Jing Yang

Determination of melamine in powdered milk by molecularly imprinted stir bar sorptive extraction coupled with HPLC.

A novel molecularly imprinted stir bar (MIP-SB) was developed with melamine (MA) as the template molecule in this study. The sorptive capacity of MIP-SB was nearly three times over that of non-imprinted stir bar (NIP-SB). The MIP-SB presented much better selectivity than NIP-SB when used to absorb MA and its analogues. An analytical method to determine MA in powdered milk was established by combining MIP-SB sorptive extraction with HPLC. The liner range was 0.0631-12.6ng/mL with good correlation coefficient of 0.9983, and the limit of detection was 0.0127ng/mL based on three times ratio of signal to noise. This method was successfully applied to the determination of MA in powdered milk with satisfactory results. The method built is simple and suitable for the determination of MA in milk products which is of great significance for quality control of milk products.

Citrate-capped Mn-modified CdSe/CdS quantum dots as luminescent probes for levodopa detection in aqueous solution.

A novel kind of citrate capped Mn-modified CdSe/CdS quantum dots (QDs) was developed. The Mn-modified CdSe/CdS QDs had a narrow, symmetric emission and strong fluorescence with quantum yield over 41%. The interaction between the QDs and levodopa was investigated. The results showed that levodopa selectively quenched the fluorescence intensity of the QDs. Based on the fluorescence quenching of the synthesized QDs by levodopa, a simple, rapid and specific quantitative method for levodopa was proposed. The factors affecting the fluorescence detection for levodopa were studied. Under the optimum conditions, the quenched intensity of the fluorescence versus levodopa concentration from 1 to 100 μM gave a linear response with an excellent correlation coefficient of 0.9996, and the limit of detection (3σ/K) was 2 × 10(-7)M. The contents of levodopa in pharmaceutical tablets were determined by the proposed method and the results agreed with the claimed values.

Preparation of a stir bar coated with molecularly imprinted polymer and its application in analysis of dopamine in urine.

A molecularly imprinted polymer coated stir bar (MIP-SB) using dopamine as a template was fabricated. The adsorptive capacity of the MIP-SB was almost 4 times over that of non-imprinted stir bar. The MIP-SB showed good extracting selectivity for dopamine when used to adsorb dopamine and its analogs. An analytical method to determine dopamine in urine sample was established by combining MIP-SB sorptive extraction with HPLC-fluorescence detector. The linear range of dopamine concentration was 0.378-18.9ng/ml with correlation coefficient of 0.9990, and the limit of quantification was about 0.0945ng/ml (S/N=10). The recoveries of dopamine with spiked urine samples at three different levels were between 92.3 and 106.9%, and the relative standard deviations were within 13.2% (n=3). The method is simple and suitable for the determination of dopamine in human urine for clinical application.

Detection of CEA in human serum using surface-enhanced Raman spectroscopy coupled with antibody-modified Au and γ-Fe₂O₃@Au nanoparticles.

In this present work, a rapid and simple method to detect carcinoembryonic antigen (CEA) was developed by using surface-enhanced Raman spectroscopy (SERS) coupled with antibody-modified Au and γ-Fe2O3@Au nanoparticles. First, Au@Raman reporter and γ-Fe2O3@Au were prepared, and then modified with CEA antibody. When CEA was present, the immuno-Au@Raman reporter and immuno-γ-Fe2O3@Au formed a complex through antibody-antigen-antibody interaction. The selective and sensitive detection of CEA could be achieved by SERS after magnetic separation. Under the optimal conditions, a linear relationship was observed between the Raman peak intensity and the concentration of CEA in the range of 1-50 ng mL(-1) with an excellent correlation coefficient of 0.9942. The limit of detection based on two times ratio of signal to noise was 0.1 ng/mL. The recoveries of CEA standard solution spiked with human serum samples were in the range of 88.5-105.9% with the relative standard deviations less than 17.4%. The method built was applied to the detection of CEA in human serum, and the relative deviations of the analysis results between the present method and electrochemiluminescence immunoassay were all less than 16.6%. The proposed method is practical and has a potential for clinic test of CEA.

Manganese modified CdTe/CdS quantum dots as a highly selective probe to detect trace copper element in beer samples

This paper describes the investigation of manganese modified CdTe/CdS quantum dots as a fluorescence probe for trace copper detection. Manganese modified CdTe/CdS quantum dots were prepared in aqueous solution and were characterized by ultraviolet-visible absorbance, fluorescence spectra, transmission electron microscopy and X-ray diffraction. The as-synthesized manganese modified CdTe/CdS QDs presented a high photoluminescence quantum yield of 84%. The functionalized nanoparticles were used as a fluorescence probe for Cu2+. The interference study demonstrated that the normal foreign ions, such as Na+, Mg2+, Al3+et al., had very low interference for the detection of Cu2+, and the calibration plot of F0/F versus concentration of Cu2+ was linear in the range of 5.0 × 10−9 to 5.0 × 10−7 mol L−1 with a correlation coefficient of 0.9991. The ultrasensitive fluorescence probe built was directly applied to the detection of trace copper element in beer samples with satisfactory results.

Preparation and application of imprinted polymer for tetrabromobisphenol A using tetrachlorobisphenol A as the dummy template

In this paper, dummy molecularly imprinted polymer (DMIP) for tetrabromobisphenol A (TBBPA) was prepared with a sol–gel process on the surface of micro-nano silica particles. Tetrachlorobisphenol A was chosen as the dummy template to avoid TBBPA bleeding. The adsorption characteristics of the DMIP for TBBPA were investigated. The DMIP for TBBPA had a large adsorption capacity (230 μmol g−1), which was about 6 times as much as that of the non-imprinted polymer, fast binging kinetics (20 min) and high selectivity for TBBPA. A method for the determination of trace TBBPA in environmental water samples was established by high performance liquid chromatography coupled with solid phase extraction using the DMIP as sorbent. Under the built method, the linear range of TBBPA standard aqueous solution was 0.2–8.0 ng mL−1 with a correlation coefficient of 0.9947 and the limit of detection was 0.1 ng mL−1. The recoveries at 1.0 ng mL−1 of TBBPA spiked with water samples were in the range of 91–93% and the relative standard deviations were all less than 9.0% (n = 5). The results showed that the properties of the DMIP were superior and could be used to separate and enrich trace TBBPA in environment water samples.

Manganese modified CdTe/CdS quantum dots as an immunoassay biosensor for the detection of Golgi protein-73

In this paper, a new fluorescence bioassay for Golgi protein-73 (GP73), a promising marker for monitoring liver tumor, was developed by using anti-GP73 antibody (GP73 Ab) capped quantum dots (QDs) coupled with protein A/G agarose beads in an attempt to improve the analysis time, cost and operation. First, carboxylic-functionalized Mn modified CdTe/CdS QDs were synthesized and covalently conjugated with GP73 Ab, then protein A/G agarose beads were specifically combined with the QDs-conjugated Ab to form the QDs-Ab-beads conjugate, which could capture and separate GP73 from the sample through simple centrifugation. It was found that the fluorescence intensity of the above QDs-Ab-beads biosensor could be specifically quenched by GP73 added. A simple, rapid and specific quantitative method for GP73 protein was proposed using the as-prepared QDs-Ab-beads as a biosensor. Under the optimized conditions, the calibration curve of the proposed assay showed good linearity with a correlation coefficient of 0.9935 in the concentration range of 20-150 ng/mL of GP73 protein. The limit of detection (defined as 3σ/K) was 10 ng/mL. The method built exhibited a great potential in the clinic test of GP73.

A novel Fe3O4/CdTe fluorescence probe for sialic acid detection based on a phenylboronic acid–sialic acid recognition system

A novel fluorescence method was established for detecting sialic acid (SA) by using phenylboronic acid (PBA)-functionalized Fe3O4/CdTe magnetic nanoparticles as fluorescence probe. Initially, Fe3O4 nanoparticles were modified with amino groups, and then 3-mercapto propionic acid-stabilized CdTe quantum dots (QDs) were covalently linked to the amino-modified Fe3O4 nanoparticles to form Fe3O4/CdTe magnetic fluorescence nanoparticles. Finally, PBA was introduced on the surface of Fe3O4/CdTe to form PBA-functionalized Fe3O4/CdTe magnetic fluorescence nanoparticles. This kind of nanoparticle can specifically recognize SA and its fluorescence intensity is quenched by SA. In addition, the conjugate of the nanoparticles and SA is easy to separate from the sample matrix due to its magnetic properties. Therefore, this nanoparticle can be used as a fluorescence probe to detect SA. Under optimal conditions, the fluorescence intensity of the nano probe was found to be inversely linear with the concentration of SA in a wide range of 50 μg ml−1–1.50 mg ml−1, and the limit of detection was 16 μg ml−1. The PBA-functionalized Fe3O4/CdTe nano probe was applied to the determination of SA in infant formula, and the result showed high accuracy and precision. The PBA-functionalized Fe3O4/CdTe nano probe has the potential to be used to monitor SA in food.

Pharmacokinetics and bioequivalence studiesof cefteram pivoxil in healthy Chinese volunteers

SummaryA simple, sensitive and specific method has been developed for the determination of cefteram in human plasma. Sample preparation was accomplished through protein precipitation with 20% trichloroacetic acid (v/v) and chromatographic separation was performed on a Cia column at 25 °C. The mobile phase consisted of methanol-aqueous 20mM ammonium acetate (18∶82, v/v) at flow rate of l.OmL/min. Wavelength was set at 235nm. The lower limit of quantification was 0.04μg/mL and the assay exhibited a linear range of 0.04–3.2μg/mL (r=0.9996). The relative recoveries of cefteram from human plasma at three different concentrations were more than 90%. The method was successfully applied to investigate the bioequivalence between two kinds of cefteram pivoxil preparations (test vs reference) in 24 healthy Chinese volunteers. After a single 100mg dose for the test and reference product, the resulting means of major pharmacokinetic parameters such asAUC0−t,AUC0−∞,Cmax andTmax of cefteram pivoxil were 4.75±1.35 vs 4.76±1.29μg h/mL, 4.89±1.36 vs 4.91±1.29μg h/mL, 1.65±0.45 vs 1.73±0.45μg/mL and 1.48±0.59 vs 1.73±0.45h, respectively, indicating that these two kinds of preparations were bioequivalent.