Facile synthesis of uniform spherical covalent organic frameworks for determination of neonicotinoid insecticides.

A uniform spherical structure covalent organic framework (TAPA-BPDA-COF) was prepared by a facile method at room temperature with tris(4-aminophenyl)amine (TAPA) and 4,4'-biphenyldicarboxaldehyde (BPDA) as building blocks. Based on the solid phase extraction with the TAPA-BPDA-COF as the sorbent and high performance liquid chromatography-diode array detection, a sensitive analytical method was established for the determination of four neonicotinoid insecticides from water and honey samples. Under the optimum conditions, good linear response for the quantification of the analytes was achieved in the range of 0.3-50.0 ng mL-1 for water samples and in the range of 8.0-500.0 ng g-1 for honey samples. The method recoveries fell in the range of 80.0-121.9% with RSDs less than 7.6%. The limits of detection at the signal to noise ratio of 3 were measured to be in the range of 0.08-0.12 ng mL-1 for water samples and 2.6-3.3 ng g-1 for honey samples, depending on compounds.

Benzoxazine Porous Organic Polymer as an Efficient Solid-Phase Extraction Adsorbent for the Enrichment of Chlorophenols from Water and Honey Samples.

Porous organic polymers have gained great research interest in the field of adsorption. A benzoxazine porous organic polymer (BoxPOP) constructed from p-phenylenediamine, 1,3,5-trihydroxybenzene and paraformaldehyde was fabricated and explored as an adsorbent for solid-phase extraction (SPE) of four chlorophenols from water and honey samples. Under the optimized SPE conditions, the response linearity for the analysis of the SPE extract of the chlorophenols by high performance liquid chromatography-diode array detector was observed in the range of 0.2-40.0 ng mL-1 for water samples and 5.0-400.0 ng g-1 for honey samples. The method detection limits of the analytes were 0.06-0.08 ng mL-1 for water samples and 1.5-2.0 ng g-1 for honey samples. The recoveries of the analytes from fortified water and honey samples ranged from 84.8 to 119.0% with the relative standard deviations below 8.4%. The results indicate that the prepared BoxPOP is an effective adsorbent for the chlorophenols. The established method provides an alternative approach for the determination of chlorophenols in real samples.

N'-(5-Bromo-2-hy-droxy-benzyl-idene)-4-nitro-benzohydrazide methanol monosolvate.

In the title compound, C(14)H(10)BrN(3)O(4)·CH(4)O, the benzohydrazide mol-ecule is nearly planar [maximum deviation = 0.110 (2) Å]. The mean planes of the two benzene rings make a dihedral angle of 8.4 (3)°. In the benzohydrazide mol-ecule, there is an intra-molecular O-H⋯N hydrogen bond and the NH group is hydrogen bonded to the methanol solvent mol-ecule. In the crystal, inter-molecular O-H⋯O hydrogen bonds involving the methanol solvent mol-ecule link the benzohydrazide mol-ecules to form chains which propagate along the a axis.

[Determination of serum proteins by resonance light scattering method with lidocaine as a probe].

A new method for the determination of bovine serum albumin (BSA) and human serum albumin (HSA) was developed by using resonance light scattering (RLS) technique via an interaction of serum albumin with lidocaine and sodium dodecylbenzene sulphonate (SDBS). The RLS intensity of serum albumin was enhanced in the presence of lidocaine and SDBS. The influences of some experimental factors, including incubation time, addition sequence of reagents, pH values, foreign substances and the concentrations of lidocaine and SDBS, on the enhancement of the RLS intensity were investigated. Under the optimal conditions, the enhanced RLS intensities were proportional to the concentrations of serum albumin in the range of 1.0-45.0 mg x L(-1) for BSA and 0.5-30.0 mg x L(-1) for HSA. The method was successfully applied to the determination of real human serum samples, with the relative standard deviations of 4.9%-5.7% (n = 5) and standard addition recoveries of 90%-103%. The method only involves the use of conventional fluorescence spectrometer and chemical reagents. It is simple, easy to operate and sensitive with the limit of detection of 0.14 mg x L(-1). The fresh human serum samples can be directly analyzed without the need of any prior pretreatment. The method can be a good alternative of choice for the determination of BSA and HSA.

Determination of triazine herbicides in environmental water samples by high-performance liquid chromatography using graphene-coated magnetic nanoparticles as adsorbent.

In this paper, a graphene-based Fe(3)O(4) magnetic nanoparticles (G-Fe(3)O(4) MNPs) was used as the adsorbent for the magnetic solid-phase extraction of some triazine herbicides (atrazine, prometon, propazine and prometryn) in environmental water samples followed by high performance liquid chromatography-diode array detection (HPLC-DAD). After the extraction, the adsorbent can be conveniently separated from the aqueous samples by an external magnet. The main factors influencing the extraction efficiency including the amount of the MNPs, the extraction time, the pH of sample solution, and desorption conditions were studied and optimized. Under the optimized experimental conditions, a good linearity was observed in the range of 0.1-50.0 ng mL(-1) for all the analytes, with the correlation coefficients (r) ranging from 0.9996 to 0.9999. The limits of detection of the method ranged between 0.025 and 0.040 ng mL(-1). Good reproducibility was obtained with the relative standard deviations below 5.2%. The developed method was applied to the analysis of the triazine herbicides in different water samples (lake, river and reservoir). The recoveries of the method were in the range between 89.0% and 96.2%.

[Study on the interaction of genistein and human serum albumin by spectroscopic method].

The interaction of genistein and human serum albumin (HSA) was investigated by fluorescence quenching spectra, synchronous fluorescence spectra and ultra-violet absorption spectra. The results showed that the quenching mechanism of the intrinsic fluorescence of HSA by genistein is due to the formation of genistein-HSA complex, resulting in a static quenching procedure. The binding constants (KA) were 1.00 x 10(6) (27 degrees C), 1.66 x 10(6) (37 degrees C) and 5.25 x 10(6) (47 degrees C), respectively. According to the Förster theory of non-radiation energy transfer, the binding distances (r) were 2.59 nm (27 degrees C), 2.65 nm (37 degrees C) and 2.90 nm (47 degrees C), respectively. The thermodynamic parameters showed that the binding power between genistein and HSA is mainly the electrostatic interaction Synchronous spectrum was used to investigate the conformational change of HSA.

[Study on the interaction of tetrandrine and bovine serum albumin].

The interaction of tetrandrine with bovine serum albumin was studied by fluorescence spectra and ultra-violet spectra. The results showed that tetrandrine could quench the intrinsic fluorescence of BSA. Both static quenching and non-radiation energy transfer were the main reasons for the fluorescence quenching. The quenching constants K(sv) at different temperatures were determined using Stern-Volmer equation. The K(sv) were 1.26 x 10(4) L x mol(-1) (300 K), 1.17 x 10(4) L x mol(-1) (310 K) and 1.12 x 10(4) L x mol(-1) (320 K). According to the Forster theory of non-radiation energy transfer, the binding distances (r) were 3.24 nm (300 K), 3.31 nm (310 K) and 3.50 nm (320 K). The binding constants (KA) between tetrandrine and BSA (300 K: 1.52 x 10(5) L x mol(-1); 310 K: 2.03 x 10(5) L x mol(-1); 320 K: 2.89 x 10(5) L x mol(-1)) and thermodynamic parameters were also obtained. The thermodynamic parameters indicated that the interaction of tetrandrine and BSA was driven mainly by hydrophobic force. Results of synchronous fluorescence spectrum showed that the binding could cause conformational changes of BSA.

[Determination of carbamate pesticides in reservoir water by hollow fiber-based liquid phase microextraction coupled with high performance liquid chromatography].

An analytical method for the determination of carbamate pesticides (carbofuran, carbaryl, isoprocarb and diethofencarb) in reservoir water using hollow fiber-based liquid phase microextraction (HF-LPME) coupled with high performance liquid chromatography (HPLC) was developed. Some main experimental parameters that affect the extraction efficiency were optimized. Toluene was selected as both the extraction solvent and the impregnation solvent. The extraction was carried out at room temperature (20 degrees C ) in a 5 mL Teflon-lined septum cap vial filled with 4.5 mL of sample solution at a stirring rate of 720 r/min for 20 min. The extract was dried under nitrogen stream at room temperature. The dried residue was then dissolved in the mobile phase for HPLC analysis. The separation was carried out on a Baseline C18 column (4.6 mm x 250 mm, 5.0 microm) with methanol-water (60:40, v/v) as the mobile phase at a flow rate of 1.0 mL/min. The detection for carbofuran, carbaryl, isoprocarb and diethofencarb was selected at 200, 223, 200 and 208 nm, respectively. The average enrichment factors for the four analytes were greater than 45. The linear range for the quantification of the four analytes was 10 - 100 microg/L (r > 0.99). The limits of detection (LODs) were 5, 1, 5 and 3 microg/L (S/N = 3) for carbofuran, carbaryl, isoprocarb and diethofencarb, respectively. Good recoveries (82.0% - 102.2%) and good reproducibilities (2.0% - 6.2%, n = 6) were achieved.

[Study on the interaction between brucine and bovine serum albumin].

The interaction between brucine and bovine serum albumin (BSA) was investigated using fluorescence spectroscopy (FS) and ultraviolet spectroscopy (UV). The experimental results showed that the brucine quenches the inner fluorescence by forming a brucine-BSA complex. It was found that both static quenching and non-radiation energy transfer were the main reasons for the fluorescence quenching. The apparent binding constants (K(A)) between brucine and BSA were 6. 3 x 10(3) (27 degrees C) and 7.7 x 10(3) (37 degrees C), and the binding sites (n) were 0.94 (27 degrees C) and 0.97 (37 degrees C). According to the Förster theory of non-radiation energy transfer, the binding distances (r) were also obtained. The process of binding was a spontaneous molecular interaction in which entropy increased and Gibbs free energy decreased, indicating that the interaction between brucine and BSA was driven mainly by hydrophobic force.

[Study on the interaction of Nimodipine and bovine serum albumin by fluorescence quenching method].

The interaction of Nimodipine and bovine serum albumin (BSA) was studied using fluorescence spectroscopy (FS) and ultraviolet spectroscopy (UV). The apparent binding constants (KA) between Nimodipine and BSA were 5.01 x 10(4) (26 degrees C) and 4.46 x 10(4) (36 degrees C), and the binding sites (n) were 1.08 +/- 0.01. According to the Förster theory of non-radiation energy transfer, the binding distances (r) were also obtained. The experimental results showed that Nimodipine could quench the inner fluorescence of BSA by forming the Nimodipine-BSA complex. It was found that both static quenching and non-radiation energy transfer led to the fluorescence quenching. The process of binding was a spontaneous molecular interaction in which entropy increased while Gibbs free energy decreased. The thermodynamic parameters indicated that the interaction of Nimodipoine and BSA was driven mainly by static electrical force.

[Simultaneous determination of levodopa and methyldopa in human serum by capillary electrophoresis].

A simple capillary electrophoresis method was developed for the determination of levodopa and methyldopa in human serum. The effects of pH and concentration of buffer, voltage and injection time on separation were investigated. As a result, an optimized separation was obtained with a fused-silica capillary of 60.2 cm (50 cm effective length) x 75 microm i. d. in a running buffer of 40 mmol/L sodium tetraborate (pH 9.5) with an applied voltage of 22 kV at 25 degrees C. Sample introduction was performed at 3.45 kPa (0.5 psi) for 7 s and on-column detection was made with a diode array detector at 200 nm. The linear responses covered the ranges from 1.0 to 64.0 mg/L (r = 0.999 8) for methyldopa and from 1.0 to 71.0 mg/L (r = 0.999 4) for levodopa. The detection limits (S/N = 3) of methyldopa and levodopa were shown to be 0.6 mg/L and 0.8 mg/L, respectively. The recoveries for levodopa and methyldopa in human serum were between 82.8% and 88.8% with relative standard deviations between 2.10% and 2.63%.