Tianlin Wang

Mesostructured Nanomagnetic Polyhedral Oligomeric Silsesquioxanes (POSS) Incorporated with Dithiol Organic Anchors for Multiple Pollutants Capturing in Wastewater

A functionalizable organosiliceous hybrid magnetic material was facilely constructed by surface polymerization of octavinyl polyhedral oligomeric silsesquioxane (POSS) on the Fe3O4 nanoparticles. The resultant Fe3O4@POSS was identified as a mesoporous architecture with an average particle diameter of 20 nm and high specific surface area up to 653.59 m(2) g(-1). After it was tethered with an organic chain containing dithiol via thiol-ene addition reaction, the ultimate material (Fe3O4@POSS-SH) still have moderate specific area (224.20 m(2) g(-1)) with almost identical porous morphology. It turns out to be a convenient, efficient single adsorbent for simultaneous elimination of inorganic heavy metal ions and organic dyes in simulate multicomponent wastewater at ambient temperature. The Fe3O4@POSS-SH nanoparticles can be readily withdrawn from aqueous solutions within a few seconds under moderate magnetic field and exhibit good stability in strong acid and alkaline aqueous matrices. Contaminants-loaded Fe3O4@POSS-SH can be easily regenerated with either methanol-acetic acid (for organic dyes) or hydrochloric acid (for heavy metal ions) under ultrasonication. The renewed one keeps appreciable adsorption capability toward both heavy metal ions and organic dyes, the removal rate for any of the pollutants exceeds 92% to simulate wastewater with multiple pollutants after repeated use for 5 cycles. Beyond the environmental remediation function, thanks to the pendant vinyl groups, the Fe3O4@POSS derived materials rationally integrating distinct or versatile functions could be envisaged and consequently a wide variety of applications may emerge.

Migration behaviour of alkali and alkaline-earth metal ion-EDTA complexes and quantitative analysis of magnesium in real samples by capillary electrophoresis with indirect ultraviolet detection

Abstract A capillary electrophoretic (CE) method was developed for the separation of some common alkali and alkaline-earth metal ions using EDTA as complexing agent and pyridine as UV chromophore for indirect detection at pH 5.00. Effects of pH and concentration of complexing agent on the differences in the effective mobilities between two ions were considered and equations derived were used to deduce the optimum conditions for their separation. Baseline separation of a group of metal ions, including K, Na, Li, Mg, Sr and Ba, was achieved in less than 4 min. The calibration range for magnesium was found to be linear up to 1.00 μg/ml when samples were prepared in the running buffer while a hyperbolic calibration curve was obtained when prepared in water. Application of the method to the analysis of magnesium in river water, urine and a solid sample of calcium carbonate was demonstrated. Magnesium in those samples was determined to be 812 μg/ml, 78.0 μg/ml and 0.023% (w/w), respectively, with reproducibilities between 5–9% R.S.D. in terms of peak height depending on sample matrices.

Separation of polyphosphates and polycarboxylates by capillary electrophoresis in a carrier electrolyte containing adenosine 5'-triphosphate and cetyltrimethylammonium bromide with indirect UV detection

Abstract A capillary electrophoresis method was developed for the separation of polyanions of environmental concern, such as polyphosphates [ortho- (P1), pyro- (P2) and tripoly- (P3)] and polycarboxylic acids (nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid and citrate) which are used as builders in detergents. A carrier electrolyte consisting of adenosine 5′-triphosphate as the UV chromophore for indirect detection at 260 nm and cetyltrimethylammonium bromide as modifier to reverse the electroosmotic flow was used. The changes in the effective mobilities of some solutes and common UV chromophores with pH were either predicted theoretically or determined experimentally. Differences in effective mobilities of the solutes were used to optimize the pH for their separation. Baseline separation for all the solutes was achieved. Detection limits for all of the solutes were in the range 2 · 10−5 −5 · 10−5 M. Application of the developed method to real samples was demonstrated by separation and determination of polyphosphates (P1, P2 and P3) in a commercial detergent. For sample preparation, only simple dilution with water and filtration were needed.

Fabrication of enrofloxacin imprinted organic-inorganic hybrid mesoporous sorbent from nanomagnetic polyhedral oligomeric silsesquioxanes for the selective extraction of fluoroquinolones in milk samples.

This paper reports a nanomagnetic polyhedral oligomeric silsesquioxanes (POSS)-directing strategy toward construction of molecularly imprinted hybrid materials for antibiotic residues determination in milk samples. The imprinted polymeric layer was facilely obtained through the copolymerization of active vinyl groups present on the nanomagnetic POSS (Fe3O4@POSS) surface and functional monomer (methacrylic acid) binding with template (enrofloxacin). Herein, the octavinyl POSS acted as not only the building blocks for hybrid rigid architectures but also the cross-linker for the formation of effective recognition sites during the imprinting process. The molecularly imprinted Fe3O4@POSS nanoparticles (Fe3O4@MI-POSS) demonstrated much higher adsorption capacity and selectivity toward enrofloxacin molecules and its analogs than the non-imprinted Fe3O4@POSS (Fe3O4@NI-POSS) materials. The imprinted particles were applied as a selective sorbent in solid-phase extraction focusing upon sample pretreatment in complex matrices prior to chromatographic analysis. The three FQs (ofloxacin, enrofloxacin, danofloxacin) could be selectively extracted from the biological matrix, while the matrix interferences were effectively eliminated simultaneously under the optimum extraction conditions. A simple, rapid and sensitive method based on the Fe3O4@MI-POSS material combined with HPLC-UV detection was then established for the simultaneous determination of three FQs from milk samples. The average recoveries of the three FQs were in the range of 75.6-108.9%. The relative standard deviations of intra- and inter-day ranging from 2.91 to 8.87% and from 3.6 to 11.5%, respectively. The limits of detections (S/N=3) were between 1.76 and 12.42 ng mL(-1). It demonstrates the effectiveness of trace analysis in complicated biological matrices utilizing magnetic separation in combination with molecularly imprinted solid-phase extraction, the rich chemistry of POSS makes it possible to be an ideal platform for generating molecular imprinted hybrid materials is also exhibited.

Sensitive determination of trace-metal elements in tea with capillary electrophoresis by using chelating agent 4-(2-pyridylazo) resorcinol (PAR)

A capillary electrophoresis method was developed for the determination of trace metals (Cu, Fe, Zn, Co and Ni) in tea based on the conversions of strong complexes between 4-(2-pyridylazo) resorcinol (PAR) and metals. Five metals can be determined in 10 min by a single run. The calibration curves showed a linear range from 50 μg/l to 5 mg/l for these metals with correlation coefficients (r2) being greater than 0.999. Detection limits (S/N=3) of Co, Fe, Cu, Zn and Ni varied from 6 to 30 μg/l. Recoveries of these metal ions ranged from 97.9 to 106.2%. The method is simple and separation time is short.

Indirect laser-induced fluorescence detection of valproic acid in human serum by capillary electrophoresis

A capillary electrophoresis (CE) method with indirect laser‐induced fluorescence detection for the analysis of valproic acid in human serum has been explored. The buffer system was optimized with 2.5 mM borate‐phosphate at pH 8.4; fluorescein sodium was used to generate background signal at a concentration of 6 μM. Hexanoic acid was selected as internal standard. Serum sample was deproteinized by acetonitrile. Analysis was performed by direct injection of the supernatant. CE separation was carried out at 30 kV and the total analysis time was less than 15 min, including sample treatment and electrophoresis time. No interference from other common anticonvulsant drugs occurred under the experimental conditions used. The interference of human serum matrix was reduced by using a high ratio of acetonitrile to serum (minimum 5:1) for deproteinization. Interference of ionic components in serum could occur, depending on the sample source. The linear range of concentrations for standard drug was between 4.5—144.0 μg/mL (r = 0.9947). The limit of detection was 0.9 μg/mL at S/N ≥ 3; the limit of quantitation at S/N ≥ 20 was 3 μg/mL. The recoveries of valproic acid spiked into serum were 69.2% and 60.2% for concentration levels of 90 and 54 μg/mL, respectively. This CE method was shown to be successful in the analysis of valproic acid in standard solutions. However, interference from the matrix was observed in the analysis of this compound in serum samples. Additional work should be done to develop a highly selective sample preparation technique.

Boronate affinity solid-phase extraction based on functionalized magnesia–zirconia composite for enrichment of nucleosides in human urine

A novel boronic acid functionalized magnesia–zirconia (ZM) based material was facile synthesized by Lewis acid–base chemisorption. The elemental analysis, inductively coupled plasma atomic emission spectrometer (ICP-AES) and Fourier transform infrared spectrometer (FT-IR) have proven the successful attachment of 3-aminophenylboronic acid derivative onto ZM surface. In the present work, the affinity of the resulting material towards cis-diols binding was evaluated by using it as the sorbent for solid-phase extraction of 4 nucleosides (namely cytidine, uridine, guanine and adenosine). The results show that such boronic acid modified magnesia–zirconia composite microparticles were excellent for capturing nucleosides in the system with a wide range of pH and high salt concentration, which could be effectively released using TFA–ACN–H2O (5u2006:u200650u2006:u200645, v/v/v) solution as elution. The 4 nucleosides spiked to untreated urine sample (i.e., no diluting or pH adjustment) were prominently enriched with recoveries in the range of 86–109% and LOD values in the range of 0.003–0.010 μg mL−1. The constructed calibration curves range from 0.05 to 2.0 μg mL−1 showing good linearity correlation coefficient (R ≥ 0.9961) and precision (RSD < 9%). The proposed material would allow for an alternative extraction strategy for identification and quantitative analysis of cis-diols structure compounds in biological samples.

Separation of synthetic inorganic polymers of condensed phosphates by capillary gel electrophoresis with indirect photometric detection

Separation of synthetic inorganic polymers of condensed phosphates was carried out by capillary gel electrophoresis with indirect photometric detection. Pyromellitic acid was employed as ultraviolet (UV) absorbing background electrolyte and absorbance of UV was measured at 254 nm. The separation of condensed phosphates in 12% (w/v) linear polyacrylamide gel was found to be mainly dependent on the size of the separands, but charge-to-size ratio played a part in the migration behaviour of orthophosphate and metaphosphates. The results presented in this paper demonstrate that the combination of capillary gel electrophoresis with indirect photometric detection provides a highly efficient and universal method which should be useful for the characterization of nonabsorbing ionic polymers.

Derivatization, extraction and concentration of amino acids and peptides by using organic/aqueous phases in capillary electrophoresis with fluorescence detection.

We report a novel method that facilitates sample pretreatment and detection in amino acid analysis by coupling solvent extraction with capillary electrophoresis. Amino acids and peptides were fluorescently labeled, concentrated into an organic solvent, and then separated by capillary zone electrophoresis with fluorescence detection. To achieve this, acetophenone was first employed to dissolve the derivatizing reagent, fluorescamine. The products, which possessed both hydrophilic and hydrophobic moieties, could be extracted and concentrated into the organic phase by suppressing the deprotonation of carboxyl groups, thus enhancing the hydrophobicity of the resulting molecules through pH modification in the aqueous solution. Furthermore, by fine‐tuning the pH value, individual amino acids and short peptide molecules could be separated selectively from the sample bulk. This convenient, chemically controllable concentration technique may be useful in sample concentration and purification of biologically related samples such as amino acids and short peptides.

Separation of inorganic phosphorus-containing anions by capillary electrophoresis

This article provides a review of separation of inorganic phosphorus-containing anions by capillary electrophoresis including capillary isotachophoresis, capillary zone electrophoresis in free solution and capillary gel electrophoresis. Method development and method evaluation on analytical performance are described. Applications are surveyed. Much attention is focused in the review on the selectivity and detectability of each capillary electrophoretic technique. Features of capillary electrophoretic methods, compared with chromatographic methods, are summarized in the view of analytical separation of inorganic phosphorus-containing anions. Light is given on problems and potentials of the capillary electrophoretic techniques in the separation of inorganic phosphorus-containing anions.