Xiashi Zhu

A fluorescence spectroscopic study of the interaction between epristeride and bovin serum albumine and its analytical application.

A new spectrofluorimetric method to determine epristeride (EP) has been developed, which based on the EP has a strong ability to quench the intrinsic fluorescence of bovine serum albumin (BSA). There was the relationship between the fluorescence quenching intensity of BSA (DeltaF=F(BSA)-F(BSA-EP)) and the concentration EP. The quenching mechanism was investigated with the quenching type, the association constants, the number of binding sites and basic thermodynamic parameters. The method had been successfully applied to the analysis of EP in real samples and the obtained results were in good agreement with the results of official method-HPLC.

Study on the inclusion interactions of β-cyclodextrin and its derivative with dyes by spectrofluorimetry and its analytical application

The inclusion interactions of beta-cyclodextrin (beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) with dyes were developed by spectrofluorimetry, and the inclusion constants of inclusion complexes were determined by direct fluorescence technique. The main factors (the host molecule, the guest molecule, and the pH) for the inclusion interaction were discussed in detail. At the same time, the inclusion interaction of HP-beta-CD and vitamin B(6) (VB(6)) was investigated with the competitive fluorescence inclusion method and the inclusion constant of HP-beta-CD and vitamin B(6) (VB(6)) was obtained by indirect fluorescence technique. On the basis of the linear relationship between the change of fluorescence intensity (DeltaF) and the concentration of VB(6), a competitive fluorescence inclusion method was used to the determination of VB(6). The method has been successfully applied to the analysis of VB(6) in synthetic samples, tablets and injections with satisfactory results.

β-Cyclodextrin-cross-linked polymer as solid phase extraction material coupled with inductively coupled plasma mass spectrometry for the analysis of trace Co(II).

A sensitive method for the separation/analysis of Co(II) was described. The beta-cyclodextrin cross-linked polymer (beta-CDCP) was synthesized and used as solid phase extraction material (SPE) to separate/pre-concentrate trace cobalt coupled with inductively coupled plasma mass spectrometry (ICP-MS) for the analysis of Co(II). The method was based on alpha-pyridylazo-beta-naphthol (PAN) as the complexing agent for Co(II)-PAN at neutral condition and the adsorption behavior of Co(II)-PAN on beta-CDCP was studied. Further, p-octylpolyethylene-glycolphenyl ether (Triton X-100) as environment-friendly eluant was used. The linear range, detection limit (DL) and the relative standard deviation (R.S.D.) was 5.0-160.0 ng/mL, 5.84 ng/L and 2.27% (n=3, c=30.0 ng/mL) respectively. The enhancement factor was 10. Moreover, the beta-CDCP could be used repeatedly and offered better recovery and estimation of standard samples.

Ionic liquid coated magnetic core/shell Fe3O4@SiO2 nanoparticles for the separation/analysis of linuron in food samples

Three hydrophobic ionic liquids (ILs) including 1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluorophosphate ([HMIM]PF6), and 1-octyl-3-methylimidazole hexafluoro-phosphate ([OMIM]PF6) coated Fe3O4@SiO2 nanoparticles with core-shell structure to prepare magnetic solid phase extraction agent (Fe3O4@SiO2@ILs) and establish a new method of magnetic solid phase extraction (MSPE) coupled with UV spectrometry for separation/analysis of linuron. The results showed that linuron was adsorbed rapidly by Fe3O4@SiO2@[OMIM]PF6 and eluanted by ethanol. Under the optimal conditions, preconcentration factor of the proposed method was 10-fold. The linear range, detection limit, correlation coefficient (R) and relative standard deviation (RSD) were found to be 0.04-20.00 μg mL(-1), 5.0 ng mL(-1), 0.9993 and 2.8% (n=3, c=4.00 μg mL(-1)), respectively. The Fe3O4@SiO2 nanoparticles could be used repeatedly for 10 times. This proposed method has been successfully applied to the determination of linuron in food samples.

Cyclodextrin polymer/Fe3O4 nanocomposites as solid phase extraction material coupled with UV-vis spectrometry for the analysis of rutin.

In this paper, carboxymethyl-hydroxypropyl-β-cyclodextrin polymer modified magnetic particles Fe3O4 (CM-HP-β-CDCP-MNPs) were prepared and applied to magnetic solid phase extraction of rutin combined with UV-visible spectrometry detection. The synthesized magnetic particles were characterized by element analysis, Fourier transform infrared spectra, thermal gravimetric analysis, and transmission electron microscopy. Several variables affecting the extraction and desorption of rutin such as pH, the amount of adsorbent, the type and volume of eluent, extraction and desorption time, and temperature were investigated. The maximum adsorption capacity was 67.0 mg g(-1) for rutin with the equilibrium time of 30 min at room temperature, and the adsorbent could be reused for 10 times. A calibration curve was linear in the range of 0.05-8.00 μg mL(-1) with a relative standard deviation of 2.9% (n=5, c=4.0 μg mL(-1)). The limit of detection was 7.0 ng mL(-1). The interaction mechanism between the adsorbent and rutin was also studied. Feasibility of this method was validated by the analysis of rutin tablets and lotus plumule.

Study on the interaction between methyl violet and bovine serum albumin by spectral analyses

In this article the interaction between methyl violet (MV) and bovine serum albumin (BSA) was studied with spectroscopy. The results indicated that the fluorescence intensity of BSA was quenched strongly by MV through a static quenching procedure. The association constants, the number of binding sites and basic thermodynamic parameters were obtained based on fluorescence quenching data. The effect of MV on the conformation of BSA had been investigated with synchronous fluorescence spectroscopy and circular dichroism (CD) spectrum.

Speciation of antimony(III) and antimony(V) by electrothermal atomic absorption spectrometry after ultrasound-assisted emulsification of solidified floating organic drop microextraction

A simple, sensitive and efficient method of ultrasound-assisted emulsification of solidified floating organic drop microextraction (USE-SFODME) coupled to electrothermal atomic absorption spectrometry for the speciation of antimony at different oxidation state Sb(III)/Sb(V) in environmental samples was established. In this method, the hydrophobic complex of Sb(III) with sodium diethyldithiocarbamate (DDTC) is extracted by 1-undecanol at pH 9.0, while Sb(V) remains in aqueous phase. Sb(V) content can be calculated by subtracting Sb(III) from the total antimony after reducing Sb(V) to Sb(III) by l-cysteine. Various factors affecting USE-SFODME including pH, extraction solvent and its volume, concentration of DDTC, sonication time, and extraction temperature were investigated. Under the optimized conditions, the calibration curve was linear in the range from 0.05 to 10.0 ng mL(-1), with the limit of detection (3σ) 9.89 ng L(-1) for Sb(III). The relative standard deviation for Sb(III) was 4.5% (n=9, c=1.0 ng mL(-1)). This method was validated against the certified reference materials (GSB 07-1376-2001, GBW07441), and applied to the speciation of antimony in environmental samples (soil and water samples) with satisfactory results.

Determination of l-tyrosine by β-cyclodextrin sensitized fluorescence quenching method

A novel beta-cyclodextrin (beta-CD) sensitized fluorescence quenching method for the determination of l-tyrosine (l-Tyr) with Mo(VI)-phenyl-fluorone (PF) as a fluorescence probe has been developed. The fluorescence intensity of Mo(VI)-PF-beta-CD was diminished as the l-tyrosine was added, the fluorescence quenching value DeltaF=F(beta-CD-Mo-PF)-F(beta-CD-Mo-PF-l-Tyr) was enhanced in beta-CD and there was a linear relationship between the DeltaF and the concentration of l-Tyr. Under the optimal conditions, the linear range of calibration curve for the determination of l-tyrosine was 0.3-20.0microgmL(-1); the detection limit was 0.094microgmL(-1). NaOH (10%, w/v) is the best reagent of hydrolysis in sample preparation. The sensitized mechanism of beta-cyclodextrin was discussed. The method has been applied to the determination of l-tyrosine in spirulina and food samples with satisfactory results.

Dispersive solvent-free ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction coupled with HPLC for determination of ulipristal acetate.

In this paper, a simple and efficient ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (UA IL-DLLME) coupled with high-performance liquid chromatography for the analysis of ulipristal acetate (UPA) was developed. UPA could be easily migrated into 1-octyl-3-methylimidazolium hexafluorophosphate [C8mimPF6] IL phase without dispersive solvent. The research of extraction mechanism showed that hydrophobic interaction force played a key role in the IL-DLLME. Several important parameters affecting the extraction recovery were optimized. Under the optimized conditions, 25-fold enrichment factor was obtained and the limit of detection (LOD) was 6.8 ng mL(-1) (tablet) or 9.3 ng mL(-1) (serum) at a signal-to-noise ratio of 3. The calibration curve was linear over the range of 0.03-6.0 µg mL(-1). The proposed method was successfully applied to the UPA tablets and the real mice serum samples.

Optimization of β-cyclodextrin cross-linked polymer for monitoring of quercetin

A novel method for the separation/analysis of quercetin was described, which was based on the investigation of the inclusion interactions of β-cyclodextrin cross-linked polymer (β-CDCP) with quercetin (Qu) and the adsorption behavior of Qu on β-CDCP. The inclusion interaction of β-CDCP with Qu was studied through FTIR, TGA and 13C NMR. Under the optimum conditions, the preconcentration factor of the proposed method was approximately 8.8, the β-CDCP could be used repeatedly for 30 times and offered better recovery. The linear range, limit of detection (LOD) and the relative standard deviation (RSD) was found to be 0.10-12.0 μg mL(-1), 4.6 ng mL(-1) and 3.10% (n=3, c=2.0 μg mL(-1)) respectively. This technique had been successfully applied to the determination of Qu in real samples.