF-AAS was developed for Se speciation in environmental water.In this paper, a method of graphene oxide (GO)–TiO2 composite solid phase extraction followed by graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the speciation of inorganic selenium in environmental waters. The adsorption behavior of inorganic Se(IV) and Se(VI) on the GO–TiO2(1:1) composite was investigated. It was found that Se(IV) was quantitatively retained on the GO–TiO2 composites within a wide pH range of 0.5–10, while Se(VI) was quantitatively adsorbed on GO–TiO2(1:1) composite at pH 0.5-2, and no obvious adsorption of Se(VI) within the pH range of 4-10 was found. By selecting pH 6.0, Se(IV) could be easily determined. After reduction of Se(VI), total Se was determined by the proposed method, and Se(VI) was calculated as the difference between the total Se and Se(IV). The factors affecting the separation/preconcentration of Se(IV) and Se(VI) were studied. Under the optimum conditions, the isothermal adsorption of Se(IV) on the GO–TiO2(1:1) composite fitted Langmuir model; a linear range over 0.1–12 ng mL−1 was obtained. The limit of detection (LOD) and precision of the method for Se(IV) was 0.04 ng mL−1 and 9.4% (cSe(IV)=0.5 ng mL−1, n=7), respectively. In order to verify the accuracy of the method, a standard water sample (GSBZ50031-94) was analyzed, and the determined value was in a good agreement to the certified value. The established method was applied to inorganic Se speciation in environmental water samples and the recovery of 87.4–102% was obtained for the spiked samples.

A graphene oxide (GO)–titanium dioxide (TiO2) composite was prepared by hydrolysis of Ti(BuO)4 to TiO2 on GO nanosheets. The mass ratio of GO–TiO2 in the composite was optimized and the GO–TiO2 (1:1) composite was selected as the adsorbent for the preconcentration of heavy metals and rare earth elements (REEs). The prepared GO–TiO2 (1:1) composite was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis and differential thermal gravimetry measurements (TGA/DTG), powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicated that the anchored TiO2 was in the nanometer-sized anatase form and the GO–TiO2 (1:1) composite inherited both features of GO and TiO2. It exhibited good stability, strong anti-interference capability, and high adsorption capacities for target ions. By using GO–TiO2 (1:1) composite as the micro-column packing material, a method for on-line solid phase extraction (SPE) coupling with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed for the quantification of heavy metals and REEs in environmental water and sediment samples. The parameters influencing the on-line SPE of target elements including pH, elution conditions, sample flow rate and sample volume were optimized. Under the optimized conditions, a wide linear range over 0.5–1000 ng mL−1 was obtained for target elements. The detection limits (LODs) and the relative standard deviations (RSDs) of Cu, Pb, La, Ce, Eu, Dy and Yb were 0.48, 2.64, 0.41, 0.24, 0.13, 0.26 and 0.21 ng mL−1 and 6.4, 9.8, 8.6, 3.2, 5.6, 4.5 and 6.2% (C = 10 ng mL−1, n = 7), respectively. For all the analytes, the overall adsorption process was controlled by diffusion and chemical reaction, and chemical reaction played a dominant role. The established method of on-line SPE-ICP-OES was validated by analyzing Certified Reference Material GBW07301a (Stream sediment), and the determined values are in good agreement with the certified values. The method was also applied for the determination of the target heavy metals and REEs in environmental water (even sea water) and sediment samples, and the recoveries were 82.4–115.5% and 83.8–114.8% for the spiked water and sediment samples, respectively.

A novel adsorbent was synthesized by grafting calconcarboxylic acid (CAA) dynamically to nanometer-sized zirconia (ZrO2) and was characterized with a transmission electron microscope, nitrogen adsorption instrument and infrared spectroscopy. By using CAA modified nanometer-sized ZrO2 as micro-column packing material, a new method of flow injection (FI) on-line preconcentration coupled with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed for simultaneous determination of trace metals (Cd, Co, Cu, Ni and Pb) in environmental water samples. The experimental parameters including pH, sample flow rate and volume, elution volume and flow rate and coexisting ions on the extraction of the target analytes were investigated, and the optimal experimental conditions were established. Under the optimized operating conditions, the limits of detection (LODs) of this method for Cd, Co, Cu, Ni and Pb were 0.16, 0.04, 0.28, 0.22, and 0.95 ng mL−1, with the relative standard deviations (RSDs) of 2.2, 3.0, 4.5, 4.1 and 7.7% (n = 7, c = 10 ng mL−1), respectively. An enrichment factor of 10 and sampling frequency of 12 h−1 were obtained by using a loading time of 200 s and elution time of 30 s. The proposed method was validated by analysis of the target metals in Certified Reference Materials of GSBZ50009-88 environmental water and real-world natural water samples.

A novel adsorbent was synthesized by grafting calconcarboxylic acid (CAA) dynamically to nanometer-sized zirconia (ZrO2) and was characterized with a transmission electron microscope, nitrogen adsorption instrument and infrared spectroscopy. By using CAA modified nanometer-sized ZrO2 as micro-column packing material, a new method of flow injection (FI) on-line preconcentration coupled with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed for simultaneous determination of trace metals (Cd, Co, Cu, Ni and Pb) in environmental water samples. The experimental parameters including pH, sample flow rate and volume, elution volume and flow rate and coexisting ions on the extraction of the target analytes were investigated, and the optimal experimental conditions were established. Under the optimized operating conditions, the limits of detection (LODs) of this method for Cd, Co, Cu, Ni and Pb were 0.16, 0.04, 0.28, 0.22, and 0.95 ng mL−1, with the relative standard deviations (RSDs) of 2.2, 3.0, 4.5, 4.1 and 7.7% (n = 7, c = 10 ng mL−1), respectively. An enrichment factor of 10 and sampling frequency of 12 h−1 were obtained by using a loading time of 200 s and elution time of 30 s. The proposed method was validated by analysis of the target metals in Certified Reference Materials of GSBZ50009-88 environmental water and real-world natural water samples.