The simultaneous entrapment of biological macromolecules and nanostructured silica-coated magnetite in sol-gel materials using a reverse-micelle technique leads to a bioactive, mechanically stable, nanometer-sized, and magnetically separable particles. These spherical particles have a typical diameter of 53 +/- 4 nm, a large surface area of 330 m(2)/g, an average pore diameter of 1.5 nm, a total pore volume of 1.427 cm(3)/g and a saturated magnetization (M(S)) of 3.2 emu/g. Peroxidase entrapped in these particles shows Michaelis-Mentan kinetics and high activity. The catalytic reaction will take place immediately after adding these particles to the reaction solution. These enzyme entrapping particles catalysts can be easily separated from the reaction mixture by simply using an external magnetic field. Experiments have proved that these catalysts have a long-term stability toward temperature and pH change, as compared to free enzyme molecules. To further prove the application of this novel magnetic biomaterial in analytical chemistry, a magnetic-separation immunoassay system was also developed for the quantitative determination of gentamicin. The calibration for gentamicin has a working range of 200-4000 ng/mL, with a detection limit of 160 ng/mL, which is close to that of the fluorescent polarization immunoassay (FPIA) using the same reactants.

Magnetite-containing spherical silica nanoparticles for biocatalysis and bioseparations （vol 76, pg 1316, 2004）

Antimony bioavailability: Knowledge and research perspectives for sustainable agricultures

Clouding behaviour in surfactant systems.

Complex-forming organic ligands in cloud-point extraction of metal ions: a review.

A novel fluorescence resonance energy transfer (FRET) system has been designed for the Cu2+ ions detection with optical visual assays. In this FRET reaction, the biocompatible, green luminescent monodisperse phenol formaldehyde resin nanoparticles (PFR NPs) synthesized by a simple hydrothermal method were used as the acceptor and the luminescent CdTe quantum dots (QDs) were selected as the donor. By the layer-by-layer method, the polyelectrolyte (PEI/PSS/PEI) were absorbed alternately on the surface of the PFR NPs. As a result, the amino groups were stably modified onto the surface of the PFR NPs. In the presence of 1-ethyl-3-(3-dimethly aminopropyl) carbodiimide (EDAC) and N-hydroxysuccinimide (NHS), the carboxyl groups coated CdTe QDs prepared by using mereaptoactetic acid (MA) as the stabilizer in water solution were coupled to the surface of amino group functionalized PFR NPs to obtain novel FRET nanocomposites. Owing to the sensitive quenching effect of Cu2+ ions on CdTe QDs and effective energy transfer from CdTe QDs to PFR NPs, the as-prepared FRET nanocomposites were utilized to monitor Cu2+ ion with optical visual detection at room temperature within 1 min. This nanoparticle-based FRET probe should promote further development of other nanocomposites for Cu2+ ion detection in the environmental field.

Phenol Formaldehyde Resin Nanoparticles Loaded with CdTe Quantum Dots: A Fluorescence Resonance Energy Transfer Probe for Optical Visual Detection of Copper(II) Ions

Cloud point extraction combined with electrothermal atomic absorption spectrometry for the speciation of antimony(III) and antimony(V) in food packaging materials

Selective cloud point extraction for the determination of cadmium in food samples by flame atomic absorption spectrometry

Determination of trace copper in food samples by flame atomic absorption spectrometry after solid phase extraction on modified soybean hull

Core-shell magnetic silica has been prepared and then chemically modified with thiol groups. It was used for magnetic solid phase extraction (MSPE) of trace Hg2+ from environmental samples, followed by its determination by cold vapor atomic absorption spectrometry (CV-AAS). The parameters for MSPE procedure, such as pH, elution conditions, ultrasonic time, and effects of co-existing ions were investigated. The results showed that Hg2+ ions are adsorbed on the thiol-modified magnetic silica at pH 6.0 after a 10-min ultrasonic treatment and were quantitatively eluted with 5.0 mL thiourea (2%, m/v) in nitric acid solution (0.1 M) after a 2-min ultrasonic treatment. Under the optimized experimental conditions, the adsorption capacity of the new sorbent was 101.0 mg g−1 for Hg2+. The detection limit of the proposed method was 0.06 n g mL−1 for Hg2+ and the enrichment factor was 16.6. The analytical data obtained from a certified reference water sample (GBW00809) were in good agreement with the certified value....

Thiol-Modified Magnetic Silica Sorbent for the Determination of Trace Mercury in Environmental Water Samples Coupled with Cold Vapor Atomic Absorption Spectrometry

Silica gel was chemically modified with polyelectrolyte and used as a solid phase extraction adsorbent for the determination of trace silver in environmental water samples by flame absorption spectrometry (FAAS). The effects of pH, sample flow rate and volume, elution conditions and co-existing ions on the recovery of the analyte were investigated. The results showed that silver could be adsorbed at pH 5.0 and eluted by 5.0 mL 2% thiourea in HNO 3 (0.1 mol L-1). Under the optimized conditions, the adsorption capacity of modified silica gel was found to be 8.6 mg g -1 for silver. The detection limit of the proposed method was 1.0 ng mL-1 for silver with an enrichment factor of 18.7. The analytical result for the certified reference water sample (GBW08610) was in a good agreement with the certified value. The proposed method has also been successfully applied to the determination of trace silver in drinking water, well water, snow water and waste water with the recoveries for spiked samples between 94% and 105%.

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Polyelectrolyte modified silica gel micro-column solid phase extraction for the determination of silver in environmental water samples by flame atomic absorption spectrometry

Xiuming Jiang

Papers

Cloud point extraction combined with electrothermal atomic absorption spectrometry for the speciation of antimony(III) and antimony(V) in food packaging materials

Selective cloud point extraction for the determination of cadmium in food samples by flame atomic absorption spectrometry

Determination of trace copper in food samples by flame atomic absorption spectrometry after solid phase extraction on modified soybean hull

Thiol-Modified Magnetic Silica Sorbent for the Determination of Trace Mercury in Environmental Water Samples Coupled with Cold Vapor Atomic Absorption Spectrometry

Polyelectrolyte modified silica gel micro-column solid phase extraction for the determination of silver in environmental water samples by flame atomic absorption spectrometry